Pathway Evolution and Modularity of Bacterial Stress Responses

Amoolya Singh, University of California, Berkeley

Background: To cope with environmentally adverse conditions, bacteria employ many ingenious mechanisms such as sporulation, chemotaxis, DNA uptake, and antibiotic synthesis. Although much is known about the genetics and biochemistry of these complex stress response networks, little is known about their evolution. We present preliminary evidence to explain the evolution of three candidate stress response pathways in bacteria: spore formation, chemotaxis, and development of genetic competence.

Methods: We use existing phylogenetic tools as well as novel algorithms and software for exhaustive comparative analysis of sequenced bacterial genomes.

Results: The “core” sporulation, chemotaxis, and competence pathways are highly conserved. In contrast, the points at which each pathway interfaces with other pathways, or with the outside environment, are less conserved. The competence phenotype appears to be older than sporulation in evolutionary age, which leads us to speculate that the ability to take up extracellular DNA may have once existed in all bacteria.

Conclusion: Stress response pathways have evolved in a modular fashion, with core functionality transferred intact from a common ancestor, and niche-specific functionality modified after speciation.

Abstract Author(s): Amoolya Singh, Denise M. Wolf, and Adam P. Arkin