Autolysis in Strains of Viridans Streptococci

Abstract

S U M M A R YSeven strains of viridans streptococci of the species Streptococcus sanguis, S. mutans and S. mitis were investigated for autolysis. The effect of pH, salt concentration and temperature on the autolytic process was studied in Na,HPO,/ NaH,PO, buffer. Whole cells and walls of all strains autolysed most rapidly at pH values above 7. Autolysis of whole cells of S. sanguis and one strain of S. mitis (ATCCI5909) was maximal in 0.05 to 0-2 M buffer, while the two S. mutans strains and S. mitis ATCCI5912 showed maximal autolysis in 0.5 and 1.0 M buffers.Cultures harvested in the stationary phase of growth possessed only slightly decreased autolytic activity compared with those from the exponential phase. Whole cells autolysed more rapidly at 37 "C than at 45 "C and 10 "C. Autolysis of isolated walls of three strains of S. mitis (ATCC903, A T C C I~~O~ and ATCCI5912) was maximal at pH 7.0 and 7.5 and in 1.0 M buffers. Streptococcus mitis A T C C I~~O~ also showed maximal lysis in 0.01 M and 0.5 M buffers. An endopeptidase action of the autolytic system of S. mitis ATCCI5912 was indicated by the progressive release of soluble amino groups during autolysis of the walls. No release of reducing groups was observed. Several free amino acids were released during autolysis of these walls, alanine, lysine and glutamic acid being in greatest quantity.

Chain formation and de‐chaining in Streptococcus sobrinus SL‐1

“…Given the range of pH values found in dental plaque, it would seem likely that continuous growth under acidic conditions would favor the growth of long chains. Enhanced autolytic activity has been reported to occur in Streptoeoccus mutans under alkaline conditions and at high salt (20) and fiuoride concentrations (13). The results presented here suggest that growth responses cotntnonly associated with enhanced autolytic activity such as short chain forrnation also occur under alkaline pH conditions.…”

Analysis of sodium dodecyl sulfate-stable cell wall aminopeptidases in strains of viridans streptococci

“…It seems less probable that the 89 kDa protein could be the result of SDS-induced aggregation although this has been shown for some bacterial proteins. Renaturation of proteins after denaturing SDS-gel electrophoresis was first described by Hager and Burgess [8] and has later been employed with modifications in studies of various SDS-stable cell wall enzymes in both Gram-positive and Gram-negative bacteria [3,9,10]. It seems most likely that the APs are in vivo firmly associated with the walls because the APs could only be released by enzymatic solubilization of the walls.…”

“…Cell walls were prepared from cells of the late exponential growth phase by freeze-pressing and differential centrifugation [3]. The cell walls were washed twice by homogenization and centrifugation in cold 10 mM potassium phosphate buffer, pH 7.0 (PP buffer), twice in PP buffer containing 0.1% Triton X-100 and twice in PP buffer and then suspended by homogenization in 50 mM sodium acetate, pH 7.2, to a final concentration of walls of approx.…”

Arginine catabolism by strains of oral streptococci

“…Cells were harvested in the late exponential growth phase and washed once in ice-cold 0.05 M potassium phosphate buffer, pH 6.0. This pH was chosen to reduce autolysis, which is maximal in the pH range 7-8 (31). Washed cells were suspended by homogenization in 0.05 M potassium phosphate buffer, pH 6.0.…”