Since it has been proposed that the role of these rarely expressed alternative sigma factors are related to host-specific conditions then the unique profile elicited by increased ssd expression demonstrates a role for Ssd in modulation of septum formation and cell division as part of the global adaptive strategy for survival in the host. Conclusion In order to survive, M. tuberculosis must adapt to a stressful intracellular environment, which requires a global alternative adaptive response. Among the adaptive responses, the Dos-response is the best characterized, and has been selleck inhibitor associated with virulence. In addition to the Dos-regulon, other adaptive responses
including regulation of cell division and cell cycle progression are involved in establishing a non-replicating persistent lifestyle. While all the components involved in regulation and metabolic adaptation regarding cessation of growth and non-replicating Screening Library research buy persistence in M. tuberculosis selleck chemicals llc have yet
to be defined, the results presented here substantiate Ssd as a component of a global regulatory mechanism that promotes a shift into an altered metabolic state. This is the first report providing evidence linking a regulatory element of septum formation with an adaptive response associated with virulence and non-replicating persistence in M. tuberculosis. Clearly, further experimentation is required to elucidate the precise mechanism of action of Ssd in regulating septum formation and its role in adaptive metabolism during stress. Methods Bioinformatic analysis To identify putative MinD or septum site determining proteins encoded in M. tuberculosis, a MinD and a Ssd consensus-model sequences Rho was created from alignments of protein sequences annotated as MinD (OMA Group 78690) or as septum site determining proteins (OMA Group 73337) from a variety of bacterial species. The resulting MinD and Ssd consensus model sequences were then used to search and identify proteins encoded in the M. tuberculosis genome. In all BLAST searches, the percent
identity and score were optimized. Molecular biology and bacterial strains The ssd (rv3660c) open reading frame was PCR amplified from M. tuberculosis H37Rv genomic DNA using AccuPrime pfx DNA polymerase (Invitrogen) with primer sequences 5′-ctgaccgatccgggg and 3′-gtgccatcccgccgt engineered with asymmetric NdeI and HindIII restriction sites respectively, to facilitate cloning into the extrachromosomal mycobacterial vector pVV16. Transformation into M. tuberculosis H37Rv and selection were performed as previously described [17]. For all experiments M. tuberculosis merodiploid and the rv3660c mutant strain (Tn mutant E150, provided by TBVTRM contract: HHSN266200400091c) were cultivated at 37°C in Middlebrook 7H9 liquid medium supplemented with 0.2% glycerol, 10% OADC (oleic acid, albumin, dextrose and catalase enrichment), and 0.