Transcript
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Introduces cell biology by explaining that all living organisms are made of cells and share deep biochemical similarities. It contrasts the diversity of life with the common genetic blueprint found across organisms.
Speaker A
Introduction to cell biology.The unity of life is what makes any organism, any life form, to be considered as such.No matter if you are a bacteria, or human being, you are going to have those characters.
So first of all, when we are talking about the unity of life, we should say that all living organisms are made of cells.And the cells, which are the basic unit of life, can be divided into unicellular organisms made up of just one cell, such as bacteria, yeast, etc., or multicellular organism made up of several to billions of cells, most plants and animals.Those cells work together to help organisms grow and survive.So the general concept of structure-function of cells are quite similar in many ways.Let's start with a short introduction.
Speaker B
A lot has happened in the intervening billions of years.Life has evolved from simple single-celled organisms to the myriad diversity of life on Earth.Nowhere is that diversity more dazzlingly displayed displayed than in the tropical rainforests that encircle the Earth's equatorial middle.Rainforest environments are a nursery for species diversity, accounting for about one-third of all the plants and animals on Earth.But faced with all that variety, when you look at the natural world from a genetic perspective, what is perhaps even more astonishing is the profound sameness of all living creatures.By sameness, I mean all organisms contain DNA as genetic material.All organisms show the same basic steps in genetic information flow.
And the biochemical machinery in biological information flow is the same in all organisms.
All mammals share 97% of all genes.3% is the small portion that differentiates species and organisms from each other.There are patterns that run through all living things.These patterns are what suggest that all living things came from the same basic blueprint.
Describes the universal traits of cellular life, including DNA, gene expression, proteins, membranes, reproduction, and energy use. It also begins contrasting how bacteria and human cells differ in appearance and size.
Speaker A
So what are those characters that you can find in all cellular life?
First, all cellular life are using what we call the central dogma of of gene expression.
They contain DNA as the genetic material.It's always double-stranded DNA, and the DNA is our genetic material.
Now, in order to talk about living organisms, living organisms by definition are expressing their DNA all the time.So when you take a cell and you are looking for the nucleic acids over there, you're going to find both.DNA and RNA, several types of RNA which are expressed from the DNA.Life is always involved with gene expression.And the messenger RNA, for example, are going to be translated into proteins.
Again, that's the basic things that related— the activities that are related to the central dogma, and all living organisms are using this all the time.DNA expressed to RNA that is translated to protein.And the proteins determine the phenotype.Now, proteins have activities such as enzymatic activity, many others, and those enzymes are mediating, are catalyzing reactions, chemical reactions, that make life to be possible.All cellular life must have a cell membrane, plasma membrane.That's a must for a living cell.And this cell membrane separates the chaos outside of the cell from the high degree of organization within the cell.All cellular life is a result of reproduction.In other words, we are talking about the fact that cells is coming from another cell dividing into 2.So all cellular life of today can be connected to the first cell that appears on this planet, theoretically of course.
All cellular life are using energy, are making and using energy.So usually it's in the form of ATP, We'll discuss this as well.So again, I mean, the cone of energy in all cellular life, it's pretty much the same as well.So there is quite a lot of sameness in cellular life.Whether you are a bacteria or human cells, you're doing a lot of things in the very same way.
However, in many ways, each organism is different from any other organism.
I— we look quite differently from bacteria or other animals, dust mites for example.
Explores how cell size varies from visible organisms to microscopic cells and viruses. The speaker compares human cells, yeast, bacteria, and viruses to show the range of biological scale.
Speaker A
So yes, animals in many ways are also quite different from each other.And we can start from the very basic.The cell size can be quite diverse.
So, uh, you can see what you can actually see with your naked eye.So you can see a finger, you can see a pin, and if you are increasing the magnification, you're going to see things that normally you cannot really see with your naked eye.Here you can see dust mite.It's actually a small animal.And you can see this compared to human hair.
But if we will increase the magnification further, We're going to enter into the level of micrometer.
So when you are looking, for example, on pollens that are coming from trees, well, I mean, those are at the level of the micrometer range.But here you can also see human cells.Human cells here, lymphocytes here, red blood cells, they look different.And even in our system, we have cells that are different from each other in their shape and their size.Red blood cells, for example, do not have a nucleus.
And this is another blood cell, a lymphocyte, which is responsible for our immune system.
But this is another cell which is quite small as compared to the lymphocytes, and this is yeast, baker's yeast.This is an organism that you are using in order to make bread or beer.
Well, let's increase the magnification further, and now you can start to see bacterial cells.Even with— when you are comparing one bacteria to another, You can see that they are different in shape and size.This is E. coli, which is rod-like bacteria, versus the Staphylococcus, which is round.It's like a ball.So here you can actually measure and see that the E. coli, the size of E. coli is around the 1 to 2 micrometers, while the diameter of the staph is smaller than this.
Now I want to take you to something which is not considered a cellular life, which is absolutely not a cellular life.And those are viruses.Viruses are not cells, but they are parasites of cells.They're not playing the rules that I mentioned earlier about the unity of life.Well, they have a lot of differences from this.
And here, when it comes to the size, you can see that viruses are quite diverse among each other.Some are very long, like this Ebola virus, which happens to be probably the longest virus that we have around.It actually is, well, at the level of micrometer thousand nanometer in range.But here, and I'm zooming towards them, you're going to see some small viruses, rhinoviruses, the virus that causes the running nose.They are considered to be quite small, and you can see that their diameter, it's approximately 20 nanometers.That's their range.
Explains the major differences between prokaryotic and eukaryotic cells, especially the presence of a nucleus, organelles, and cell walls. The section uses simple analogies to illustrate their structural organization.
