SpareHeadOne

Getting around to it

12237 0 6 39
Forum Posts Wiki Points Following Followers

Devolution

Organisms that have adapted by losing genes and traits.

Sometimes, devolution offers an advantage.

No Caption Provided

For example, Jeffrey Morris, from Richard Lenski's lab at Michigan State University in East Lansing and his colleagues initially watched thousands of generations of replicating Escherichia coli, a stand in for ocean-dwelling Prochlorococcus, cope with hydrogen peroxide and showed that helper cells leaking the hydrogen peroxide–detoxifying enzyme KatG enabled beneficiary bacteria to reduce their genomes and, therefore, to replicate with greater efficiency. They call this “the black queen hypothesis” (BQH), after the queen of spades in the game of hearts—the costly card everyone wants to avoid.

-

No Caption Provided

Many microbial plankton species have jettisoned the genes needed for producing key vitamins, and now outsource the function. One account suggests, "... most of the time, the fitness advantages of smaller genomes and lower cell replicating costs offset the potential fitness gains that would come from vitamin manufacture when the required nutrients are in short supply."

-

No Caption Provided

As is exemplified by Prochlorococcus, extensive gene loss exists even among Cyanobacteria, a group that otherwise contains some of the most complex bacteria on Earth. But the reconstruction of archaeal genomes provides the most compelling evidence for the dominance of genome reduction and simplification in nature, according to Eugene V. Koonin and Yuri Wolf, at the National Institutes of Health's National Center for Biotechnology Information. “The pattern of gene loss and gain in archaea is not trivial; there seems to have been some net gain at the base of each major archaeal branch that was invariably followed by substantial gene loss,” they note in the journal Bioessays (doi:10.1002/bies.201300037).

Scientist Giovannoni comments on the importance of “streamlining theory” to the BQH, explaining that it originally showed how gene loss works. He also notes that, although “some lost functions make interactions more complicated in ways predicted by the BQH, others enable cells to use resources more efficiently, without increasing interaction.”

5 Comments