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1.
Unsmoked Wiltshire bacon was produced with and without nitrate and with different concentrations of nitrite. Micrococci, Moraxella spp. and Moraxella -like organisms were the most common bacteria on the bacon after maturation when there was little difference between the microflora of the various back bacon. Collar bacon cured without nitrate carried much higher numbers of Moraxella spp. than that cured with nitrate. Micrococci and lactic acid bacteria usually predominated after vacuum-packed storage. Inclusion of nitrate in the cure increased the numbers of micrococci but did not reduce stability on storage. The highest numbers of lactic acid bacteria were present on bacon containing the lowest initial concentration of nitrite (34 parts/106 ) and it is thought that nitrite may delay the souring which these bacteria cause in vacuum-packed bacon. 相似文献
2.
The number of aerobic bacteria in a blanket peat decreased with depth from 26 times 106 /g dry peat in the surface layers to 0.5 times 106 /g dry peat at 30–40 cm down the profile, thereafter remaining roughly constant. Obligate psychrophiles comprised <2.5% of this population. Anaerobes were most numerous, 9 times 106 /g dry peat at 6–10 cm depth, decreasing to 0.5 times 106 /g at 20–30 cm. Calculations indicated that these counts, 103 –104 -fold lower than the direct counts, substantially underestimated the active microbial population. Gram negative rods, the predominant aerobes in the surface layers, were replaced by unidentified Bacillus strains at 10–20 cm depth but became increasingly more numerous further down the profile. The Gram negative rods were the most numerous organisms/m2 but the Bacillus strains, one third of which were present as spores, made the largest contribution to the biomass/m2 . Gram positive cocci, Arthrobacter and, infrequently, Nocardia were also isolated. Actinomyces -like forms were the predominant obligate anaerobes and were approximately three times more numerous than clostridia and a curved Gram negative rod. 相似文献
3.
Michael Krämer Manfred Baumgärtner Martin Bender Ralf Conrad 《FEMS microbiology letters》1990,73(4):345-350
Abstract The methanotrophs Methylomonas angile (type I) and Methylosinus trichosporium (type II) produced nitrite, nitrate and N2 O during growth on methane, apparently by heterotrophic nitrification of ammonium. The methanotrophs were also able to consume NO but did not produce it. After incubation of soil from a drained paddy field in the presence of CH4 the numbers of methanotrophs increased from 105 to 107 per gram dry weigth. The thus enriched soil showed increased rates of NO consumption while rates of NO production did not change. 相似文献
4.
Membrane inlet mass spectrometric analysis of N-isotope labelling for aquatic denitrification studies 总被引:1,自引:0,他引:1
Abstract: Techniques are described for measuring the isotope distribution in dissolved nitrate and N2 using membrane inlet mass spectrometry, which allows several gases to be measured in a water sample without the need for any separation steps. The isotope distribution in dissolved nitrate was measured using denitrifying Pseudomonas nautica to reduce the nitrate to N2 which was then measured by mass spectrometry. Pseudomonas nautica NCIMB 1967 was easily grown in nitrate-limited continuous culture minimising intra- or extracellular nitrate or nitrite pools, and the bioassay was tolerant of a range of salinities. The precision of the bioassay when measuring samples with high 15 NO3 − contents (0.5 μmol) was 0.05 atom%; with 0.1 μmol 15 NO3 − , the precision was around 0.2 atom%. Differences in labelling of N2 in preserved samples obtained from 15 NO3 − incubations of water-covered sediment cores were measured on parallel samples with membrane inlet MS and GC-MS. The membrane inlet technique was accurate but the precision on ratio measurements was lower than by GC-MS. 相似文献
5.
Gari was examined for its post-processing microbial content. Aerobic mesophilic bacteria and fungi were isolated from all samples. The total viable bacterial counts ranged from 2.0 × 102 to 8.0 × 104 cfu/g. Fungal counts ranged from 1.0 × 102 to 1.5 × 104 cfu/g. The total viable counts of fresh samples were much lower than those of market and packaged samples. Bacillus, Micrococcus and Proteus spp. were the bacteria isolated, Aspergillus niger, Aspergillus flavus and Penicillium spp. the fungi. Food borne parasites and pathogens such as Staph. aureus and Clostridium perfringens were not found. The gari samples were quite stable, having a shelf life of 3–6 months. The water activities of the samples ranged from 0.52 to 0.68. Based on the microbial counts of the samples, the critical upper limit for the safety of gari was set at 104 cfu/g dry sample. 相似文献
6.
