metallireducens genome (Additional files 7,8,9: Figures S3, S4 and S5, Additional file 5: Table S4) may be recognized by different combinations of IHF/HU proteins. A fourth set found in G. metallireducens (Additional file 15: Figure S6, Additional file 5: Table S4) is similar to multicopy sequences in many other genomes. Two transposons (ISGme8 and ISGme9) were found inserted near putative IHF/HU-binding sites of Class 1 (Additional file 5: Table S4). No such putative global regulatory sequence elements were identified in G. sulfurreducens. CYT387 in vivo However, pirin, a Fe(II)-binding protein that
associates with DNA in eukaryotic nuclei [118, 119], is present in G. sulfurreducens as GSU0825, but in G. metallireducens only as a frameshifted fragment, Gmet_3471. These genetic differences indicate that the proteins that decorate and bend the chromosome are very different Selleck VX-680 in the two species. Table 4 Integration host factor (IHF) and histone-like (HU) genes of G. metallireducens and G. sulfurreducens. Locus Tag G. metallireducens gene G. sulfurreducens gene
ihfA-1 Gmet_1417 GSU1521 ihfA-2 none GSU2120 ihfA-3 Gmet_3057 none ihfA-4 Gmet_3056* none ihfB-1 Gmet_1833 GSU1746 ihfB-2 Gmet_0868 GSU2602 hup-1 Gmet_0355 GSU3132 hup-2 Gmet_1608 none *Gmet_3056 is frameshifted near the N-terminus, but may be expressed from an internal start codon. The functions and associations of the various IHF alpha (ihfA), IHF beta (ihfB), and HU (hup) genes are yet unknown, as is their correspondence to any of the predicted regulatory sites illustrated in Figures S3, S4, S5, and S6. Although no quorum sensing through N-acylhomoserine lactones (autoinducers) Selleck Enzalutamide has ever been demonstrated for any Geobacteraceae, this kind of signalling may be possible for G. metallireducens because it possesses
a LuxR family transcriptional regulator with an autoinducer-binding domain (Gmet_1513), and two divergently transcribed genes with weak sequence similarity to autoinducer synthetases (Gmet_2037 and Gmet_2038). Both Gmet_2037 and Gmet_2038 have atypically low G+C content (Additional file 1: Table S1) and may have been recently acquired by G. metallireducens. The presence of a conserved nucleotide sequence on the 5′ side of Gmet_2037 and in 15 other locations on the chromosome (Additional file 16: Figure S7, Additional file 5: Table S4) suggests that Gmet_2037 may be an unusual autoinducer LDC000067 synthetase that is regulated by a riboswitch rather than an autoinducer-binding protein. This conserved sequence is also found on the 5′ side of many genes (frequently c-type cytochromes) in the genomes of G. sulfurreducens, G. uraniireducens, and P. propionicus, and overlaps with predicted cyclic diguanylate-responsive riboswitches . The genomes of G. metallireducens and G. sulfurreducens differ in several other aspects of regulation. Nine pairs of potential toxins and antitoxins were identified in the G.