Seven annotated monocation/proton antiporters and twelve symporters were identified. The presence of multi-copy transporters such as ten sodium/sulfate symporters, eight ABC-type cobalamin/Fe(III)-siderophores transport
systems, three dctPQM TRAP dicarboxylate transporters, three Fe(II) transporters, and four L-lactate permeases suggests the importance of their substrates in cellular metabolism. Conclusions The genomic analysis of D. hafniense DCB-2 described in this paper suggests that the strain is highly self-sufficient FHPI datasheet in various aspects of metabolism and adaptation. D. hafniense Y51 and DCB-2 contain the largest Mocetinostat chemical structure number of molybdopterin oxidoreductase genes known, which suggests that they may impart to these organisms their anaerobic AZD5363 ic50 respiration and reduction versatilities. Only a few genes among the 53 Mo-oxidoreductase genes in DCB-2 were identified with a predictable function. Potential electron acceptors used by these enzymes could
include, among others, metal ions. Unlike the Gram-negative metal reducers such as S. oneidensis MR-1- and G. sulfurreducens, in which multi-heme cytochrome c proteins were shown to reduce metals, D. hafniense DCB-2 contains a very limited number of cytochrome c genes. This fact, along with its rich pool of Mo-oxidoreductases, would make this strain a convenient model system for the study of metal reduction in Gram-positive bacteria. Our transcriptomic studies have identified candidate genes for the reduction of Fe(III), Se(VI), and U(VI), suggesting targets for mutant analysis to delineate function. The presence of 19 fumarate reductase paralogs, presumably functioning as dehydrogenase, oxidase, or reductase of unidentified substrates, could also enrich the cell’s repertoire of reductive capacities. In addition, D. hafniense DCB-2 is likely
to possess enzymes or enzyme systems that are novel, as seen in the genetic components for dissimilatory nitrate reduction and nitrogen fixation. The cell’s ability to respire nitrate, in the absence of the conventional Nar system, could lead to the elucidation of additional function of the Nap nitrate reductase or to the identification of an alternative system for respiratory nitrate reduction. Similarly, the presence of three additional Sclareol nifHDK homologs, all associated with transporter genes, and their different induction patterns indicate that these operons may have functions other than conventional nitrogen fixation. Many lines of evidence support the ability of D. hafniense DCB-2 to cope with changes of growth conditions and environmental stresses. These include the possession of genes for 59 two-component signal transduction systems, 41 methyl-accepting chemotaxis proteins, 43 RNA polymerase sigma factors, about 730 transporter proteins, and more than 300 transcriptional regulators.