Prokaryotic Diversity: Study with Video Lessons, Practice Problems & Examples

Prokaryotes include diverse lineages such as proteobacteria, chlamydia, spirochetes, cyanobacteria, actinobacteria, and firmicutes. Proteobacteria, known for nitrogen fixation, gave rise to mitochondria. Chlamydia are gram-negative parasites lacking peptidoglycan. Spirochetes, with their corkscrew shape, cause diseases like Lyme disease and syphilis. Cyanobacteria, responsible for oxygenic photosynthesis, are crucial for atmospheric oxygen and form ancient stromatolites. Actinobacteria, including Streptomyces, produce antibiotics, while firmicutes, like Lactobacillus, are vital for yogurt and gut health.

Prokaryote Lineages 1

Hi. In this video, we're going to take a quick tour of some of the major lineages of prokaryotes. We're going to begin with proteobacteria, a diverse clade of gram-negative bacteria that's actually organized into 5 subgroups that are named with Greek letters alpha, beta, gamma, delta, and epsilon. And you can see a phylogenetic tree of proteobacteria right here. Now you might notice that this also includes zeta proteobacteria. This is a newer grouping, and your books likely won't include it. Now, many species of proteobacteria are involved in nitrogen fixation. Don't forget that it was proteobacteria that was engulfed by a cell and eventually would become mitochondria. So, and of course, they led to a super important structure in eukaryotes. Now, moving on, we have Chlamydia which is a group of gram-negative bacteria that lack peptidoglycan in their cell walls. Hopefully, remember that gram-negative bacteria usually have a thin layer of peptidoglycan, below the outer lipopolysaccharide layer. Well, these bacteria don't have that peptidoglycan at all. They're also all parasites. All of the species in this group are parasites that live inside host cells and you can see a picture of that happening right here. These translucent blobs are those host cells and you can see these 3 have these brown spots inside them. Those brown spots are the Chlamydia cells that have been stained with a particular stain, turning them brown so that we can visualize them. Those cells have been infected with Chlamydia. The Chlamydia is living inside of them. Again, if this name sounds familiar, it's because the famous STD, Chlamydia, is caused by bacteria in this group. We often just refer to it as Chlamydia though, the sort of group name. Now, spirochetes are gram-negative heterotrophs and what's distinct about them is their corkscrew shape that you can see in these two pictures. This sort of zoomed-out one, those little dark squiggles, these cells that are stained in yellow in this image. And for a more zoomed-in look, an image of a spirochete, much more zoomed in. You can really see that corkscrew shape of the bacteria. Spirochetes have 2 famous diseases caused by spirochetes that you've probably heard of. Those are Lyme disease and the STD syphilis. Lovely things, spirochetes, right? Lovely diseases. All right. With that, let's and I'm sorry. I'm just making a joke. I'm being sarcastic. Don't mean to make light of diseases caused by these bacteria. But yeah. Basically, the endpoint is nasty little guys, these spirochetes. Alright. With that, let's turn the page to talk about some other bacteria.

Prokaryote Lineages 2

Cyanobacteria are gram-negative photoautotrophs, and many species actually perform nitrogen fixation. Now they are sometimes termed blue-green algae, but this is a bit of a misnomer, as they are in fact prokaryotes, not eukaryotes at all. They're actually the only bacteria that perform oxygenic photosynthesis, and it's pretty incredible because they're responsible for the origin of oxygen in the atmosphere. And you can see a nice up-close image of some cyanobacteria here. These are cyanobacteria that grow in filaments. Some grow as free-floating little cells and others form colonies. And you can see that this is a satellite photo here. And this green mass here, that is just cyanobacteria. That is a huge bloom of cyanobacteria, obviously generating a bunch of oxygen because it's performing a bunch of photosynthesis. I mean, pretty amazing. This is a satellite photo and there are so many of these tiny microorganisms that we can see it from space. And actually, the oldest fossils we have of life on Earth come from cyanobacteria. These are stromatolites. These blobs of what look like rock, it's actually calcium carbonate, and this is exuded by certain types of cyanobacteria. And, basically, the oldest fossils we have of life on Earth are stromatolites from cyanobacteria. These are modern, you know, living cyanobacteria, but we have stromatolites that look like these from, you know, over a billion years ago. It's amazing. Now, and also, don't forget, lastly, that cyanobacteria are the organisms that were engulfed and eventually became chloroplasts.

Now, actinobacteria are high GC gram-positive bacteria. And what that means is they have a large, or a high percentage of guanine-cytosine, right, GC from DNA in their chromosome. So they have a high GC content, so to speak. They're gram-positive bacteria and they include the genus Streptomyces, which is responsible for many antibiotics. Many antibiotics have come from this genus of actinobacteria. Now, these were initially misclassified as fungi because they have a fungus-like morphology. And as you'll see in the name, it ends with myces. What you'll see once we or when we discuss fungi is that the names, the Latin names for fungi end in 'myces'. So these were initially thought to be fungi, actually, bacteria. Now, the misclassification comes from the fact that chains of cells form these branching mycelia. And it's these structures that caused biologists to think that these were actually fungi.

