Archaea: The 'Dark Matter' of the Microbial World • Hacker News Board

Re: Archaea: The 'Dark Matter' of the Microbial World

#31

Post by jhbadger » Fri, Mar 10, 2017, 10:50 AM UTC

jessriedel wrote: post #3

Is it known why there are no evolutionary intermediates between archea and eubacteria? Nick Lane's book The Vital Questions has been highly recommended by the HN commentariat, and I think it more or less deserves its esteem. Lane gives an extensive theoretical analysis of the sequence of events wherein a eubacterium was engulfed by an archea, and the resulting endosymbiosis that was the beginning of complex (eukaryot…

I like Lane's book, but it is annoying how he praises Bill Martin and basically ignores the actual pioneers of the field. Carl Woese, who discovered the archaea and who fought a long battle to get the world to understand that they weren't just bacteria, gets like a sentence in the whole book.

Re: Archaea: The 'Dark Matter' of the Microbial World

#32

Post by jessriedel » Fri, Mar 10, 2017, 2:15 PM UTC

jhbadger wrote: post #31

jessriedel wrote: post #3

Is it known why there are no evolutionary intermediates between archea and eubacteria? Nick Lane's book The Vital Questions has been highly recommended by the HN commentariat, and I think it more or less deserves its esteem. Lane gives an extensive theoretical analysis of the sequence of events wherein a eubacterium was engulfed by an archea, and the resulting endosymbiosis that was the beginning of complex (eukaryot…

I like Lane's book, but it is annoying how he praises Bill Martin and basically ignores the actual pioneers of the field. Carl Woese, who discovered the archaea and who fought a long battle to get the world to understand that they weren't just bacteria, gets like a sentence in the whole book.

Yea OK, but it's really hard to expect authors to dole out praise of scientists in proportion to the size of their contributions as assessed by the community. Individuals will naturally disagree with the community's assessment (which needn't always be correct), and will like their friends disproportionately, etc.

A lower bar is just that the author correctly represent the evidence and arguments about the scientific issues, especially with regard to identifying the consensus position and representing it fairly. If Lane fails to do that, it's a more serious charge.

Re: Archaea: The 'Dark Matter' of the Microbial World

#33

Post by throwaway91111 » Fri, Mar 10, 2017, 9:02 PM UTC

jballanc wrote: post #25

throwaway91111 wrote: post #23

Earlier quoted context omitted.

So, if I'm understanding correctly, these pre-cellular replicons are distinctly less efficient at survival than both archaea and eubacteria, hence their not existing in any (recognizable) form today. Is this correct? This opposed to the idea that the archaea existed, then the bridge (which went extinct), then archaea.

That is an excellent question! I should start by saying that we don't know, for sure, that pre-cellular replicons don't still exist. They may, and we may just not have figured out the right place to look for them. That said, gaining a membrane is a huge advantage for life. The current working hypothesis is that life started as a series of autocatalytic chemical reactions, but for this to work there must have been jus…

Excellent answer, thank you!

Re: Archaea: The 'Dark Matter' of the Microbial World

#34

Post by lawpoop » Fri, Mar 10, 2017, 9:20 PM UTC

throwaway91111 wrote: post #23

jballanc wrote: post #21

Earlier quoted context omitted.

Archaea and Eubacteria have different Ribosomes. In the world of biology, if DNA is the source code then ribosomes are the compiler. In other words, while both families use DNA to store information and RNA to translate it, all the rest of the machinery used by cells in that process is different. This is why there are no intermediates. Likely (and this is a guess, if an educated one) this split happened before cells w…

So, if I'm understanding correctly, these pre-cellular replicons are distinctly less efficient at survival than both archaea and eubacteria, hence their not existing in any (recognizable) form today. Is this correct? This opposed to the idea that the archaea existed, then the bridge (which went extinct), then archaea.

Like others said, we don't really know, but most likely, they just got eaten, ingested, or sopped up by cellular life when it arrived. They couldn't have been much more than symbiotic molecules, not complex things like modern cells with organelles that we know today.