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排序方式: 共有263条查询结果,搜索用时 15 毫秒
91.
Paul J. Weimer 《Archives of microbiology》1993,160(4):288-294
The ruminal cellulolytic bacterium Fibrobacter succinogenes S85 was grown in cellulose-fed continuous culture at 22 different combinations of dilution rate (D, 0.014–0.076 h-1) and extracellular pH (6.11–6.84). Effects of pH and D on the fermentation were determined by subjecting data on cellulose consumption, cell yield, product yield (succinate, acetate, formate), and soluble sugar concentrationto response surface analysis. The extent of cellulose conversion decreased with increasing D. First-order rate constants at rapid growth rates were estimated as 0.07–0.11 h-1, and decreased with decreasing pH. Apparent decreases in the rate constant with increasing D was not due to inadequate mixing or preferential utilization of the more amorphous regions of the cellulose. Significant quantities of soluble sugars (0.04–0.18 g/l, primarily glucose) were detected in all cultures, suggesting that glucose uptake was rather inefficient. Cell yields (0.11–0.24 g cells/g cellulose consumed) increased with increasing D. Pirt plots of the predicted yield data were used to determined that maintenance coefficient (0.04–0.06 g cellulose/g cells · h) and true growth yield (0.23–0.25 g cells/g cellulose consumed) varied slightly with pH. Yields of succinate, the major fermentation endproduct, were as high as 1.15 mol/mol anhydroglucose fermented, and were slightly affected by dilution rate but were not affected by pH. Comparison of the fermentation data with that of other ruminal cellulolytic bacteria indicates that F. succinogenes S85 is capable of rapid hydrolysis of crystalline cellulose and efficient growth, despite a lower max on microcrystalline cellulose. 相似文献
92.
C. G. Orpin 《Archives of microbiology》1976,111(1-2):155-159
The rumen bacterium Eadie's Oval was examined by means of cell wall analysis and biochemical tests with a view to determine its taxonomic position.The purified cell walls contained components consistent with the organism being a Gram-negative bacterium, and despite its large size no abnormal cell wall constituents were found. The biochemical tests indicate that Eadie's Oval is not a member of a previously described family. The name Magnoovum gen. nov. eadii sp. nov. is proposed.Abbreviations Used EO
Eadie's Oval
- ARF
autoclaved rumen fluid (supernatant after centrifuging for 5 min at 1000 g)
- GC
ratio of Guanine and cytosine to Adenine and Thymine in DNA 相似文献
93.
B. A. DEHORITY 《The Journal of eukaryotic microbiology》1978,25(4):509-513
SYNOPSIS. Six protozoa-free sheep, 3 fed alfalfa hay and 3 fed a concentrate diet, were inoculated with rumen contents from a steer fed the same alfalfa hay. All 24 species of protozoa in the inoculum became established in the sheep fed alfalfa hay, while only 9 species established in the sheep fed concentrate. Percentage species composition in the alfalfa-fed sheep was fairly similar to that of the inoculum. Rumen volumes of the alfalfa hay-fed sheep were significantly higher than those of the concentrate-fed sheep; however, fluid turnover rates were similar. Total protozoan numbers per ml of rumen contents were significantly higher in the concentrate-fed sheep, but after adjustment for rumen volume, there was no significant difference in the total number of protozoa in the rumen. 相似文献
94.
Investigations on the possible impact of a glyphosate‐containing herbicide on ruminal metabolism and bacteria in vitro by means of the ‘Rumen Simulation Technique’ 下载免费PDF全文
95.
The Methanogens are a diverse group of organisms found in anaerobic environments such as anaerobic sludge digester, wet wood
of trees, sewage, rumen, black mud, black sea sediments, etc which utilize carbon dioxide and hydrogen and produce methane.
They are nutritionally fastidious anaerobes with the redox potential below −300 mV and usually grow at pH range of 6.0–8.0
[1]. Substrates utilized for growth and methane production include hydrogen, formate, methanol, methylamine, acetate, etc.
They metabolize only restricted range of substrates and are poorly characterized with respect to other metabolic, biochemical
and molecular properties. 相似文献
96.
