Transcriptional p of B. burgdorferi containing a unique bosR allele identifies a putative oxidative stress regulon

Borrelia burgdorferi regulates gene expression in response to environmental conditions, including temperature, pH, redox potential, and host factors. B. burgdorferi encodes a PerR homologue designated BosR which presumably serves as a global regulator of genes involved in the oxidative stress response. Infectious B. burgdorferi strain B31 is resistant to oxidative stressors in vitro whereas our non-infectious isolate is sensitive due, in part, to a point mutation that converts an arginine to a lysine at residue 39 of BosR. Subsequent insertional inactivation of this bosRR39K allele (bosRR39K::kanR) restores resistance to oxidative stressors. These observations suggest that the B. burgdorferi non-infectious bosRR39K::kanR strain may transcribe genes that are also expressed in infectious B. burgdorferi cells, but are repressed in the bosRR39K background, thus explaining the different oxidative stress phenotypes observed between these isolates. To test this hypothesis, macroarray technology and quantitative RT-PCR was utilized to compare the transcriptional profiles from the isogenic bosRR39K and bosRR39K::kanR isolates. Array data indicated that 88 ORFs were significantly expressed in the absence of BosRR39K. Since most genes affected mapped to the chromosome, it is likely that these genes define an important physiologic response for B. burgdorferi. Included within the genes identified was the detoxification gene sodA as well as other loci not overtly linked to oxidative stress. These results suggest that a putative BosR regulon, as defined by the bosRR39K allele, is required to combat toxic oxidative intermediates, but may also be involved in adaptive strategies that are independent of reactive oxygen species. Keywords: genetic modification JS167, containing bosRR39K::kanR allele, and CHP100, containing bosRR39K allele, were labeled with P33 and hybridized to nylon membrane arrays. The arrays were spotted in duplicate and the experiment was performed in triplicate resulting in 6 data points for each ORF spotted.