Expression of Ropy and Mucoid Phenotypes in Lactococcus lactis

Strains of Lactococcus lactisssp. lactisand Lactococcus lactisssp. cremoriswere 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. lactisssp. cremorisRopy 352 and L. lactisssp. cremorisHollandicus, 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.