Journal
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
Volume 72, Issue 8, Pages 5486-5491Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/AEM.00855-06
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Multiple reductive dehalogenase (RDase), hydrogenase (H(2)ase), and other respiration-associated (RA) oxidoreductase genes have been identified in cultured representatives of Dehalococcoides. Although their products are likely to play key roles in the environmentally important process of reductive dechlorination, very little information is available about their regulation and specific functions. Here we show increased expression and temporal variability in the expression of five RDase genes and in the expression of genes for a putative formate dehydrogenase (Fdh) and two H(2)ases, including a periplasmic [Ni/Fe] H(2)ase (Hup) and a cytoplasmic [Fe] H(2)ase (Vhu). mRNA transcripts extracted from tetrachloroethene-dechlorinating mixed cultures corresponding to Fdh, the H(2)ase Hup, and the RDase targets TceA and DET0162 were expressed most highly, with average levels 34 (+/- 7.5)-, 23 (+/- 6.7)-, 16 (+/- 3.3)-, and 13 (+/- 3.3)-fold higher, respectively, than that for RNA polymerase (RpoB). H(2)ase and RA transcripts reached their respective expression maxima within the first 2 h after feeding. RDase transcripts, however, were most highly expressed after 3 h and exhibited greater temporal variability than other transcripts. Comparison with D. ethenogenes strain 195 pure culture expression levels indicated that RDase DET1545 was more highly expressed in mixed cultures, where, on average, its transcript level was sixfold higher than that of RpoB. While the specific functions of several of these gene products remain elusive, the high expression levels and temporal variability reported here suggest that these groups of enzymes are metabolically important for the respiration of chlorinated ethenes in mixed cultures containing Dehalococcoides.
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