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.