The rise in antibiotic resistance has severely depleted our arsenal for combatting deadly bacterial pathogens. Meanwhile, despite increased appreciation of the myriad ways that microbiome bacteria impact human health, most of the signals that bacteria use to influence hosts remain unknown. This proposal seeks to address both of these challenges by leveraging our team’s unique expertise and recent discovery that animals can directly sense and respond to bacterial small RNAs (sRNAs). Since the discovery of antibiotics in the 1920s, the pathogenesis field has primarily focused on small molecules: nearly all known antibiotics and bacterial signaling molecules are small molecules. But we sorely need new, orthogonal approaches. Nucleic acid-based therapies have emerged as an exciting new platform for rapid drug development. Due to their chemical similarity, the pharmacology of nucleic acids is established, such that once we know what sequence to target, the drug development pipeline is relatively streamlined (at least in comparison to small molecule drugs). For example, a Batten disease patient was recently successfully treated with a personalized synthetic antisense RNA, less than a year after her genome was sequenced. RNA-based interventions have typically not been considered for bacteria because bacterial RNAs were thought to function exclusively within the bacteria. However, we recently overturned this paradigm by proving that model animal hosts can directly “read” the sRNAs produced by the human pathogen, Pseudomonas aeruginosa, using the RNA-interference (RNAi) machinery to respond to the bacterial sRNAs. This result is particularly exciting because it suggests a previously unappreciated role for the RNAi machinery in sensing and responding to bacteria. It also suggests that understanding sRNA-based microbe-host signaling could help develop new therapies to help hosts ward off pathogens or promote commensal colonization. However, advancing such new antimicrobial strategies is currently hindered by our lack of knowledge regarding the space of sRNA-mediated bacteria-host interactions and the molecular mechanisms by which they function. Here, we propose to build off our discovery of sRNA-host signaling to significantly close this knowledge gap. This will be accomplished in three complementary parts that span multiple hosts and microbes: globally mapping human gut microbiome community sRNA-host interactions and functions, determining how mammalian cells respond to pathogen sRNAs, and using C. elegans to characterize the molecular mechanisms of sRNA-host interactions. To achieve these goals we will combine the expertise of our team, comprised of leaders in the fields of human microbiome and computational biology (Donia), microbial pathogenesis and antibiotic development (Gitai), and C. elegans behavior and genomics (Murphy). Our combined efforts thus have the potential to establish new paradigms for microbe-host interactions and pave the way to desperately-needed new therapies.

Project Narrative: Bacteria have huge positive and negative impacts on human health, and we desperately need new strategies to combat pathogens and shape microbiome composition. We recently found that bacteria don't just affect us through chemicals, but also through their small RNAs (sRNAs). Building off our paradigm-shifting results, here we propose innovative new strategies to identify the sRNAs that “talk” to hosts from pathogens and the healthy microbiome, define how they function, and develop them as candidate immune-modulating therapeutics.