EXOPOLYSACCHARIDE PRODUCTION BY STREPTOCOCCUS-SALIVARIUS SSP THERMOPHILUS CULTURES .2. DISTINCT MODES OF POLYMER PRODUCTION AND DEGRADATIONAMONG CLONAL VARIANTS

A population of Streptococcus salivarius ssp. thermophilus S22 was clo nally heterogeneous in polymer production and the mucoid character of colonies. Weak, moderate, or hyperproducing clones could be selected o n selective medium showing that strain S22 was composed of cell types with different polymer production. Optimal polysaccharide production w as induced either by lactose or by sucrose and required defined condit ions of temperature and initial growth pH. In liquid medium, two degra dative systems appeared to be active on short or mature polysaccharide s. Environmental signals may trigger either of the two modes of produc tion and degradation in the different types in the population.