Speaker A
So yes, I mean, the organisms that are populating our Earth can be quite different in size.Well, from virus cells that are not cells, but they are parasites of cells, and they are much smaller than the cells that they need to infect.
And here you can see bacteria is a cell, it's cellular life, and all the unity, the character of the unity of life are actually related to bacteria as well.And here you see eukaryotic cells, mean you're going to see the yeast, you're going to see here the human cell, the lymphocytes, and here again you have the active— the, the— you can see quite a lot of variability among their size.
So actually we talked about 2 different cells, bacterial cells and eukaryotic cells.There are differences between the prokaryotic and eukaryotic cells, although there are a lot of things in common.
So, prokaryotic cells do not have a nucleus, while the eukaryotic cells are cells with nucleus.
Covariate is actually come from the word nucleus in Latin.Now, if you have a nucleus, you can separate the translation machinery from the RNA synthesis, and that's actually give the RNA a chance to be processed in the nucleus.Actually, a very important activity that make one gene to make a lot of different proteins, after all.So the eukaryotic cells can have RNA processing, but that's not taking place in prokaryotic cells.
Organelles.Organelles actually can be found in eukaryotic cells but not in prokaryotic cells.Actually, as the eukaryotic cells are larger than prokaryotic cells, organelles which are in the size of bacterial cell are going to be in eukaryotic cells, but of course this type of organelle, the size of organelle, is not found in prokaryotic cells.And there is another difference that you can find in prokaryotic cells versus animal cells, and this is a cell wall.All prokaryotic cells in general have cell wall, and eukaryotic cells, animal cells, do not have such a structure.
Speaker B
Eukaryotes, like the cells of plants and animals, are designed like this office building with many floors and rooms.Eukaryotes are complex and compartmentalized, including structures such as lysosomes, mitochondria, ribosomes, and chloroplasts.They have an internal membrane structure and a true nucleus to enclose their DNA.Cell structures may differ slightly slightly, but plants, fungi, and animals, including you and me, share the eukaryotic cell plan.
Bacteria are prokaryotic.Prokaryotes are designed kind of like this baseball stadium.
The floor plan has very few internal structures.
Most prokaryotes Prokaryotes have a cell wall.Some have a slime layer around the outside, but none have a distinct membrane-enclosed nucleus.The DNA is found free-floating along with ribosomes responsible for protein synthesis.
Describes how prokaryotes survive across a wide temperature range, from cold environments to boiling water. It introduces psychrophiles, mesophiles, thermophiles, and hyperthermophiles.
Speaker A
So, uh, let's talk about the diversity of prokaryotes.Let's go to the environmental conditions.
Well, here you're going to see that prokaryotic cells can be found pretty much everywhere, and temperature is not a limitation that will make no prokaryotic cells to grow on a regular surface.So you can find the prokaryotic cells in cold temperatures, well below 20 degrees Celsius.Well, we call them psychophiles.Well, that's from medical and industrial point of view a problem in a meat— in the meat industry.
So here we have certain bacterial cells, such as Listeria, that can infect the meat product even when they are in the refrigerator, 4 degrees Celsius.That's a big problem.So from here, from time to time you hear about this problem where the meat cannot be used when there is such a bacteria over there.
Helminth bacterial cell can even live on ice glacier, which is almost 0 degrees Celsius.This yellow pigment is bacterial cells that are alive.Well, I mean, they are getting probably some heat from the sun.They are, they are not going to live, to replicate when they are inside the ice glacier, but on the surface, when they are getting some extra heat from the sun, they can survive and also replicate and have metabolism as well.That's obviously bacterial cells that like to live in cold temperature.
Many other organisms, most of them probably, prefer the intermediate range, which is something between 20 to 50 degrees Celsius.Those bacterial cells that are infecting us humans and are causing a significant disease, usually they are in the range of the 30 35, 34, and then they're going to grow in the nose, that it's a bit cooler than the other part of the body, to the 38-ish or so.That, that's actually the temperature that they, that they prefer.And when you have a fever, you actually make them not to be extremely happy.So because those 2 degrees Celsius that you can gain from a fever because you're sick, well, can help you in many ways.But you can find them in milk products, you can find them in blood products.All of them must keep the intermediate temperature range in the body.
So, uh, what about higher temperature?So higher temperature is usually not so hospitable for most of the organisms, but you can still find some that prefer above 50 degrees Celsius.We call them thermophiles.So, well, I mean, there are thermophiles, there are extreme thermophiles that can really live in almost boiling water, but in general, there are a lot of organisms that can live in very hot places.Like here, this thermophile that can grow in boiling water.So what you see here is boiling water.If you pick up a sample from this water, you're going to find that it's actually going to have some bacterial cells that can grow there.And of course, I mean, they don't really like the very, very hot temperature in general, but if you are looking around this very hot pond, you are going to find them growing quite a lot.
And you can see it according to the pigments that they have So, uh, that's actually— you can see here a gradient of temperatures from very hot to 0 degrees Celsius.And in each of them, in each of those environments, you're going to find bacterial cells.From the boiling water, or almost boiling water, up to the 0 degrees Celsius, which is the ground which is covered with ice or snow.
And indeed, you can find psychophiles that can live close to 0 degrees Celsius.Here, the definition, up to 20 degrees Celsius.Mesophiles, that actually like our temperature.And of course, and there is a certain range, I mean, in the environment where you have the temperature that those mesophiles can live.I mean, that's going to make those bacterial cells to be environmental bacterial cells.
They can live in the environment and they live everywhere.
