INVESTIGADORES
RAYA Raul Ricardo
artículos
Título:
Isolation and characterization of a slowly milk-coagulating variant of Lactobacillus helveticus deficient in purine biosynthesis.
Autor/es:
HEBERT EM, DE GIORI GS, RAYA RR.
Revista:
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
Editorial:
AMER SOC MICROBIOLOGY
Referencias:
Lugar: Washington, Estados Unidos; Año: 2001 vol. 67 p. 1846 - 1850
ISSN:
0099-2240
Resumen:
A slowly milk-coagulating variant (Fmc(-)) of Lactobacillus helveticus
CRL 1062, designated S1, was isolated and characterized. Strain S1
possessed all the known essential components required to utilize casein
as a nitrogen source, which include functional proteinase and peptidase
activities as well as functional amino acid, di- and tripeptide, and
oligopeptide transport systems. The amino acid requirements of strain S1
were similar to those of the parental strain. However, on a
purine-free, chemically defined medium, the growth rate of the Fmc(-)
strain was threefold lower than that of the wild-type strain. L.
helveticus S1 was found to be defective in IMP dehydrogenase activity
and therefore was deficient in the ability to synthesize XMP and GMP.
This conclusion was further supported by the observation that the
addition of guanine or xanthine to milk, a substrate poor in purine
compounds, restored the Fmc(+) phenotype of L. helveticus S1.