ToIC and DsbA are needed for the secretion of STB, a heat‐stable enterotoxin of Escherichia coli

Abstract
STB secretion-deficient mutants were isolated using the synthetic transposon Tn beta laM. Cultures were plated using a double-membrane system of cellulose acetate and nitrocellulose placed on Luria agar plates containing carbenicillin. The STB bound to the underlying nitrocellulose membrane was detected with anti-STB antibodies. The altered genes of two STB secretion-deficient mutants were identified by conjugation and complementation as tolC and dsbA. In cultures of well-characterized dsbA and tolC mutants, STB was absent from the culture supernatant. The role of TolC and DsbA in the secretion of peptides is discussed.