Thermophiles, it's something above the 40-42 degrees Celsius up to 80 or so.But here you can talk even about hyperthermophiles.That can reach a temperature which is above 100 degrees Celsius.So when we are using an autoclave, we are going here to 120 degrees Celsius, and we are using it in such a way that almost no organisms like spores will be able to survive, but definitely not vegetative cells.
So temperature, up until a certain point, is not a barrier to some sort of microbial life.To grow on a certain surface.Very cold to very hot, you can find there bacterial cells of some kind.
Covers how microbes tolerate acidic, neutral, and basic environments, using Helicobacter pylori and stomach ulcers as an example. It also explains acidophiles, neutrophiles, and alkalophiles.
Speaker A
What about pH or acidic, basic environments?Actually, even here you're not going to to see a major problem for something to be found there.So let's think about our stomach.1 to— the pH there, it's something between 1 to 2.It's very acidic environment.
And, well, I mean, for many years we thought about peptic ulcer as a result of psychological stresses and, you know, nobody thought about the pertussis as something that can be caused by bacterial cells.
But indeed, like 20 years ago, it was found that the Helicobacter pylori, certain bacteria can be found in the peptic ulcer.Well, I mean, initially nobody believed this Australian scientist that got the Nobel Prize afterwards, of course, for his discovery.And he decided to take the culture of bacterial cells that he was able to pick up from the stomach and to drink it on his own and he got something that looked like peptic ulcer or some other type of activities and he was able to treat himself with antibiotics and everything became normal.Well, scientists usually are not doing those kind of things but this time he did this in order to prove his point.So yes, Helicobacter pylori is the cause of peptic ulcer.
And today you can treat peptic ulcer by antibiotics.Fortunately, there is today more and more cases that Helicobacter pylori is becoming antibiotic resistant, but that's a different story.Now, peptic ulcer is inflammation which is a result of infection by Helicobacter pylori.Pylori.And inflammation can cause cancer.20% of human cancer is about inflammation.
So gastric cancer is actually a result of long time of infection with Helicobacter pylori.Yes, that's actually The only cancer, I believe, that you can prevent by antibiotics.So yes, Helicobacter pylori is acidophile.Mean it's like it really love an acidic environment.
Most of the organisms around us prefer neutral pH.And they can grow in milk product that actually have pH which is around 7 or so.Blood product can also be contaminated by those type of bacterial cells.And we call them— Neutrophils prefer neutral pH environment.There are also bacterial cells that can live in basic pH.
We call them alkalophiles.So even pH is not something— the acidic or basic environment are not a limitation for some sort of bacterial cells to grow there.
Discusses water as an essential requirement for life and how some bacteria survive dry conditions by forming spores. It then explains halophiles and their ability to live in highly salty environments.
Speaker A
What about water?Well, water is a major condition for life.Most cells require water in order to replicate, in order to survive.
However, some bacterial cells can make spores.Although spores are not replicating and they don't have metabolism on their own when they are spores, well, I mean, they are going to keep those properties for the time being.So spores are made by bacterial cells.One of the inducers for this is a dry environment.And think about the soil in your backyard.
Sometimes you have rainy days, sometimes you don't have, and the soil is becoming quite dry.Terrestrial cells know how to make spores in order to buy for themselves sometimes, and in many cases, this sometimes can be extended to many, many, many years.Least 4 years, that's what we checked.But spores are extremely stable in dry environment and they are coming back to the regular vegetative cell life when you are adding the water back.So in the Sahara Desert, when you have years without rain, when you have rain at certain point, you are going to see bacterial cells, in their vegetative state, simply because they were kept as spores for quite a while.
What about the salt content?Well, I mean, we need some salt usually in order to reproduce— the cell to reproduce and to survive.And that's correct for most of the organisms.Cannot really survive without any salt.But, well, I mean, if you want to keep your food to stay for longer, in other words, to prevent bacterial cells from growing there, you probably want to add some salt to the food, like pickles, for example.But you're going to see that some bacterial cells are going to grow even when you're adding quite a lot of salts.Actually, some cells exist in a very high salt concentration and they like this type of environment.We call them halophiles.So you can find them, for example, here in a place that you make salt from, from the seawater.Here the water is evaporating up to the level that what you have, it's pretty much dry salt.
This orange and red pigments are actually bacterial cells that can grow in those type of environment of very, very high salt content.
Explains how microbes differ in oxygen use, from aerobic to anaerobic lifestyles. It also introduces organisms like cyanobacteria that can build organic molecules from inorganic sources.
Speaker A
So, other environmental conditions.What about oxygen availability?We need oxygen.I mean, we cannot survive without oxygen.And many prokaryotic cells, bacterial cells, require oxygen for growth.They actually learn how to use this oxygen in such a way that is very, very important for their metabolism.Actually, there are other bacterial cells that from them, the oxygen is toxic material.They're going to die pretty much immediately if they're exposed to oxygen.And those are anaerobic bacterial cells.So between aerobic bacterial cells that require oxygen for growth and anaerobic bacterial cells, you have all the range of the amount of oxygen that you can have in order to promote the activity of different type of bacterial cells.
So oxygen, again, it's not a limitation for life on this planet.What about nutrient availability?Well, if you have those organic molecules, you'll probably want to use them.So in general, most microorganisms require organic and inorganic nutrients to grow and survive.But actually, there are some that can simply pick up the inorganic compounds from the atmosphere or from Earth and can use them in order to make more complicated ones.
Cyanobacteria is one example for this.It can grow in the absence of all those key nutrients We must have.But they can convert CO2, nitrogen from air into organic cellular molecules.They can make nucleotides and all the other things that you have in mind simply from inorganic compounds.
Shows how microbes shaped Earth’s history by producing oxygen and filling ecological niches over billions of years. The speaker outlines major milestones in Earth’s early evolution and the rise of aerobic life.
