Therefore, we attempted to construct an in-frame deletion and several gene replacement mutations of nla6S that would not disrupt transcription of genes downstream of nla6S. However, we were unable to construct any of these strains, which is consistent with the idea that Nla6S is important for growth. In summary, our work suggests Nla6S is the founding member of a
new family of HKs found in fruiting members of the Cystobacterineae suborder of the myxobacteria. The goal of future work will be to determine whether Nla6S-like HKs play crucial roles in fruiting body development and to determine whether their mechanisms of action are similar to well-characterized HKs. Zaara Sarwar was OSI-906 manufacturer funded in part by an
International Fellowship from the American Association of University Women (AAUW). This work was supported by National Science Foundation Grant IOS-0950976 to A.G. Please note: Wiley-Blackwell is not responsible for the content or functionality of any supporting materials supplied by the authors. Any queries (other than missing material) should be directed to the corresponding author for the article. “
“SoxS,MarA, and Rob are homologous transcriptional activators of numerous superoxide- and antibiotic resistance genes but many of the regulated genes are yet to be characterized. In this study, microarrays and RT-PCR analysis were used to show the overexpression of the ompN porin and its upstream gene, ydbK, in an Escherichia coli multidrug-resistant mutant and in a strain constitutive for SoxS. However, transcriptional 17-AAG fusions revealed that SoxS 3-oxoacyl-(acyl-carrier-protein) reductase (not MarA or Rob) only activated the ydbK promoter but not the ompN upstream region. RT-PCR experiments showed the overexpression of a combined ydbK–ompN transcript in the SoxS-overexpressing strain. Surprisingly, a bioinformatic approach revealed no soxbox upstream of the ydbK
promoter. Thus, the ydbK and ompN genes are coexpressed in an operon and are likely activated by SoxS indirectly. It is known that YdbK is involved in superoxide resistance. Thus, individual ompN and ydbK mutants were tested for superoxide susceptibility. Nonetheless, only the ydbK mutant was susceptible to paraquat, a superoxide generator. These mutants, as well as an OmpN-overproducing strain, were further tested for antibiotic resistance. No significant decreased susceptibility was observed. Thus, ydbK plays a role in superoxide resistance but no role for either gene is found in resistance to the antibiotics tested. MarA, SoxS, and Rob of Escherichia coli are highly homologous members of the AraC/XylS family of positive regulators. Overproduction of MarA and SoxS and post-translational activation of Rob are needed to exert their regulatory role (Gallegos et al., 1997). MarA transcription is controlled by the repressor function of MarR (encoded within the marRAB operon; Cohen et al.