TEMPERATURE-DEPENDENT REGULATION OF YERSINIA-ENTEROCOLITICA CLASS-IIIFLAGELLAR GENES

Temperature is a key environmental cue for Yersinia enterocolitica as well as for the two other closely related pathogens, Yersinia pestis a nd Yersinia pseudotuberculosis, Between the range of 30 degrees C and 37 degrees C, Y. enterocolitica phase-varies between motility and plas mid-encoded virulence gene expression. To determine how temperature re gulates Y.enterocolitica motility, we have been dissecting the flagell ar regulatory hierarchy to determine at which level motility is blocke d by elevated temperature (37 degrees C). Here we report the cloning, DNA sequences, and regulation of the two main regulators of Class III flagellar genes, fliA (sigma(F)) and flgM (anti-sigma(F)), and a third gene, flgN, which we show is required for filament assembly. Identifi cation of the Y. enterocolitica fliA and flgM genes was accomplished b y functional complementation of both S. typhimurium and Y.enterocoliti ca mutations and by DNA sequence analysis. The Y. enterocolitica fliA gene, encoding the flagellar-specific sigma-factor, sigma(F), maps imm ediately downstream of the three flagellin structural genes. The flgM and flgN genes, encoding anti-of and a gene product required for filam ent assembly, respectively, map downstream of the invasin (inv) gene b ut are transcribed in the opposite (convergent) direction, By using No rthern blot analyses we show that transcription of both fliA and flgM is immediately arrested when cells are exposed to 37 degrees C, coinci dent with the timing of virulence gene induction, Unlike S. typhimuriu m flgM(-) mutants, Y. enterocolitica flgM(-) mutants are fully virulen t.