Chain formation and de-chaining in Streptococcus sobrinus SL-1.

Regulation of chain length by chain-forming bacteria is believed to depend on wall-associated autolytic activity and environmental conditions. In this study, the chain length of Streptococcus sobrinus SL-1 was determined under various initial culture and pH conditions and NaF concentrations. Crude wall extracts were prepared by dilute alkali treatment of whole cells and were tested for de-chaining activity. The results indicate that S. sobrinus SL-1 grows primarily as short chains under alkaline growth conditions and at high (3.0 mM) medium fluoride levels, and growth as long chains occurs under acidic growth conditions. De-chaining activity was observed following incubation of the longer chain form of the organism with crude wall extracts. The evidence suggests that the chain length of S. sobrinus SL-1 depends on environmental conditions, including pH and fluoride, and that cell wall-associated factors may be active in regulating the chain length of the organism.