gingivalis [106] either, and so their substrate specificity cannot be assigned at present. In G. metallireducens, duplicate kup genes, predicted to encode low-affinity potassium/proton symporters, are found in one place (Gmet_0038 = GSU3342; Gmet_0039 = GSU2485, 29% and 31% identical to the E. coli protein [108]), apart from the kdpABCDE genes (Gmet_2433-Gmet_2437 = GSU2480-GSU2484, 38–49% identical

to ITF2357 clinical trial the homologs in E. coli [109, 110]) encoding an osmosensitive potassium-translocating ATPase complex. In G. sulfurreducens, one of these kup genes (GSU2485) is located 3′ of the kdp gene cluster, apparently under control of an osmosensitive riboswitch (GSU2484.1, sequence coordinates 2728254 to 2728393), and there is a third kup gene (GSU2350, 49% identity to E. coli) not found in other Geobacteraceae. G. sulfurreducens also has at least two

potassium/proton antiporters (GSU1203, 34% identical to CvrA of Vibrio parahaemolyticus [111]; GSU2759, 31% identical to KefB of E. coli [112]) and a sodium/proton antiporter complex (mrpABCDEFG GSU2344-GSU2338, 29–48% identical to the homologs in B. subtilis [113]) that are not found in G. metallireducens. Three mechanosensitive ion channels are common to the two species (Gmet_1942 = GSU1633; Gmet_2581 = GSU2316; and Gmet_2522 = GSU2794); two more are unique to G. sulfurreducens (GSU1557; GSU1723). Thus, control of monovalent cation homeostasis appears to be more complex in G. sulfurreducens. Several heavy metal efflux pumps are conserved between the two species, but their substrate specificity is uncertain. Transporters present GDC-0449 research buy in G. sulfurreducens but not G. metallireducens include that for uracil (GSU0932, 48% identical to the Bacillus caldolyticus protein [114]). Transporters present in G. metallireducens but not G. sulfurreducens include those for nitrate/nitrite

(Gmet_0333-Gmet_0334) and chromate (Gmet_2732-Gmet_2731), which are each present as two paralogous genes rather than gene fusions such as their homologs that have been characterized in other bacteria [36, 115]. Signalling, chemotaxis and Celecoxib global regulation G. metallireducens possesses orthologs of the six sigma factors of RNA polymerase identified in G. sulfurreducens (Table 3), as well as a seventh factor (Gmet_2792) not found in other Geobacteraceae, related to the extracytoplasmic sigma-Z factor of B. subtilis [116]. Intriguingly, a particular anti-anti-sigma factor gene is frameshifted in both genomes: GSU1427 has frameshifts in the phosphatase Stem Cells inhibitor domain, resulting in an in-frame protein, whereas the homologous Gmet_1229 is shifted out of frame in the kinase domain. These differences imply that global regulatory networks may be different in the two species. Table 3 Sigma factors of G. metallireducens and G. sulfurreducens. Locus Tag Annotation G. metallireducens gene G.