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

Abstract

A greater understanding of the molecular mechanisms that Borrelia burgdorferi uses to survive during mammalian infection is critical for the development of novel diagnostic and therapeutic tools to improve the clinical management of Lyme disease. By use of an in vivo expression technology (IVET)-based approach to identify B. burgdorferi genes expressed in vivo, we discovered the bb0318 gene, which is thought to encode the ATPase component of a putative riboflavin ABC transport system. Riboflavin is a critical metabolite enabling all organisms to maintain redox homeostasis. B. burgdorferi appears to lack the metabolic capacity for de novo synthesis of riboflavin and so likely relies on scavenging riboflavin from the host environment. In this study, we sought to investigate the role of bb0318 in B. burgdorferi pathogenesis. No in vitro growth defect was observed for the ⌬bb0318 clone. However, the mutant spirochetes displayed reduced levels of survival when exposed to exogenous hydrogen peroxide or murine macrophages. Spirochetes lacking bb0318 were found to have a 100-fold-higher 50% infectious dose than spirochetes containing bb0318. In addition, at a high inoculum dose, bb0318 was found to be important for effective spirochete dissemination to deep tissues for as long as 3 weeks postinoculation and to be critical for B. burgdorferi infection of mouse hearts. Together, these data implicate bb0318 in the oxidative stress response of B. burgdorferi and indicate the contribution of bb0318 to B. burgdorferi mammalian infectivity.

Blood treatment of Lyme borreliae demonstrates the mechanism of CspZ ‐mediated complement evasion to promote systemic infection in vertebrate hosts

“…Subcutaneous needle infection of spirochetes with the dose close to ID 50 (the dose that infects 50% of animals) often reveals subtle in vivo phenotypes conferred by spirochete genes that are expressed in hosts (Blevins, Hagman, & Norgard, ; Hyde et al, ; Seshu et al, ; Shi, Xu, Seemanaplli, McShan, & Liang, ; Weening et al, ). We thus introduced 10 3 cells of WT strain B31‐A3 or B31‐A3Δ cspZ ‐V into BALB/c mice (the ID 50 of strain B31‐A3 is ~10 3 cells; Showman, Aranjuez, Adams, & Jewett, ; Tilly et al, ). We then used quantitative PCR (qPCR) to quantify spirochete burdens in the bloodstream and tissues.…”

Borrelia burgdorferi bbk13 Is Critical for Spirochete Population Expansion in the Skin during Early Infection

“…The primary goal of this study was to identify B. burgdorferi genes on lp36 that contribute to disseminated infection, which was initially screened for by the reisolation of spirochetes from the tissues of mice at 3 weeks postinoculation. Typically, the reisolation assay is scored by microscopy analysis for the presence or absence of spirochetes following incubation of tissues in BSKII medium for up to 2 weeks (39)(40)(41)(42). This method has been sufficient to detect strong loss of infectivity phenotypes (41) but is not likely to identify subtle phenotypes resulting from reduced numbers, rather than the complete absence, of spirochetes at distal tissues.…”

“…This may suggest that the members of this protein family are not direct virulence determinants. B. burgdorferi, however, is a unique bacterial pathogen in that it lacks classical virulence factors and physiological functions that contribute to survival mechanisms that have been shown to be significant components of B. burgdorferi infectivity (39,40,42,44,45).…”

A high-throughput genetic screen identifies previously uncharacterized Borrelia burgdorferi genes important for resistance against reactive oxygen and nitrogen species

“…Three genes ( bb0017 , bb0412 , and bb0631 ) had overall frequency ratios < 0.33 in both the H 2 O 2 and TBHP screens, and all three encode predicted inner membrane proteins. The other genes with overall frequency ratios < 0.33 after TBHP treatment were spo0J , encoding a chromosome segregation protein, and bb0317 , which encodes the permease subunit of a riboflavin ABC transporter previously shown to be involved in H 2 O 2 resistance (Table 1) [23]. The H 2 O 2 screen identified more genes than the TBHP screen, and the strongest phenotypes were for Tn mutants with insertions in genes encoding predicted transmembrane proteins or transporters: bb0164 , bb0473 , bb0202 , and chbB (Table 1).…”

“…Genes known to be involved in ROS resistance in B . burgdorferi include a manganese-dependent superoxide dismutase (SodA), a manganese transporter (BmtA), and a riboflavin ATP-binding cassette transport system [21–23]. BicA (also called Dps or NapA) is involved in metal homeostasis, and bicA mutants are actually more resistant to oxidative stress under metal replete conditions [19].…”