Borrelia burgdorferi CheD Promotes Various Functions in Chemotaxis and the Pathogenic Life Cycle of the Spirochete

Abstract

b Borrelia burgdorferi possesses a sophisticated chemotaxis signaling system; however, the roles of the majority of the chemotaxis proteins in the infectious life cycle have not yet been demonstrated. Specifically, the role of CheD during host colonization has not been demonstrated in any bacterium. Here, we systematically characterized the B. burgdorferi CheD homolog using genetics and biochemical and mouse-tick-mouse infection cycle studies. Bacillus subtilis CheD plays an important role in chemotaxis by deamidation of methyl-accepting chemotaxis protein receptors (MCPs) and by increasing the receptor kinase activity or enhancing CheC phosphatase activity, thereby regulating the levels of the CheY response regulator. Our biochemical analysis indicates that B. burgdorferi CheD significantly enhances CheX phosphatase activity by specifically interacting with the phosphatase. Moreover, CheD specifically binds two of the six MCPs, indicating that CheD may also modulate the receptor proteins. Although the motility of the cheD mutant cells was indistinguishable from that of the wild-type cells, the mutant did exhibit reduced chemotaxis. Importantly, the mutant showed significantly reduced infectivity in C3H/HeN mice via needle inoculation. Mouse-tickmouse infection assays indicated that CheD is dispensable for acquisition or transmission of spirochetes; however, the viability of cheD mutants in ticks is marginally reduced compared to that of the wild-type or complemented cheD spirochetes. These data suggest that CheD plays an important role in the chemotaxis and pathogenesis of B. burgdorferi. We propose potential connections between CheD, CheX, and MCPs and discuss how these interactions play critical roles during the infectious life cycle of the spirochete.

Gene bb0318 Is Critical for the Oxidative Stress Response and Infectivity of Borrelia burgdorferi

“…3; Table 2). The ID 50 values for the wild-type and ⌬bb0318/pBSV2G bb0318 spirochetes identified in this experiment are slightly higher than those reported previously for the B31 A3 genetic background (28,44,46,47). Together, these data suggest that bb0318 promotes B. burgdorferi mammalian infectivity.…”

TheBorrelia burgdorferiCheY3 response regulator is essential for chemotaxis and completion of its natural infection cycle

“…In several species of pathogenic bacteria, the CheY response regulator has been shown to play an important role in chemotaxis, which is also needed for virulence (Butler and Camilli, ; McGee et al , ; Antunez‐Lamas et al , ; Lertsethtakarn et al , ). To date, only two studies have shown that chemotaxis – specifically involving the histidine kinase cheA2 and phosphatase enhancer cheD – is essential for the infectious life cycle of B. burgdorferi (Sze et al , ; Moon et al , ).…”

Borrelia burgdorferi CheY2 Is Dispensable for Chemotaxis or Motility but Crucial for the Infectious Life Cycle of the Spirochete

“…At least three independent assays were performed. The chemotactic swarming ability of individual bacterial colonies of each strain was determined by plating no more than 50 cells into a 95-mm by 15-mm petri dish containing semisolid P-BSK diluted as described above (12,13). Plates were incubated for 4 weeks, at which time colony diameters were measured.…”

“…2A). A modified swarm plate assay was also performed to more accurately assess the chemotactic behavior of individual bacteria (12,13). The swarm plate assay is a group event where millions of bacteria attempt to migrate from the initial site of inoculation (in a semisolid plate) as they respond to chemotactic materials and metabolize neighboring nutrients, resulting in a swarm ring.…”