The most rapidly changing individual functions in the Shewanellae were related to "breathing" metals and sensing mechanisms, which represent the first line of adaptive response to different environmental conditions. Shewanella bacteria live in environments that range from deep subsurface sandstone to marine sediment and from freshwater to saltwater. All but one of the strains was able to reduce several metals and metalloids. That one exception had undertaken a unique evolution resulting in an inability to exploit strictly anaerobic habitats.
"Let's say you have a strain of Shewanella that is unable to convert uranium dissolved in contaminated groundwater to a form incapable of dissolving in water," explained Konstantinidis. "If you put that strain in an environment that contains high concentrations of uranium, that microbe is likely to acquire the genes that accept uranium from a nearby strain, in turn preventing uranium from spreading as the groundwater flows."
This adaptability of bacteria is remarkable, but requires further study in the bioremediation arena, since it frequently underlies the emergence of new bacterial strains. Konstantinidis' team at Georgia Tech is currently investigating communities of these Shewanella strains in their natural environments to advance understanding of the influence of the environment on the evolution of the bacterial genome and identify the key genes in the genome that respond to specific environmental stimuli or conditions, such as the presence of heavy metals.
Ongoing studies should broaden the researchers' understanding of the relationship between genotype, phenotype, environment and evolution, he said.
|Contact: Abby Vogel|
Georgia Institute of Technology Research News