BACKGROUND:Escherichia coli, can respire anaerobically using dimethyl sulfoxide (DMSO) or trimethylamine-N-oxide (TMAO) as the terminal electron acceptor for anaerobic energy generation. Expression of the dmsABC genes that encode the membrane-associated DMSO/TMAO reductase is positively regulated during anaerobic conditions by the Fnr protein and negatively regulated by the NarL protein when nitrate is present. RESULTS:The regions of dmsA regulatory DNA required for Fnr and NarL interactions in response to anaerobiosis and nitrate, respectively, were examined. Mutations within the Fnr site that deviated from the wild type sequence, TTGATaccgAACAA, or that removed an entire half-site, either impaired or abolished the anaerobic activation of dmsA-lacZ expression. The region for phosphorylated NarL (NarL-phosphate) binding at the dmsA promoter was identified by DNase I and hydroxyl radical footprinting methods. A large 97 bp region that overlaps the Fnr and RNA polymerase recognition sites was protected by NarL-phosphate but not by the non-phosphorylated form of NarL. Hydroxyl radical footprinting analysis confirmed the NarL-phosphate DNase I protections of both dmsA strands and revealed 8-9 protected sites of 3-5 bp occurring at ten bp intervals that are offset by 3 bp in the 3' direction. CONCLUSION:These findings suggest that multiple molecules of phosphorylated NarL bind along one face of the DNA and may interfere with Fnr and/or RNA polymerase interactions at the dmsA regulatory region. The interplay of these transcription factors insures a hierarchical expression of the dmsABC genes when respiration of the preferred electron acceptors, oxygen and nitrate, is not possible.

Black adolescent males use available mental health services at a disproportionately lower rate compared to males of other racial groups. This study examines barriers to school-based mental health resource (SBMHR) use among Black adolescent males, as a means of addressing reduced usage of available mental health resources and to improve these resources to better support their mental health needs. Secondary data for 165 Black adolescent males were used from a mental health needs assessment of two high schools in southeast Michigan. Logistic regression was employed to examine the predictive power of psychosocial (self-reliance, stigma, trust, and negative previous experience) and access barriers (no transportation, lack of time, lack of insurance, and parental restrictions) on SBMHR use, as well as the relationship between depression and SBMHR use. No access barriers were found to be significantly associated with SBMHR use. However, self-reliance and stigma were statistically significant predictors of SBMHR use. Participants who identified self-reliance in addressing their mental health symptoms were 77% less likely to use available mental health resources in their school. However, participants who reported stigma as a barrier to using SBMHR were nearly four times more likely to use available mental health resources; this suggests potential protective factors in schools that can be built into mental health resources to support Black adolescent males use of SBMHRs. This study serves as an early step in exploring how SBMHRs can better serve the needs of Black adolescent males. It also speaks to potential protective factors that schools provide for Black adolescent males who have stigmatized views of mental health and mental health services. Future studies would benefit from a nationally representative sample allowing for more generalizable results regarding barriers and facilitators to Black adolescent males use of school-based mental health resources.