Wednesday, February 22, 2006

The World of Microbes . Question 2.

In what ways have Bacteria and Archaea influenced the evolution of eukaryotes in the past?

How do they influence it in the present?

Discuss in the comments panel.



Anonymous suze said...

hi. i need a feedback on this because this is more of an educated guess.
ok. Bacteria and Archaea aretwo groups of pokaryotes that arise from a commonancestor. when the two types of prokaryotes split into two different domeins, one stayed strictly prokaryotic, and that is bacteria, whereas the other one, archaea started evolving vvveeerrrryyyy sllooooowwwlllyyyyy towards eukaryotic cells. My guess is from looking at the phylogenetic tree that mitochondria and chloroplast come from the early versions of archaea. Considering the great difference between the bacteria and archaea i.e. different chem structure of cell membrane and the cell wall between the two, as well as bacterial sensitivity, and Archaeaic insensitivity to most antibiotic as well as the fact that archaea live as extreme thermophyles and producers of methane, the posssible evolutionary effect this could have is evolution of eucaryotic organisms to become less sensitive to extreme living conditions. thnx :)

February 28, 2006 11:47 am  
Anonymous Anonymous said...

Guesses are useful but its helpful to look at detailed factual evidence for more precise answers.

Yes symbiosis is a major part of the interaction.

The precursor of mitochondria is known fairly accurately. What is it?

Some of the stages in early evolution of cells are extremely speculative too.
And what about infection and disease?
Are their any essential nutrients processed by bacteria?

The question is designed to make you think.

Microbe Pundit

February 28, 2006 3:28 pm  
Blogger Archeak9 said...

The Mitochondrial precursor is believed to be a Proteobacteria, and the Chloroplast precursor is believed to be a Cyanobacteria. Both taken up by endosymbiosis by a Eukaryotic precursor archea. Since these two organelles represent the powerhouses of eukaryotic cells it is fair to say the eukaryotes evolution is intwined with bacteria.

In regards current impacts bacteria have until recent times been the major source of nitrogen fixation.(see recent Newscientist) They are also responcible for breaking down most organic matter into digestable components, completing most cycles. We are therfore entirely dependent on them.

March 06, 2006 9:57 am  
Anonymous Anonymous said...

Newscientist 21 Jan 2006 pp40-43.

March 06, 2006 3:06 pm  
Blogger Microbe Pundit said...

The N fixation comment is really valuable. The protobacterial origins of mitochondria is correct for sure, as for chloroplasts the Pundit has to check his texts to be certain but believes it to be correct.

March 06, 2006 5:21 pm  
Anonymous Anonymous said...

Doesn't the insertion of genetic material by some infectious bacteria into eukaryotes also influence the way they progress in evolution?


March 07, 2006 12:21 pm  
Blogger Microbe Pundit said...

The transfer of genetic material currently from bacteria to eucaryotes (or the reverse)is sometimes important, perhaps in single celled eucaryotes more significantly. These are very rare events but the total opportunities are huge.
Cross Gene transfer by non cellular organisms such as transposons or retrotransposons (if you consider them organisms) is significant in metazoal evolution.

But death from infection is a major evolutionary force - its mainly why we have such a complicated immune systeme for a start.

Symbiosis is another related area to think more about, especially in insects and other organisms we are less familiar with.

Fig 11.2 of Schaechter shows the 16s evolutionary tree with chloroplasts branching from cyanobacteria

March 08, 2006 10:37 am  
Blogger Microbe Pundit said...

Remember all oxygen in the atmosphere comes from prokaryotes (cyanob. and chloroplasts). Hence us mammals would never have evolved without prokatyotes genetating an oxygen atmosphere.

March 09, 2006 4:05 pm  
Anonymous CoronaV said...

I think the biggest influence that Bacteria have had on eukaryotic evolution in the past is the presence of cyanobacteria about 3 billion years ago, creating an aerobic environment which eukaryotes evolved in.

There are also some other (more recent) interesting examples of microbes influencing eukaryotic evolution. For example the genes for cystic fibrosis are realtively prevalent in the Causasian population (I think its something like 1/25 is a carrier). It is hypothesised that this is in fact the result of the selective presure of the cholera (Vibrio cholera) epidemics around in the 17th century. This is the explaination from Human Genetics

"Cholera opens chloride channels, letting chloride and water leave cells. The CFTR [cystic fibrosis] protein does just the opposite, closing chloride channels and trapping salt and water in cells, which dries out mucus and other secretions. A person with CF cannot contract cholera, because the toxin cannot open the chloride channels in the small intestine."

Therefore, the prevalence of the CF allele in Caucasian populations may infact be a good example of how a bacterium influenced eukaryotic evolution and selected for people with this genotype. A similar example is available with the plague epidemics where it is thought the Yersinia pestis actually influenced eukaryotic evolution by only killing people with certain cell surface receptors. Hence, these receptors are less in the population prevelent today.

March 21, 2007 6:01 pm  
Anonymous Anonymous said...

Those are pretty important and interesting comments about both cyanobacteria AND cholera.

Microbe pundit speaking

April 04, 2007 5:26 pm  

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