Characterization of NanR Regulation of Sialidase Production, Sporulation and Enterotoxin Production by Type F Strains Carrying a Chromosomal Enterotoxin Gene.

type F food poisoning (FP) strains produce enterotoxin (CPE) to cause a common bacterial food-borne illness in the United States. During FP, CPE is synthesized in the intestines when sporulates. Besides CPE, FP strains also produce sialidases. Most FP strains carry their gene on the chromosome and all surveyed chromosomal (c-) FP strains produce NanH sialidase or both NanJ and NanH sialidases. NanR has been shown previously to regulate sialidase activity in non-FP strains. The current study investigated whether NanR also regulates sialidase activity or influences sporulation and CPE production for c- FP strains SM101 and 01E809. In sporulation medium, the SM101 null mutant showed lower sialidase activity, sporulation, and CPE production than its wild-type parent, while the 01E809 null mutant showed roughly similar sialidase activity, sporulation, and CPE production as its parent. In vegetative medium, the null mutants of both strains produced more spores than their parents while NanR repressed sialidase activity in SM101 but positively regulated sialidase activity in 01E809. These results demonstrate that NanR regulates important virulence functions of c- strains, with this control varying depending on strain and culture conditions.