Determining the effect of the loss of small RNAs OmrA and OmrB on type 1 pili expression in Escherichia coli

Abstract

Uropathogenic Escherichia coli (UPEC) cause up to 90% of the seven million annual cases of urinary tract infections in the United States. Expression of type 1 pili is necessary for pathogenicity and allows UPEC to attach to the host bladder epithelium. Under high osmolality, OmpR regulates type 1 pili expression through the recombinases FimB and FimE. OmpR also regulates transcription of the small RNAs OmrA and OmrB under the same environmental conditions. In this study, a ΔomrAB mutant strain was created to see its effects on type 1 pili expression in vitro under varying pH and osmolality and in vivo. Changes in fimB, fimE, and fimA transcription were determined by a β-galactosidase assay. The orientation of the reversible fimS element that contains the promoter for fimA was determined using a multiplex PCR, while surface expression of type 1 pili was estimated using hemagglutination. A low pH and high osmolality growth condition resulted in significantly less type 1 piliation in the mutant strain and reduced in vivo survival, suggesting regulation of type 1 pili by OmrA and OmrB. Additional experiments are needed to determine the exact mechanism by which OmrA and OmrB regulate type 1 pili expression.