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1.
SUMMARY: A simple medium and dilution count technique was evolved for determining the viable count of rumen bacteria. Material from three fistulated cows was examined and the viable population found to vary within the range 107 -1012 /g; the most frequently occurring values were 108 -1010 /g (94.0% of 350 counts). Observations were made of the homogeneity of rumen contents, of variations in count with time after sampling and between cows, and of variation from day to day, hour to hour, before and after feeding and on different diets. The variations in the viable count, even with gross changes in diet, were never greater than those occurring in a single animal on a fixed diet. Microscopic examinations showed Gram-positive cocci and rods to be the most frequently occurring types of bacteria, Gram-negative organisms of the coli-aerogenes type being present only in low numbers. 相似文献
2.
SYNOPSIS. The colorless flagellate, Astasia longa , grows to high cell densities (5–6.6 × 106 cells/ml) with ethanol instead of acetate as carbon source in a chemically defined medium. The generation time was the same on the two substrates. The dry weight of ethanol-grown Astasia was 23% higher than acetate-grown Astasia , largely due to a higher carbohydrate content which offset a reduced lipid content. Protein, RNA, and DNA contents were comparable in the two cases whereas O2 uptake was 17% higher in the ethanol-grown Astasia. The high population densities on ethanol are examined in terms of these biochemical differences as well as changes in the medium during growth. 相似文献
3.
The planktonic and benthic bacterial populations of Lough Neagh 总被引:3,自引:1,他引:2
The planktonic and benthic bacterial populations of Lough Neagh, Northern Ireland, were studied over a one-year period. Direct counts of bacteria in the water column averaged 6 times 107 /ml with limited spatial or temporal variation; viable counts, however, showed a pronounced late spring maximum of 1.7 times 106 /ml and were consistently higher at a littoral sampling station. Direct counts of bacteria in the profundal sediments averaged 8 times 109 /ml whilst viable benthic counts rose steeply during spring to reach a June maximum of 1 times 108 /ml. Direct: viable count ratios were much greater in the more sandy littoral zone. The predominant benthic isolate was an Aeromonas sp. which was also common in samples from the water column. These results confirm the eutrophic status of Lough Neagh indicated by other biological and chemical surveys. 相似文献
4.
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
5.
The effects of physical and chemical factors on the production of H2 O2 from Escherichia coli cells were studied. When 20 mmol 1-1 Tris-HCl buffer was used for this purpose the electron transport system (ETS) showed the highest activity at pH 7.6-8.2. KCN promoted the production of H2 O2 from E. coli cells, and the optimum concentration was changed in different reaction times and pH values. Glucose, 5 mg ml-1 , increased the ETS activity about twofold. The other substrates and surfactants did not increase the chemiluminescence intensity. NaNO2 and Na2 SO4 in inorganic salts significantly reduced the ETS activity above 70%. In addition, the optimum temperature for the production of H2 O2 was 30°C in this study. When glucose (5 mg ml-1 ) and KCN (0.2 mmol 1-1 ) were added to the reaction buffer containing 0.5 mmol 1-1 menadione, the detectable minimum cell densities (averages of triplicate assay) of E. coli, Enterobacter cloacae and Serratia marcescens were 5 times 103 cells ml-1 , 104 cells ml-1 and 104 cells ml-1 respectively. 相似文献
6.
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
7.
SYNOPSIS. Euplotes vannus , a hypotrich ciliate. grows well over broad ranges of temperature and salinity. It requires higher densities of food (> 1 × 104 cells/ml) for rapid reproduction than do the other herbivores, the foraminiferan Al-logromia laticollaris (> 1 × 102 cells/ml), and the nematode Chromadorina germanica (∼ 1 × 103 cells/ml), to which it was compared. If food levels were initially very high (∼ 1 × 108 cells/ml) the ciliates reproduced rapidly and consumed the algae faster than it could reproduce. Some balance between the algae and the ciliates was achieved at initial algal concentrations of ∼ 1 × 105 cells/ml. In microcosm experiments at 25 C with equal numbers of C. germanica and A. laticollaris. E. vannus proved to be a very poor competitor; reaching only 20% of control levels when grow with C. germanica and only 13% when cultured with A. laticollaris . It was a better competitor in 2-species microcosms, at lower temperatures, and when its ratio to the other species was initially higher.
The experimental evidence suggests that E. vannus is best adapted to being a migrating initial colonizer of fresh algal blooms. 相似文献
The experimental evidence suggests that E. vannus is best adapted to being a migrating initial colonizer of fresh algal blooms. 相似文献
8.
