SUMMARYThe properties of a bacteriocin derived from Lactobacillus fermenti strain 466 were investigated. The bacteriocin was present in low titre in supernatant fluids from overnight broth cultures and was not inducible by ultraviolet radiation. It was purified and concentrated to a titre of I/IOOO by dialysis, chromatography on Sephadex G IOO and calcium phosphate gel columns. The bacteriocin is heat stable, and sensitive to trypsin and pepsin but not to lysozyme. No migration was demonstrated in electrophoretic fields in agar gel. Electron microscopy of the bacteriocin did not show any phage components. The bacteriocin is a macromolecular lipocarbohydrate protein which consists of 16 amino acids, four sugars, hexosamine and phosphorus. The biological activity of this complex is dependent on its structural integrity.

Peptides deduced from the C-terminal end (residues 191 to 227) of pestivirus envelope protein E rns were used to develop enzyme-linked immunosorbent assays (ELISAs) to measure specifically antibodies against different types of pestiviruses. The choice of the peptide was based on the modular structure of the E rns protein, and the peptide was selected for its probable independent folding and good exposure, which would make it a good candidate for an antigenic peptide to be used in a diagnostic test. A solid-phase peptide ELISA which was cross-reactive for several types of pestivirus antibodies and which can be used for the general detection of pestivirus antibodies was developed. To identify type-specific pestivirus antibodies, a liquid-phase peptide ELISA, with a labeled, specific classical swine fever virus (CSFV) peptide and an unlabeled bovine viral diarrhea virus peptide to block cross-reactivity, was developed. Specificity and sensitivity of the liquid-phase peptide ELISA for CSFV were 98 and 100%, respectively. Because the peptide is a fragment of the E rns protein, it can be used to differentiate between infected and vaccinated animals when a vaccine based on the E2 protein, which is another pestivirus envelope protein, is used.

S U M M A R YSixty different isolates of methionineless auxotrophs of Proteus mirabilis were arranged in nine biochemical groups according to their growth responses to methionine or its precursors. These requirements suggested that P. mirabilis possesses a route for methionine biosynthesis which is similar to the pathway operating in Escherichia coli and Salmonella typhimurium. In contrast to findings with the latter organisms syntrophism was not observed between these mutants of P. mirabilis even with sonically disrupted potential feeder strains. Two methionineless auxotrophs of E. coli fed auxotrophs of P. mirabilis which had metabolic blocks earlier in this pathway. These results, which suggested an inability of methionineless auxotrophs of P. mirabilis to accumulate precursors of metabolic blocks, were confirmed by a quantitative comparison of methionine precursors in wild-type and mutant strains of P. mirabilis and E. coli. The presence of S-methylcysteine (SMC) was demonstrated in wild-type and methionineless auxotrophs of P. mirabilis and E. coli. The growth responses of methionineless auxotrophs of P. mirabilis to SMC supported a hypothesis for the participation of this amino acid in the synthesis of methionine via an alternative route.

SUMMARYOne hundred and eighteen different strains of Proteus vulgaris were investigated for bacteriocinogeny. These and an additional 44 strains of P.vulgaris were used as indicators. Sixty-seven of the strains had a nontransmissible killing effect on one or more of the indicator organisms and 3o of these 67 bacteriocins with different spectra of activity were further investigated. Individual bacteriocins killed from 5 to 87 of the P. vulgaris indicators and a number of 44 different P. mirabilis strains but had no action on strains of other species of the family Enterobacteriaeeae. Broth cultures of bacteriocinogenic strains are inducible by ultraviolet fight and yield bacteriocin titres of about I/IOO. Activity is sedimentable by high-speed centrifugation. Electron microscopy of all 3o preparations revealed similar phage-tail-like structures with a contractile sheath round a hollow core. The structures consisted of protein and did not contain DNA. The particles resembled some pyocins and also the tail of a P. vulgaris transducing phage. In z preparations a few phage-like particles resembling other Proteus phages were also seen. Bacteriocin activity was always associated with uncontracted sheaths, and triggered tails did not adsorb to susceptible organisms. We conclude that the tail-like structures are the products of defective lysogeny. The high incidence of the latter state may be accounted for by the selection of genes favourable to the host which were originally acquired through transduction by lysogenization or lysogenic conversion.

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