DNA Damage and Reactive Nitrogen Species are Barriers to Vibrio cholerae Colonization of the Infant Mouse Intestine

Ingested Vibrio cholerae pass through the stomach and colonize the small intestines of its host. Here, we show that V. cholerae requires at least two types of DNA repair systems to efficiently compete for colonization of the infant mouse intestine. These results show that V. cholerae experiences increased DNA damage in the murine gastrointestinal tract. Agreeing with this, we show that passage through the murine gut increases the mutation frequency of V. cholerae compared to liquid culture passage. Our genetic analysis identifies known and novel defense enzymes required for detoxifying reactive nitrogen species (but not reactive oxygen species) that are also required for V. cholerae to efficiently colonize the infant mouse intestine, pointing to reactive nitrogen species as the potential cause of DNA damage. We demonstrate that potential reactive nitrogen species deleterious for V. cholerae are not generated by host inducible nitric oxide synthase (iNOS) activity and instead may be derived from acidified nitrite in the stomach. Agreeing with this hypothesis, we show that strains deficient in DNA repair or reactive nitrogen species defense that are defective in intestinal colonization have decreased growth or increased mutation frequency in acidified nitrite containing media. Moreover, we demonstrate that neutralizing stomach acid rescues the colonization defect of the DNA repair and reactive nitrogen species defense defective mutants suggesting a common defense pathway for these mutants

Coordinated Regulation of Accessory Genetic Elements Produces Cyclic Di-Nucleotides for V. cholerae Virulence

SummaryThe function of the Vibrio 7th pandemic island-1 (VSP-1) in cholera pathogenesis has remained obscure. Utilizing chromatin immunoprecipitation sequencing and RNA sequencing to map the regulon of the master virulence regulator ToxT, we identify a TCP island-encoded small RNA that reduces the expression of a previously unrecognized VSP-1-encoded transcription factor termed VspR. VspR modulates the expression of several VSP-1 genes including one that encodes a novel class of di-nucleotide cyclase (DncV), which preferentially synthesizes a previously undescribed hybrid cyclic AMP-GMP molecule. We show that DncV is required for efficient intestinal colonization and downregulates V. cholerae chemotaxis, a phenotype previously associated with hyperinfectivity. This pathway couples the actions of previously disparate genomic islands, defines VSP-1 as a pathogenicity island in V. cholerae, and implicates its occurrence in 7th pandemic strains as a benefit for host adaptation through the production of a regulatory cyclic di-nucleotide

Factors relateed to rapid Deceleration Events among a Large Cohort of Older Drivers.

Studies over the past two decades have attempted to document and understand factors related to crashes involving older drivers to develop more effective countermeasures to reduce the frequency and severity of these crashes. Studies in which vehicle acceleration data can be recorded have begun to explore the relationship between rapid deceleration events (RDEs) and functional abilities among older drivers as a surrogate measure of unsafe driving. Recent naturalistic driving studies with older adults have found differing results using different thresholds to define an RDE. The present study examined the relationship among RDE rates, demographics, visual abilities, cognitive abilities, and driving comfort among a large cohort of older drivers, using two definitions of RDEs—longitudinal deceleration of 0.35 g or greater (RDE35) and longitudinal deceleration of 0.75 g or greater (RDE75). The study utilized objective driving, objective functioning, and reported driving comfort data from 2774 participants of the multi-site AAA Longitudinal Research on Aging Drivers (LongROAD) study. RDE rates for each threshold were calculated per 1000 miles driven. Multivariate regression models with backward elimination were developed to examine how outcome measures were related to RDE rates. Too few RDE75 events were found for meaningful analysis. RDE35 rates were significantly associated with several covariates. RDE35 rates were related to declining functional abilities, but many other factors also played a significant role in the rate of RDE35s among older drivers, diminishing the value of using RDE35 rates as a surrogate measure of driving safety. In addition, because the AAA LongROAD sample was relatively healthy and high functioning, other ability-related covariates may also be significantly related to RDE35s but the lack of variance in these measures in the current study prevented these effects from emerging.http://deepblue.lib.umich.edu/bitstream/2027.42/193072/2/1-s2.0-S1369847819301056-main.pdfPublished versio