Use of antibiotic resistance mutations to track strains of obligately anaerobic bacteria introduced into the rumen of sheep 总被引:3,自引:2,他引:1
Selective plating procedures were used to follow the fate of rifampicin-resistant mutant strains of the obligately anaerobic species Bacteroides multiacidus and Selenomonas ruminantium after their introduction at numbers around 107 /ml into the rumen of sheep. Bacteroides multiacidus strain F100 showed an initially rapid rate of loss (49%/h) but subsequently numbers declined more gradually approaching the limits of detection (103 /ml) after 100 h. Viable cell numbers also decreased in vitro upon addition of F100 cells to whole rumen contents, but remained stable upon addition to cell-free rumen fluid, suggesting protozoal predation. F100 cells were able to grow in vitro in whole rumen contents in the presence of an added utilizable substrate such as sorbitol, but addition of sorbitol to the rumen failed to enhance survival in vivo . In the case of S. ruminantium , introduced rifR strains persisted in the rumen at levels around 106 ml for at least 30 days. 相似文献
9.
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
10.
Effect of high-temperature, short-time (HTST) pasteurization on milk containing low numbers of Mycobacterium paratuberculosis 总被引:2,自引:1,他引:2
The efficacy of high-temperature, short-time (HTST) pasteurization (72 °C/15 s) when low numbers (≤ 103 cfu ml −1 ) of Mycobacterium paratuberculosis are present in milk was investigated. Raw cows' milk spiked with Myco. paratuberculosis (103 cfu ml−1 , 102 cfu ml−1 , 10 cfu ml−1 , and 10 cfu 50 ml−1 ) was subjected to HTST pasteurization using laboratory pasteurizing units. Ten bovine strains of Myco. paratuberculosis were tested in triplicate. Culture in BACTEC Middlebrook 12B radiometric medium detected acid-fast survivors in 14·8% and 10% of HTST-pasteurized milk samples at the 103 and 102 cfu ml−1 inoculum levels, respectively, whereas conventional culture on Herrold's egg yolk medium containing mycobactin J detected acid-fast survivors in only 3·7% and 6·7% of the same milk samples. IS900-based PCR confirmed that these acid-fast survivors were Myco. paratuberculosis . No viable Myco. paratuberculosis were isolated from HTST-pasteurized milk initially containing either 10 cfu ml−1 or 10 cfu 50 ml−1 . 相似文献
11.
Alberto Yáñez Ana Flores Celia Murciano José-Enrique O'Connor Daniel Gozalbo M. Luisa Gil 《Cellular microbiology》2010,12(1):114-128
We have previously demonstrated that inactivated yeasts and hyphae of Candida albicans induce in vitro the proliferation of murine haematopoietic stem and progenitor cells (HSPCs, sorted as LKS cells: Lin- c-Kit+ Sca-1+ ) as well as their differentiation to lineage-positive cells, through a MyD88-dependent pathway. In this work, we have found that this process is mainly mediated by TLR2, and that expanding cells express myeloid and not lymphoid markers. Incubation of long-term repopulating HSCs (Lin- CD105+ and Sca-1+ ) with C. albicans yeasts resulted in their proliferation and up regulation of the common myeloid progenitors (CMPs) markers, CD34 and FcγRII/III, by a TLR2/MyD88-dependent signalling pathway. In addition, this TLR2/MyD88 signalling promotes the differentiation of CMPs and granulocyte and macrophage progenitors (GMPs) into cells with the morphology of macrophages and neutrophils, characterized by an increase in the expression of CD11b, F4/80 and Ly6G, independently of the presence of growth and differentiation factors. These differentiated cells were able to phagocytose C. albicans yeasts and to produce proinflammatory cytokines. In conclusion, C. albicans may be sensed by TLRs on haematopoietic stem and progenitor cells to promote the host capability for rapidly replenishing myeloid cells that constitute the first line of defence against C. albicans . 相似文献
12.
The Yeasts of Strawberries 总被引:2,自引:2,他引:0
SUMMARY: Nine hundred and fiftyseven strains of yeasts were isolated from fresh marketed strawberries over 2 seasons. There were c. 105 viable yeasts/g of strawberry: many more were isolated at 5° than at 25°. Most of the yeasts belonged to the genus Cryptococcus . Every yeast colony counted was subjected to identification tests selected by means of a computer-made key, and identifications were done chiefly by semiquantitative aerobic growth tests combined with fermentation tests and microscopical examination of vegetative cells. 相似文献
13.
