ABSTRACT
Streptococci, both the saprophytic and parasitic species, occur in milk because of their fastidious nature. The natural reservoir for members of the Streptococcus genus is green plant material and these bacteria also find the nutrients needed for growth. Because of their occurrence in milk, the streptococci were among the first genus of microorganisms to receive research attention by bacteriologists. The lactose-fermenting and resultant acid-producing capability of lactic streptococci enable them to perform several important functions in milk and milk products. In cheese they concentrate and stabilize the curd by coagulating the protein and expelling moisture. Lactobacilli have fewer plasmids than streptococci. Most strains so far studied have only one or two plasmids and many have none. In contrast the lactic streptococci may have up to 14 plasmids varying in molecular weight from 1 to 90 mdal. Lactic streptococci produce more than 10% of their weight per minute in lactic acid.