Lastly, we have the Firmicutes, which are low GC gram-positive bacteria. So, the high GC is basically in comparison to these low GC bacteria. And this group includes the genus Lactobacillus, which is super important to humans. Not only are they responsible for yogurt production, obviously very important, and also they're involved in cheese production, very important. And most important to me, they're involved in sour beer production. If you've never heard of sour beer, you should try it. It's delicious. And it involves fermentation with Lactobacillus inside humans that are super important, for our health. I mean, many species live in our gut and help us with digestion. There are species that live in the vagina that help maintain that environment, and that's actually what this image is depicting. This is a human cell and you can see all these little dark rods. Those are Lactobacillus, and they are a species of Lactobacillus that live in the vagina.

An organism that requires an environment of high salt concentration describes an Extreme…

• A. Halophile.
• B. Thermophile.
• C. Acidophile.
• D. Alkaliphile.

A cell is most likely to experience plasmolysis (contraction or shrinking of the cell) when…

• A. The solute concentration inside of the cell is equal to the solute concentration outside the cell.
• B. The solute concentration inside of the cell is less than the solute concentration outside of the cell.
• C. The solute concentration inside of the cell is greater than the solute concentration outside of the cell.

All organisms have specific environmental conditions in which they thrive. Most organisms cannot live in extremely salty environments. If a bacterium that normally lives in a fresh water environment is placed in an environment that is excessively salty, what will happen?

• A. The bacterium's cytoplasm will fill with water and cause the plasma membrane to rupture.
• B. Water will leave the bacterium's cytoplasm causing the plasma membrane to shrivel.
• C. Nothing will happen, salt concentrations outside of the cell do not affect the cytoplasm within the cell.

There are two groups of bacteria which live in the Great Salt Lake: Halobacterium and Halococcus. The Great Salt Lake's average salinity is around 13%. What class of microbes do the Halobacterium and Halococcus species belong to?

• A. Non-halotolerant.
• B. Halotolerant.
• C. Halophile.
• D. Extreme Halophile.

Reviewing the Environmental Factors of Microbial Growth

In this video, we're going to begin reviewing the environmental factors of microbial growth. And so in this video, once again, we're only going to review information that we've already covered in our previous lesson videos. And so if you're already feeling good, then feel free to skip this video if you'd like. However, if you need a little bit of extra help, then stick around because this video could be very helpful for you. And so here in this example problem, it wants us to fill in the following blanks throughout the flowchart that's down below, reviewing all of those environmental factors of microbial growth that created these different classes.

And so over here on the far left, what we have is the classification of microbes by growth temperature. And notice that there are these 5 groups that are classifying these microbes based on their growth temperature. And so the first group that we have over here are the psychrophiles. And the psychrophiles are going to be organisms that love the cold because 'psychro' is a root that means cold and 'phile' is a root that means loving. These are going to grow between negative 5 degrees Celsius to 15 degrees Celsius in extremely cold environments. Then what we have are the psychrotrophs. And the psychrotrophs also have that root 'psychro', so they're going to also grow in cold environments. But 'trophs' is a root that means nutrients. And so these are gonna grow in cool environments such as your refrigerator, for example, which is going to have temperatures between 0 and 35 degrees Celsius.

Then, what we have next are the mesophiles. And the mesophiles also grow on me and you, as they grow in temperatures between 10 and 45 degrees Celsius, and human body temperature is right around 35 degrees Celsius approximately. Then what we have next are the thermophiles. And the thermophiles are going to grow in hotter temperatures, between 40 and 80 degrees Celsius. And last but not least, what we have are the hyperthermophiles, which are going to grow in even hotter environments than the thermophiles. They grow between 65 and 115 degrees Celsius. Next, what we have are the classification of microbes based on their oxygen requirements. And so recall that for the electron transport chain, a lot of microbes require oxygen as the final electron acceptor. And those that require oxygen are called aerobes, whereas those that do not require oxygen are referred to as anaerobes.

We've got these 5 groups here. So the first one that we have are the obligate aerobes. And obligate aerobes are going to be obligated to aerobic conditions. So they require oxygen in order to grow, and they will not grow in any other regions that do not have oxygen. Then what we have next are the facultative anaerobes. And the facultative anaerobes can grow in the presence or the absence of oxygen. However, they grow better in the presence of oxygen, and that's simply because oxygen allows for more energy, more ATP to be generated, and that allows for better and more growth. However, facultative anaerobes, they will grow in both the presence and absence of oxygen, but they grow better in the presence of oxygen. Then next, what we have are the microaerophiles, and micro is a root that means small. So these require a small amount of oxygen in order to survive.

Too much oxygen is toxic, and no oxygen is also going to not be good for them. So, it needs a small amount of oxygen. Next, what we have are the obligate anaerobes. And the obligate anaerobes are practically the opposite of the obligate aerobes because the obligate anaerobes cannot grow with oxygen. They can only grow in anaerobic environments. They are obligated to anaerobic environments that lack oxygen. Then last but not least, what we have are the aerotolerant anaerobes, and these can grow equally in, with or without oxygen. And so, oxygen is not toxic to these organisms, and they really will grow equally with or without oxygen.

