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Appl. Environ. Microbiol., Jul 1997, 2722-2728, Vol 63, No. 7
G Buist, H Karsens, A Nauta, D van Sinderen, G Venema and J Kok
The optical density of a culture of lactococcus lactis MG1363 was reduced
more than 60% during prolonged stationary phase. Reduction in optical
density (autolysis) was almost absent in a culture of an isogenic mutant
containing a deletion in the major autolysin gene, acmA. An acmA mutant
carrying multiple coples of a plasmid encoding AcmA lysed to a greater
extent than the wild-type strain did. Intercellular action of AcmA was
shown by mixing end-exponential-phase cultures of an acmA deletion mutant
and a tripeptidase (pepT) deletion mutant. PepT, produced by the acmA
mutant, was detected in the supernatant of the mixed culture, but no PepT
was present in the culture supernatant of the acmA mutant. A plasmid was
constructed in which acmA, lacking its own promoter, was placed downstream
of the inducible promoter/operator region of the temperate lactococcal
bacteriophage r1t. After mitomycin induction of an exponential-phase
culture of L. lactis LL302 carrying this plasmid, the cells became subject
to autolysis, resulting in the release of intracellular proteins.
Copyright © 1997, American Society for Microbiology
Autolysis of Lactococcus lactis caused by induced overproduction of its major autolysin, AcmA
Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
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