Project description:We previously developed a directed evolution model that passaged biofilm populations of in S. Typhimurium under antibiotic stress, which identified trade-offs between biofilm formation and antibiotic resistance, conferred by increased efflux activity (Trampari et al., 2021). We applied this same model to expose biofilm populations of S. Typhimurium to RND efflux inhibitor PAβN or non-antibiotic efflux substrate acriflavine. The aim was to identify mutations responsible for restoring biofilm formation in populations exposed to PAβN and to identify how cells in the biofilm can upregulate efflux in the presence of acriflavine. We hypothesised that comparing the mutations selected in both conditions would identify intersecting regulatory relationships between efflux activity and biofilm formation. Parallel linages of S. Typhimurium were grown on glass beads and in planktonic culture in the presence of a subinhibitory concentration of PAβN or acriflavine (or an untreated control) and passaged into new treated media every 48-72 hours. After one, five and ten passages (corresponding to 2, 17 and 35 days of continuous exposure), the populations were stored, DNA was extracted and sequenced to determine mutations selected in these conditions. We compared mutations from conditions treated with efflux substrates to untreated controls in planktonic and biofilm conditions. To explore phenotypic heterogeneity in these populations, we streaked biofilm populations from passages five and ten onto LB agar and picked three single colonies at random to sequence alongside the populations.
Project description:Phosphine (PH3) is a highly toxic, corrosive, flammable, heavier-than-air gas that is a commonly used fumigant. Although the mechanism of toxicity is unclear, PH3 is thought to be a metabolic poison. PH3 exposure induces multi-organ toxicity and no effective antidotes or therapeutics have been identified. To better characterize the mechanism(s) driving PH3-induced toxicity we have performed transcriptomic analysis on conscious adult male Sprague-Dawley rats following whole-body inhalation exposure to phosphine gas at three concentrations. PH3 exposure induced concentration- and time-dependent changes in gene expression across multiple tissues.