Feed samples collected from different poultry farms and feed mills situated in Andaman and Nicobar islands in India were assessed for microflora and aflatoxin B1 contamination. The bacterial counts ranged from 1.0 times 107 to 8.8 times 107 cfu/g of the feeds, while counts of fungi ranged from 1.0 times 103 to 8.7 times 103 cfu/g. The mycoflora comprised mainly of Aspergillus spp., A. flavus being most dominant. Aflatoxin B1 was detected by monoclonal antibody-based enzyme linked immunosorbent assay technique and the content in different feed samples ranged from 5.5 to 90 ng/g. 相似文献
7.
Hera Maheshwari Purwoko Benedicte Hald Jens Wolstrup 《Letters in applied microbiology》1991,12(6):212-215
The content of aflatoxin and associated fungi was determined in 56 samples, including 34 of corn, 10 of soybean meal, nine of rice bran and three of broken rice, collected from different poultry farms and poultry feedmills situated around Jakarta-Bogor, Indonesia.
Ninety-one per cent of the corn samples contained aflatoxins and the total concentration ranged from 22 to 6171 μ g/kg. With rice bran, 100% of the samples were positive for aflatoxin B1 , ranging from 36 to 71 μ g/kg. No aflatoxin was detected in samples of soybean meal or broken rice. All the samples were contaminated by several fungi (8 times 103 –5 times 106 cfu/g) and further identification was limited to Aspergillus flavus and A. parasiticus. The dominant species was A. flavus (2 times 103 –4 times 106 cfu/g in corn samples, 1·0 times 103 –1·0 times 105 cfu/g in soybean meal, 2 times 104 –4·4 times 105 cfu/g in rice bran and 2 times 104 –6 times 104 cfu/g in broken rice). Some of the corn samples also contained A. parasiticus (2 times 103 –9·5 times 104 cfu/g). 相似文献
Ninety-one per cent of the corn samples contained aflatoxins and the total concentration ranged from 22 to 6171 μ g/kg. With rice bran, 100% of the samples were positive for aflatoxin B
8.
The distribution of microbial populations that decomposed sugar, cellulose and lignin-related substrates was examined in a beech Fagus grandifolia Ehrh. and maple Acer saccharum Marsh. dominated woodlot developed on glacial till. The topography of the woodlot, characterized by rises, depressions and more extensive level areas about 1 m in diameter with a 0.5 m vertical maximum, produced a mosaic of decomposer habitats designated as high, level and low sites.
In general, populations of sugar, cellulose and lignin decomposing organisms (based on ten estimates made from April to October) were two to four times higher in litter and soil samples from low sites than those from high sites. Sugar decomposing bacteria in litter were most abundant at all topographic sites. 135 × 106 g−1 dry litter at high sites, 396 × 106 g−1 at level sites and 456 × 106 g−1 at low sites; lignolytic fungi were least abundant, 391 × 102 g−1 dry litter at high sites. 700 × 106 g−1 at level sites and 954 × 102 g−1 at low sites. Numbers of microbial decomposers in the topographic sites were correlated with organic matter content. Distribution of fungal genera did not appear to be related to topographic site. Most populations examined showed two numerical peaks, one in late May or June and one in late September or October. It is suspected that these peaks were influenced by the coincident timing of favourable physical conditions and priming by soluble nutrients leached from litter. 相似文献
In general, populations of sugar, cellulose and lignin decomposing organisms (based on ten estimates made from April to October) were two to four times higher in litter and soil samples from low sites than those from high sites. Sugar decomposing bacteria in litter were most abundant at all topographic sites. 135 × 10
9.
OBSERVATIONS ON THE MICROFLORA OF MINCED CHICKEN MEAT IRRADIATED WITH 4 MeV CATHODE RAYS 总被引:4,自引:3,他引:1
MARGARET J. THORNLEY 《Journal of applied microbiology》1957,20(2):286-298
SUMMARY: Experiments are described in which minced chicken meat, packed anaerobically, was irradiated at room temperature and in the frozen state with a wide range of doses of 4 MeV cathode rays. Sterility was achieved in 14 out of 15 samples which had received 2 × 106 rads or more. Doses of 0·5 and 1·0 × 106 rads allowed survival of a few bacteria/g, usually spore formers. Bacterial counts indicated an approximately logarithmic decrease in numbers at lower doses, while freezing reduced the bactericidal effect.
