Search

Background Previous studies have highlighted the antimicrobial activity of caffeine, both individually and in combination with other compounds. A proposed mechanism for caffeine's antimicrobial effects is inhibition of bacterial DNA repair pathways. The current study examines the influence of sub-lethal caffeine levels on the growth and morphology of SOS response pathway mutants of Escherichia coli. Methods Growth inhibition after treatment with caffeine and methyl methane sulfonate (MMS), a mutagenic agent, was determined for E. coli mutants lacking key genes in the SOS response pathway. The persistence of caffeine's effects was explored by examining growth and morphology of caffeine and MMS-treated bacterial isolates in the absence of selective pressure. Results Caffeine significantly reduced growth of E. coli recA- and uvrA-mutants treated with MMS. However, there was no significant difference in growth between umuC-isolates treated with MMS alone and MMS in combination with caffeine after 48 h of incubation. When recA-isolates from each treatment group were grown in untreated medium, bacterial isolates that had been exposed to MMS or MMS with caffeine showed increased growth relative to controls and caffeine-treated isolates. Morphologically, recA-isolates that had been treated with caffeine and both caffeine and MMS together had begun to display filamentous growth. Conclusions Caffeine treatment further reduced growth of recA- and uvrA-mutants treated with MMS, despite a non-functional SOS response pathway. However, addition of caffeine had very little effect on MMS inhibition of umuC-mutants. Thus, growth inhibition of E. coli with caffeine treatment may be driven by caffeine interaction with UmuC, but also appears to induce damage by additional mechanisms as evidenced by the additive effects of caffeine in recA- and uvrA-mutants. Keywords: Caffeine, DNA repair, SOS response pathway, Escherichia coli, Author(s): Alyssa K Whitney[sup.1] and Tiffany L Weir[sup.1] Background Caffeine is derived from plant leaves and is commonly found in consumed beverages such as tea and coffee at concentrations of [...]

This article examines place-based poverty in Indian Country, emphasizing that reservation characteristics are influenced by the system of federal Indian policy that affects American Indian self-determination and antipoverty strategies within reservation boundaries. Using data from the American Community Survey five-year file, 2006-10, I model poverty rates using multivariate, nested regression along key dimensions associated with American Indian antipoverty strategies and place-based poverty. The results indicate that rates of female-headed households and opportunity structures, such as lack of work, contribute to higher rates of reservation poverty while gaming acts as a slight buffer against poverty. Surprisingly, natural-resource-related occupations, thought to be associated with expropriation of tribal resources, was not associated with higher poverty, while self-governance compacts, acting as a proxy for tribal autonomy, had no significant impact on poverty rates. As tribal governments seek to address poverty through strategies enabled by self-determination policies, there is a critical need for more comprehensive and reliable data to understand how and whether tribal governments can effectively adapt federal policies to specific reservation conditions. [ABSTRACT FROM AUTHOR]