2006 Annual Science Report
University of Washington Reporting | JUL 2005 – JUN 2006
Bacterial Tubulin and the Evolution of the Eukaryotic Cell; Sea Ice Bacteria
Our lab has continued to study the evolution of the tubulin-containing bacteria in the bacterial phylum, Verrucomicrobia. Recent research indicates Prosthecobacter, which contains homologs for alpha- and beta- tubulin, BtubA and BtubB, are unlikely to be the progenitors of the eukaryotic cell. Evidence for this comes from a comparative genomic study of their other proteins, only 10 of which produced high-scoring matches against a database of 347 eukaryotic signature proteins (Staley et al., 2005). The source of these genes in Prosthecobacter species is unknown but they likely came from an ancient horizontal gene transfer event. The genes have been cloned and expressed in E. coli and the resultant proteins produced protofilaments that, like eukaryotic microtubules have GTPase activity (Sontag et al., 2005). Our recent report indicates that Verrucomicrobium spinosum, a close relative of Prosthecobacter, which does not have tubulin genes, produces a unique bacterial FtsZ a divergent homolog of tubulins (Yee et al., submitted).
We have also proposed a model for the formation of desert varnish from the discovery of opal in varnish coatings (Perry et al., 2006). This model explains the hardness of desert varnish as well as chemical signatures incorporated into varnish from biological and non-biological sources.
More recently our lab research has focused on the Black Sea’s suboxic zone which is a model for early Earth environments as well as Europa. We reported that several other groups of the Planctomycetes phylum, in addition to anammox bacteria, reside at different redox positions in the suboxic zone (Kirkpatrick et al., 2006). Furthermore the Black Sea has unique bacteria involved in denitrification based upon their nirS and nirK genes (Oakley et al., in press).
Finally, the bacterium that, based on growth curves has the lowest recorded growth temperature for any organism (-12°C), was named Psychromonas ingrahamii (Auman et al., 2006).