Speaker A
And that's going to take us to the evolution of life on Earth.Let's start with a short introduction.
Speaker B
It was the microbes that made this planet a viable place for all other life forms.Although plants are generally credited with developing the ability to convert the sun's rays to food energy— photosynthesis— it was actually ancient microorganisms, the cyanobacteria, that first produced oxygen as a byproduct of photosynthesis a billion years before the first plants ever existed.Over the next 3.5 billion years, microbes evolved to fill every niche, creating an environment In which plants, animals, and humans thrive.
Speaker A
So, let's see some important events that took place in Earth's history.Earth formation began something like 4.6 billion years ago.And at a certain point, we got water on our planet.Where it was coming from?Probably from icy asteroids that landed on the new Earth.
And soon afterwards, 400 million years afterwards, We have some signs of life.We can say that the first evidence of life was probably around like 3.8 billion years ago.How this life form was developed, there are many ideas about this.But in general, we have a good idea, indication at least, that life started to be around on this planet like 3.8 billion years ago.And life was evolved at that time at a certain level that brought us towards more and more complicated organisms to live here.
So again, prokaryote cells were the only residents of this planet from 3.8 to about 2 billion years old.So from here to here, we had only prokaryotic cells, bacteria, bacterial cells.They were the only organism on our planet.The first microbes actually came to Earth, well, was evolving on Earth or came to Earth that had no complicated organic molecules.And these cyanobacteria-like bacterial cells were able to use the inorganic molecules that you had during that time in CO2, nitrogen, and other things in order to make the more complicated organic molecules.
And here, you know, if you are using the CO2 in order to make organic molecules which consist of carbon, you're going to have O2 to be left behind.O2 is oxygen.And this oxygen initially was a problem for those organisms.That was the garbage.That was the things that need to be recycled or to be taken away because it was toxic to those bacterial cells at that time.They were anaerobic.They didn't like oxygen.So actually, for quite a while, they were around when they were able to escape this oxygen.But the oxygen kept accumulating on our planet.And over the evolution, some bacterial cells were evolved in such a way that they learn how to use the oxygen for their purposes.
First, to make it not toxic for themselves, and second, to take the characters from the oxygen which are going to help them to use it to develop energy, for example.And other things.So that was the time that the prokaryotic cells, the anaerobic prokaryotic cells, were evolved to atmospheric or aerobic cells.So anaerobic cells were evolved to aerobic cells that can live with oxygen.And of course, I mean, both of them can be found today as well.I mean, they are part of our environment.
Explores theories about the emergence of the nucleus, the rise of multicellular eukaryotes, and the last universal common ancestor. It also compares bacteria, archaea, and eukaryotes in terms of evolution, metabolism, and DNA evidence.
Speaker A
Now think about this.You have oxygen, which is the garbage.It really created a challenge for many forms of life initially, but it provided other organisms an opportunity to exploit new ecosystems.So, okay, the common ancestor of multicellular eukaryote cells is actually— happened— it's dated to 1.5 billion years ago.So we are talking about here.
Well, before, like 2 billion years ago, we had another important event that large cells were able to develop a large organelle called the nucleus.Now, what is exactly how nucleus was really evolved is very clear, but there are some suggestions that we are talking about a large virus, like mimivirus, a very large virus that entered into large cell.So, and this cell with the virus actually were able to collaborate nicely together, and the virus there actually start to act like the nucleus of today?We don't know for sure, but when we discovered the very, very large viruses, mimiviruses and Pandora and many other very, very large viruses and highly complicated, we found that they have quite a lot in common with the nucleus.So those viruses are infecting amoeba, for example, It was a very, very early organism, eukaryotic organism on our planet.So probably these single-celled eukaryotic cells were evolved from this type of maybe an accident that went to be a very effective way for cells to do better as compared to other cells.
Okay, so at a certain point cells start to understand that working together can give them benefits versus them working one by one.So cells start to be grouped together, initially it was unicellular organisms that learned to group with each other I must say that prokaryotic cells also know this trick.They know how to group together and to make a biofilm, which really helps them to communicate, to, to create a system which is much, much better for them, and in some cases it can be not so great for us.But the multicellular eukaryotic cells were actually evolved by the interactions between cells that start to speak with each other.Even the single-celled eukaryotic cells are talking with each other in many ways, but when they are together, when they are placed together, they can do it in a more efficient way.
And that led, after all, to the development of the very basic animal, Some animals consist of less than 1,000 cells.Nematodes, for example, C. elegans, is 956 cells, if I remember it right.More or less, that's the number.And you can see different systems there.So digestive system, reproductive system, in an organism that is made out of less than 1,000 cells.
So actually, that's the way that we were evolved at a certain point.I mean, we were evolved in the last 5 seconds of this clock.I mean, we are here, you cannot see us because we just came.Homo sapiens is around for like 200,000 years.That's it.The diversion between the humanoid-like and monkeys actually took place like around a million or 2 million years ago.So actually we are talking about something that happened here in the last 5, 10 seconds of this clock.
So, yes, some modesty.
Speaker C
Yeah.Over 4 billion years ago, we didn't have intact cells.Life was a series of chemical reactions on the surfaces of metals, other things in the ocean, to eventually develop a cell that became self-replicating with the duplication of the the DNA molecule that eventually over billions of years became us, became all the other living species that are present on the earth today.
Speaker A
Started with an origin of life.Don't know exactly what was this origin of life, and actually from this origin of life we had a lot of different directions and of the evolution.But one of them happened to be quite successful.
