| Borrelia burgdorferi is the causative agent of Lyme disease that exhibits a complex lifecycle involving the arthropod tick vector, Ixodes scapularis, and the white-footed mouse reservoir. Humans are accidental hosts. The tick bloodmeal and transmission to the mammalian host results in an increase of cellular respiration and reactive oxygen species (ROS) requiring adaptation by B. burgdorferi. In response to these and other host signals, B. burgdorferi alters its gene expression and antigenic profile. Specifically, B. burgdorferi adapts to changes in temperature and pH, which are known to vary between the tick-vector and mammalian host. In regard to the B. burgdorferi response to oxidative stress, very little is known. We, along with others, identified a global regulator designated BosR that presumably regulates the oxidative stress response. We hypothesize that BosR would be required to adapt to redox environments encountered within the vectors and mammalian hosts. As such, we have evaluated the global transcription profile of different bosR alleles and the effect of dissolved gases, oxygen and CO 2, on specific borrelial genes important for regulation and host-adaptation. Initially, macroarray technology was utilized to analyze the transcriptional profile of oxidative stress resistant B. burgdorferi isolates with the bosR (MSK5) or bosRR39K::kan R (JS167) allele relative to oxidative stress sensitive bosRR39K strain. 41 ORFs were significantly expressed in oxidative resistant strains, MSK5 and JS167, with predicted functions in metabolism, host-adaptation and resolving oxidative toxic intermediates. Subsequently, the response of BosR and other borrelial genes involved in the oxidative stress response and host-adaptation were found to be responsive to changing dissolved gas levels in vitro, in some instances in a RpoS-dependent manner, which may serve as a mechanism exploited by B. burgdorferi to quickly modulate gene expression and adapt to the disparate environments it can occupy. In these studies, infectious B. burgdorferi was grown under anaerobic (5% CO2, 3% H, 0.087 PPM dO2) and microaerophilic (1% CO2, 3.8 PPM dO2) conditions resulting in the increased synthesis of several borrelial lipoproteins, proteins to combat oxidative stress, as well as, regulatory proteins in the anaerobically grown samples. |
