Exobiology and Evolutionary Biology

Borrowing Biological Innovation: HGT in an Ancient Mariene Heterotroph (2)

PI: Janet Siefert

We propose a case study of how an ancient heterotrophic bacterium responds to its environment today and how those adaptations affect a current globally distributed population of related species. But more than that, this proposal seeks to understand how adaptive strategies of this specific bacterium might be extrapolated to the larger context of adaptive heterotrophy in an exobiological context. Therefore the research is designed to provide a better understanding of heterotrophy in the contact of metabolic lifestyles pivotal to early earth microbial colonization as well as one that might be exploited by biology extra terrestrially.

We utilize a keystone microbe, Bacillus coahuilensis, a heterotroph from a Mexican desert hydrologic system, rich in sulfide salts, poor in phosphorus, and part of an ancient marine ecosystem from 100 million years ago. Through genome sequence and analysis we know that this bacterium has undergone significant genome reduction while picking up important biological innovations from its neighbors that have allowed it to become a major constituent in this low phosphorus environment. This isolate provides a fortuitous opportunity. By using it’s genome in comparison with 5 globally dispersed but closely related relatives known to be integral to marine and saline ecologies, yet under differing phosphorus adaptive constraints, we can access the genome dynamics necessary to provide adaptive responses in geographic and biologically isolated populations.

Our work plan rests on investigating this unique set of closely related geographic isolates through rapid but accurate and cheap genome characterization of their genomes. We will use Solexa technology for genome acquisition. We will use B.coahuilensis as the scaffold on which to base the genomic characterization. Genetic inventory analysis of the genomes will be used to define the mobile gene pool (the horizontal gene transfer events – HGT) as well as the 'the bacterial IQ’ of each isolate (interactive/sensory elements). These results will be used to create analysis of the dynamics of each isolates’ genome. Genome dynamics will then be intercompared for each genome with its cognate geography, biogeochemistry, phylogenomic, and genetic history included in the analysis. Initially, this will allow a better understanding for the role that an essential element (phosphorus in this case) might play in the adaptive potential of a common heterotroph.

This research will be targeting results that will provide insight into long term evolutionary response. This information can be used to evaluate the potential for colonization of habitats where essential element constraint may impose evolutionary obstacles probable in early earth scenarios or extraterrestrial habitats. Additionally, this study contributes to two long standing questions in microbial evolution: the infinite mobility of bacteria and whether or not a bacteria species should be defined by what it does in its local environment.