Universal ancestor that learned to use the DNA, the central dogma, pretty much had the same type of activities that we call them the unity of life.So this universal ancestor was evolved further.Well, I mean, probably it was like a bacteria to start with, so it was evolved to all those different bacterial cells that we have today, but it was also evolved to another prokaryotic organism.And these archaeal cells actually look very, very similar to bacterial cells, but their metabolism was totally different.So they were evolved quite differently.
And the universal ancestor was evolved into eukarya.Which is cell with a nucleus that was evolved further from unicellular eukarya to plants, animals, including us.But actually, I prefer this one from PNAS that is describing the 3 of life.And here they describe this, the tree of life, with the distinction of morphology.So archaeal cells and bacterial cells are quite similar in their morphology.When you're looking under the microscope, you can see something quite similar, but their metabolism is very, very, very different.Bacterial cells, archaeal cells have totally different metabolism.In, in fact, archaeal cells have a lot in common with eukaryotes, more even than what they have in terms of the metabolism, with bacterial cells.Now, all this distinction that you can see here between Eukarya, Bacteria, and Archaea is based on DNA sequencing.Initially, this was done by DNA sequencing of a ribosomal RNA, and actually the finding was suggesting that the prokaryotic cells are not one kingdom, but actually there are 2 kingdoms: archaea and bacteria.
But later on, when we learn the, the differences between archaea and bacteria, we realize that although they look similar, under the microscope they are quite different when it comes to their metabolism.
So the eukarya are different.They have a nucleus, they are larger, they are more complicated with organelles.All those things are making the eukaryotic cells to look very, very different as compared to bacteria.Their size is usually different as well.And when we talk about the last universal common ancestor, we are talking about the organisms that from which all those kingdoms were evolved.
So again, I mean, we try to understand what is this look for organisms that have characters which are going to be related to archaea, to bacteria, and to eukarya.And we are not there as yet.I mean, it's still an organism that we never were able to find around, but it seems like that you can find some organisms that that are getting closer and closer towards the LUCA type of organism that was the last universal common ancestor for our planet.Of course, LUCA was evolved from other things as well.I mean, that's a different story.
Describes unicellular eukaryotes, fungi as model organisms, and the distinct biology of archaea. It emphasizes how archaea thrive in extreme habitats such as hot springs, salty lakes, and methane-rich environments.
Speaker A
Now, most of those eukaryotic cells are unicellular.I mean, we, animals, fungi, are actually— the plants are located at the very, very top of this evolution.But as you can see, there are quite a lot of other branches.That were evolved independently, and obviously they are very different from us.Interestingly, you can use fungi in order to understand several things related to human cells because there is some similarities.Cell cycle, for example, between fungi and the more advanced eukaryotic cells like our cells.So you can use fungi, yeast, in order to understand our cell cycle, for example.So in general, The prokaryotic cells are bacteria and archaea.Prokaryotic means that cells without a nucleus, as simple as that.And the fact that the bacteria is different from metabolic point of view from the archaea make them to live in different environment in many cases.
The archaea in a lot of, in a lot of cases can be found in extreme environments, such as environment with high salt, rich with methane, and also hot and acidic places.You're not going to find bacterial cells in such environments.They prefer the less aggressive conditions.But the archaea, actually, they are using the basic evolution principle that if you can adapt to the new environment, you are going to be the only one that will be able to live there.So they actually take advantage of the fact that they can adapt to environments that nobody else wants to live there.
And of course, eukaryotic cells with the nucleus, it's separate altogether from structure, morphology, and of course function as well.Here, unicellular, probably the most organisms, plants, animals, they are all evolved as part of the eukaryotic, or as a eukaryotic organism.
So let's talk a bit about archaea.
So morphologically, the 2 kingdoms of prokaryotic cells appear similar.However, they have major biochemical genomic differences.
Most archaeal cells live in extreme environments.You can find them, for example, in hot and acidic places.Among them, sulfur springs that are hot and acidic.If you're going to the underwater, to the bottom of the ocean, you're going to see that there is water which is coming from below when it is really, really, really hot.Actually, you are going to see the temperature over there of the water reach 380 degrees Celsius.Well, there is a lot of pressure there coming from above, so water can reach to this level of temperature, while the water which is the— of the ocean itself, it's 2 degrees Celsius.So we have a gradient of 380 degrees Celsius to 2 degrees Celsius, and you're going to have different environment on these gradients which are based on temperature.When you reach to the 100 degrees Celsius, when the 380 and the 2— 380 degrees Celsius and the 2 degrees Celsius are mixed together to reach to this level, you're going to see that there are organisms that are going to live over there in this temperature.
And as you're going farther away, from the spring, the hot springs, the temperature is going to be reduced and other organisms will be able to live there.So there are extremophiles and those are usually archaeal cells.
So archaeal cells can live also in environments which are rich with methane.So you can make methane from CO2, and there are some organisms that can use this.So you can find them a lot in places like wetlands, swamps.Interestingly, you can find them in the digestive system of ruminants.Cows, for example, they have an extra stomach called rumen, which is kind of an incubator of microorganisms that help the cow to digest the grass, and they're making a lot of Methane.Archaeal cells can be found in places that are very, very rich with salt.This is the Dead Sea.You know, people are really enjoying themselves over there, and well, I mean, they are not alone.There are, there are bacterial cells there as well.There are archaeal cells that can live there.According to what we think Charles Darwin said, it is not the strongest of the species that survives, nor the most intelligent that survives.
It is one that is most adaptable to changes.That was the general idea of Darwin's theory.And actually, that's what you can say about the archaeal cells.They learn how to survive, how to adapt themselves to environment that nobody else want to be there.And they are getting, of course, the benefits because they can actually be there without competition from other bacterial cells.
Highlights the vast abundance and diversity of microbes on Earth and their role in maintaining ecological balance. It also introduces field research in Yellowstone and the importance of microbes in chemistry, recycling, and industry.
