Investigator: Brett Pellock, Providence College

Mentor: Mary Allen, Wellesley College

Scientific Theme: Molecular Toxicology

Abstract: Bacteria use small, non-coding RNAs (sRNAs) are genes to regulate the expression of other genes in response to changing environmental conditions. sRNAs base pair with their mRNA targets and mediate either positive or negative regulatory outcomes. Many sRNAs interact with a highly conserved protein called Hfq, an RNA chaperone that mediates both sRNA folding and interactions between sRNAs and their mRNA targets.

To better understand how sRNAs function, we have constructed and characterized a null allele of the hfq gene in the metal-reducing bacterium Shewanella oneidensis. Loss of Hfq results in defects in aerobic and anaerobic growth, terminal culture cell density, stationary phase survival, and chromium reduction. Our preliminary data suggest that the growth and survival defects of the hfq mutant are at least partially due to
defects in heme biosynthesis and adaption to reactive oxygen species.

Because genetic analyses of hfq in other systems suggests that Hfq has distinct functions in different bacteria, we hypothesize that Hfq plays novel, species-specific regulatory roles in S. oneidensis sRNA function that underlie the hfq mutant phenotypes. Here we propose experiments that will elucidate the mechanisms underlying S. oneidensis hfq mutant phenotypes that are highly likely to be related to the metal reducing physiology of the organism. Specifically, we will investigate the role of heme biosynthesis in the growth defect of the hfq mutant and explore the mechanisms by which Hfq promotes cell survival when cells experience oxidative stress and growth phase stress. We will complement these physiological analyses by using next generation RNA sequencing methods to identify novel sRNAs and analyze sRNA function.

Human Health Relevance: Understanding how bacteria use sRNAs to adapt to changing conditions has application to human interactions with all bacteria, including pathogens, in which sRNAs regulate the expression of some virulence genes. In addition, understanding how metal-reducing bacteria metabolize toxic compounds will positively impact the potential use of these bacteria as bioremediative agents.