The storage life at 5° was prolonged only slightly by doses of 5 × 104 and 10 × 104 rads, and highly variable results were obtained with 17·5 × 104 rads. A dose of 25 × 104 rads, however, increased the storage life very considerably. The types of bacteria present initially, and after irradiation with low doses and storage at 5°, were studied. After storage for 12 days or more various types of nonsporing Gram-positive rods were predominant in almost all samples, both control and irradiated. Streptococci were also important where irradiation with 17·5 × 104 and 25 × 104 rads was followed by long storage. 相似文献
The storage life at 5° was prolonged only slightly by doses of 5 × 10
10.
Two rapid methods, direct epifluorescent microscopy (DEM) and the direct epifluorescent filter technique (DEFT) on swab resuspension fluids, were compared with the traditional total viable count (TVC) on swab resuspension fluids for their ability to enumerate surface populations of attached bacteria. The degree of error in estimating surface populations was shown to be significantly less with DEM than DEFT followed by TVC. DEM estimated populations in the range 3 times 103 to 5 times 107 colonies/cm2 whilst DEFT enumerated populations above 3 times 104 colonies/cm2 and TVC above 3 times 105 colonies/cm2 (as measured by DEM). Swabbing was shown to remove a constant proportion of organisms from the surface populations tested, although below 3 times 105 colonies/cm2 most of the organisms remained in the cotton matrix and were difficult to resuspend. DEFT was more able to enumerate swab resuspension fluids obtained from surface populations below 3 times 105 colonies/cm2 than was TVC. 相似文献
11.
Effects of nitrate, chloride and chlorate ions upon nitrate and chlorate uptake by roots of maize ( Zea mays L., cv. B73) seedlings were examined. Net nitrate uptake, 36 ClO3 − influx and 36 Cl− influx (the latter two in a background of 0.5 m M KNO3 ) displayed similar pH profiles with optima at pH 5.5 and below. External, non-labeled chloride had little effect on the accumulation of 36 ClO3 − (both in 5 h and 20 min uptake assays), while nitrate and chlorate had almost identical, marked inhibitory effects. Nitrate pretreatment caused an apparent induction of both 36 ClO3 − and 15 NO3 − uptake activities. After 5 h of treatment in nitrate, the uptake activities of chloride- and chlorate-pretreated plants increased to that of nitrate-pretreated plants. During 6 h exposure to chlorate, 36 ClO3 − uptake activity of nitrate-pretreated plants decreased to that of chlorate- and chloride-pretreated plants. The results support the existence of a shared nitrate/chlorate transport system in maize roots which is not inhibited by external chloride, and which is induced by nitrate, but not by chlorate or chloride. The suggestion is made that selection of chlorate-resistant mutants of maize can identify nitrate uptake as well as nitrate reductase mutants. 相似文献
12.
M. C. Rea T. Lennartsson P. Dillon F.D. Drinan W.J. Reville M. Heapes T.M. Cogan 《Journal of applied microbiology》1996,81(1):83-94
The structure of six Irish kefir samples was studied in the electron microscope, and the microbial composition and fermentation kinetics during growth in 10% reconstituted skim milk at 21°C. The microbial composition of the six samples was similar; at the end of the fermentation the counts of lactococci, leuconostocs, lactobacilli, acetic acid bacteria and yeasts were 109 , 108 , 5 × 106 , 105 and 106 ml−1 respectively; the levels of acetic acid bacteria and lactobacilli showed some intersample differences. Lactate was the major metabolite followed in order by ethanol, acetate and acetoin. The final concentrations of L-lactate produced (66–90 mmol kg−1 ) were 10-fold higher than those of D-lactate. Acetate and ethanol concentrations varied from 4 to 14 and 2 to 40 mmol kg−'1 respectively. The rates of citrate utilization and concentration of acetoin produced during growth differed between samples. Scanning electron microscopy showed not only variation between the interior and exterior of the sample but also large variation between different sections of the interiors and exteriors of the same sample. Long and short, and straight and curved rods and yeasts were seen in all samples, the curved rods observed in the interior, but lactococci were seen on the surface of only one sample. There were no gross differences in structure between samples. 相似文献
13.
