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This team, based at University of Connecticut, studied genes controlled by the RpoS pathway, the regulatory system that facilitates transmission and mammalian infection by Borrelia burgdorferi. They were particularly interested in whether RpoS-controlled genes are needed for chronic infection. They were able to show, contrary to current hypotheses, that OspA was expressed on spirochetes delivered via tick, then quickly turned off via RpoS repression. OspA remains repressed until subsequent acquisition by feeding larvae. RpoS is known to be required for the early stages of infection. But it’s been hard to study RpoS during chronic infection, because mutant strains of bacteria that lack RpoS aren’t virulent. Using a creative approach, the team confirmed that expression of RpoS is required throughout infection. In support of these findings, they identified an RpoS-regulated protein that imports peptides, OppA5, that are required to maintain bacterial persistence during chronic infection. OppA5 has thus been deemed a “persistence” gene, validating the hypothesis that a specific subset of RpoS-regulated genes are essential for maintenance of chronic infection.

Published in Frontiers in Microbiology: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6719511/
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/31507550