3Cl-4OH-BA; 3-chloro-4-hydroxybenzoate, o-BP; ortho-bromophenol, 3,5-DCP; 3,5-dichlorophenol. Nitrogen fixation After see more noting multiple genes for nitrogenase in the D. hafniense DCB-2 genome, we tested the strain for its ability to grow on N2 in a medium free of fixed nitrogen (Table 2). The strain readily grew Selleck Fosbretabulin under these conditions and formed cell aggregates tightly bound to the inner surface of a culture bottle. No growth was detected when argon gas instead of N2 was used. N2 fixation in bacteria is primarily catalyzed by the molybdenum-dependent nitrogenase (Mo-nitrogenase) which is composed of a MoFe nitrogenase complex, NifDK, and a nitrogenase Fe protein, NifH. Four putative

nif operons were identified in the DCB-2 genome with different sets of associated genes, (Nif operon I-IV, Figure 6) (Dhaf_1047-1059, Dhaf_1350-1360, Dhaf_1537-1545, and Dhaf_1810-1818). Phylogenetic analysis of

28 NifH sequences from selected archaeal and bacterial species that contain multiple nifH genes in each genome indicated that Dhaf_1049 belongs to the most conserved group which has at least one nifH gene from each species (Figure 7). The operon containing Dhaf_1049 (Nif operon I) harbors, in addition to nifDK, genes required for MoFe cofactor biosynthesis and two upstream LGX818 mouse genes for nitrogen regulatory protein PII, an arrangement similarly found in methanogenic Archaea [58]. Other nifH genes of D. hafniense DCB-2 (Dhaf_1815 and Dhaf_1353), are distantly related to each other but have close orthologs in Clostridium

kluyveri DSM 555 and Geobacter sp. FRC-32, respectively. We observed that the nifH gene and other components of the Nif operon IV including a gene encoding Megestrol Acetate an AraC-type transcriptional regulator (Dhaf_1818) were highly upregulated when cells were exposed to oxygen, suggesting that the operon plays a role in cellular defensive/adaptation mechanisms under oxidative stresses. NifK and NifD encoded by Dhaf_1354-1355 of Nif operon II contain VnfN- and VnfE-like domains that are components of vanadium nitrogenases (V-nitrogenase) of Azotobacter vinelandii and Anabaena variabilis [59, 60]. These proteins may serve as scaffolding proteins for FeV-cofactor synthesis. V-nitrogenases enable cells to fix N2 in the presence of vanadium and in the absence of molybdenum. We observed that D. hafniense DCB-2 could also fix N2 when grown with vanadium in Mo-free medium, a result we also saw in three other dehalorespiring organisms; D. chlororespirans, D. frappieri PCP-1, and D. frappieri DP7 (data not shown). Thus, Nif operon II is implicated in V-dependent N2 fixation in D. hafniense DCB-2. Microarray studies using different anaerobic respiration conditions indicated that all the nif operons in DCB-2 were expressed even when NH4 + was used as a major N source.