Günter Jost Willm Martens-Habbena Falk Pollehne Bernhard Schnetger & Matthias Labrenz 《FEMS microbiology ecology》2010,71(2):226-236
Oxic–anoxic interfaces harbor significant numbers and activity of chemolithoautotrophic microorganisms, known to oxidize reduced sulfur or nitrogen species. However, measurements of in situ distribution of bulk carbon dioxide (CO2 ) assimilation rates and active autotrophic microorganisms have challenged the common concept that aerobic and denitrifying sulfur oxidizers are the predominant autotrophs in pelagic oxic–anoxic interfaces. Here, we provide a comparative investigation of nutrient, sulfur, and manganese chemistry, microbial biomass distribution, as well as CO2 fixation at the pelagic redoxcline of the eastern Gotland Basin, Baltic Sea. Opposing gradients of oxygen, nitrate, and sulfide approached the detection limits at the chemocline at 204 m water depth. No overlap of oxygen or nitrate with sulfide was observed, whereas particulate manganese was detected down to 220 m. More than 70% of the bulk dark CO2 assimilation, totaling 9.3 mmol C m−2 day−1 , was found in the absence of oxygen, nitrite, and nitrate and could not be stimulated by their addition. Maximum fixation rates of up to 1.1 μmol C L−1 day−1 were surprisingly susceptible to altered redox potential or sulfide concentration. These results suggest that novel redox-sensitive pathways of microbial sulfide oxidation could account for a significant fraction of chemolithoautotrophic growth beneath pelagic chemoclines. A mechanism of coupled activity of sulfur-oxidizing and sulfur-reducing microorganisms is proposed. 相似文献
14.
Olivier Rabin Lajos Hegedus Jean-Marie Bourre Quenlin R. Smith 《Journal of neurochemistry》1993,61(2):509-517
Abstract: 54 Mn2+ uptake into brain and choroid plexus from the circulation was studied using the in situ rat brain perfusion technique. Initial uptake from blood was linear with time (30 s to 6 min) and extrapolated to zero with an average transfer coefficient of ∼6 × 10-5 ml/s/g for brain and ∼7 × 10-3 ml/s/g for choroid plexus. Influx from physiologic saline was three- to fourfold more rapid and exceeded that predicted for passive diffusion by more than one order of magnitude. The lower uptake rate from blood could be explained by plasma protein binding as the free fraction of 54 Mn2+ in rat plasma was ≤30%. Purified albumin, transferrin, and α2 -macroglobulin were each found to bind 54 Mn2+ significantly and to restrict brain 54 Mn2+ influx. The results demonstrate that 54 Mn2+ is readily taken up into the CNS, most likely as the free ion, and that transport is critically affected by plasma protein binding. The results support the hypothesis that Mn2+ transport across the blood-brain barrier is facilitated by either an active or a passive mechanism. 相似文献
15.
Diana B. Holland Richard A. Bojar Anthony H. T. Jeremy Eileen Ingham & Keith T. Holland 《FEMS microbiology letters》2008,279(1):110-115
This was a preliminary investigation to define the conditions of colonization of a human skin equivalent (SE) model with cutaneous microorganisms. SEs of 24 mm diameter were constructed with a dermal matrix of fibrin containing fibroblasts and a stratified epidermis. Microbial colonization of the SEs was carried out in a dry environment, comparable to ' in vivo ' skin, using a blotting technique to remove inoculation fluid. The microbial communities were sampled by scrub washing and viable cells enumerated on selective growth medium. Staphylococcus epidermidis , Propionibacterium acnes and Malassezia furfur (human skin commensals) and Staphylococcus aureus (transient pathogen) were colonized at inoculum densities of 102 –106 CFU SE−1 on the surface of replicate SEs. Growth of all species was supported for upto 72–120 h, with recovery densities of between 104 –109 CFU SE−1 . A novel, real-time growth monitoring method was also developed, using S. aureus containing a lux cassette. Light output increased from 20 to 95 h, and colonization increased from 102 to 108 CFU SE−1 , as confirmed by conventional recovery. Thus, the SE model has potential to investigate interactions between resident and transient microbial communities with themselves and their habitat, and for testing treatments to control pathogen colonization of human skin. 相似文献
16.