Speaker D
3.5 billion years ago, the sun scorched the planet, oceans boiled, and there was no free oxygen.Yet microbes inhabited Earth long before any other living things.The question is, how?Microbes have developed amazing strategies to obtain energy and nutrients.No matter where one looks, even on the rock surface of this cave, microbes are in abundance.And because of their keen ability to exploit their environment, microbes have evolved to fill just about every niche on Earth.Today, the genetic and metabolic diversity of microbes is greater than all eukaryotes combined.There are 5,000 known species, but scientists estimate that true diversity could range between 400,000 and 4 million species.But what are these microbes, and what are they doing?
Scientists are devoting lifetimes to finding out.
Speaker E
Wherever we go, whenever we come back from a field trip, we always come back with big surprises, brand new branches of life that we never realized existed.So there are huge discoveries around the corner.Just if we look, we'll find them.Let's just walk down here.Just be careful, okay?Just stay on—
Speaker D
Professor Anna-Louise Reisenbach is a microbial ecologist.She's in Yellowstone National Park with some of her students studying organisms that thrive in the steamy hydrothermal springs.
Speaker E
That search for the unknown is one of the biggest challenges, and that's really what drives my science.
It leaves me in amazing awe of nature because there's so little we know and And it's just so complex, and it's— but it's beautifully complex.You know, it's really incredibly clever.
Speaker D
Raisenbach is searching for microbial clues that will help her understand the evolution of early Earth.
Speaker E
In Fahrenheit, it's 194.
Speaker D
Places like Yellowstone provide a natural laboratory for research.
Speaker E
These thermal features may be relics or fossils from what it was like on early Earth.And so understanding the types of processes that occur in these systems may help us understand what it was really like 3.5 billion years ago.
Speaker D
Prokaryotic microbes used to be grouped together in a single kingdom, but in the late 1970s, Dr. Carl Woese, using ribosomal RNA sequencing, identified a genetically distinct group of organisms.He called this new domain on the tree of life, the Archaea.Archaea and bacteria often look similar.They both have outer cell membranes and a cell wall.But bacteria contain peptidoglycan, a chemical that archaeal cell walls lack.Using gene sequencing, scientists discovered that Archaea may be more closely related to eukaryotes than other bacteria.Many Archaea Archaea and some bacteria are extremophiles, thriving in extremely salty, cold, or acidic environments.Thermophiles like it hot and require high temperatures to survive.
Speaker E
The one thing that's really amazing about Yellowstone is that all the different colors of the different pools do reflect huge chemical and temperature gradients, you know, and so that whole range of pHs and the whole range of temperatures provides all these different environments for a huge diversity of microbes.And that's how a microbe works.If there's energy, I'll be there.
Speaker D
While some biofilms and bacteria are infectious, most microbes are not pathogenic.And because of their great abundance and diversity, they wield tremendous power.That's because the biosphere is driven by chemistry, and microbes maintain the balance.They are the recyclers and decomposers, unlocking carbon, nitrogen, and other elements essential to life.We continue to learn and benefit from these master chemists.While they're making a living, they're doing everything from cleaning up our environment to helping us be more efficient in industry.Microbes— with new molecular tools, scientists are just beginning to grasp the scope of their incredible diversity and chemical talents.
They are profoundly changing how we think about the evolution of life and life beyond Earth.
Connects microbial research to astrobiology and the search for life on Mars and other worlds. The speaker explains why scientists study extreme environments and how microbes may inform the search for extraterrestrial life.
Speaker E
We brought a rock back from Mars.What do we look for in the rock record?What are those signatures of life that we need to look for?On Mars, there's evidence for water.There was also evidence for some volcanic activity, and so So the types of organisms that live in these hot springs may have existed on Mars many years ago.The diversity of microbes is greater than the diversity of all plants and animals put together.We've only just started to scratch that surface of what is the diversity of the microbial world.
Speaker A
So diversity of microbes other than prokaryotes.So eukaryotic cells are— can be found as animal cells, multicellular, plants, also multicellular, and unicellular organisms.And most of the eukaryotic cells on our planet are unicellular organisms.
Fungi, like eukaryotic— is eukaryotic organism.There are different types of fungi.One of them is yeast.
They have a nucleus.They are in their micrometer range, 5 to 10 micrometers in size, oval shape.
So yeast, it's a fungi eukaryotic unicellular organism.We're using it quite a lot in the food industry.I would say that The fact that we are agricultural society is actually because we learn how to use the yeast in order to make food.Because many things that we are making in the farm can be processed by yeast.For example, you can make bread by using yeast, require aerobic conditions, temperature which is like 37 degrees Celsius, and then the yeast is going to help you to make bread and all the other things related to this.
But if you put the yeast under anaerobic conditions, colder temperature, you are going to get alcohol production.The yeast is going to turn their metabolism towards alcohol production.It's actually the same type of yeast that can do both, simply based on different conditions.Now, yeast in general is not highly involved with human diseases.When we see yeast infection that can cause a severe human disease, It's usually in people which are immunocompromised.
Now yes, yeast infection, we all know about them, but usually they are treated and they are not considered really severe diseases.However, people that their immune system is not working, like people with AIDS, here things are quite different.You are talking about a situation that people that have no immunity that can protect them from the negative effect of yeast are actually coming with quite a lot of diseases that are in a— that are— that yeast is responsible for this.One of them, it's pneumocystis carinii pneumonia that is very commonly found among people with AIDS.But there are a few others, cryptococcal meningitis that can also cause some meningitis, the infection of the brain and spinal cord.
And here again, we have another is that can actually lead to problems, mainly in people which have AIDS, which are highly immunocompromised because of HIV virus.
