How did scientists do experiments on archaebacterias if they only live in extreme places?

They don't live only in extreme environments. Approximately 40 % of your own microflora are actually archaea. In the past few decades we found out that many prokaryotes that we thought were bacteria are actually archaea.

Why mycoplasmas included in gram positif when it dont have cell wall?

Because of the criteria used. Mycoplasma is not classified under 'gram positive' based on Gram staining (which does not give results) but based on *genetics*. Comparison of DNA sequences and 16s ribosomal RNA tend to support this idea and Mycoplasma are now categorized as gram-positive.

If bacteria and archaea are prokaryotes, why does figure 3, the lineage diagram near the top, indicate that archaea and eukarya have a more recent ancestor? Doesn't common ancestry dictate classification?

Excellent observation! You are correct, prokaryote is not a good phylogenetic grouping — it really just means "not a eukaryote". Prokaryote is an old term that is no longer considered valid in a phylogenetic context, but is too useful to give up. The accepted explanation for the evolution of the Eukarya is that a Bacteria ended up inside (was eaten or infected) an Archaea — this is known as symbiogenesis, or the endosymbiotic theory. This is the most fundamental example of a limitation in thinking of phylogenies as trees — sometimes the branches fuse! The diagrams on the right in this wikipedia article may help you visualize the "true" relationship among the three domains: https://en.wikipedia.org/wiki/Prokaryote#Classification

Did Archea and Bacteria branch before or after Eukarya appeared? If before, from which of these domains did Eukarya branch?

Yes, Archea and Bacteria branched before the Eukarya appeared. Only after they branched did the Eukarya branch off from Archea. Evolutionists think this because Archea and Eukarya are similar, Archea and Bacteria are similar, but Eukarya and Bacteria aren't very similar. And using DNA hybridization and things they hypothesized this, though there really is no proof.

to which kingdom do mold belong

That depends on the mold! Most molds are fungi — Kingdom: Fungi https://en.wikipedia.org/wiki/Mold Other things called molds include: • "water molds" (Kingdom Chromista): https://en.wikipedia.org/wiki/Oomycete • "slime molds", which aren't Fungi, but whose classification is still uncertain: https://en.wikipedia.org/wiki/Slime_mold

What is the difference between Archea and Bacteria?

Differences Between Bacteria and Archaea •Different cell wall proteins •Different lipids in plasma membrane •Different ribosomal proteins and RNA •Archaea ribosomal proteins resemble eukaryotic ribosomal proteins.

what are Prokaryotes are found in

Prokaryotes are found practically everywhere, from inside other organisms (like digestive bacteria) to in really extreme environments that have high heat or acidity, for example.

Main content

Course: Biology library > Unit 23

Lesson 2: Prokaryote metabolism and ecology

Prokaryote classification and diversity

Google Classroom

Different groups of prokaryotes. Evolutionary relationships of bacteria and archaea. Extremophiles.

Key points:

The two prokaryote domains, Bacteria and Archaea, split from each other early in the evolution of life.
Bacteria are very diverse, ranging from disease-causing pathogens to beneficial photosynthesizers and symbionts.
Archaea are also diverse, but none are pathogenic and many live in extreme environments.
A DNA sequencing approach called metagenomics lets scientists identify new species of bacteria and archaea, including ones that can't be cultured.

Introduction

Prokaryotes, which include both bacteria and archaea, are found almost everywhere – in every ecosystem, on every surface of our homes, and inside of our bodies! Some live in environments too extreme for other organisms, such as hot vents on the ocean floor.

Although they are found all around us, prokaryotes can be hard to detect, count, and classify. The prokaryotic species we know of today are a tiny fraction of all prokaryotic species thought to exist.

^{1}

In fact, the very idea of a “species” becomes complicated in the world of prokaryotes!

In this article, we'll first look at major groups of prokaryotes. Then, we'll explore why it’s often tricky to identify and classify them. Finally, we'll see how DNA sequencing methods are helping us get a better picture of the prokaryotes around us.

A prokaryote "family tree"

For a long time, all prokaryotes were classified into a single domain (the largest taxonomic grouping).

However, work by microbiologist Carl Woese in the 1970s showed that prokaryotes are divided into two distinct lineages, or lines of descent: Archaea and Bacteria. Today, these groups are considered to form two out of three domains of life. The third domain (Eukarya) includes all eukaryotes, such as plants, animals, and fungi.

