The plasma membrane ofStreptococcus cremoris:isolation and partial characterization

Characteristics of the autolysis of variants ofLactococcus lactissubsp.cremoris

Two slime-forming strains (T5and MLS96) and a non-slime-forming strain (HA)of Lactococcus lactissubsp.cremoriswere investigated for autolysis and optimal conditions for the autolytic process were developed. The rate of autolysis was maximal in exponential phase cells in 0·01 M-Na phosphate buffer, pH 6·5–7·5, at 30–45 °C. Autolysis of the native exponential phase walls was activated by trypsin and inhibited by lipoteichoic acid and cardiolipin. Decreased trypsin activation was found in intact exponential phase cells and no activation in stationary phase cells.N-acetylmuramylhydrolase action in the autolytic system ofLc. lactissubsp.cremorisstrains was indicated by the progressive release of reducing groups. No amidase or endopeptidase action was found. Great variation in the rate of autolysis of whole cells was observed between the two slime-forming strains. Intact cells of strain T5exhibited decreased autolytic activity, but a higher rate of autolysis of isolated exponential phase walls. Autolysins from strain T5walls exhibited lower hydrolytic activity against sodium dodecyl sulphate-treated walls of the other two strains as compared with strains MLS96 and HA. Quantitative analysis revealed higher protein and phosphorus and lower hexosamine and rhamnose in cell wall preparations of strain T5compared with the other two strains. Results suggest that the decreased rate of autolysis of strain T5cells may at least in part be caused by cell surface components other than cell-wall peptidoglycan. It is proposed that the difference in autolytic characteristics should be used as a criterion when selecting starter strains of lactococci (streptococci).

Inhibitory effect of sulfur dioxide and other stress compounds in wine on the ATPase activity of Oenococcus oeni

Malolactic fermentation (MLF) is carried out by Oenococcus oeni under very harsh conditions. This paper shows that stress compounds in wine such as SO(2), fatty acids and copper have an inhibitory effect on cell growth and MLF duration, and relates this effect to an inhibition of ATPase activity. Of the stress compounds, SO(2) and dodecanoic acid had the strongest effect, decreasing the ATPase specific activity to 37% and 58%, respectively. It can be concluded that ATPase is a good indicator of the physiological state of the cells and their ability to lead MLF.

The F1-ATPase from Streptococcus cremoris: isolation, purification and partial characterization

1. The F1-ATPase from the plasma membrane of Streptococcus cremoris HA was released by low ionic shock wash and purified by gel filtration and ion exchange chromatography. 2. The specific activity of the purified F1-ATPase was 25.8 mumol Pi/mg protein/min. 3. Km for ATP was 0.80 mM, and Ki for ADP as a competetive inhibitor 0.40 mM. 4. The purified F1-ATPase consisted of five subunits, alpha, beta, gamma, delta and epsilon, with molecular masses of 47.0, 45.0, 29.5, 22.0 and 13.0 kDa, respectively. 5. The isoelectric point of the enzyme complex was found to be 4.4.

Properties of the N,N'-dicyclohexylcarbodiimide resistant ATPase of Streptococcus cremoris

1. The specific activity of the membrane-bound ATPase of Streptococcus cremoris HA was 1.30 mumol Pi/mg protein/min. 2. Km for ATP as substrate was 0.8 mM. 3. The pH optimum was 8.0 at +37 degrees C. 4. The ATPase was maximally activated with Mg2+/ATP molar ratio of 1:2. 5. Cations activated the enzyme in order: Mg2+ greater than Co2+ greater than Mn2+ greater than Zn2+ greater than Ca2+ greater than K+ greater than Na+. 6. The enzyme was inhibited by oligomycin (27-77%), sodium azide (13-33%) and ouabain (15-22%). N,N'-dicyclohexylcarbodiimide had no effect on the enzyme activity.