Mold, it's another fungi, and actually it's quite different.It looks like that.Probably everybody can find them in the back of the fridge when you forget your apple or— sorry, orange in most cases— and/or a piece of bread.So those are filamentous fungi with mycelial structure, which means that actually this mycelium structure is highly branched system of tubes that contain mobile cytoplasm with many nucleus.So it's kind of a fusion, I would call it this way, of many cells that are actually making one cell with several, many nucleus over there that are acting together.
So here again, mold are used for production.I mean, we're using this in production of antibiotics, for example.The first antibiotics that was developed, penicillin, is a product of mold.As simple as that.I mean, Alexander Fleming found that a certain mold that contaminated his plate are killing bacterial cells.So he decided to take those type of molds and to see what they are making.Of course, it took many, many years and other people, biochemists, were able to find exactly the penicillin, the first penicillin that start to be used around the '40s on people.
Molds are also— can be involved with some mild problems like allergic reactions.Usually it's not a very severe type of allergic reactions that can come from other type of causes.Some allergic reaction can be quite severe, but those from molds are usually making people to have mild allergic reaction in most cases.But mold can cause some disease that is taking place in people with opportunistic infection.Again, health problems with fungi is usually linked to immunocompromised people.In other words, people that are— that their immune system cannot protect them from those type of organisms.
Introduces protozoa and then returns to fungi, focusing on yeast and molds as unicellular and filamentous eukaryotes. It covers their roles in food production, disease, antibiotics, and opportunistic infections.
Speaker A
Okay, from here let's move to protozoa, which is another unicellular eukaryotes.Do not have cell wall.They— yeast have a cell wall, but different than prokaryotic cells.But here we are talking about an organism that lacks a cell wall.And they can be involved with quite a lot of human diseases such as malaria.It kills something like 2 million people every year globally.So again, malaria, it's a unicellular parasite.That can infect blood cells, red blood cells, and they need the oxygen in order to make more progenies, and the best place to find it is in red blood cells that carry the hemoglobin.And cells are going to be killed and many other pathogens are going to be released.From the dead cell to infect other cells, including the liver.It's much more complicated life cycles, but actually it's one of the problems that we still have.
We don't have good vaccines against this, and also the drugs that we had against malaria is not so great, but we were able to control the disease in some ways.
Protzoa, actually, you can find them everywhere.I mean, when you're going to the lake, you're probably going to be exposed to quite a lot of them.And they are not causing— those are not causing a human disease.I mean, those lakes are safe, but you still have a lot of protozoan cells.So they are involved in the digestion of— in cows, for example, in the rumens you can find protozoal cells as well.
When you are going to those places that you are treating water, wastewater, well, I mean, what's really doing the job is the protozoal cells that are eating bacterial cells.They really like to eat bacterial cells.And yes, I mean, this is Tetraemena that you can find it pretty much in your— in the lake, and they help to remove bacteria from wastewater.And yes, it is also quite beautiful if you are using the appropriate stained antibodies to look at them.Here you can see 2 Tetraemena Protozoal cells that are exchanging genetic information.
Explains what viruses are, how they infect plants, animals, and bacteria, and how they depend on host cells. It also describes viral genomes, retroviruses, and the structure of viral coats and envelopes.
Speaker A
And viruses— well, viruses, it's a really, really interesting topic by itself.So viruses are everywhere.They are not cellular life, they are parasites of cellular life.They are complexes of nucleic acid and proteins.When viruses are outside of the cell, they are just packs of nucleic acids covered with proteins, sometimes also with the membrane.
That's it.And we have viruses that can infect a lot of different cell types.Every cell in general can be infected with a virus.Plants, plant cells, human cells, bacterial cells, they all have their own viruses.So plants, we know about tobacco mosaic virus that is infecting tobacco leaves.
Human— well, I mean, there are so many coronaviruses, like the SARS of 2003, 2020, polioviruses.There are a lot, a lot of them.And bacterial cells are also infected with bacteriophages, which are viruses of bacteria.So here again, we have bacteria that can be infected with viruses, and actually it keeps the number of bacterial cells to the appropriate level that we also have placed on our planet.Without viruses, probably the amount of bacteria was going up dramatically.Viruses are killing a lot of bacterial cells in the ocean and everywhere.Every time that you have one bacteria, you're probably going to find like 100 bacteriophages which are around.And all those viruses are using the function of the host cell and they are simply taking the functions that we have structures that we have and taking advantage of the cells for their purposes.They're not cellular life, they're not cells, and they are not considered to be life when they're outside of the cell.
Although when they're inside the cell, they are so complicated and they are so clever, so, well, I mean, many people say, well, I mean, when they're inside the cells, they act like some sort of a life form.
The viral parasites can cause changes in the cells.They are using the cell metabolisms, structures, metabolism for the— in order to make new virus particles that— and they can cause the damage to the cell.They can make the cell to die, they can also make the cell to become cancerous.Or there are viruses that can cause cancer in humans.Human papillomavirus, for example, can— is probably responsible for 100% of cervical cancer, but there are a few others that are also involved with human cancer.
And just to get a general idea what viruses are all about, how viruses act as parasites, I chose for you a bacteriophage which is infecting a bacterial cell.So here you are going to see this activity in action.This is the bacteriophage which is going to land on this large bacterial cell.And this bacteriophage have a way to recognize the surface of the bacterial cells.The bacteriophage have attachments and they, they can, that can recognize some structures on the surface of the bacterial cell, and then the bacteriophage is going to stick stabilize itself on the surface of the bacteria, and then to inject the genetic material inside the bacterial cell.
