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51.
Summary. An in vitro experiment was conducted to test the ability of mixed rumen bacteria (B), protozoa (P), and their mixture (BP) to utilize
the oxidized forms of methionine (Met) e.g., methionine sulfoxide (MSO), methionine sulfone (MSO2). Rumen contents were collected from fistulated goats to prepare the microbial suspensions and were anaerobically incubated
at 39°C for 12 h with or without MSO (1 mM) or MSO2 (1 mM) as a substrate. Met and other related compounds produced in both the supernatants and hydrolyzates of the incubation
were analyzed by HPLC. During 6- and 12-h incubation periods, MSO disappeared by 28.3 and 42.0%, 0.0 and 0.0%, and 40.6 and
62.4% in B, P, and BP suspensions, respectively. Rumen bacteria and the mixture of rumen bacteria and protozoa were capable
to reduce MSO to Met, and the production of Met from MSO in BP (156.6 and 196.1 μmol/g MN) was about 17.3 and 14.1% higher than that in B alone (133.5 and 171.9 μmol/g MN) during 6- and 12-h incubations, respectively. On the other hand, mixed rumen protozoa were unable to utilize MSO.
Other metabolites produced from MSO were found to be MSO2 and 2-aminobutyric acid (2AB) in B and BP. MSO2 as a substrate remained without diminution in all-microbial suspensions. It was concluded that B, P, and BP cannot utilize
MSO2; but MSO can be utilized by B and BP for producing Met.
Received December 28, 2001 Accepted May 21, 2002 Published online October 14, 2002
Acknowledgements The authors are extremely grateful to Professor H. Ogawa, the University of Tokyo, Japan and Dr. Takashi Hasegawa, Miyazaki
University, Japan for inserting permanent rumen fistulae in goats. We would like to thank MONBUSHO for the award of a research
scholarship to Mamun M. Or-Rashid since 1996–2001.
Authors' address: Shaila Wadud, Laboratory of Animal Nutrition and Biochemistry, Division of Animal Science, Miyazaki University, Miyazaki
889-2192, Japan, Fax. +81-985-58-7201, E-mail: rafatkun@hotmail.com 相似文献
52.
Cortizo M.C. Fernández Lorenzo de Mele M. 《World journal of microbiology & biotechnology》2003,19(8):805-810
The combination of a conventional optical microscope with a specially designed glass flow cell was used to visualize in situ biofilms formed on opaque thin biomaterials through a simple non-invasive way (optical microscopy of thin biofilms, OMTB). Comparisons of OMTB with scanning electron microscopy (SEM) images were made. Thin metallic dental biomaterials were used as substrata. They were immersed in a synthetic saliva and in a modified Mitis–Salivarius medium inoculated with a consortium of oral microorganisms. To study the effect of bacterial motility, Pseudomonas fluorescens cultures were also used. The processes which give rise to the formation of the biofilm were monitored through OMTB. Biofilm microstructures like pores, water channels, streamers and chains of Streptococci, attached to the surface or floating in the viscous interfacial environment, could be distinguished. Thickness and roughness of the biofilms formed on thin substrata could also be evaluated. Distortions introduced by pretreatments carried out to prepare biological materials for SEM observations could be detected by comparing OMTB and SEM images. SEM images (obtained at high magnification but ex situ, not in real time and with pretreatment of the samples) and OMTB images (obtained in situ, without pretreatments, in real time but at low magnification) in combination provided complementary information to study biofilm processes on thin substrata. 相似文献
53.
54.
D.W. Hopkins J.A. Chudek D.E. Bignell J. Frouz E.A. Webster T. Lawson 《Biodegradation》1998,9(6):423-431
Solid-state 13C nuclear magnetic resonance spectroscopy has been used to characterize the C in samples of the food (wood), gut contents and faeces from the wood-feeding termite, Microcerotermes parvus; soil in the guts and mound material from the soil-feeding termite, Thoracotermes macrothorax; and the food and faeces from the litter-feeding, coprophagous larvae of the dipteran fly, Bibio marci. Spectra from the wood-feeding termite indicated preferential loss of polysaccharide and accumulation of lignin with some modification to the O-aromatic-C and methoxyl-C (O-methyl-C) components during passage through the gut. Spectra for the soil-feeding termite indicated little change in the distribution of 13C between resonances following passage through the gut, except for some evidence of preferential polysaccharide loss. Interpretation of the spectra from these organisms was restricted by the relatively low C content of the soils and mound material, and by the large contribution to the NMR spectra from the gut tissue rather than the gut contents. Spectra for the litter-feeding dipteran larvae indicated preferential feeding on the polysaccharide-rich component of the litter and then overall loss of polysaccharide-C and accumulation of both aromatic-C and methoxyl-C in the gut. These changes were greater for the second passage than for the first passage through the gut, suggesting that principally mechanical and physical changes occurred initially and that chemical digestion was prevalent during the second passage. 相似文献
55.
