Transcriptional regulation of virulence-related genes in Bordetella spp.

Classical Bordetella species rely on a two-component regulatory system, BvgAS, to control the majority of their virulence factors, including Type Three Secretion System. We report a regulatory node involving an extracytoplasmic function sigma factor BtrS and its secretable antagonist BtrA that control a previously unidentified sub-regulon of factors which includes several known direct targets of BvgAS. A global transcriptional analysis of wild type B. bronchiseptica strain RB50, various isogenic regulatory gene mutants (?btrA, ?btrS, ?btrA?btrS, ?bvgS) and over-expressed regulators (btrA and btrS) was undertaken to delineate the BtrA/BtrS regulon. Bacterial cultures were grown in Stainer-Scholte liquid medium at 37°C until mid-logarithmic growth phase. RNA was isolated from two biological replicates of each strain and after removal of rRNA, cDNA libraries were constructed and sequenced on an Illumina HiSeq2000.