《Archives of animal nutrition》2013,67(3):277-293
The addition of Na‐lactate (50–150 mmol/1) to media with glucose had only marginal effect on the growth of rumen lactate‐producing bacteria at pH between 6.5 and 5.8. Butyrivibrio fibrisolvens was somewhat more sensitive to external lactate than Streptococcus bovis, Lactobacillus fermentum and Selenomonas ruminantium. It can be concluded that rumen lactate producers, which proliferate at the onset of rumen lactic acidosis, are not influenced by the lactate accumulation, except some non‐specific osmotic effects. 相似文献
97.
Colin S. Stewart Sylvia H. Duncan Anthony J. Richardson Colette Backwell Robert Begbie 《FEMS microbiology letters》1992,97(1-2):83-87
The degradation of filter paper by the anaerobic fungus Neocallimastix frontalis strain RE1 was reduced by the addition of cell-free supernates from cultures of Ruminococcus albus strain J6 and R. flavefaciens strains 17 and 007. Fungal uptake of, and growth on, glucose was not affected. After gel permeation and anion exchange chromatography, inhibitory activity towards fungal cellulolysis was recovered in a fraction from strain 17 that contained at least five negatively charged polypeptide components, molecular mass 45-68 kDa, on SDS-PAGE. 相似文献
98.
Michael A. Cotta Matthew B. Wheeler Terence R. Whitehead 《FEMS microbiology letters》1994,124(3):355-359
Abstract An examination of cAMP levels in predominant species of ruminal bacteria and other anaerobic bacteria was conducted. Cellular cAMP concentrations of glucose-grown cultures of Butyrivibrio fibrisolvens 49, Prevotella ruminicola D31d, Selenomonas ruminantium HD4 and D, Megasphaera elsdenii B159, Sreptococcus bovis JB1, Bacteroides thetaiotaomicron 5482, and Clostridium acetobutylicum ATCC 824 were determined at various times during growth by a competitive binding radioimmunoassay procedure. The results were compared to those for Escherichia coli NRRL B3704. The levels of cAMP ranged from undetectable for B. thetaiotaomicron to approximately 15 pmol/mg cell protein for P. ruminicola D31d. Varying the growth substrate in a manner previously shown to elicit regulatory response did not alter the level of cAMP in these organisms. In general, cAMP concentrations present in these organisms were much lower than the 6–25 pmol/mg cell protein observed for E. coli . The levels of cAMP in P. ruminicola were consistently higher than levels in other anaerobes, particularly during the early exponential and stationary phases of growth. Based on these data it seems unlikely that cAMP is involved in regulation of substrate catabolism in the anaerobic bacteria examined except in P. ruminicola where it may have an unknown regulatory function. 相似文献
99.
J.Doré B.Morvan F.Rieu-Lesme I.Goderel P.Gouet P.Pochart 《FEMS microbiology letters》1995,130(1):7-12
Abstract A method is proposed that allows the enrichment and most probable number estimation of H2 /CO2 -utilizing acetogenic bacteria. It is based on the difference in acetate production for serial dilutions incubated under either a test H2 /CO2 (4:1), or a control N2 /CO2 (4:1) headspace atmosphere. A nutritionally non-selective medium was used, containing bromoethane-sulfonic acid as inhibitor of methanogenic archaea and 10% pre-incubated clarified rumen fluid. Acetogenic bacteria were enumerated in rumen and hindgut contents of animals and in human feces. They ranged from below 102 to above 108 per gram wet weight gut content and their population levels were the highest in the absence of methanogenesis. The method described therein should prove useful to better understand the diversity and ecological importance of dominant gut acetogens. 相似文献
100.
Analysis of restriction and modification activities in lactate-utilizing bacteria belonging to the Megasphaera elsdenii and Mitsuokella multiacida species revealed the presence of GATC-specific, MboI isospecific, restriction-modification (R-M) systems in all strains tested. While restriction endonucleases isolated from M. elsdenii strains were found to be sensitive to Dam methylation, enzymes from M. multiacida cleaved DNA irrespective of Dam methylation. The comparison of type II R-M systems specificities in three closely related lactate-utilizing ruminal bacterial species indicated complete lack of restriction and/or modification enzymes previously characterized from Selenomonas ruminantium in tested M. elsdenii and M. multiacida strains. R-M systems are believed to represent the main defense tool against phage infection. Based on the results of our experiments it could be assumed that M. elsdenii and M. multiacida use the different strategy for bacteriophage protection compared to S. ruminantium. 相似文献