^{2}

Woese made his breakthrough discovery by studying ribosomal RNA sequences from many different organisms. Ribosomal RNA (rRNA) genes are often used to build evolutionary trees, or phylogenies, that show relationships among species. rRNA genes are good for determining evolutionary relationships among species (how related one species is to another) because they have the same function across organisms and evolve slowly over time.

^{3}

In general, more differences in rRNA sequences correspond to a more distant evolutionary relationship between two organisms, while fewer differences indicate a closer evolutionary relationship. You can learn more about this idea in the phylogenetic trees video.

Since splitting off from one another millions of years ago, both Bacteria and Archaea have split off into many groups and species.

Bacteria

Domain Bacteria contains

5

major groups: proteobacteria, chlamydias, spirochetes, cyanobacteria, and gram-positive bacteria.

The proteobacteria are subdivided into five groups, alpha through epsilon. Species in these groups have a wide range of lifestyles. Some are symbiotic with plants, others live in hot vents deep under the sea, and others yet cause human diseases, such as stomach ulcers (Helicobacter pylori) and food poisoning (Salmonella).

Image credit: "Structure of prokaryotes: Figure 4," by OpenStax College, Biology, CC BY 4.0. Original work credits: “Rickettsia rickettsia”: modification of work by CDC; credit “Spirillum minus”: modification of work by Wolframm Adlassnig; credit “Vibrio cholera”: modification of work by Janice Haney Carr, CDC; credit “Desulfovibrio vulgaris”: modification of work by Graham Bradley; credit “Campylobacter”: modification of work by De Wood, Pooley, USDA, ARS, EMU; scale-bar data from Matt Russell.

The other four major groups of bacteria are similarly diverse. Chlamydias are pathogens that live inside host cells, while cyanobacteria are photosynthesizers that make much of Earth's oxygen. Spirochetes include both harmless bacteria and harmful ones, like the Borrelia burgdorferi that cause Lyme disease. The same is true of Gram-positive bacteria, which range from probiotic bacteria in yogurt to the Bacillus anthracis that cause anthrax.

^{4}

Archaea

Domain Archaea contains

4

major groups. Intriguingly, so far, no archaea that are human pathogens have yet been discovered.

Archaea do live in our bodies and those of animals—for instance, in the gut—but all of them seem to be harmless or beneficial. Although there are hypotheses, no one yet knows exactly why archaea are all "friendly," i.e., why no disease-causing species have evolved.

^{5}

Alongside the archaea that enjoy the comfy environment of the human gut, there are many extremophile species that live in much more inhospitable places. These include volcanic hot springs, undersea hot vents, and very salty places like the Dead Sea.

Both bacteria and archaea that are adapted to grow under extreme conditions are called extremophiles, meaning “lovers of extremes.” Extremophiles have been found in all kinds of places: the depth of the oceans, hot springs, the Artic and the Antarctic, in very dry places, deep inside Earth, in harsh chemical environments, and in high-radiation environments, just to mention a few.

There are a number of groups of extremophiles, defined by their preferred (or at least, survivable) conditions. Of course, habitats can be extreme in multiple ways. For example, a soda lake is both salty and alkaline, so organisms that live in it must be both halophiles (salt-loving) and alkaliphiles (high pH-loving).

The table below lists classes of extremophiles and the conditions they prefer:

Extremophile type	Typical conditions for growth
Acidophiles	$pH$ ‍ $3$ ‍ or below
Alkaliphiles	$pH$ ‍ $9$ ‍ or above
Thermophiles	Temperature $60$ ‍ $-$ ‍ $80$ ‍ $° C$ ‍ ( $140$ ‍ $-$ ‍ $176$ ‍ $° F$ ‍)
Hyperthermophiles	Temperature $80$ ‍ $-$ ‍ $122$ ‍ $° C$ ‍ ( $176$ ‍ $-$ ‍ $250$ ‍ $° F$ ‍)
Psychrophiles	Temperature of $- 15$ ‍ $-$ ‍ $10$ ‍ $° C$ ‍ ( $5$ ‍ $-$ ‍ $50$ ‍ $° F$ ‍) or lower
Halophiles	Salt concentration of at least $0.2$ ‍ $M$ ‍
Osmophiles	High sugar concentration

Table from OpenStax College, Biology.

