Co‐ordinate, temperature‐sensitive regulation of the three Yersinia enterocolitica flagellin genes

Yersinia enterocolitica cells, when cultured at 30°C or below, are flagellated and motile. Cells cultured at 37°C or above lack flagella and are non‐motile. To identify flagellin genes that are a target of this temperature‐dependent regulation, a library of Y. enterocolitica genomic inserts in a phage λ vector was probed with the Salmonella typhimurium fliC (flagellin) gene. A DNA fragment subcloned from a recombinant phage which hybridizes with the probe complements a non‐motile S. typhimurium fliC−fljB− (flagellin‐minus) mutant. DNA sequence analysis shows that Y. enterocolitica contains three tandem flagellin genes, designated fleA , fleB and fleC . All three genes are co‐ordinately transcribed at low, but not high, temperature from fliA ‐dependent (σ F ) promoters. Flagellin transcription arrests rapidly after upshift to 37°C (host temperature). In contrast, flagellin transcription resumes only after several generations when cells cultured at 37°C are downshifted to 28°C.