title: Strain diversity and phage resistance in complex dairy starter cultures.
abstract: The compositional stability of the complex Gouda cheese starter culture Ur is thought to be influenced by diversity in phage resistance of highly related strains that co-exist together with bacteriophages. To analyze the role of bacteriophages in maintaining culture diversity at the level of genetic lineages, simple blends of Lactococcus lactis strains were made and subsequently propagated for 152 generations in the absence and presence of selected bacteriophages. We first screened 102 single-colony isolates (strains) from the complex cheese starter for resistance to bacteriophages isolated from this starter. The collection of isolates represents all lactococcal genetic lineages present in the culture. Large differences were found in bacteriophage resistance among strains belonging to the same genetic lineage and among strains from different lineages. The blends of strains were designed such that 3 genetic lineages were represented by strains with different levels of phage resistance. The relative abundance of the lineages in blends with phages was not stable throughout propagation, leading to continuous changes in composition up to 152 generations. The individual resistance of strains to phage predation was confirmed as one of the factors influencing starter culture diversity. Furthermore, loss of proteolytic activity of initially proteolytic strains was found. Reconstituted blends with only 4 strains with a variable degree of phage resistance showed complex behavior during prolonged propagation.
authors.affiliation: TI Food and Nutrition, PO Box 557, 6700 AN Wageningen, the Netherlands; Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, the Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Spus
authors.affiliation: TI Food and Nutrition, PO Box 557, 6700 AN Wageningen, the Netherlands; Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, the Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.affiliation: TI Food and Nutrition, PO Box 557, 6700 AN Wageningen, the Netherlands; Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, the Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Alexeeva
authors.affiliation: TI Food and Nutrition, PO Box 557, 6700 AN Wageningen, the Netherlands; Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, the Netherlands.
authors.forename: J C M
authors.initials: JC
authors.lastname: Wolkers-Rooijackers
authors.affiliation: Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, the Netherlands.
authors.forename: M H
authors.initials: MH
authors.lastname: Zwietering
authors.affiliation: Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, the Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: Abee
authors.affiliation: TI Food and Nutrition, PO Box 557, 6700 AN Wageningen, the Netherlands; Laboratory of Food Microbiology, Wageningen University, PO Box 17, 6700 AA Wageningen, the Netherlands. Electronic address: eddy.smid@wur.nl.
authors.forename: E J
authors.initials: EJ
authors.lastname: Smid
mesh_terms: D001435:Bacteriophages / Q000502:physiology*; D002611:Cheese / Q000382:microbiology* / Q000821:virology; D005511:Food Handling; D005516:Food Microbiology; D013294:Lactococcus lactis / Q000235:genetics / Q000502:physiology* / Q000821:virology*
keywords: bacteriophage; diversity; proteolytic activity; starter culture