Short Genome CommunicationsThe complete genome of the tetrachloroethene-respiring Epsilonproteobacterium Sulfurospirillum halorespirans

- The second genome from an organohalide-respiring Epsilonproteobacterium.
- The organohalide respiration region is nearly identical in both genomes.
- Differences observed in regulatory regions and the reductive dehalogenase gene.
- A unique vitamin B12 derivative is presumably also synthesized by S. halorespirans.
- The first organohalide-respiring bacterium with proteins for thiosulfate oxidation.

Sulfurospirillum halorespirans is a bacterium that couples the reductive dehalogenation of chlorinated ethenes to growth. This process is called organohalide respiration (OHR), which can be of importance for bioremediation. Here, we report the complete genome of S. halorespirans, the second one of an organohalide-respiring Epsilonproteobacterium after that of Sulfurospirillum multivorans. With both genomes at hand, we were able to ascertain that the genomic region encoding OHR proteins in Epsilonproteobacteria differs from that found in organohalide-respiring bacteria (OHRB) affiliated to other phyla and that the production of a unique cobamide, norpseudo-B12, might not be limited to the model organism S. multivorans. The OHR region is virtually identical in both organisms with differences only in the gene sequence of the key enzyme of OHR, the PCE reductive dehalogenase (PceA), and in regulatory regions. This is of interest, since the availability of natural, closely related variants opens an avenue to study the poorly understood OHRB, which withstand systematic genetic manipulation so far.