Survival and infectivity of a Rhizobium meliloti strain maintained in water and buffer suspensions 总被引:2,自引:0,他引:2
Rhizobium meliloti B323 cells were suspended in deionized water, phosphate buffer pH 6.5 and 5.5 and these buffers supplemented with Ca2+ , Mg2+ (1 mmol/l) and Fe3+ (0.1 mmol/l). Initial cell count was 1.108 cells/ml. The viable count of rhizobia suspended in buffer at pH 6.5, with and without salts, remained constant or even increased during storage. Cells suspended in buffer at pH 5.5 with salts, decreased in numbers in the first 5 months, then, until the 10th month, the count remained at 105 cells/ml. Rhizobia suspended in buffer at pH 5.5 and deionized water decreased in viability almost to zero by the 10th month. In those suspensions where viability was maintained, the symbiotic infectivity of cells was also maintained as compared with a control performed with fresh cultured rhizobia. In suspensions in deionized water and buffer at pH 5.5 where the viability diminished during the experiment, the rhizobia lost their ability to infect roots immediately after inoculation but maintained their capacity to form late nodules on the hosts. 相似文献
14.
Enumeration of some microbial groups in thermophilic poultry waste digesters and enrichment of a feather-degrading culture 总被引:1,自引:0,他引:1
Methane-producing, cellulolytic, feather-degrading, and total anaerobic microbial populations were enumerated in four laboratory-scale (l l) thermophilic (50°C) poultry waste digesters over a 40d period. Four different operation conditions were: 5 d retention time (RT), 6% volatile solids (VS); 5 d RT, 3% VS; 10 d RT, 6% VS; and 10 d RT, 3% VS. Laying hen manure was the sole source of substrate and micro-organisms. At theoretical steady state (day 40) the biogas volumetric rate was near 3.0 l/l digester volume (l/l/d) in all but the 10 d RT, 3% VS digester which was 2 l/l/d. The total viable anaerobic population was > 106 cfu/ml digester fluid at the first sampling and stabilized at 107 –108 cfu/ml between days 20 and 40 in all digesters. Methane-producing bacteria increased from ≤ 10/ml early in the sampling period to 105 /ml at steady state in all but the 5 d RT, 3% VS digester which was highest at 107 /ml. Cellulolytic micro-organisms were low throughout the 40 d, generally less than 10/ml. Feather-degrading micro-organisms ranged from near 102 –105 at steady state and were decreasing in number near day 40 in all but the 10 d RT, 6% VS digester which maintained 105 /ml after day 20. A feather-degrading culture was enriched from this digester and subsequently adapted to grow in a medium with feather as the sole source of carbon. Results of this study provide information regarding potential biological upgrading of poultry waste digesters for increased operational efficiency and potential industrial application of a feather-hydrolytic micro-organism. 相似文献
15.
Abstract: We examined correlations among growth kinetics, cell shape, and cytoskeletal protein content in rat astrocytes grown in primary culture. Cell suspensions from brains of newborn rats were seeded at densities from 0.2 to 3 × 105 /cm2 . At initial densities above 1 × 105 the population increased to reach confluency by 10–12 days, after which cell number remained stable for many weeks. At low initial densities, 0.2–0.4 × 105 /cm2 , cells did not increase in number. Final density increased with increasing plating densities. High-density cells had small perikarya and several long cytoplasmic processes; low-density cells appeared flat and polygonal. All cultures were almost entirely astrocytic, as judged by immunofluorescent staining with antiserum against glial fibrillary acidic protein (GFAP). Cytoskeletal proteins were analyzed by gel electrophoresis after extraction from cells with nonionic detergent. Relative amounts of the proteins differed, in that low-density cells contained large amounts of cytoskeletal actin relative to the intermediate filament (IF) proteins vimentin and GFAP, whereas high-density cells contained relatively less actin and more IF proteins. Such differences in cytoskeletal proteins between the high- and low-density cultures were mirrored in the relative rates of synthesis of the cytoskeletal proteins. In the low-density cells amino acid incorporation into cytoskeletal-associated actin was more active than that into the IFs, whereas in the high-density cells higher rates of IF protein synthesis were observed. 相似文献
16.
A.C.P. Rodrigues R.M. Nardi E.A. Bambirra E.C. Vieira J.R. Nicoli 《Journal of applied microbiology》1996,81(3):251-256
A.C.P. RODRIGUES, R.M. NARDI, E.A. BAMBIRRA, E.C. VIEIRA AND J.R. NICOLI. 1996. Saccharomyces boulardii was shown to be capable of inhibiting multiplication of enteropathogenic bacteria in vitro and is currently used for its anti-diarrhoea properties. We studied the capacity of this yeast to antagonize Salmonella typhimurium and Shigella flexneri in the intestinal tract of conventional or gnotobiotic NMRI mice. Conventional animals were given daily 10 mg doses of S. boulardii , whereas germ-free animals were given a single 10 mg dose. Both groups were challenged orally 5 d later with the pathogenic bacteria (108 or 102 viable cells, respectively). Control groups were treated with saline instead of S. boulardii. Mortality and/or histopathological data showed a protective effect against the pathogenic bacteria in yeast-treated mice. Saccharomyces boulardii colonized the digestive tract of gnotobiotic mice and the number of viable cells ranged around 1010 g-1 of faeces. In experimental and control gnotobiotic animals, Salm. typhimurium and Sh. flexneri became rapidly established at a level of about 1010 viable cells g-1 of faeces and remained at high levels until the animals died or were sacrificed. The protection against Salm. typhimurium and Sh. flexneri obtained in conventional and/or gnotobiotic mice previously associated with S. boulardii is not due to the reduction of the bacterial populations in the intestines. 相似文献
17.
