\u3cem\u3eBorrelia burgdorferi\u3c/em\u3e RevA Significantly Affects Pathogenicity and Host Response in the Mouse Model of Lyme Disease

The Lyme disease spirochete, Borrelia burgdorferi, expresses RevA and numerous outer surface lipoproteins during mammalian infection. As an adhesin that promotes bacterial interaction with fibronectin, RevA is poised to interact with the extracellular matrix of the host. To further define the role(s) of RevA during mammalian infection, we created a mutant that is unable to produce RevA. The mutant was still infectious to mice, although it was significantly less well able to infect cardiac tissues. Complementation of the mutant with a wild-type revA gene restored heart infectivity to wild-type levels. Additionally, revA mutants led to increased evidence of arthritis, with increased fibrotic collagen deposition in tibiotarsal joints. The mutants also induced increased levels of the chemokine CCL2, a monocyte chemoattractant, in serum, and this increase was abolished in the complemented strain. Therefore, while revA is not absolutely essential for infection, deletion of revA had distinct effects on dissemination, arthritis severity, and host response

Analysis of Environmental Bacteria Capable of Utilizing Reduced Phosphorus Compounds

ABSTRACT\ud ANALYSIS OF ENVIRONMENTAL BACTERIA CAPABLE\ud OF UTILIZING REDUCED PHOSPHORUS COMPOUNDS\ud by\ud Brandee L. Stone\ud Master of Science in Biological Sciences\ud California State University, Chico\ud Summer 2011\ud Although bacterial metabolic pathways to oxidize the reduced\ud phosphorus compounds hypophosphite and phosphite have been characterized,\ud bacterial reduced phosphorus oxidation in the environment and the impact of this\ud activity on P biogeochemistry has largely been overlooked. In this study, I\ud attempted to answer two of the basic questions in this field: (1) how abundant are\ud culturable reduced phosphorus oxidizing bacteria in a variety of soils and\ud sediments; and (2) how common are previously characterized bacterial pathways\ud to oxidize hypophosphite and phosphite. To determine how common the ability is\ud in the environment to oxidize hypophosphite and phosphite, I used a 5-tube most\ud probable number method to estimate the concentrations of viable hypophosphite\ud and phosphite oxidizing bacteria from 12 natural aquatic and terrestrial\ud environments in northern California. The percent of total culturable bacterial\ud concentrations able to use these reduced phosphorus compounds as a sole\ud source of phosphorus were: hypophosphite, 7-100%; phosphite, 10-67%; and\ud aminoethylphosphonate, 34-270%. Relatively high concentrations of reduced\ud phosphorus oxidizing bacteria were found in both pristine sites and sites with\ud urban and agricultural disturbance, and did not correlate with likely\ud concentrations of reduced phosphorus compounds. Concentrations of reduced\ud phosphorus oxidizing bacteria in anoxic sediments were similar to those in soils. I\ud isolated 19 bacteria able to grow on reduced phosphorus sources, including\ud Proteobacteria (Pseudomonas, Acinetobacter, Variovorax, and Bradyrhizobium),\ud and two actinobacteria, suggesting a far wider phylogenetic occurrence of\ud reduced phosphorus oxidation than previously known. To detect pathways\ud responsible for reduced phosphorus oxidation, I characterized one gene\ud responsible for hypophosphite oxidation, htxA, and one gene for phosphite\ud oxidation, ptxD, in these isolates. These genes have previously only been\ud described for a few closely related taxa. I found all isolates possessed a ptxD\ud ortholog, though not all were capable of growth on phosphite. Partial sequence\ud analysis showed ptxD was 100% identical to one previously characterized.\ud Thirteen isolates possessed htxA, though two were not capable of growth on\ud hypophosphite. My results indicate reduced phosphorus oxidizing bacteria and\ud the genes required for the oxidation of hypophosphite and phosphite are\ud abundant in the environment, and provide strong evidence for the importance of\ud bacterial phosphorus oxidation in nature.CSU, Chic