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This Week in PLOS: Sep 16, 2014

By analyzing hundreds of individual microbial cells collected from the honeybee gut, a team from Yale University and the Bigelow Laboratory for Ocean Sciences was able to begin tallying up the genetic diversity that exists within two symbiotic microbial species called Gilliamella apicola and Snodgrassella alvi. As they report in PLOS Genetics, the researchers sorted more than 300 single bacterial cells found in midgut or ileum samples taken from 10 worker bees. Based on 16S ribosomal RNA sequences generated for 126 of the individual cells, combined with subsequent genome sequencing and assembly of G. apicola and S. alvi, the authors concluded that "despite minimal divergence at 16S rRNA genes, in situ diversification occurs within gut communities and generates bacterial lineages with distinct ecological niches."

Soil bacteria may take on the ability to act as endosymbionts to legume plants with the help of hyper-mutation processes prompted by horizontal gene transfer, according to a PLOS Biology study. A French team did whole-genome sequencing on nine soil microbes that had been coaxed to become nitrogen-fixing legume symbionts during the course of just a few hundred generations. Results of the analysis indicate that horizontal transfer of key symbiotic plasmids between soon-to-be symbiotic soil microbes coincides with the transfer of error-prone DNA polymerase enzymes that bump up the mutation rate of the microbes, increasing their genetic diversity.

Canadian and Lebanese researchers reporting in PLOS One present findings from a whole exome sequencing study of Usher syndrome. Using exome sequence profiles for 11 unrelated individuals from Lebanon or the Middle East with type I or type II Usher syndrome, the team tracked down new forms of truncating mutations in genes already implicated in the recessive, inherited conditions. "Our data highlight the genetic diversity of Usher syndrome in the Lebanese population," the study's authors say, "and the time and cost-effectiveness of [the] whole-exome sequencing approach for mutation analysis of genetically heterogeneous conditions caused by large genes."