NanR Regulates Sporulation and Enterotoxin Production byClostridium perfringensType F Strain F4969
ABSTRACTClostridium perfringenstype F strains, which produceC. perfringensenterotoxin (CPE), are a major cause of gastrointestinal infections, including the second most prevalent bacterial foodborne illness and 5 to 10% cases of antibiotic-associated diarrhea. Virulence of type F strains is primarily ascribable to CPE, which is synthesized only during sporulation. Many type F strains also produce NanI sialidase and carry ananoperon that likely facilitates uptake and metabolism of sialic acid liberated from glycoconjugates by NanI. During vegetative growth of type F strain F4969, NanR can regulate expression ofnanI. Given their importance for type F disease, the current study investigated whether NanR can also influence sporulation and CPE production when F4969 or isogenic derivatives are cultured in modified Duncan-Strong sporulation (MDS) medium. An isogenic F4969nanRnull mutant displayed much less sporulation and CPE production but more NanI production than wild-type F4969, indicating that NanR positively regulates sporulation and CPE production but represses NanI production in MDS. Results for thenanRmutant also demonstrated that NanR regulates expression of thenanoperon. AnanI nanRdouble null mutant mirrored the outcome of thenanRnull mutant strain but with a stronger inhibition of sporulation and CPE production, even after overnight incubation. Coupled with results using ananInull mutant, which had no impairment of sporulation or CPE production, NanR appears to carefully modulate the availability of NanI,nanoperon-encoded proteins and sialic acid to provide sufficient nutrients to sustain sporulation and CPE production when F4969 is cultured in MDS medium.