coli [43]. Also, the induction of genes associated with starvation, i.e., a condition that could activate the lytic cycle of prophages [43], was confirmed in the expression analysis. Conclusion The involvement of several regulatory controls has complicated the interpretation of gene expression patterns and functions in Shewanella spp. Results from selleck the above etrA deletion mutant studies suggest a global regulatory role

for EtrA, but one which works in conjunction with other regulators to fine-tune the expression of key genes in anaerobic metabolic pathways in S. oneidensis strain MR-1. Besides confirming and clarifying previous reports on Fnr regulation, we also provide experimental evidence for a positive regulatory role of EtrA in the DMSO reduction pathway of strain MR-1. Furthermore, our whole-genome transcriptional profile shows the effects of EtrA on the expression of genes not previously evaluated (e.g. nqr, fdh-1, phage- and stress-related genes), and differences in the expression pattern of genes previously analyzed (e.g. cydAB and sdhC)[6, 12]. These

observations are consistent with results obtained by Gralnick et al. [4] suggesting a distinctive regulatory system, although very similar to Fnr in E. coli. A stringent sequence analysis of the regulatory region of the genes affected by the mutation suggest direct interaction of EtrA to those in the “”histone deacetylase activity Energy

metabolism”" category, while stress- and phage-related buy HSP990 genes are up-regulated indirectly as a consequence of a secondary perturbation. This and previous work taken together suggest that this regulator is more properly termed Fnr. Methods Bacterial strains and culture conditions The bacterial strains, plasmids, primers and, Galeterone probes used in this study are described in Table 4. S. oneidensis strain MR-1 and its mutant strains were grown in HEPES medium as described [44]. The medium was supplemented with 20 mM lactate and KNO3 was added as electron acceptor in concentrations specified below. Oxygen was removed from the medium by boiling and purging with helium [45]. Cultures of E. coli strain β2155 (auxotroph of diaminopimelic acid [DAP]) were grown in Luria-Bertani (LB) medium supplemented with 100 μg/ml of DAP at 37°C. S. oneidensis strain MR-1 was cultivated in aerobic LB medium at 30°C during the mutagenesis process. Antibiotics used for the selection of MR-1 transformants were added in the following concentrations: 25 μg/ml of kanamycin, 7.5 μg/ml of gentamycin, and 10 μg/ml of tetracycline. Vessels that received no inoculum or no KNO3 served as negative controls. Table 4 Bacterial strains, plasmids, primers and oligonucleotides used in this study.