ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb01679.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

1. Introduction, 4032. Acid end products, 403 3. DNA base composition, 404 4. Cell walls, 404 5. Enzymes, 407 6. Lipids, 408 6.1 Pigments, 408 6.2 Fatty acids, 408 6.3 Polar lipids, 409 6.4 Menaquinones, 411 7. Taxonomic considerations, 412 8. Conclusions, 414 9. References, 414

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb01680.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Direct microscopical observations of single developing cysts in sealed slide microcultures prepared from 5‐days‐old tube cultures of the Reiter treponeme revealed two distinct phases in the life cycle. In one phase transverse fission was the main method of multiplication while in a second phase, occurring when conditions in the medium became unfavourable for propagation, cysts developed. These could release large numbers of actively motile treponemes when returned to optimum growth conditions. These observations, together with results of the dilution method for the calculation of the Most Probable Number and the absence of a response in treponemes killed by high temperature (45°C) or abnormal pH (10), showed that the cysts were viable and a mode of propagation for the Reiter trepo

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb01681.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Bacteria were separated from raw meat homogenate by a simple three‐stage process. Centrifugation (10 s at 2000 g) removed coarse particles; stirring with the cation exchange resin Bio‐Rex 70 removed smaller particles and filtration through 0.22 μm membranes removed soluble materials. By this process 70—80% of the microbial populations of meat homogenates were consistently isolated on the filters. A linear relationship was found between log10microbial ATP and log10colony count of meat over the range 105—109cfu/g. The value of ATP/cfu for meat samples was within the range previously reported for pure cultures. These data indicated that ATP extracted from the filters originated from bacteria in the meat samples. Several samples can be analysed simultaneously in an elapsed time of 20—25 min. The variability associated with estimates of both colony counts and ATP levels has been

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb01682.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

A total of 203 samples of faeces from 124 cows was examined for the presence ofYersinia enterocoliticaand related species by a variety of isolation procedures. Cold enrichment at 5°C for three weeks, followed by plating on cefsulodin‐irgasannovobiocin agar yieldedYersiniaspecies most frequently.Yersinia enterocoliticaor related species were isolated from 50% of the co

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb01683.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The antibiotic resistant faecal flora of a domestic dog suffering from an acute enteric infection was examined. The flora exhibited overall resistance to a wide variety of antibiotics. However, following restoration of the animal to normal health, overall resistance to ampicillin (Ap), tetracycline (Tc), chloramphenicol (Cm) and streptomycin (Sm) was lost, although low numbers of bacteria resistant to these four antimicrobial agents could still be isolated up to one year later. A total of 11 strains were purified for further study. All 11 were positively identified asEscherichia coliand shown to be resistant to various combinations of the above antibiotics, and additionally to kanamycin (Km). Each strain harboured from one to five plasmids, although only four proved capable of transferring antibiotic resistance toEscherichia coliK‐12. One of the strains was found to harbour two conjugal plasmids pNJ101 (60 Md) and pNJ102 (133 Md) which coded for resistance to Cm, Tc, Ap and Cm, Tc, Km respectively. A third plasmid pNJ103 (29 Md) remains cryptic. The possession of the two plasmids pNJ101 and pNJ102 appears to be an unstable situation as variants arose harbouring one or other of the plasmid

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb01684.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Saccharomyces uvarum, Geotrichum candidum, Endomycopsis burtoniiandHansemula canadensishave been isolated from deteriorated silages and/or spoiled lactic acid fermented foods. All yeasts could grow in relatively high (100 mmol/l) concentrations of acetate or lactate in Wickerham's assimilation broth but were inhibited by increasing concentrations of these acids. Propionate was much more inhibitory than acetate or lactate. Growth rate, but not final cell yield, was adversely affected by increasing concentrations of these acids. The three acids used in combination were synergistically inhibitory toH. canadensisandG. candidum. Saccharomyces uvarumwas inhibited by synergistic mixtures of acetate/propionate.Endomycopsis burtoniiandH. canadensiswere inhibited by synergistic mixtures of acetate/lactate, acetate/propionate and lactate/propionate. Lactate and propionate had a synergistic inhibitory effect onG. candidum.The mechanism of inhibition of growth ofS. uvarumby acetate and propionate was further investigated. Acetate and propionate each caused a reduction in cellular efficiency (Y, μg cells/μmole glucose consumed). Mixtures caused a drastic reduction in growth rate and Y. These results suggest that the cells may expend energy in reducing intracellular concentrations of acetate while propionate probably acts in a different manne

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb01685.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

When grown on solid or in liquid Brain Heart Infusion at 37°C,Staphylococcus epidermidisNCIB 11536 produced antibiotic activity against a wide range of Gram positive bacteria. Production was influenced by aeration, pH, glucose concentration and specific growth rate. Inhibitory activity could be concentrated by ammonium sulphate precipitation (30–55% saturation). On Sephadex G50 using 0.05 mol/1 sodium phosphate buffer, pH 6.0, two peaks of antibiotic activity were detected. The first peak eluted with the void volume (Kd= 0) and the second peak was retained by the gel (Kd= 0.73–0.77). These two substances did not represent the monomeric and polymeric forms of a staphylococcal bacteriocin. The low mol. wt inhibitor, which was responsible for over 95% of the recovered activity on Sephadex G50, could be partially purified by a combination of gel filtration on Biogel P2 and ion‐exchange chromatography on Sephadex C‐25. Yields were increased by combining these two steps into a single procedure (duocolumn). The semi‐purified inhibitor was desalted using Sep‐pak C18cartridges. Biological activity was resistant to enzymic denaturation except by high concentrations of trypsin (50 units/μg, 3 h, 25°C). This peptide antibiotic is different from any previously described staphylococ

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb01686.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Residual nitrite was lost from chub‐packed luncheon meat during storage through both chemical breakdown and microbial consumption. The relative importance of these mechanisms in this pasteurized product was determined by the speed of development of the spoilage microflora, which is influenced by storage conditions. The nitrite half‐life due to chemical loss was 13 d at 25°C and 36 d at 10°C. When microbial growth occurred these half‐lives were reduced to 2.6 d and 21 d, respectively. Qualitative differences in the microflora that developed at these two temperatures (denitrifyingBacillusspp. at 25°C and non‐denitrifyingStreptococcusspp. at 10°C) account for the large temperature effect. Growth ofStreptococcusspp. increased the rate of chemical nitrite loss in chubs by reducing the pH value. Nitrite did not inhibit the aerobic growth of eitherBacillusorStreptococcusspecies associated with spoilage but did inhibit the anaerobic growth ofBacillusspp. This bacteriostatic effect of residual nitrite in anaerobic conditions will decrease during storage as nitrite level falls and oxygen penetrates the chub pack. Nitrite‐mediated bacteriostasis does not obviate the need for refrigerated storage but does afford a real, if ephemeral, safeguard against spoilage occurring during short periods of temp

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb01687.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Bacteria from a methanogenic wastewater population could be separated with a self‐generating density gradient of Percoll. The separation was performed by centrifugation for 30 min at 30000 g in a simple angle‐head rotor. Three types of bacteria were concentrated to apparent homogeneity in different bands; these were attributed to the methanogensMethanosarcinaandMethanothrix, and to the dissimilatory sulphate‐reducing bacteriumDesulfovibrio.The described technique will contribute to a rapid diagnosis of the bacterial types that are active in waste‐water tr

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1983.tb01688.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY