Title

Loss of plasmidmediated oligopeptide transport system in lactococci: another reason for slow milk coagulation

Document Type

Article

Journal/Book Title/Conference

Plasmid

Volume

35

Issue

3

Publisher

Elsevier

Publication Date

1996

First Page

145

Last Page

155

DOI

10.1006/plas.1996.0017

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. InLactococcus lactissubsp.lactis(L. lactis) C2O, lactose metabolism (Lac) and Prt were linked to pJK550 and the Opp system to pJK430. InLactococcus lactissubsp.cremorisSK11, 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 inL. lactisC2 encoded both the Prt and Opp systems. Fmc−derivatives ofL. lactisC2 were missing theprtgenes 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.

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