Induction of Methanethiol Production by Brevibacterium linens CNRZ 918

Laboratoire de Microbiologie Laitière, Institut National de la Recherche Agronomique, Centre de Recherches de Jouy-en-Josas, 78350 Jouy-en-Josas, France ABSTRACT SUMMARY: A non-inducing medium (NID) was defined for studying the induction of methanethiol production by Brevibacterium linens CNRZ 918. The lowest L -methionine concentration capable of inducing maximal methanethiol production by the cells was 7 m M . The peptides L -Ala- L -Met and L -Met- L -Ala induced greater methanethiol production than free L -methionine. D -Methionine, L -cysteine, S -methyl- L -cysteine and L -ethionine were poor inducers. Culture temperature affected the duration of induction. An Na + concentration of 1 M in the culture medium led to maximal methanethiol production capacity of both cells and cell extracts. L -Methionine and L -ethionine were the best substrates for the crude soluble cells extract (with release of methanethiol and ethanethiol respectively). Neither the derivatives of L -methionine that acted as inducers, nor D -methionine, were substrates for demethiolation. Demethiolation activity of the crude extract was thermolabile, not stimulated by Na + and strongly inhibited by Zn 2+ , Mn 2+ and Cu 2+ . The shortest generation time obtained for B. linens CNRZ 918 in NID medium + L -methionine was 4 h at 26 °C. Only coccoid forms were present when the culture temperature was 30 °C. The presence of L -methionine in the medium favoured their appearance. The strain grew best in the presence of 1% NaCl but tolerated concentrations up to 15%. The induction of methanethiol production was due to the induction of L -methionine- -demethiolase. The level of induction was probably related to the intracellular concentration of L -methionine. The transport system of L -methionine by B. linens CNRZ 918 was constitutive and Na + dependent.