The Journal of applied bacteriology最新文献

Bacterial luciferase was used to investigate the relationship between the thermostability of a cytoplasmic reporter molecule and cellular heat resistance. The luciferase activity of Vibrio fischeri was expressed in strains of Escherichia coli, Salmonella typhimurium, Listeria monocytogenes and Brochothrix thermosphacta following transformation with plasmid pSP13 carrying the luxAB genes. The thermostability of intracellular luciferase varied depending on the organism in which it was expressed, but was not related to the cellular heat resistance of the different organisms. Addition of xylitol to the heating medium protected against loss of viability and inactivation of intracellular luciferase. Glycerol also protected against loss of viability but was less effective at preventing thermal denaturation of luciferase.

Isolates of the salmonid pathogen Vagococcus salmoninarum were recovered from Atlantic salmon, rainbow trout and brown trout with peritonitis. The phenotypes of these isolates and the type strain of Vag. salmoninarum NCFB 2777 were determined by morphological, biochemical and physiological tests and whole cell protein profiles by SDS-PAGE. There was a high level of phenetic similarity between the salmonid isolates and the type strain. The species forms short Gram-positive rods, hydrolyses L-pyrrolidonyl-beta-naphthylamide, is alpha-haemolytic on sheep's blood agar, grows at pH 9.6 and 10 degrees C but not at 40 degrees C or in 6.5% NaCl and is catalase-negative; a Lancefield group N antigen is not present. Vagococcus salmoninarum can be distinguished phenetically from similar fish pathogens including Carnobacterium piscicola, Enterococcus seriolicida and Lactococcus piscium.

Variations between and within individuals, and correlations between concentrations of bacterial metabolites, including putrefactive products, ammonia and short chain fatty acids (SCFAs), enzyme activities, moisture and pH, as well as bacterial composition, were studied in faecal samples from seven healthy adults over a period of 7 months. Large variations, both between and within individuals, were observed in concentrations of putrefactive products. Although values for ammonia, SCFAs, enzyme activities, moisture and pH were generally variable, significant person-to-person differences were observed. While ranges of log viable counts of the predominant bacteria such as eubacteria, bifidobacteria and bacteroides in each subject remained between 0.2 and 1.3, those of enterobacteria, streptococci (including enterococci) and lecithinase-negative clostridia varied between 0.4 and 3.0. Levels of bifidobacteria, enterobacteria, streptococci and total aerobic bacteria showed inter-individual variations. Correlations were found among certain of the parameters: moisture correlated negatively with p-cresol (r = -0.707), pH (r = -0.671) and beta-glucosidase activity (GS) (r = -0.608), and positively with acetic acid (r = 0.621), while negative correlations were observed in pH with acetic and butyric acids (r = -0.690 and -0.623, respectively). No significant correlations were found between bacterial compositions, and other faecal factors such as pH, moisture, metabolic enzyme activities and concentrations of putrefactive products.

Forty-seven tetracycline-resistant staphylococci from the skin of pigs were examined for genes mediating this resistance. Seventeen isolates were also resistant to minocycline and all hybridized with the tet(M) gene; 23 carried the tet(K) gene and 10 the tet(L) gene. Three carried more than one gene and two did not hybridize with any of the three probes tested. Maps were constructed for two plasmids carrying the tet(K) gene, all were very similar in size (4.35-4.7 kb) and structure and closely resembled the plasmid pT181. Four plasmids which bore the tet(L) gene differed in size, ranging from 4.3 to 11.5 kb, and were dissimilar in structure except for the portion bearing the gene.

The traditional indicators Escherichia coli (in practice currently, though ecologically inaccurately, represented by 'thermotolerant coliforms' at 44 degrees C) and Enterococcus spp. proved to be suitable for the diagnosis of heavy and frequent faecal pollution observed in potentially dangerous waters, especially those originating from karstic aquifers. On the other hand, natural and treated waters, slightly and inconsistently contaminated, occasionally showed a variable Gram-negative flora, difficult to classify by routine tests. In that case, complete identification of isolates may be necessary to ensure a valid decision on the potability of the supply. At any rate some of the Enterobacteriaceae contained in the 'faecal coliform' group and many other 'coliforms', distinct from E. coli, lack sanitary significance although their presence at certain levels may indicate inadequate disinfection, hiatuses in the integrity of the distribution system or both.

Heat resistance of the Pseudomonas fluorescens P-26 proteinase in terms of D-value was studied in whole milk, skim milk, whey and 0.05 mol l-1 phosphate buffer at 72.5, 130, 135, 140, 145 and 150 degrees C subsequent to its partial purification through (NH4)2 SO4 precipitation (45-65% saturation) and solvent fractionation with 1.0 to 2.0 volumes of isopropanol. The D-value was maximum for the proteinase at all temperatures when determined in whole milk (D150 = 0.088).

Salmonella senftenberg and Salmonella typhimurium survived the production of gelatin sheets containing nutrient broth although there was some evidence of cell damage. Both strains survived but did not grow in glassy states with an a(w) of 0.45-0.28 and rubbery states with an a(w) of 0.93-0.96 for at least 28 d. Survival was less in intermediate states with an a(w) between 0.55 and 0.74. The results suggest that salmonellas should be excluded from glassy state products in order to prevent salmonellosis.

The requirement for essential amino acids and vitamins was determined in wild-type Lactobacillus plantarum strains isolated from green olive fermentation brines. All the strains were found to be auxotrophic with respect to the amino acids but some of them were prototrophic for pyridoxal, p-aminobenzoic acid and/or nicotinic acid. Their growth response to these nutrients was also studied and found to be quite heterogeneous. Nutritional requirement pattern as a criteria for selecting starter cultures is discussed.

A total of 712 strains of lactic acid bacteria isolated from forage grasses were studied for their ability to ferment fructans of phlein- as well as inulin-type. Only 16 strains utilized phlein and eight of these also fermented inulin. They were identified as Lactobacillus paracasei subsp. paracasei, Lact. plantarum, Lact. brevis and Pediococcus pentosaceus. In the species Lact. paracasei subsp. paracasei, all strains gave positive results, whereas the other positive strains possessed unique properties within their own species. In all but two cases (strains of the species Lact. plantarum), the phlein was more intensively fermented than the inulin, as indicated by a lower pH and a higher lactic acid concentration. On the basis of the outcome of this study it seems worthwhile to inoculate grasses of low sugar content before ensiling with an active strain that can ferment fructans.

Sixty strains of Bacillus sphaericus, including 31 insect pathogens were studied by multilocus enzyme electrophoresis and were classified into 44 zymovars (electrophoretic types). Among the entomopathogenic strains, 11 belong to the same zymovar (Z59) indicating a widespread frequent genotype. Bands of enzyme activity were not detected among the strains for the loci GPI (E.C.5.3.1.9), G6P (E.C.1.1.1.49), 6PG (E.C.1.1.1.44) and ME (E.C.1.1.1.40). The enzymatic loci NP (E.C.2.4.2.1) and ACON (E.C.4.2.1.3) were monomorphic while the other enzymes, MDH (E.C.1.1.1.37), LeDH (E.C.1.4.1.9), ADH (E.C.1.4.1.1), EST (E.C.3.1.1.1), PEP-2 (E.C.3.4.11.1), PEP-3 (E.C.3.4.11) and PEP-D (E.C. 3.4.13.9) were polymorphic. The genetic variation in the non-insect pathogenic group seemed to be greater than in the entomopathogenic group. This latter group appears to be distinct from other strains of these species. All insect pathogens were recovered in the same phenetic cluster and a diagnostic allele is reported for the identification of entomopathogenic strains.