A deficiency in aspartate biosynthesis in Lactococcus lactis subsp. lactis C2 causes slow milk coagulation

A mutant of fast milk-coagulating (Fmc+) Lactococcus lactis subsp. lactis C2, designated L. lactis KB4, was identified. Although possessing the known components essential for utilizing casein as a nitrogen source, which include functional proteinase (PrtP) activity and oligopeptide, di- and tripepti...

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Bibliographic Details
Published in:	Applied and environmental microbiology 1998-05, Vol.64 (5), p.1673-1679
Main Authors:	Wang, H. (University of Minnesota, St. Paul, MN.), Yu, W, Coolbear, T, O'Sullivan, D, McKay, L.L
Format:	Article
Language:	eng
Subjects:	Animals Aspartic Acid - biosynthesis Aspartic Acid - deficiency Bacteria Biological and medical sciences Biology of microorganisms of confirmed or potential industrial interest BIOSINTESIS BIOSYNTHESE BIOSYNTHESIS Biotechnology Blotting, Southern Carbon Dioxide - metabolism COAGULACION COAGULATION Food industries Food Microbiology Fundamental and applied biological sciences. Psychology Genes, Bacterial LACTOCOCCUS LACTIS Lactococcus lactis - metabolism LAIT LECHE Microbiology MILK Milk - metabolism Milk and cheese industries. Ice creams Mission oriented research Mutation Physiology and metabolism Polymerase Chain Reaction Pyruvate Carboxylase - physiology Serine Endopeptidases - physiology
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Summary:	A mutant of fast milk-coagulating (Fmc+) Lactococcus lactis subsp. lactis C2, designated L. lactis KB4, was identified. Although possessing the known components essential for utilizing casein as a nitrogen source, which include functional proteinase (PrtP) activity and oligopeptide, di- and tripeptide, and amino acid transport systems, KB4 exhibited a slow milk coagulation (Fmc-) phenotype. When the amino acid requirements of L. lactis C2 were compared with those of KB4 by use of a chemically defined medium, it was found that KB4 was unable to grow in the absence of aspartic acid. This aspartic acid requirement could also be met by aspartate-containing peptides. The addition of aspartic acid to milk restored the Fmc+ phenotype of KB4. KB4 was found to be defective in pyruvate carboxylase and thus was deficient in the ability to form oxaloacetate and hence aspartic acid from pyruvate and carbon dioxide. The results suggest that when lactococci are propagated in milk, aspartate derived from casein is unable to meet fully the nutritional demands of the lactococci, and they become dependent upon aspartate biosynthesis
ISSN:	0099-2240 1098-5336