Elsevier

Journal of Dairy Science

Volume 80, Issue 8, August 1997, Pages 1528-1536
Journal of Dairy Science

Article
Expression of Ropy and Mucoid Phenotypes in Lactococcus lactis

https://doi.org/10.3168/jds.S0022-0302(97)76082-XGet rights and content
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Abstract

Strains of Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris were cultured under aerobic and anaerobic conditions on plates of whey agar, Elliker agar, and M17L agar at 15, 20, and 30°C to determine the environmental conditions required for the expression of the ropy phenotype. Two strains, L. lactis ssp. cremoris Ropy 352 and L. lactis ssp. cremoris Hollandicus, exhibited two distinct polysaccharide phenotypes, ropy and mucoid. Expression of these phenotypes could be induced individually or simultaneously. The inducible nature of this response suggests that genetic regulators were present. Western blots were used to determine whether or not Lon protease and RcsA, two regulators of polysaccharide expression in Escherichia coli, were present in lactococci. Lon, a negative regulator, and RcsA, an unstable positive regulator, have been shown at the structural level to be conserved in a number of Gram-negative and Gram-positive microorganisms. The present study found evidence for structural conservation of Lon protease in lactococci. Less of the Lon-like protein was observed in the ropy strains than in the nonropy strains.

Key words

ropy phenotype
mucoid phenotype
Lactococcus lactis
Lon protease

Abbreviation Key

EPS
exopolysaccharide
LAB
lactic acid bacteria
TBST
Tris-buffered saline plus 1% Tween 20

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