Then what we have over here are the classification of microbes by the pH requirement. And so we have 3 groups here. We have the acidophiles, and the acidophiles are going to have an optimum pH of less than 5.5. So they have an acidic optimum pH. Next, what we have are the neutrophiles which, as their name implies, they are going to have an optimum pH near neutral, between 5.5 and about 7.9, close to neutral. And then, the last group that we have here are the alkalophiles. And the alkalophiles are going to have a pH that is about, or is a basic or alkali, pHs above, equal to or greater than 8.

So they have basic pHs or alkali pHs, optimum pHs. Then last but not least, what we have over here are the classification of microbes by salt tolerance. And we've got these 4 different groups here. First, we have the nonhalotolerant organisms, which do not tolerate salt concentrations. They really don't tolerate sodium chloride concentrations. So they must grow in areas that do not have salt or do not have a lot of salt concentration at all. Then what we have are the halotolerant organisms. The halotolerant organisms, as their name implies, are capable of tolerating medium or moderate concentrations of salt, such as your skin, for example. Then we have the halophiles. And once again, philes means is a root that means loving.

So these grow in high concentrations of salt between 1 and 14% sodium chloride concentration. And then last but not least, what we have are the extreme halophiles, which are going to be growing in salt concentrations that are greater than 15% sodium chloride here. So they grow in even saltier environments than the halophiles. And so, really, this is just a recap and a review of all of the information that we talked about in our previous lesson videos. And so, I'll see you all in our next video.

Methanopyrus kandleri is a species of archaea that lives in the hydrothermal vents of the Pacific Ocean. This species' optimal temperatures are between 100-122 ºC. This species also does not require oxygen, as it survives off of hydrogen gas and releases methane gas. What environmental classifications would this archaeal species fit into?

• A. Mesophile & Obligate Aerobe.
• B. Non-halotolerant & Psychrophile.
• C. Neutrophile & Facultative Aerobe.
• D. Hyperthermophile & Obligate Anaerobe.

Acidobacterium capsulatum is a species of bacteria that grows better in the absence of oxygen but can survive if oxygen is present. This species of bacteria also thrives in soil and water with a pH between 3.0 and 6.0. What environmental classifications would this bacterial species fit into?

• A. Extreme Halophile & Mesophile.
• B. Facultative Anaerobe & Acidophile.
• C. Facultative Aerobe & Alkaliphile.

Here’s what students ask on this topic:

What are the major lineages of prokaryotes and their characteristics?

Prokaryotes include diverse groups such as proteobacteria, chlamydia, spirochetes, cyanobacteria, actinobacteria, and firmicutes. Proteobacteria are known for nitrogen fixation and gave rise to mitochondria. Chlamydia are gram-negative parasites lacking peptidoglycan. Spirochetes, with their corkscrew shape, cause diseases like Lyme disease and syphilis. Cyanobacteria are responsible for oxygenic photosynthesis, crucial for atmospheric oxygen, and form ancient stromatolites. Actinobacteria, including Streptomyces, produce antibiotics. Firmicutes, like Lactobacillus, are vital for yogurt production and gut health.

How do cyanobacteria contribute to the Earth's atmosphere?

Cyanobacteria are gram-negative photoautotrophs that perform oxygenic photosynthesis, producing oxygen as a byproduct. They are the only bacteria capable of this process and are responsible for the origin of oxygen in the Earth's atmosphere. Cyanobacteria's photosynthetic activity led to the Great Oxygenation Event, which dramatically increased atmospheric oxygen levels, enabling the evolution of aerobic life forms. Additionally, cyanobacteria form ancient stromatolites, which are some of the oldest fossils on Earth.

What diseases are caused by spirochetes?

Spirochetes are gram-negative heterotrophs with a distinct corkscrew shape. They are responsible for causing several diseases, most notably Lyme disease and syphilis. Lyme disease is transmitted through tick bites and can lead to symptoms such as fever, headache, fatigue, and a characteristic skin rash. Syphilis is a sexually transmitted infection that progresses through multiple stages, potentially causing severe health issues if left untreated.

What is the significance of proteobacteria in the evolution of eukaryotes?

Proteobacteria are a diverse clade of gram-negative bacteria, some of which are involved in nitrogen fixation. A significant evolutionary event involving proteobacteria is their endosymbiotic relationship with early eukaryotic cells. A proteobacterium was engulfed by a primitive eukaryotic cell, eventually evolving into mitochondria, the powerhouse of eukaryotic cells. This endosymbiotic event was crucial for the development of complex eukaryotic life, providing cells with efficient energy production capabilities.

How do actinobacteria contribute to antibiotic production?

Actinobacteria are high GC gram-positive bacteria, meaning they have a high percentage of guanine and cytosine in their DNA. This group includes the genus Streptomyces, which is renowned for its role in antibiotic production. Streptomyces species produce a variety of antibiotics, such as streptomycin, which are used to treat bacterial infections. These antibiotics are derived from the secondary metabolites produced by Streptomyces, making actinobacteria crucial in medical and pharmaceutical fields.