Growth associated exopolysaccharide expression in Lactococcus lactis subspecies cremoris Ropy352

A natural lactococcal isolate, Lactococcus lactis ssp. cremoris Ropy352, ha s been previously shown to express two phenotypically distinct exopolysacch arides (ropy and mucoid). This natural isolate was cultured on various medi a to explore the carbon requirements for exopolysaccharide expression. Ropy exopolysaccharide expression was optimal when grown in defined media rathe r than on M17-based media. Ropy352 was examined for inducible lysogenic pha ges. No lytic burst was observed in Ropy352 with ultraviolet light or mitom ycin C for phage induction. The sugar compositions of the two phenotypicall y distinct exopolysaccharides were determined. The ropy exopolysaccharide i s composed of galactose and glucose in the molar percents of 42 and 58%, re spectively. The mucoid exopolysaccharide is composed of galactose, glucose, and mannose in the molar percents of 58, 29, and 13%, respectively. Mutati onal analysis revealed that mutations impairing ropy exopolysaccharide expr ession but not affecting mucoid exopolysaccharide expression could be isola ted.