H-NS controls pap and daa fimbrial transcription in Escherichia coli in response to multiple environmental cues

A comparative study was completed to determine the influence of various env ironmental stimuli on the transcription of three different fimbrial operons in Escherichia coli and to determine the role of the histone-like protein H-NS in this environmental regulation. The fimbrial operons studied include d the pap operon, which encodes pyelonephritis-associated pill (P pill), th e daa operon, which encodes F1845 fimbriae, and the fan operon, which encod es K99 fimbriae. Using lacZYA transcriptional fusions within each of the fi mbrial operons, we tested temperature, osmolarity, carbon source, rich medi um, oxygen levels, pH, amino acids, solid medium, and iron concentration fo r their effects on fimbrial gene expression. Low temperature, high osmolari ty, glucose as a carbon source, and rich medium repressed transcription of all three operons. High iron did not alter transcription of any of the oper ons tested, whereas the remaining stimuli had effects on individual operons . For the pap and daa operons, introduction of the hns651 mutation relieved the repression, either fully or partially, due to low temperature, glucose as a carbon source, rich medium, and high osmolarity. Taken together, thes e data indicate that there are common environmental cues that regulate fimb rial transcription in E. call and that H-NS is an important environmental r egulator for fimbrial transcription in response to several stimuli.