Characteristics of the Inhibition of Brochothrix thermosphacta by Lactobacillus brevis

When cultures of Brochothrix thermosphacta and Lactobacillus brevis were grown together or separated by a dialysis membrane (M.W. cut off = 3,500 daltons), the growth of Brochothrix was inhibited. This phenomena occurred under both aerobic and anaerobic conditions and was unaffected by the presence of catalase (412 units/ml). The antagonism appeared to be pH-mediated since it depended on glucose concentration, but low pH (4.5) alone did not directly affect the viability or salt tolerance of singular cultures of B. thermosphacta . Electron microscopy of thin sections of B. thermosphacta after 24 to 48 h of exposure to L. brevis revealed distinct lesions within the peripheral cell wall fabric. These were not seen in control cells of the same age or in cells exposed to 0.01 to 0.1 M acetic acid. Induction of autolysis in B. thermosphacta by cell wall metabolism imbalance was believed to be the cause of the growth inhibition.