Expression of <i>Borrelia burgdorferi</i> OspC and DbpA is controlled by a RpoN–RpoS regulatory pathway

TLDR

RpoS and RpoN are alternative sigma factors involved in bacterial stress responses, yet no experimental evidence has shown they directly regulate each other. The authors disrupted and complemented rpoN and rpoS in Borrelia burgdorferi strain 297 to delineate a regulatory network governing these factors. They found that RpoN activates RpoS, which in turn controls the expression of the lipoproteins OspC and DbpA and likely other virulence factors, laying groundwork for understanding B.

Abstract

RpoS and RpoN are two alternative sigma factors typically associated with general stress responses in bacteria. To date, there has been no experimental evidence that RpoS and RpoN can directly control the expression of one another. Herein, using a combined strategy of gene disruption and genetic complementation targeting rpoN and rpoS in Borrelia burgdorferi strain 297, we describe a regulatory network for B. burgdorferi . In this network, RpoN controls the expression of RpoS, which, in turn, governs the expression of two important membrane lipoproteins, outer surface protein C and decorin-binding protein A, and likely other proteins of B. burgdorferi . Our findings provide a foundation for elucidating further key regulatory networks that potentially impact many aspects of B. burgdorferi 's parasitic strategy, host range, and virulence expression.