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J. Bacteriol., Jun 1995, 2982-2989, Vol 177, No. 11
JD Marugg, W Meijer, R van Kranenburg, P Laverman, PG Bruinenberg and WM de Vos
Transcriptional gene fusions with the Escherichia coli beta- glucuronidase
gene (gusA) were used to study the medium- and growth- dependent expression
of the divergently transcribed genes involved in proteinase production
(prtP and prtM) of Lactococcus lactis SK11. The results show that both the
prtP and prtM genes are controlled at the transcriptional level by the
peptide content of the medium and, to a lesser extent, by the growth rate.
A more than 10-fold regulation in beta-glucuronidase activity was observed
for both prtP and prtM promoters in batch and continuous cultures. The
level of expression of the prtP and prtM promoters was high in whey
permeate medium with relatively low concentrations of peptides, whereas at
increased concentrations the expression of the promoters was repressed. The
lowest level of expression was observed in peptide- and amino acid-rich
laboratory media, such as glucose-M17 and MRS. The addition of specific
dipeptides, such as leucylproline and prolylleucine, to the growth medium
negatively affected the expression of the prtP-gusA fusions. The repression
by dipeptides was not observed in mutants defective in the uptake of
di-tripeptides, indicating that the internal concentration of dipeptides or
derivatives is important in the regulation of proteinase production.
Copyright © 1995, American Society for Microbiology
Medium-dependent regulation of proteinase gene expression in Lactococcus lactis: control of transcription initiation by specific dipeptides
Department of Biophysical Chemistry, NIZO, Ede, The Netherlands.
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