P. Gyaneshwar G. Naresh Kumar L.J. Parekh 《World journal of microbiology & biotechnology》1998,14(5):669-673
Native microflora present in the alkaline vertisols and two phosphate-solubilizing bacteria (PSB) isolated from soil using conventional screening media could not release phosphorus from alkaline Indian vertisol soils supplemented with carbon and nitrogen sources. The two PSBs could solubilize both rock phosphate and di-calcium phosphate in unbuffered media but failed to solubilize rock phosphate in buffered media. The organic acids secreted by these PSBs were 20–50 times less than that required to solubilize phosphorus from alkaline soil. 相似文献
56.
The origin of prokaryotic life is discussed with an emphasis on the self-assembly of early life in a microscale environment where ordered cellular structures and integrated functions evolved from disorder. Early molecular evolution may have been due to both molecular chaos and evolving molecular order. 相似文献
57.
Leaf litter breakdown budgets in streams of various trophic status: effects of dissolved inorganic nutrients on microorganisms and invertebrates 总被引:7,自引:1,他引:6
V. BALDY V. GOBERT F. GUEROLD E. CHAUVET D. LAMBRIGOT J.-Y. CHARCOSSET 《Freshwater Biology》2007,52(7):1322-1335
1. We investigated the effect of trophic status on the organic matter budget in freshwater ecosystems. During leaf litter breakdown, the relative contribution of the functional groups and the quantity/quality of organic matter available to higher trophic levels are expected to be modified by the anthropogenic release of nutrients. 2. Carbon budgets were established during the breakdown of alder leaves enclosed in coarse mesh bags and submerged in six streams: two oligotrophic, one mesotrophic, two eutrophic and one hypertrophic streams. Nitrate concentrations were 4.5–6.7 mg L−1 and the trophic status of each stream was defined by the soluble reactive phosphorus concentration ranging from 3.4 (oligotrophic) to 89 μg L−1 (hypertrophic). An ammonium gradient paralleled the phosphate gradient with mean concentrations ranging from 1.4 to 560 μg L−1 NH4‐N. The corresponding unionised ammonia concentrations ranged from 0.08 to 19 μg L−1 NH3‐N over the six streams. 3. The dominant shredder taxa were different in the oligo‐, meso‐ and eutrophic streams. No shredders were observed in the hypertrophic stream. These changes may be accounted for by the gradual increase in the concentration of ammonia over the six streams. The shredder biomass dramatically decreased in eu‐ and hypertrophic streams compared with oligo‐ and mesotrophic. 4. Fungal biomass increased threefold from the most oligotrophic to the less eutrophic stream and decreased in the most eutrophic and the hypertrophic. Bacterial biomass increased twofold from the most oligotrophic to the hypertrophic stream. Along the trophic gradient, the microbial CO2 production followed that of microbial biomass whereas the microbial fine particulate organic matter and net dissolved organic carbon (DOC) did not consistently vary. These results indicate that the microorganisms utilised the substrate and the DOC differently in streams of various trophic statuses. 5. In streams receiving various anthropogenic inputs, the relative contribution of the functional groups to leaf mass loss varied extensively as a result of stimulation and the deleterious effects of dissolved inorganic compounds. The quality/quantity of the organic matter produced by microorganisms slightly varied, as they use DOC from stream water instead of the substrate they decompose in streams of higher trophic status. 相似文献
58.
Repeated heating and cooling in lethal (2–52°C) and nonlethal (2–37°C) temperature ranges resulted in cell death of Escherichia coli B/r and E. coli BS?1 suspended in 0.01 M phosphate buffer, pH 7.0 at varying osmotic pressure, but not in cow’s milk. The lethal effect increased with the rate of heating and cooling and with increasing suspension media tonicity; it may be caused by the temperature destabilization of cellular osmotic homeostasis. 相似文献
59.
The numbers of epiphytic yeasts on the leaves and flowers of 25 plant species throughout their vegetation period was determined. The numbers of yeasts on the leaves were found to change regularly throughout the year. The average dynamics for all of the plant species investigated included an increase in yeast numbers during spring and summer with the maximum in late autumn and early winter. The character of the yeasts’ dynamics depends on the ecological characteristics of the plants and the duration of the ontogenesis of their leaves and flowers. Three types of dynamics of epiphytic yeasts were revealed: year-round with an increase in autumn-winter, year-round without visible changes, and seasonal with a terminal increase for annual plants. 相似文献
60.