Isolation and characterization of a temperate bacteriophage from a ruminal acetogen.

Nine acetogenic bacterial cultures recently isolated from the bovine rumen were tested for phage susceptibility by plaque formation. Both clear plaques and plaques with turbid centers were occasionally seen, but could not be used repeatedly to lyse pure cultures of acetogens, suggesting the possibility of a temperate phage. Five of the nine acetogenic isolates showed a response to mitomycin C induction.

Production of proteases by psychrotrophic microorganisms.

Six milk-derived psychrotrophic microbial cultures were screened for the ability to grow at refrigerated temperatures and produce proteases in reconstituted skim milk. Of these, two cultures, Pseudomonas fluorescens M3/6 and Pseudomonas fragi K122, produced extracellular protease(s) beginning 7 d postinoculation when the cultures had entered late log or early stationary phases of growth. Further work with these two cultures showed that intracellular proteases were present after only 20-h incubation, before detection of the extracellular proteases.

Isolation and characterization of microorganisms associated with the traditional sorghum fermentation for production of sudanese kisra.

Sorghum flour obtained from Sudan was mixed with water in a 1:2 (wt/vol) ratio and fermented at 30 degrees C for 24 h. The bacterial populations increased with fermentation time and reached a plateau at approximately 18 h. At the end of 24 h, sorghum batter pH had dropped from 5.

Calcium alginate-immobilized cultures of lactic Streptococci are protected from bacteriophages.

Calcium alginate-immobilized cultures of lactic streptococci were grown in milk and assessed for their sensitivity to homologous bacteriophage, proteolytic activity, and acid production. Immobilized cultures of Streptococcus lactis C2 and Streptococcus cremoris HP were protected from attack by bacteriophage due to the exclusion of phage particles from the gel matrix. These cultures were also functionally proteinase-deficient when immobilized in calcium alginate beads and grown in milk.

Conjugal transfer of plasmid DNA between streptococci immobilized in calcium alginate gel beads.

A rapid and simple technique was developed for conjugation between group N and group D streptococci by using cells entrapped within calcium alginate gel beads. With this method, the frequencies of transfer of lactose metabolism from Streptococcus lactis ME2 to S. lactis LM2302 were comparable to those achieved with agar surface matings.