The many "mystery prokaryotes"

For many years, the main approach to studying prokaryotes was to grow them in the lab. If an organism could be grown on an agar plate or in a liquid culture, then it could be studied, analyzed, and added to our growing catalog of prokaryotic species and strains.

Some prokaryotes, however, can't grow in a laboratory setting (at least, not under the conditions scientists have tried). In fact, an estimated

99 %

of bacteria and archaea are unculturable!

This represents a pretty huge gap in our understanding of what prokaryotes are out there. For context, there are

8.7

million

known eukaryotic species

^{6}

. If the culturability problem applied to eukaryotes in the same degree as prokaryotes, we would only know of

87,000

of these species. This would make for a very empty tree of life, and a very incomplete understanding of what eukaryotes (as a group) are like. For instance, we might know that there were animals, but be in the dark about plants or fungi!

What is a prokaryotic species?

In order to talk about finding prokaryotic species, we probably need to define what they are. This may seem like a basic question, but it's a complex and even controversial one if you're a microbiologist.

For eukaryotes, most scientists define a species as a group of organisms that can interbreed and have fertile offspring. This definition makes sense for species that reproduce sexually, but it doesn't work so well for organisms like bacteria. Bacteria reproduce asexually to make clones of themselves—they don't interbreed.

Scientists instead classify bacteria and archaea into taxonomic groups based on similarities in appearance, physiology, and genes.

^{7}

Many are given names using traditional Linnean taxonomy, with a genus and species. Still, the question of how and whether prokaryotes should be grouped into species remains a topic of debate among scientists. The right “species concept” for these organisms is still a work in progress.

^{8}

Metagenomics: A new window on microbes

Scientists estimate there may be millions of prokaryotic species (or species-like groups), but we know very little about most of them.

^{1}

This is starting to change thanks to large-scale DNA sequencing.

DNA sequencing makes it possible for scientists to study entire prokaryotic communities in their natural habitats – including the many prokaryotes that are unculturable, and would previously have been "invisible" to researchers.

The collective genome of such a community is called its metagenome, and the analysis of metagenome sequences is known as metagenomics. Prokaryotic metagenomics is one of the areas of biology that I find coolest and most mysterious.

For example, a DNA sample can be taken from a hot spring microbial mat, such as the beautiful, multicolored mats found in Yellowstone National Park. Even a tiny sample from this rich community includes many, many individuals of different species.

^{9}

By sequencing and analyzing metagenome DNA samples, scientists can sometimes piece together entire genomes of previously unknown species. In other cases, they use sequence information from specific genes to figure out what types of prokaryotes are present (and how they are related to each other or to known species). The genes found in the DNA samples can also provide clues about the metabolic strategies of the organisms in the community.

^{10}

Attribution:

This article is a modified derivative of the following articles:

"Structure of prokaryotes," by OpenStax College, Biology, CC BY 4.0. Download the original article for free at http://cnx.org/contents/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.12.
"Prokaryotic diversity," by OpenStax College, Biology, CC BY 4.0. Download the original article for free at http://cnx.org/contents/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.12.

The modified article is licensed under a CC BY-NC-SA 4.0 license.

Works cited:

