Here at Bioscience:
For example, many microbial plankton species have jettisoned the genes needed to produce one or more essential vitamins and instead outsource them from or exchange them with other cells in their environment, says Stephen J. Giovannoni, from Oregon State University, in Corvallis. He argues that “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.”
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).
So all those genes just happened by accident and evolution consists in their loss?
Eric Anderson, Barry Arrington, where are you anyway?
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