The RpoS Gatekeeper in Borrelia burgdorferi: An Invariant Regulatory Scheme That Promotes Spirochete Persistence in Reservoir Hosts and Niche Diversity

The study explored the role of the RpoS σ factor in the regulatory pathway of Borrelia burgdorferi, crucial for its persistence in reservoir hosts and niche diversity. RpoS was confirmed as a genuine homolog and shown to repress tick phase genes until transmission to a new host. It was essential for maximal fitness during the mammalian phase, as demonstrated by plasmid retention studies with a ΔrpoS mutant. The research identified bba34/oppA5 as a persistence gene and highlighted two cohorts of RpoS-regulated genes: conserved syntenic genes necessary for maintenance and plasmid-encoded variable surface lipoproteins that contribute to strain diversity and virulence. This diversity in RpoS regulons may influence the range of reservoir hosts and spirochete virulence.