Starch hydrolyzing streptococci.

The ability to hydrolyze starch is a property that is scattered among streptococcal species in 3 of the 4 physiological divisions described by Sherman (1937), the exception being members of the Enterococcus. A single reference to a starch hydrolyzing enterococcus is Mann's (Mann et al., 1954) report of a "starch-fermenting Streptococcus faecalis." Outstanding among the nonhemolytic streptococci for ability to hydrolyze starch is Streptococcus bovis and to a much lesser extent, Streptococcus equinus and some strains of Streptococcus uberis. Streptococcus thermophilus is reported to attack this substrate "on a favorable medium" (Breed et al., 1957). Sherman (1937) noted also that a few strains of Streptococcus lactis gave a very slight reaction on starch. A renewed interest in the starch hydrolyzing streptococci has resulted from the fact that S. bovis, or organisms of similar characteristics, have been shown to be present in considerable numbers in the rumina of the cow and the sheep. This fact has increased thought and speculation concerning the role of the starch splitting streptococci in the digestion of starchy feeds and in the general economy of the ruminants. For a reaction that has served as an important reference point in the delimitation of species of streptococci (S. bovis and Streptococcus inulinaceus) there has been remarkably little effort to standardize either the test or the interpretation of results. It is possible that a reexamination of cultural conditions and methods of testing would uncover species more marked in starch hydrolyzing potential than those revealed by the usual empirical methods. In addition to being an inhabitant of the