Following an initial log phase, the cells bleb and enter a death phase before recovering and entering a second exponential phase . Second, Tilly et al  demonstrated that cells cultured without free GlcNAc, but supplemented with chitobiose, exhibit normal growth and reach high cell densities. Based on these results they hypothesized that the second exponential phase might be due to the import of chitobiose via a phosphotransferase system (PTS) encoded by three genes (BBB04, #see more randurls[1|1|,|CHEM1|]# BBB05 and BBB06) on circular plasmid 26 (cp26). Annotation of the genome sequence originally identified this group
of genes (celB, celC and celA) as a cellobiose (dimer subunit of cellulose) transport system. However, functional analysis of BBB04 (celB) by Tilly et al [10, 11] revealed that this group of genes is responsible for the import of chitobiose. Based on these findings they proposed renaming this set of genes, with BBB04 (celB), BBB05 (celC) and BBB06 (celA) now designated chbC, chbA and chbB, respectively . We have adopted this nomenclature for this communication. Finally, Tilly et al  demonstrated that a chbC mutant can be maintained in ticks and mice, and that the mutation of this gene does not affect transmission of spirochetes. While these results suggest that chbC is not essential
for virulence of B. burgdorferi, the studies were conducted in pathogen-free ticks and mice in a controlled laboratory environment. We hypothesize that chbC may still play an important Selleck CP673451 role for survival of spirochetes in a natural setting, as ticks are often infected with more than one pathogen  and chbC may be important for B. burgdorferi to compete
with other microorganisms to colonize the tick midgut. Therefore, this Loperamide study was conducted to further investigate the regulation of chbC. Alternative sigma factors are an important mechanism used by many bacteria to regulate gene expression, and can coordinate the expression of multiple genes needed to adapt to a variety of stresses . B. burgdorferi encounters differences in temperature, pH and nutrient availability as it cycles between vector and host. Substantial investigation has focused on the differential expression of genes key to colonization, survival, and transmission of spirochetes during its enzootic life cycle [14, 15]. Examination of the B. burgdorferi genome reveals this organism possesses only two genes that encode for alternative sigma factors, BB0771 (rpoS) and BB0450 (rpoN) . Studies have demonstrated that these two sigma factors regulate the expression of numerous genes in different environments, and are essential for colonization and survival in both the tick and mammal [17–19]. In this investigation we examine the role of RpoS and RpoN on biphasic growth, the utilization of chitobiose, and the expression of chbC in the absence of free GlcNAc.