PHOTOMICROGRAPH of strain CJ2. Note coccoid shape of 2 dividing cells, rough surface texture from extra-cellular polysaccharide, absence of flagella, and size (1-2 um) visible in scanning electron microscopy

Polaromonas naphthalenivorans strain CJ2, ATCC BAA-779; DSM 15660 is shown to be responsible for metabolizing naphthalene in situ, in sediment in a contaminated field site.

Organic environmental pollutants are among the major concerns of the Department of Energy. Of crucial significance to DOE is understanding the ecological fitness traits of microorganisms that allow them to survive in field sites and be active in situ. One class of important contaminants is polycyclic aromatic hydrocarbons (PAHs), whose simplest member is naphthalene.

PAHs are proven carcinogens commonly found at DOE's energy production sites. Polaromonas naphthalenivorans strain CJ2 grows on naphthalene, favors in situ temperatures, accelerates naphthalene metabolism when inoculated into the sediment microbial community, and is host to a naphthalene dioxygenase allele previously shown to be expressed (as mRNA) in situ in sediment.

Strain CJ2 features taxonomic and physiological novelty and synergistic links to other bacteria. To our knowledge, only one member of the Comamonadaceae has been sequenced to date. This is "beta-bacterium strain JS666" that grows on the chlorinated pollutant cis -dichloroethene . The 16S rRNA gene sequences of strain CJ2, strain JS666, and Polaromonas vacuolata indicate close evolutionary relatedness. But phenotypic traits (motility, colony type on plates, temperature optima, catabolic breadth, ability to accumulate physiological carbon storage reserves, etc.) indicate immense diversity. Strain CJ2's naphthalene catabolic gene cluster is an interesting variant on the nag catabolic cluster recently described in the beta proteobacterioum, Ralstonia sp. strain U2. We seek to discover if this catabolic gene cluster is the cause of strain CJ2's ecological success. Alternatively, genetic features unlinked to catabolism may be essential for ecological success. An underlying motivation for obtaining genomic sequence of strain CJ2 is to weave together a comparative scheme of evolutionary relatedness, physiological versatility, ecological fitness, and horizontal gene transfer.

REFERENCES

C. Jeon , W. Park, P. Padmanabhan, C. DeRito, J. R. Snape, E. L. Madsen. 2003. Discovery of a novel bacterium, with distinctive dioxygenase, that is responsible for in situ biodegradation in contaminated sediment. Proc. Nat. Acad. Sci. USA 100:13591-13596.