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Appl. Environ. Microbiol., Oct 1995, 3598-3603, Vol 61, No. 10
HM Ostlie, G Vegarud and T Langsrud
Lactococcal strains were screened for bacteriolytic activity against
Micrococcus luteus cells, lactococcal cells, and cell walls. Thirty strains
were screened for bacteriolytic activity against cells and cell walls
incorporated into agar medium. Enzymes from all strains hydrolyzed the
substrates; however, the activity against Micrococcus cells was much higher
than against Lactococcus cells or cell walls. Electrophoretic profiles of
bacteriolytic activities of culture supernatants, sodium dodecyl
sulfate-treated cell extracts, cell wall fractions, and cell extracts were
analyzed in sodium dodecyl sulfate-polyacrylamide gels containing M. luteus
cells or lactococcal cell walls as the substrate. The 22 strains tested
contained two to five lytic bands in the culture supernatant, ranging in
size between 32 and 53 kDa. The cell extracts, the sodium dodecyl
sulfate-treated cell extracts, and the cell wall fractions revealed two
lytic bands of 47 and 53 kDa. Effects of external factors on autolysis of
some strains were determined in buffer systems. Optimal autolysis was
observed in the exponential growth phase at pH 6.0 to 7.5 and at a
temperature of 30(deg)C. Two of three strains tested seemed to contain a
glycosidase, and all three strains contained an N-acetylmuramyl-l-alanine
amidase or an endopeptidase.
Copyright © 1995, American Society for Microbiology
Autolysis of Lactococci: Detection of Lytic Enzymes by Polyacrylamide Gel Electrophoresis and Characterization in Buffer Systems
Department of Food Science, Agricultural University of Norway, N-1432 As, Norway
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