ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1990.tb02879.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1990.tb02880.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Twelve derivatives ofEscherichia colistrain HB101 which contained different sizes of plasmids ranging from 3.9 Kb to 48 Kb and encoding resistance to various antibiotics were used. When these organisms were introduced into natural river water, the population declined rapidly and by day 3, the majority (i.e. more than 99.9%) of them could no longer be detected on antibiotic‐amended culture plates. If the river water was filter sterilized first, the added organisms maintained their population for up to 7 d without any significant decrease in numbers. Similar results were also observed in sterilized tap water or distilled water. This indicated that the disappearance of these organisms in the aquatic environment was caused mainly by biotic factor(s). The loss of the ability to grow in the presence of antibiotics by some of theE. coliwas not observed unless they were allowed to grow in the antibiotic‐free environment first. When the test organisms were added to natural silt loam, a large portion of the original population still remained viable after 16 d. There was no relationship between the percentage survival ofE. coliin natural river water and the sizes of plasmid harboured. On the other hand, when these bacteria were added to natural soil, survival appeared to increase as plasmid size increased. and accepted 19 August

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1990.tb02881.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The possible role ofAeromonasspp. as potential food‐borne psychrotrophic pathogens was investigated by examining organisms isolated from processed raw chicken for their biochemical characteristics, ability to produce exotoxins and to grow at chill temperatures. These strains, in particularA. sobria, with identical characteristics to human diarrhoea‐associated aeromonads were readily found. Chicken, and human and environmental (water) strains characterized in a previous study, were investigated for their ability to grow at refrigeration temperatures (5 ± 2°C) and, for selected strains, the theoretical minimum temperature for growth (Tmin) was determined from the growth pattern in a temperature gradient incubator. All enterotoxigenic chicken strains tested were typical mesophiles, with an optimal growth temperature of ˜37°C andTminvalues ˜4.5°C. They were rapidly outgrown by a psychrotrophicPseudomonassp. typical of spoilage biota found on food. Enterotoxin was not produced below 15°C by any of the toxigenic food strains tested. TheAeromonasstrains isolated from chickens in this study seem unlikely therefore to be a significant health risk, provided the chickens are properly stored and cooked. This would appear to be substantiated by the lack of reports of food‐associated outbreaks of illness from t

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1990.tb02882.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

At a city abattoir, a wholesaler and 10 different supermarkets, surface microbiological samples were taken of carcasses, hands and apron fronts of members of staff and equipment (mincers and saws). In addition, minced meat, packaged and displayed in chilled cabinets, was also sampled. Carcasses, personnel surfaces and equipment were monitored by a modified agar sausage technique. From each of the highest dilution psychrotrophic plate counts, five colonies were selected randomly, isolated and identified (1265 in total). Microbes developing on chilled meat were also isolated from other surfaces in the production chain. On chilled meat (51%) and at the abattoir (36%) pseudomonads were the predominant organisms followed by the Gram‐positive cocci on chilled meat and byAcinetobacter, MoraxellaandAlcaligenesspp. at the abattoir. At the wholesaler Gram‐positive cocci (32%) predominated, followed byAlcaligenes, MoraxellaandAlcaligenesspp.Pseudomonas, Alcaligenes, Neisseriaceaeand related genera, Gram‐positive cocci, species from the coryneform groups of bacteria and yeasts were identified from all the surfaces monitored. Identification with the API NE20 was unsatisfactory. Enterbacteriaceae, lactobacilli and endospore‐forming bacteria were identified occasionally, but their significance as contaminating organisms seems low. NoSalmonellaspp. were identified. and accepted 25 J

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1990.tb02883.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The survival ofStreptococcus uberis, Strep. bovis, Enterococcus faecalisspp.faecalisandEnt. faeciumin animal feed and on wheat straw was studied for one month.Streptococcus bovissurvived the best in feed andStrep. uberisthe worst while on strawEnt. faeciumwas the most resilient species and there was little to choose between the other three. The recovery of all species, exceptingStrep. bovis, on selective and non‐selective agar was comparable. The growth ofStrep. bovis, on the other hand, was inhibited on both Edward's medium and inulin aga