Ward, B. B. (2002). How many species of prokaryotes are there? Proc. Natl. Acad. Sci., 99(16), 10234-10236. http://dx.doi.org/10.1073/pnas.162359199.
Eisen, J. and Coil, D. (n.d.). Fact sheet: rRNA in evolutionary studies and environmental sampling. In microBEnet. Retrieved from http://microbe.net/simple-guides/fact-sheet-rrna-in-evolutionary-studies-and-environmental-sampling/.
Eisen, J. and Coil, D. (n.d.). Fact sheet: Ribosomal RNA (rRNA), the details. In microBEnet. Retrieved from http://www.microbe.net/simple-guides/fact-sheet-ribosomal-rna-rrna-the-details/.
Yogurt. (2013, November 30). Retrieved October 29, 2016 from MicrobeWiki: https://microbewiki.kenyon.edu/index.php/Yogurt.
Gill, Erin E. and Brinkman, Fiona S. L. (2011). The proportional lack of archaeal pathogens: Do viruses/phages hold the key? Bioessays, 33, 248. http://dx.doi.org/10.1002/bies.201000091.
Sweetlove, L. (2011, August 23). Number of species on Earth tagged at 8.7 million. In Nature. Retrieved from http://www.nature.com/news/2011/110823/full/news.2011.498.html.
Purves, W. K., Sadava, D., Orians, G. H., and Heller, H. C. (2003). Bacteria and archaea: The prokaryotic domains. In Life: The science of biology (7th ed., pp. 533). Sunderland, MA: Sinauer Associates, Inc.
Gevers, D., Cohan, F. M., Lawrence, J. G., Spratt, B. G., Coenye, T., Feil, E. J., Stackebrandt, E., Van de Peer, Y., Vandamme, P., Thompson, F. L., and Swings, J. (2005). Re-evaluating prokaryotic species. Nat. Rev. Microbiol., 3, 733-739. http://www.ncbi.nlm.nih.gov/pubmed/16138101.
Klatt, C. G., Wood, J. M., Rusch, D. B., Bateson, M. M., Hamamura, N., Heidelberg, J. F., Grossman, A. R., Bhaya, D., Cohan, F. M., Kühl, M., and Bryant, D. A. (2011). Community ecology of hot spring cyanobacterial mats: predominant populations and their functional potential. ISME J, 5, 1262-1278. Retrieved from https://dpb.carnegiescience.edu/sites/dpb.carnegiescience.edu/files/Klatt_2011.pdf.
Sharpton, Thomas J. (2014). An introduction to the analysis of shotgun metagenomic data. Front. Plant Sci. http://dx.doi.org/10.3389/fpls.2014.00209.

References:

American Society for Microbiology. (2006). Archaea: Where they're found. In Microbe world. Retrieved from http://www.microbeworld.org/types-of-microbes/archaea/where-they-re-found.

Boundless. (2015, July 21). Shared features of archaea and eukaryotes. In Boundless Microbiology. Retrieved from https://www.boundless.com/microbiology/textbooks/boundless-microbiology-textbook/microbial-genetics-7/archaeal-genetics-78/shared-features-of-archaea-and-eukaryotes-437-4635/.

Cooper, G. M. (2000). The origin and evolution of cells. In The cell: A molecular approach. (2nd ed.). Sunderland, MA: Sinauer Associates. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK9841/.

Doolittle, W. F. and Zhaxybayeva, O. (2009). On the origin of prokaryotic species. Genome Res., 19, 744-756. http://dx.doi.org/10.1101/gr.086645.108.

Eisen, J. (n.d.). Fact sheet: rRNA in evolutionary studies and environmental sampling. In microBEnet. Retrieved from http://microbe.net/simple-guides/fact-sheet-rrna-in-evolutionary-studies-and-environmental-sampling/.

European Food Information Council. (1999). Lactic acid bacteria - their uses in food. In Functional foods. Retrieved from http://www.eufic.org/article/en/nutrition/functional-foods/artid/lactic-acid-bacteria/.

Gevers, D., Cohan, F. M., Lawrence, J. G., Spratt, B. G., Coenye, T., Feil, E. J., Stackebrandt, E., Van de Peer, Y., Vandamme, P., Thompson, F. L., and Swings, J. (2005). Re-evaluating prokaryotic species. Nat. Rev. Microbiol., 3, 733-739. http://www.ncbi.nlm.nih.gov/pubmed/16138101.

Gill, Erin E. and Brinkman, Fiona S. L. (2011). The proportional lack of archaeal pathogens: Do viruses/phages hold the key? Bioessays, 33, 248-254. http://dx.doi.org/10.1002/bies.201000091.

Klatt, C. G., Wood, J. M., Rusch, D. B., Bateson, M. M., Hamamura, N., Heidelberg, J. F., Grossman, A. R., Bhaya, D., Cohan, F. M., Kühl, M., and Bryant, D. A. (2011). Community ecology of hot spring cyanobacterial mats: predominant populations and their functional potential. ISME J, 5, 1262-1278. Retrieved from https://dpb.carnegiescience.edu/sites/dpb.carnegiescience.edu/files/Klatt_2011.pdf.

National Research Council (US) Committee on Metagenomics. (2007). Why metagenomics? In The new science of metagenomics: Revealing the secrets of our microbial planet. Washington, DC: National Academies Press. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK54011/.

Niederberger, T. (2015, July 31). Archaea. In Encyclopedia Britannica. Retrieved from http://www.britannica.com/science/archaea.

OpenStax College, Biology. (2016, May 18). Perspectives on the phylogenetic tree. In OpenStax CNX. Retrieved from http://cnx.org/contents/GFy_h8cu@10.12:J1tiQMqk@5/Perspectives-on-the-Phylogenet.

Pace, N. R. (2009). Mapping the tree of life: Progress and prospects. Microbiol. Mol. Biol. Rev., 73(4), 565–576. http://dx.doi.org/10.1128/MMBR.00033-09.

Psychrophile. (2016, January, 31). Retrieved March 24, 2016 from from Wikipedia: https://en.wikipedia.org/wiki/Psychrophile.

Purves, W. K., Sadava, D., Orians, G. H., and Heller, H. C. (2003). Bacteria and archaea: The prokaryotic domains. In Life: The science of biology (7th ed., pp. 524-542). Sunderland, MA: Sinauer Associates, Inc.

Railsback, B. L. (n.d.) A paean to prokaryotes. In Bruce Railsback's geoscience resources. Retrieved from http://www.gly.uga.edu/railsback/11111misc/Prokaryotes.html.

Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B. (2011). Bacteria and archaea. In Campbell biology (10th ed., pp. 567-575). San Francisco, CA: Pearson.

Rosselló-Mora, R. and Amann, R. (2006). The species concept for prokaryotes. FEMS Microbio. Rev., 25(1), 39-67. Retrieved from http://femsre.oxfordjournals.org/content/femsre/25/1/39.full.pdf.

Sabres, Z.l., Rondon, M.R., and Handelsman, J. (2009). Metagenomics. In M. Schaechter (Ed.), Encyclopedia of microbiology (3rd ed, pp. 622-632). Academic Press. Retrieved from http://www.yale.edu/handelsmanlab/publications/pdf/Sabree%20Rondon%20Handelsman%20Metagenomics.pdf.

Sharpton, Thomas J. (2014). An introduction to the analysis of shotgun metagenomic data. Front. Plant Sci. http://dx.doi.org/10.3389/fpls.2014.00209.

Sulfolobus. (2010, August, 6). Retrieved March 24, 2016 from MicrobeWiki: https://microbewiki.kenyon.edu/index.php/Sulfolobus.

Sulfolobus. (2016, March 1.) Retrieved March 25, 2016 from Wikipedia: https://en.wikipedia.org/wiki/Sulfolobus.

Ward, B. B. (2002). How many species of prokaryotes are there? Proc. Natl. Acad. Sci., 99(16), 10234-10236. http://dx.doi.org/10.1073/pnas.162359199.

Yogurt. (2013, November 30). Retrieved March 24, 2016 from MicrobeWiki: https://microbewiki.kenyon.edu/index.php/Yogurt.

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bet .
Posted 7 years ago. Direct link to bet .'s post “How did scientists do exp...”
How did scientists do experiments on archaebacterias if they only live in extreme places?
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- ++§ Αλεκσανδαρ
  Posted 6 years ago. Direct link to ++§ Αλεκσανδαρ's post “They don't live only in e...”
  They don't live only in extreme environments. Approximately 40 % of your own microflora are actually archaea. In the past few decades we found out that many prokaryotes that we thought were bacteria are actually archaea.
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Hubertus Damay Triwibowo
Posted 7 years ago. Direct link to Hubertus Damay Triwibowo's post “Why mycoplasmas included ...”
Why mycoplasmas included in gram positif when it dont have cell wall?
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- Ivana - Science trainee
  Posted 5 years ago. Direct link to Ivana - Science trainee's post “Because of the criteria u...”
  Because of the criteria used.
  Mycoplasma is not classified under 'gram positive' based on Gram staining (which does not give results) but based on genetics.
  
  Comparison of DNA sequences and 16s ribosomal RNA tend to support this idea and Mycoplasma are now categorized as gram-positive.
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  (3 votes)
kyle marvin
Posted 6 years ago. Direct link to kyle marvin's post “If bacteria and archaea a...”
If bacteria and archaea are prokaryotes, why does figure 3, the lineage diagram near the top, indicate that archaea and eukarya have a more recent ancestor? Doesn't common ancestry dictate classification?
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(2 votes)
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- tyersome
  Posted 6 years ago. Direct link to tyersome's post “Excellent observation! Y...”
  Excellent observation!
  
  You are correct, prokaryote is not a good phylogenetic grouping — it really just means "not a eukaryote".
  
  Prokaryote is an old term that is no longer considered valid in a phylogenetic context, but is too useful to give up.
  
  The accepted explanation for the evolution of the Eukarya is that a Bacteria ended up inside (was eaten or infected) an Archaea — this is known as symbiogenesis, or the endosymbiotic theory.
  
  This is the most fundamental example of a limitation in thinking of phylogenies as trees — sometimes the branches fuse!
  
  The diagrams on the right in this wikipedia article may help you visualize the "true" relationship among the three domains:
  https://en.wikipedia.org/wiki/Prokaryote#Classification
  Comment on tyersome's post “Excellent observation! Y...”
  (4 votes)
Alexander Wu
Posted 7 years ago. Direct link to Alexander Wu's post “Did Archea and Bacteria b...”
Did Archea and Bacteria branch before or after Eukarya appeared? If before, from which of these domains did Eukarya branch?
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- Lau Sky
  Posted 7 years ago. Direct link to Lau Sky's post “Yes, Archea and Bacteria ...”
  Yes, Archea and Bacteria branched before the Eukarya appeared. Only after they branched did the Eukarya branch off from Archea. Evolutionists think this because Archea and Eukarya are similar, Archea and Bacteria are similar, but Eukarya and Bacteria aren't very similar. And using DNA hybridization and things they hypothesized this, though there really is no proof.
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claudine zirimwabagabo
Posted 6 years ago. Direct link to claudine zirimwabagabo's post “to which kingdom do mold ...”
to which kingdom do mold belong
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- tyersome
  Posted 6 years ago. Direct link to tyersome's post “That depends on the mold!...”
  That depends on the mold!
  
  Most molds are fungi — Kingdom: Fungi
  https://en.wikipedia.org/wiki/Mold
  
  Other things called molds include:
  • "water molds" (Kingdom Chromista):
  https://en.wikipedia.org/wiki/Oomycete
  
  • "slime molds", which aren't Fungi, but whose classification is still uncertain:
  https://en.wikipedia.org/wiki/Slime_mold
  Comment on tyersome's post “That depends on the mold!...”
  (3 votes)
James Leelayuvat
Posted 4 years ago. Direct link to James Leelayuvat's post “What is the difference be...”
What is the difference between Archea and Bacteria?
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- Alreem
  Posted 3 years ago. Direct link to Alreem's post “Differences Between Bacte...”
  Differences Between Bacteria and Archaea
  •Different cell wall proteins
  •Different lipids in plasma membrane
  •Different ribosomal proteins and RNA
  •Archaea ribosomal proteins resemble eukaryotic ribosomal proteins.
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  (3 votes)
Gabriel Baca
Posted 4 years ago. Direct link to Gabriel Baca's post “what are Prokaryotes are ...”
what are Prokaryotes are found in
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- Hecretary Bird
  Posted 4 years ago. Direct link to Hecretary Bird's post “Prokaryotes are found pra...”
  Prokaryotes are found practically everywhere, from inside other organisms (like digestive bacteria) to in really extreme environments that have high heat or acidity, for example.
  Button navigates to signup page
  (2 votes)
sofhae.calvo
Posted 3 years ago. Direct link to sofhae.calvo's post “what is the difference be...”
what is the difference between the three domains?
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lwang21
Posted 5 years ago. Direct link to lwang21's post “what is an extremophile?”
what is an extremophile?
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- tyersome
  Posted 5 years ago. Direct link to tyersome's post “An organism§ that loves "...”
  An organism§ that loves "extreme" environments — of course "extreme" is relative to what we think of as "normal".
  
  These "extreme" environments include:
  • undersea thermal vents (e.g. "black smokers") with temperatures up to 122°C
  • acidic drainage from mine tailings with pH values less than 1
  
  The wikipedia article on this seems like a good place to start learning more:
  https://en.wikipedia.org/wiki/Extremophile
  
  §Note: Extremophiles are usually members of the Archaea.
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noor fatima
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Which has smaller size.cillia or pillicle or extended pseudopod?
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