Ingolf F. Nes

Characterization of the bacteriophage B2 of Lactobacillus plantarum ATCC 8014.

Bacteriophage B2 of Lactobacillus plantarum ATCC 8014, isolated in 1971, belonged to Bradleys group B. Electron microscopy revealed an isometric head (110 nm) and a long non-contractile and flexible tail (500 nm) containing about 75 regularly aligned lateral striations. Burst size was 12-14 phages per infectious centre. The latent period for phage development was 75 min and the rise period approximately 90 min. The phage particle contained 5 major proteins. The buoyant density of the phage in CsCl was measured as 1.575 g/cm3. B2 genome was a linear double-stranded DNA molecule of 37 +/- 1% guanosine-cytosine. Its size was 73 kilobase pairs (kbp). Restriction analysis of the genome showed that 4 restriction enzymes (Xba I, Sac I, Bgl II and Sma I) gave single site cuts in the DNA, while Ava I and Sal I formed 2 and 5 cuts, respectively.

Slaughterhouse by-products preserved by Lactobacillus plantarum fermentation as feed for mink and foxes

Lactic acid fermentation was evaluated as a method to preserve abattoir waste for use in fur animal diets. The method used involved grinding, acidifying to pH 5–5.2 by formic acid and propionic acid, addition of 6% molasses as a carbohydrate source and a starter culture of Lactobacillus plantarum. Fermentation was completed after 2–3 days at 25°C. The final pH of the fermented product was 3.8–4.1. Storage experiments revealed satisfactory stability. The fermented products could be kept for weeks at room temperature (20°C) and for months in a cold room (4°C). The amino acid composition of the 4 types of abattoir waste tested was not significantly changed by fermentation. Digestibility studies with mink revealed slight, but significant (P < 0.05), effects of fermentation. The digestibility of cystine and threonine was reduced and that of glycine and proline increased. Two types of fermented abattoir waste were investigated in 2 long-term feeding experiments with mink and blue foxes. In the mink trial, diets with 10 or 20% fermented abattoir waste supported normal reproduction, kit mortality and body growth. In one experiment, there was a significant reduction in mink kit body weights with 20%, but not with 10% fermented abattoir waste in the diet. In the fox trial, litter sizes and kit viability tended to improve with 20% fermented abattoir waste, while kit body weights were unaffected. It is concluded that fermentation could be an acceptable process for the preservation of abattoir waste intended for the feeding of fur animals.

Mutagen formation in fried meat emulsion containing various amounts of creatine.

The formation of mutagens in fried, minced meat emulsion was evaluated by the Ames Salmonella test system. Exogenous addition of creatine to the emulsion prior to frying greatly enhanced the mutagenicity of the emulsion. Addition of 5% creatine resulted in a 40-fold increase in the mutagenicity of the fried meat emulsion in the frameshift test strain, TA98, and in a 8-fold increase in the base substitution test strain, TA100. The present results suggest that creatine is an important factor in the mutagen formation in fried meat products.

Nonnisin Bacteriocins in Lactococci: Biochemistry, Genetics, and Mode of Action

I. Summary In recent years we have seen a rapid increase in our knowledge of the structure, genetics, and mode of action of a number of bacteriocins that are produced by certain strains of lactococci. A number of the new bacteriocins have been purified to homogeneity, allowing their amino acid sequence analysis. The genetic information for both the production of and immunity against a number of lactococcins has been analyzed at the nucleotide level and has revealed that these bacteriocins are processed at their amino-terminal end. In addition to the bacteriocin structural and immunity genes, two genes have been identified that are essential for lactococcin production and, on the basis of protein homology studies, the products of these genes tentatively form a dedicated secretion system for lactococcin. The effect of purified lactococcin A on whole lactococcal cells and vesicles indicates that the bacteriocin increases the permeability of the cytoplasmic membrane of sensitive lactococci in a voltage-independent way. The specificity of lactococcin A for lactococci seems to stem from the fact that the bacteriocin recognizes a Lactococcus- specific membrane receptor protein.

The Nonlantibiotic Heat-Stable Bacteriocins in Gram-Positive Bacteria

ABSTRACT Gram-positive bacteria produce a range of antimicrobial peptides, and most of them are classified as bacteriocins. Most of these bacteriocins are found in the lantibiotic (Class I) and in the heat stable, nonlantibiotic group (Class II). Class II comprises by far the most numerous and diverse group with respect to peptide sequence, production, and range of target specificity. The pediocin-like bacteriocins (Class IIA) are the largest unifying subgroup and the most studied. This review summarizes the diversity of Class II bacteriocins, by reference to the most thoroughly biochemically and/or genetically characterized bacteriocins.

Formation of mutagens in an amino acid-glucose model system and the effect of creatine

Abstract Heating of amino acids and glucose in a water solvent system produces substantial amounts of mutagens only at alkaline pH (10·5). Positive response was demonstrated with the Salmonella tester strains TA 98, TA 1538, TA 97, TA 1537 and TA 100. When creatine was added to this system prior to heating, mutagens were formed at all pHs tested (pH 4, 7, 9 and 10·5) and highest mutagenic activity was recorded at pH 9·0 and pH 7·0. The amount of mutagen produced was dependent on the creatine concentrations. A linear increase of mutagenic activity was recorded in the threonine-glucose system when creatine concentration increased to 0·5 m . Similar results were also demonstrated in the glycine-glucose system up to 0·2-0·3 m creatine. The increased amount of mutagenic activity found in the presence of creatine was demonstrated to be active only against the frame shift tester strains (TA 98 and TA 97) and not when tested with the TA 100 strain. HPLC analyses indicated that the mutagenic activity found in the pure amino acid glucose system at alkaline pH was also found in the presence of creatine; however, the major peak of mutagenic activity in the creatine containing system was not found in the absence of creatine.