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Applied and Environmental Microbiology, November 1998, p. 4142-4148, Vol. 64, No. 11
Institut National de la Recherche
Agronomique, Unité de Recherche de Biochimie et Structure des
Proteines, Domaine de Vilvert, 78352 Jouy-en-Josas Cedex, France
Received 22 August 1997/Accepted 11 August 1998
Lactococcus lactis subsp. cremoris AM2 was
previously shown to lyse early and extensively during cheese ripening
(M.-P. Chapot-Chartier, C. Deniel, M. Rousseau, L. Vassal, and J.-C.
Gripon, Int. Dairy J. 4:251-269, 1994). We analyzed the bacteriolytic
activities of autolytic strain AM2 by using renaturing sodium dodecyl
sulfate-polyacrylamide gel electrophoresis performed with two different
substrates in the gel, Micrococcus lysodeikticus and
L. lactis autoclaved cells. Several lytic activities were
detected in L. lactis AM2; a major lytic activity,
designated A2 (46 kDa), was found only with the L. lactis
cell substrate. This activity appears to be different from major
peptidoglycan hydrolase AcmA characterized previously (G. Buist, J. Kok, K. J. Leenhouts, M. Dabrowska, G. Venema, and A. J. Haandrickman, J. Bacteriol. 177:1554-1563, 1995), which has a similar
molecular mass. The two enzymes differ in substrate specificity as well
as in sensitivity to pH and different chemical compounds. L. lactis AM2 is lysogenic and mitomycin C inducible. Enzyme A2 was
shown to be inducible by mitomycin C and to be prophage encoded. It was
identified as an enzyme similar to the lysin encoded by lactococcal
small isometric temperate bacteriophages. A prophage-cured derivative
of L. lactis AM2 was obtained, and this isolate exhibited different autolytic properties than AM2. After prolonged incubation in
the stationary phase after growth on M17 medium, the extent of lysis of
an AM2 culture was 60%, whereas over the same period there was almost
no lysis in a prophage-cured derivative strain culture. These results
suggest that the prophage lytic system is involved in the strain AM2
lysis observed in liquid medium and that it could also be involved in
the lysis observed during cheese ripening.
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Copyright © 1998, American Society for Microbiology. All rights reserved.
Analysis of the Bacteriolytic Enzymes of the
Autolytic Lactococcus lactis subsp. cremoris
Strain AM2 by Renaturing Polyacrylamide Gel Electrophoresis:
Identification of a Prophage-Encoded Enzyme
*
Corresponding author. Mailing address: INRA,
Unité de Recherche de Biochimie et Structure des Proteines
Domaine de Vilvert, 78352 Jouy-en-Josas Cedex, France. Phone: 01 34 65 22 68. Fax: 01 34 65 21 63. E-mail:
chapot{at}biotec.inra.jouy.fr.
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