Extremophils in your gut

Scientists from the Japanese Agency for Marine-Earth Science and Technology publish their findings online today in the Proceedings of the National Academy of Sciences.

The helicobacter, which causes ulcers, and campylobacter, which causes food-borne diarrhoea, share many similar genes
with two harmless proteobacteria -- sulfurovum and nitratiruptor -- found deep on the ocean bed

They grow in extreme environments.

They also have few DNA repair genes, allowing frequent mutations to occur -- they can therefore adapt quickly to changing conditions and to the immune response of a symbiotic host.

Such characteristics suggest that these pathogens evolved from a deep-sea ancestor, and acquired further virulence factors while living in symbiosis with humans

Evolution of Symbiotic Bacteria in the Distal Human Intestine

http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0050156

The adult human intestine contains trillions of bacteria, representing hundreds of species and thousands of subspecies.

Little is previous known about the selective pressures that have shaped and are shaping this community's component species, which are dominated by members of the Bacteroidetes and Firmicutes divisions.

We sequenced the genomes of two members of the normal distal human gut microbiota, Bacteroides vulgatus and Bacteroides distasonis, and by comparison with the few other sequenced gut and non-gut Bacteroidetes, analyzed their niche and habitat adaptations.

The results show that lateral gene transfer, mobile elements, and gene amplification have played important roles in affecting the ability of gut-dwelling Bacteroidetes to vary their cell surface, sense their environment, and harvest nutrients in the distal intestine.

These processes drive the adaptation of Bacteroidetes to the distal gut environment.