The effect ofpH on growth and gas production by streptococci and lactobacilli

The p H ranges of growth of streptococci and lactobacilli in dextrose yeast casein digest broth have been studied. Nearly all the group I and II streptococci grew at p H 8·8, but only the enterococci grew at p H 4·8; all group III types (heterofermentative) grew at p H 4·4. Only a few lactobacilli grew at p H. 8·8 but most were able to grow at p H 4 if other conditions were favourable. The enterococci, Str. lactis and Str. cremoris could be differentiated by the alkaline limits of growth.