Biology subjects

Gill, M. O.

Publications and source records attributed to Gill, M. O..

2 recordsLinked to original sources

bioRxiv2026

Capsular polysaccharide can sensitize bacteria to non-antibiotic drugs

Medications administered over long durations, such as phenothiazine antipsychotics, accumulate in the gut at concentrations that affect microbial growth. However, the bacterial features influencing sensitivity to these non-antibiotics remain poorly understood. Bacterial capsular polysaccharides (CPSs) typically confer protection against environmental stressors, including chemical, viral, and immunological pressures within the gut. But their roles under non-antibiotic drug pressure are unknown. Here, we show that the K5 CPS of Escherichia coli Nissle 1917 (EcN) sensitizes it to thioridazine (TDZ) and related antipsychotics. Among a panel of E. coli strains grown in minimal medium, EcN exhibited the highest sensitivity to TDZ. Experimentally evolving EcN under gut-relevant TDZ concentrations selected for resistant populations with convergent variants affecting the CPS locus, and TDZ-resistant clones correspondingly had lower CPS expression than their drug-susceptible counterparts. Genetic, transcriptomic, and phenotypic analyses confirmed that the K5 CPS enhances, rather than mitigates, TDZ sensitivity. These findings demonstrate that canonically protective surface structures can become vulnerabilities under non-antibiotic pharmaceutical pressure. Human medications may therefore inadvertently shape the expression and evolution of bacterial surface structures in the gastrointestinal tract, challenging presumptions of CPS-mediated environmental protection.

microbiology↗

bioRxiv2023

Intragenic DNA inversions expand bacterial coding capacity

Bacterial populations that originate from a single bacterium are not strictly clonal. Often, they contain subgroups with distinct phenotypes. Bacteria can generate heterogeneity through phase variation: a preprogrammed, reversible mechanism that alters gene expression levels across a population. One well studied type of phase variation involves enzyme-mediated inversion of specific intergenic regions of genomic DNA. Frequently, these DNA inversions flip the orientation of promoters, turning ON or OFF adjacent coding regions within otherwise isogenic populations. Through this mechanism, inversion can affect fitness, survival, or group dynamics. Here, we develop and apply bioinformatic approaches to discover thousands of previously undescribed phase-variable regions in prokaryotes using long-read datasets. We identify intragenic invertons, a surprising new class of invertible elements found entirely within genes, in bacteria and archaea. To date, inversions within single genes have not been described. Intragenic invertons allow a gene to encode two or more versions of a protein by flipping a DNA sequence within the coding region, thereby increasing coding capacity without increasing genome size. We experimentally characterize specific intragenic invertons in the gut commensal Bacteroides thetaiotaomicron, presenting a roadmap for investigating this new gene-diversifying phenomenon. One-Sentence SummaryIntragenic DNA inversions, identified using long-read sequencing datasets, are found in many phyla across the prokaryotic tree of life.

microbiology↗