title: Expression of prophage-encoded endolysins contributes to autolysis of Lactococcus lactis.
abstract: Analysis of autolysis of derivatives of Lactococcus lactis subsp. cremoris MG1363 and subsp. lactis IL1403, both lacking the major autolysin AcmA, showed that L. lactis IL1403 still lysed during growth while L. lactis MG1363 did not. Zymographic analysis revealed that a peptidoglycan hydrolase activity of around 30 kDa is present in cell extracts of L. lactis IL1403 that could not be detected in strain MG1363. A comparison of all genes encoding putative peptidoglycan hydrolases of IL1403 and MG1363 led to the assumption that one or more of the 99 % homologous 27.9-kDa endolysins encoded by the prophages bIL285, bIL286 and bIL309 could account for the autolysis phenotype of IL1403. Induced expression of the endolysins from bIL285, bIL286 or bIL309 in L. lactis MG1363 resulted in detectable lysis or lytic activity. Prophage deletion and insertion derivatives of L. lactis IL1403 had a reduced cell lysis phenotype. RT-qPCR and zymogram analysis showed that each of these strains still expressed one or more of the three phage lysins. A homologous gene and an endolysin activity were also identified in the natural starter culture L. lactis subsp. cremoris strains E8, Wg2 and HP, and the lytic activity could be detected under growth conditions that were identical as those used for IL1403. The results presented here show that these endolysins of L. lactis are expressed during normal growth and contribute to autolysis without production of (lytic) phages. Screening for natural strains expressing homologous endolysins could help in the selection of strains with enhanced autolysis and, thus, cheese ripening properties.
authors.affiliation: Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747, AG, Groningen, the Netherlands.|Department of Immunology, University of Oslo, Rikshospitalet, Sognsvannsveien 20, 0372, Oslo, Norway.
authors.forename: Ganesh Ram R
authors.initials: GR
authors.lastname: Visweswaran
authors.affiliation: Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747, AG, Groningen, the Netherlands.
authors.forename: Dorota
authors.initials: D
authors.lastname: Kurek
authors.affiliation: Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747, AG, Groningen, the Netherlands.
authors.forename: Monika
authors.initials: M
authors.lastname: Szeliga
authors.affiliation: Department of Medical Microbiology, University of Groningen, University Medical Centre Groningen, Hanzeplein 1, 9700, Groningen, RB, the Netherlands.
authors.forename: Francisco Romero
authors.initials: FR
authors.lastname: Pastrana
authors.affiliation: Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747, AG, Groningen, the Netherlands.
authors.forename: Oscar P
authors.initials: OP
authors.lastname: Kuipers
authors.affiliation: Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747, AG, Groningen, the Netherlands. jan.kok@rug.nl.
authors.forename: Jan
authors.initials: J
authors.lastname: Kok
authors.affiliation: Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747, AG, Groningen, the Netherlands.|Department of Medical Microbiology, University of Groningen, University Medical Centre Groningen, Hanzeplein 1, 9700, Groningen, RB, the Netherlands.
authors.forename: Girbe
authors.initials: G
authors.lastname: Buist
mesh_terms: D001433:Bacteriolysis; D002611:Cheese / Q000382:microbiology; D010450:Endopeptidases / Q000235:genetics* / Q000378:metabolism; D013294:Lactococcus lactis / Q000235:genetics / Q000254:growth & development / Q000502:physiology* / Q000821:virology; D009113:Muramidase / Q000235:genetics; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000235:genetics / Q000502:physiology; D039002:Prophages / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D017384:Sequence Deletion
chemical_list: C092497:AcmA protein, Lactococcus lactis; D009113:Muramidase; D010450:Endopeptidases; C001143:endolysin; D009238:N-Acetylmuramoyl-L-alanine Amidase
keywords: Autolysis; Bacteriophage; Endolysins; Lactococcus lactis