Effect of secondary metabolites on the organisms producing them: effect of nisin on Streptococcus lactis and enterotoxin B on Staphylococcus aureus.

The effect of secondary metabolites added to cultures of the organisms producing them was investigated. Nisin was added to growing cultures of a nisin-producing strain of Streptococcus lactis (354/07) and enterotoxin B to strains of Staphylococcus aureus (S6 and 243) producing enterotoxin B. One quarter (12 mug/ml) of the amount of nisin formed by the culture of S.

Change in the absorbancy of bacterial suspensions before initiation of growth.

The apparent absorbancy of suspensions of stationary-phase cells of Streptococcus lactis strain 354/07 decreased immediately after being placed in fresh media. This optical effect also occurred in defined mixtures of buffer glucose and KCl. CaCl(2) caused the absorbancy to increase.

Electron microscopic study of membranes and walls of bacteria and changes occurring during growth initiation.

Thin sections of stationary-phase Streptococcus lactis cells showed that the wall and membrane are 20 and 7 nm thick, respectively. Whole cells were examined by negative staining with ammonium molybdate and by shadowing. On air-drying of whole cells, the membrane pulled away from the wall revealing adhesions between these organelles.