Why Sequence Two Caulobacter Species?

As ubiquitous inhabitants of aquatic ecosystems, particularly nutrient-poor ("oligotrophic") habitats, Caulobacters may be exploitable for bioremediation applications. To gain further insight into the biological and environmental activities of oligotrophs in general, and Caulobacters in particular, researchers would like to compare the genomes of species from each of the major Caulobacter habitats. The genomic DNA sequence of Caulobacter crescentus CB15, a surface freshwater strain, has already been published. This project will obtain the genomic DNA sequences of Maricaulis washingtonensis, from the marine branch of the Caulobacter family, and Caulobacter strain K31, a groundwater isolate.

Each of these related species produces adhesive stalks that enhance nutrient uptake and biofilm formation. The polar stalk is a key appendage in the Caulobacter life cycle, in which the stalked cell acts as a stem cell to generate a motile "swarmer" cell. This fascinating, obligatory cell cycle has made Caulobacter crescentus one of the dominant prokaryotic model systems for studying molecular mechanisms of cell-cycle control and cellular differentiation. Comparative analysis of the new genome sequences will not only provide great insight into genomic and physiological diversity in the Caulobacter group, but will also aid researchers exploring the prokaryotic cell cycle and morphogenetic regulatory genes and systems.

Finally, this project will expand the potential of the Caulobacters for practical applications. Maricaulis washingtonensis is salt-tolerant, surprisingly thermotolerant, resistant to high levels of mercury, and able to grow anaerobically. Strain K31 is adapted to a low-oxygen groundwater habitat, and its chlorophenol resistance may have relevance to groundwater bioremediation. Deeper understanding of the genomes and genetics of these organisms is a prerequisite for possibly engineering Caulobacter strains for aquatic applications, including remediation of contaminated groundwater.

CSP project participants: Craig Stephens (proposer, Santa Clara Univ.) and Patrick Viollier (Case Western Reserve Univ.).

Genome Portal Sites: Caulobacter sp. K31 and Maricaulis maris MCS10