Powerful methods to establish chromosomal markers in Lactococcus lactis: an analysis of pyrimidine salvage pathway mutants obtained by positive selections.

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    Abstract

    Using different 5-fluoropyrimidine analogues, positive selection procedures
    for obtaining mutants blocked in pyrimidine and purine salvage genes of
    Lactococcus lactis were established. Strains lacking the following enzyme
    activities due to mutations in the corresponding genes were isolated: uracil
    phosphoribosyltransferase (upp), uridindcytidine kinase (udk), pyrimidine
    nucleoside phosphorylase (pdp), cytidine/deoxycytidine deaminase (dd),
    thymidine kinase (tdk) and purine nucleoride phosphorylase (pup). Based on
    an analysis of the mutants obtained, the pathways by which L. lactis
    metabolizes uracil and the different pyrimidine nucleosides were verified. The
    substrate specificities of the different enzymes were determined. It was
    demonstrated that a single pyrimidine nucleoside phosphorylase accounts for
    the phosphorolytical cleavage of uridine, deoxyuridine and thymidine, and a
    single purine nucleoside phosphorylase has activity towards both the
    ribonucleoside and deoxyribonucleoside derivatives of adenine, guanine and
    hypoxanthine. No phosphorylase activity towards xanthosine appeared to be
    present. The selection procedures developed during this work may be
    employed in establishing markers on the chromosome of many related lactic
    acid bacteria.
    Original languageEnglish
    JournalMicrobiology
    Volume141
    Pages (from-to)1883-1890
    ISSN0026-2617
    Publication statusPublished - 1995

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