Staphylococcus aureus produces various proteins in response to discret
e signals from the external environment like many other pathogenic mic
roorganisms. Certain staphylococcal exoproteins including toxic shock
syndrome toxin-1 (TSST-1) are secreted according to the stimuli from t
he environment, and the quantity synthesized is influenced by a number
of different parameters. Using a transposon Tn551-mediated mutagenesi
s, a mutant (RN 6390) defective in TSST-1 from synthesis was construct
ed. TSST-1 from wild strain and mutant strain were purified and quanti
tated from culture supernatants of Staphylococcus aureus. The mutant s
train RN 6390 produced only 2% of TSST-1 compared with that produced b
y the wild strain RN4282. Southern blot hybridization with a tsf (TSST
-1 gene) probe indicated that the inactivated chromosomal locus is dis
tinct from the tst. These results suggest that transposition by Tn551
inactivated a chromosomal locus whose activity was essential for the e
xpression of the TSST-1 gene.