Loss of Plasmid-Mediated Oligopeptide Transport System in Lactococci: Another Reason for Slow Milk Coagulation

Authors: Yu W.¹; Gillies K.²; Kondo J.K.³; Broadbent J.R.⁴; McKay L.L.¹

Source: Plasmid, Volume 35, Number 3, May 1996 , pp. 145-155(11)

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Abstract:

Fast milk-coagulating (Fmc + ) strains of lactococci are known to segregate slow milk-coagulating (Fmc - ) variants, which has been attributed to loss of proteinase (Prt) activity encoded by plasmid DNA. It was found that the Fmc - phenotype could also be due to loss of a plasmid encoding an oligopeptide permease (Opp) system. In Lactococcus lactis subsp. lactis ( L. lactis ) C2O, lactose metabolism (Lac) and Prt were linked to pJK550 and the Opp system to pJK430. In Lactococcus lactis subsp. cremoris SK11, known to possess Prt on a 78-kb plasmid, DNA sequence analysis of a 7.4-kb region from the Lac plasmid, pSK11L, revealed that it possessed the Opp system. The Lac plasmid in L. lactis C2 encoded both the Prt and Opp systems. Fmc - derivatives of L. lactis C2 were missing the prt genes and had Opp integrated into the chromosome, possibly due to transposition events. Growth studies showed the Opp systems were functional and, in combination with Prt, produced the Fmc + phenotype.

Language: English

Document Type: Research article

Affiliations: 1: Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, Minnesota, 55108 2: Rhone-Poulenc, Marschall Products, 601 Science Drive, Madison, Wisconsin, 53711 3: Quest International, 2402 7th Street N.W., Rochester, Minnesota, 55901 4: Department of Nutrition and Food Sciences, Utah State University, Logan, Utah, 84322

Publication date: 1996-05-01