So the process is quite complicated.The bacteriophage need to learn how to cross certain boundaries.Of the bacteria.But again, I mean, that's not the place to talk so much about the bacteriophages, but that's the general idea how bacteriophages are infecting bacteria.And well, when we are talking about viruses like HIV, we have different type of methods of infections.
And just to get an idea what is a virus, and this is actually structure of a virus, retrovirus like HIV, and viruses in general can, you can have a genetic material which is DNA or RNA.Actually, the viruses don't need to follow the rules of the central dogma, which says that the genetic material must be DNA, double-stranded DNA.They actually can use different types of nucleic acids in order to use them as their genome, as their genetic material.Some viruses are using DNA, some of them are even double-stranded DNA.Most of the DNA viruses are double-stranded DNA, but there are viruses that simply using single-stranded DNA, that's it.
You know, the system that later on makes the second strand when they're inside the cell.But many of the pathogens that we hear about them quite often are RNA viruses.In other words, they're using RNA as their genetic material.So those viruses are— actually need to find different ways to eventually make proteins after all.So again, viruses have like 7 different methods in order to get to the level that they are making proteins.
Again, we will not get there so much.When it comes to HIV, which is retrovirus, it's an RNA virus, but it makes DNA from the RNA when it is inside the cell, and from here it's actually the DNA is the genes of the virus that are going to be expressed.
The viruses in general have a protein coat, like, you know, every virus must have a protein coat that protects their genetic material, and a lot of time that's everything that the virus has, so the coat also need to put the virus, to help the virus to infect the cell.But there are many other viruses that are using also envelope, lipid envelope.And again, they are using this lipid envelope in order to help them to enter the cell.We will talk about it.A bit more when we talk about membranes, vesicles.You're going to see those viruses that have a membrane are acting like vesicles.
Concludes by emphasizing how much of microbial life remains undiscovered and how microbes shaped all life on Earth. It ends with synthetic biology, alternative genetic codes, and the idea that organisms evolve as environments change.
Speaker A
So, the diversity of life.Well, I mean, you can imagine that life is highly diverse.And we know, we still know, that we do not know anything about over 90% of the organisms on this planet.For example, when we went deep to the ocean, we had some research submarines that helped us to pick some samples from very, very deep of the ocean, we're able to find quite a lot of organisms that we never had the chance to see before.And one of the questions that we ask ourselves, are we going to find here life 2.0?
Some organisms that are not obeying the central dogma rules.In other words, maybe are using RNA as genetic material, but the answer is no.All the organisms that was found on our planet so far are actually working according to the central dogma.DNA in all organisms made with the same 4 nucleotides and the protein code is quite similar among different organisms.But Curiosity, which is the name of the vehicle which we have on Mars, is there in order to find some other form of life.We are looking for water, and there is quite a good idea that sometimes in the past Mars was like Earth, full of water, and probably we had some sort of life form over there.So that's the main reason that we are going to Mars, and that's the reason that we are thinking about other types of moons of other planets in our system, like Europa and others that We think that they have the condition to maintain life on themselves.
So that's actually the general idea of going to Mars, look for other type of organisms that maybe have different type of ways of expressing themselves.So Well, I mean, I can tell you that there is life on Mars today, most likely, because when we sent this vehicle to Mars, we kind of forgot to sterilize it to the way— so we know that there are like 60 different organisms that can stay on the surface of this vehicle.And now they are on Mars.Probably they are not going to go too far, but if we are going to find something over there, we need to check it very, very carefully if it is really something that was evolved on Mars and not microbes that came from Florida in the United States.And actually, when we— we're using filters in space in order to find some sort of organisms, microorganisms, and we find them.
And all of them is a result of the fact that people that are taking the mission to space also need to go to the washroom.So to speak, and you cannot keep the sewage forever in their spaceship.So you can imagine that when you are checking for microbes in space, but actually there are microbes that are originated on Earth.
So yes, we are looking, we are still looking, and we try to find Life 2.0.Okay, we cannot find it as of yet, but we can make it in the lab.Well, I mean, in general, the DNA on life on Earth naturally is actually stored information in just 4 key chemicals: guanine, cytosine, adenine, and thymine.The GCAT.So the big question is whether life can be developed from DNA with an alternative structure, and scientists show that theoretically the answer is yes.You can make an organism with DNA that consists of 6 different nucleotides instead of 4.And scientists were able to make an artificial tRNA with artificial amino acids, and they were able to show that actually, if you really want to make an organism with an alternative genetic material and alternative protein, you can do it.In the lab.So why nature is not doing it anyway?
Probably the diversity that we have with 4 nucleotides, it's good enough.
With 4 nucleotides and 20 amino acids or so, that's good enough in order to have all the activities that we have around.And then scientists went from 6 nucleotides in the DNA to 8 different nucleotides, and they were able to show that this is making DNA that looks quite similar, in structure at least, to the normal DNA.In other words, you can add more nucleotides to the DNA, different nucleotides to the DNA, and you can still have probably something that can act like the original DNA made out of 4 nucleotides.So, is there a chance that somewhere, sometimes, we are going to find organisms that are actually using those type of tricks?The time will probably give us the answer For this.
Speaker B
Microbiology, as the name implies, quite literally focuses on organisms too small to study with the unaided eye.They are protozoa, algae, fungi, bacteria, And with the invention of the electron microscope, viruses.The invisible microbial world is rich in its diversity.It is populated by more different kinds of organisms than all of the visible world combined.The diversity of all life is derived from the microscopic crucible of life, starting with the first microbes.Microbes reproduce quickly.Their generations fly by.And because they've been around for billions of years, they've had the opportunity to shuffle and reshuffle every possible combination of their genetic information, their DNA.As the environment changes, so do the organisms, which in turn can change the environment.