Bacteria grew to viable populations of 108 –109 cfu/g during the fermentation of soybeans into tempe with the fungus, Rhizopus oligosporus. Bacillus pumilus and B. brevis were the predominant bacterial species, reaching populations of approximately 108 cfu/g during the 48 h fermentation. Species of Streptococcus faecium, Lactobacillus casei, Klebsiella pneumoniae and Enterobacter cloacae also contributed to the fermentation and achieved populations of 106 –107 cfu/g. and accepted 25 May 1989 相似文献
17.
In vitro and in planta sensitivity of an indirect enzyme-linked immunoassaytechnique, using a monoclonal antibody specific for the lipopolysaccharide (LPS) of Xanthomonas campestris pv. vesicatoria , was increased 10-foldby using a newextraction buffer (gl of : KH2 PO4 , 2; NaHPO4 , 11·5; EDTAdisodium, 0·14; thimerosal, 0·02; and lysozyme, 0·2). The procedure improvedsensitivity without increasing background levels. In vitro , the limit of detection wasbetween 1×107 and 1×108 cells ml−1 with the conventionalextraction buffer phosphate-buffered saline (PBS) and less than 1×106 cells ml−1 when lysozyme extraction buffer was substituted for PBS. In comparing 22 X. c.vesicatoria strains, absorbance readings were increased close to three-fold with the lysozymeextraction buffer as opposed to PBS. When leaf tissue extract was spiked with the bacterium, thelimit of detection was 1×107 cfu ml−1 and 1×108 cfu ml−1 with the lysozyme solution and PBS, respectively, as the extraction buffers. Whenusing the lysozyme extraction buffer in combination with a commercial amplification system, thelimit of detection was decreased to less than 1×105 cfu ml−1 in leaftissue. The addition of the lysozyme and EDTA to the phosphate buffer resulted in release of asignificant quantity of LPS and concomitant dramatic increase in sensitivity. The new procedure,termed lysozyme ELISA (L-ELISA), should increase sensitivity of ELISA reactions where LPS isthe reacting epitope. 相似文献
18.
Abstract Oral immunization of suckling mice with Cryptosporidium parvum results in a humoral response to a limited set of antigens. Six-day-old BALB/c mice were each inoculated orally with 1 × 106 viable oocysts and subsequently administered oral inoculations of 2 × 106 viable oocysts at 30 and 60 days following the primary infection. After 45 days, mice were boosted with 1 × 106 oocysts orally, plus soluble extracts equivalent to 2 × 106 and 1 × 106 oocysts given intravenously and intraperitoneally, respectively. Four days later, splenic lymphocytes were fused to Ag8 myeloma cells. Using this method, we have been able to select for monoclonal antibodies that predominately recognize sporozoite surface and apical complex antigens. 相似文献
19.
Influence of continuous challenge via the feed on competitive exclusion of salmonellas from broiler chicks 总被引:3,自引:1,他引:2
A survey has been made of the bacterial and fungal populations carried at three different sites on the feet of 60 individuals. The bacteria found at the three sites were quantitatively similar and Micrococcaceae and aerobic coryneform bacteria predominated. The carriage of other bacterial groups was generally low. There was a quantitative variation between sites—mean total counts were 1.04 ± 107 cfu/cm2 skin in the fourth toe cleft, 4.08 ± 105 cfu/cm2 skin on the sole and 1.21 ± 103 cfu/cm2 skin on the dorsal surface. Staphylococci were most often dominant on the sole and dorsal surface whereas aerobic coryneforms predominated in the majority of fourth toe clefts. The higher the total count at a given site the more likely it was that aerobic coryneform bacteria predominated. The skin surface pH was significantly higher on the sole (mean value 6.25) than on the dorsal surface (mean value 5.23). Factors controlling the microbial ecology of the foot are discussed. 相似文献
20.
The dense microbial flora of the rabbit caecum consisted chiefly of bacteria (1011 /g) with small numbers of yeast cells (106 /g). Using strictly anaerobic techniques, 23% of the direct microscopic cell count was cultivated and 55% of the cultivatable bacteria utilized ammonia as the sole source of nitrogen. Ureolytic bacteria were isolated from the caecal lumen and mucosa and were identified as Bacteroides vulgatus, Clostridium clostridiiforme, Bacillus spp. and Staphylococcus spp. Ammonia assimilation by the bacterial flora of the caecum was by incorporation into α-oxoglutarate catalysed by NADPH-linked glutamate dehydrogenase. 相似文献