Abstract Characteristics of the lactobacilli colonizing the various regions of the porcine gastrointestinal tract were investigated. The lumenal contents from the gastric, jejunal, cecal and colonic regions, and biopsies from the gastric non-secreting and secreting regions were homogenized and serial dilutions were spread on Rogosa agar and colonies (50 per region and animal) were randomly sampled. The lactobacillus isolates were grouped according to their protein profiles of lysozyme-treated whole cells. Several different groups of lactobacillus could be detected. Specific groups were associated and often unique for the stomach, jejunal, cecal and colonic regions of the gastrointestinal tract. A few groups were uniformly distributed through the tract. Although published studies of lactobacilli colonizing stomach mucosa have been restricted mainly to the non-secreting region, significant levels were also detected on the secreting stomach tissue. Population densities ranged from 2 × 104 to 2 × 106 CFU per cm2 on both the secretory and non-secretory regions. Of the isolates which colonized the gastric secreting epithelium, 26% formed smooth colonies and 74% formed rough colonies. In contrast, the non-secreting epithelium was mainly colonized by lactobacilli forming smooth colonies (67%). From this study, one can suggest that different lactobacilli are associated with specific regions of the gastrointestinal tract, and that some specific groups appear to be restricted to defined regions. 相似文献
18.
Thirty-nine samples of freshly drawn ewes' milk collected at 13 farms, and 120 samples of raw ewes' milk collected on arrival at a dairy were examined. Farm samples had geometric mean counts of 4.4 × 102 Enterobacteriaceae/ml, 3.9 × 102 coliforms/ml and 2.0 × 102 faecal coliforms/ml, whereas the respective mean counts were 6.2 × 103 /ml, 5.4 × 103 /ml and 1.3 × 103 /ml for dairy samples. Salmonellas were not detected by enrichment procedures in any of the 159 samples examined. Escherichia coli (47.5% strains), Enterobacter cloacae (17.7%), Ent. agglomerans (11.3%), Hafnia alvei (6.5%) and Klebsiella oxytoca (6.0%) were the predominant species in 434 Enterobacteriaceae strains isolated from farm samples. Levels and species of Enterobacteriaceae found in the present work in raw ewes' milk imply a considerable risk of early blowing in cheese-making from unpasteurized milk. 相似文献
19.
CHISA YASUNAGA MASAKO FUNAKOSHI TAKESHI KAWARABATA 《The Journal of eukaryotic microbiology》1994,41(2):133-137
ABSTRACT. Spores of Nosema bombycis Y9101, isolated from the beet armyworm, Spodoptera exigua , were primed with an alkaline solution and inoculated into Antheraea eucalypti cell cultures. Infected cells were subcultured every five days at three cell densities (2.5 × 103 , 5.0 × 103 , and 1.0 × 104 cells/cm2 ). A difference was observed in the spread of N. bombycis Y9101 infection between low-density and higher-density cultures of host cells. The host cell density did not affect the productivity of secondary infective forms of the parasite. The principal factor determining the rate of microsporidian infection in vitro was the number of host cells existing within the reach of extruded short-coiled polar tubes from spores germinated intracellularly. 相似文献
20.
Generation Time and Growth Rate of the Human Intestinal Parasite Blastocystis hominis 总被引:3,自引:0,他引:3
ABSTRACT. Blastocystis hominis , an anaerobic intestinal protozoan parasite of man, has a generation time (GT) in axenic culture of 8.5–19.4 h, depending on the strain tested. Average GT of the eight strains was 11.7 h. Zero growth time cell counts of 5.0 × 105 /ml to 2.0 × 106 /ml rose in 3–5 days to 1 × 107 or 1 × 108 cells/ml. The GT was determined for the 24-h period during which the most rapid growth occurred; about 2% of the B. hominis cells were in division during this time. Division under the culture conditions provided was by binary fission, the usual mode for B. hominis in vitro as well as in vivo. Division times were determined also by direct observation of individual dividing cells in slide cultures. These were usually ca. 40–60 min but sometimes as low as 20 min. 相似文献