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1990.tb02884.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Cultivation of the cellulolytic anaerobeRuminococcus flavefaciensstrain 007 on a nutrient medium containing cellobiose as energy source resulted in a four‐ to five‐fold reduction in the cotton‐degrading activity of the strain after 15–18 subcultures. Two single colony re‐isolations also lost cotton‐degrading activity after repeated cultivation on cellobiose. When the form with poor cotton‐degrading activity (007S) was serially subcultured on cotton fibres, high cotton‐degrading activity was recovered after 7–13 subcultures. One (of three) single colony re‐isolations of 007S also recovered cotton‐degrading activity under these conditions. The time course of these changes in activity suggests that they resulted from mutations. The cotton degrader (007C) was slightly more active against Avicel, Sigmacell and filter paper than was 007S, but 007S and 007C showed similar activity against acid‐swollen cellulose. Strain 007C was not significantly more active than 007S in degrading barley straw (with or without ammonia treatment) or wheat straw. The property that enables strain 007C to degrade cotton appears to play at most a minor role in the degradation of straw.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1990.tb02885.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

An X‐prolyl dipeptidyl peptidase (EC 3.4.14.5) has been purified from a crude intracellular extract fromLactococcus lactisspp.lactisNCDO 763 by ion‐exchange chromatography and gel filtration. One protein band was detected after electrophoresis of the purified enzyme in the presence or absence of sodium dodecyl sulphate. The enzyme is a 190 kDa dimer composed of identical subunits. Optimal activity occurs at pH 8.5 and 40–45°C and the enzyme is inhibited by reagents specific for serine proteases, such as diisopropylfluorophosphate. The enzyme hydrolyzesp‐nitroanilide‐ or β‐naphthylamide‐substituted X‐Pro dipeptides, as well

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1990.tb02886.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Pure cultures of five microbial species were used to test the formation of exopolysaccharides (EPS) when grown in agitated sucrose (5% w/v) containing liquid cultures. These test species were isolated from stems of freshly harvested cut flowers (Chrysanthemum, GerberaandRosa) or from the vase water of these flower cultivars. The partial conversion of sucrose into other saccharides was demonstrated by HPLC and colorimetric analysis. The final polymeric character of the newly formed saccharides was investigated. SEM preparations of xylem vessels ofRosamaintained in EPS‐containing vase water showed blockage, disorganization and injury of the vessel structure. EPS were shown not to pass the xylem pit membranes. Recovery from the first symptoms of disturbed water flow (wilting) due to EPS was possible in young flowers by cutting off the blocked part of the stem (15–20 cm. The higher the microbial conversion rate of sucrose into polysaccharides, the more disturbed were the water relations of the roses placed in the EPS‐containing fluid, as was demonstrated by the decrease of: (1) water conductivity ofRosastem segments (ml/30 min); (2) water uptake (ml/d); (3)Rosavase life (d); and (4) flower bud development. Bacterial EPS (presumably levans and dextrans) could be concentrated in the retentate by molecular filtration with a cut‐off level of 10000 Da. Filtrates did not causeRosaxylem blockage and ‘bent‐neck’of the flower stems, but still may be toxic to roses. Two simple methods were also used for diagnostic investigations: (1) the beetroot tissue cube test to detect microbial products causing injury of the plant cell membranes, (2) the acid fuchsin test, to show the extent and location ofRosaxylem ves

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1990.tb02887.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Ninety‐seven strains ofCapnocytophagaisolated from the oral cavity and the type strains ofC. ochracea, C. sputigenaandC. gingivaliswere compared by one‐dimensional SDS‐PAGE of whole cell proteins. The protein patterns were highly reproducible and were used as the basis for numerical taxonomic analysis. The clusters containing the type strains ofC. ochraceaandC. sputigenasegregated at the 78% similarity level. Some of the eight clusters obtained at this level showed good correlation with grouping based on the results of biochemical testing for lactose and galactose fermentation and nitrate reduction. No consistent association was found between protein profiles and colony type, size or colour or cell length but all agar‐adherent colony types segregated into a single cluster. and accepted 25 J

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1990.tb02888.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY