ISSN:0008-4166    

DOI:10.1139/m81-059

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A newly developed technique using ruthenium red to detect foci of bacterial digestion in mounts of whole leaflets that had been incubated with rumen bacteria was used to compare the digestion of alfalfa, a bloat-causing legume, and sainfoin, a bloat-safe legume. When whole leaflets were suspended in an artificial rumen medium and inoculated with rumen bacteria, massive bacterial adhesion and proliferation were noted at the stomata of alfalfa leaflets after 6 h of incubation, whereas only a few isolated bacteria adhered near the stomata of sainfoin leaflets. After 22 h of incubation, the epidermal layers of alfalfa leaflets had peeled away in many areas, revealing an extensive bacterial invasion of the underlying mesophyll tissue in which large bacterial microcolonies had formed in intercellular spaces, and in intracellular spaces in several areas where plant cell walls had broken down. After 22 h of incubation, the surface of sainfoin leaflets resembled that of alfalfa leaflets at 6 h, with bacterial microcolonies adhering to the area surrounding the stomata, but without sloughing of the epidermis. Uninoculated control leaflets of both species showed no surface alterations but part of their normal bacterial flora had proliferated to form microcolonies on the surface after 22 h of incubation.Dry matter loss due to leaching or bacterial digestion when whole leaflets of legumes were suspended in an artificial rumen medium, alone or with rumen bacteria, was significantly higher in the bloat-causing group. Values of leaching and of bacterial digestion were positively correlated.We conclude that reported differences in plant anatomy, and in cell wall chemistry, produce distinct rates of organic nutrient release from legume leaflets, and that these same differences produce an equally distinct susceptibility of leaflets to bacterial invasion, plant cell rupture, and the consequent release of intracellular plant components. The rate of release of organic nutrients from legume leaflets may be important in the etiology of foamy pasture bloat.This technique ofin vitrodigestion of whole leaflets followed by ruthenium red staining shows some promise of providing a rapid and qualitative test to distinguish, within a species, cultivars that may differ in their bloat-related characteristics.

ISSN:0008-4166    

DOI:10.1139/m81-060

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Protoplasts were prepared from conidiospores ofAspergillus nidulans. The mononucleated conidia gave protoplasts of a uniform size, approximately 5-μm diameter, depending on the strain and the stabilizing medium used. Conidia were preincubated with 2-deoxy-D-glucose in a minimal medium at 37 °C for 3 h. The swollen conidia were collected, resuspended in a buffer containing 0.4 M(NH4)2SO4as stabilizer, and incubated withOerskovialytic enzymes at 30 °C for 3 or 4 h. Approximately 80% of the conidia were converted into protoplasts. The protoplasts were separated from cell wall fragments and intact conidia by centrifugation over 30% sucrose. This isolation procedure gives a suspension of mononucleated or binucleated protoplasts suitable for recombination experiments and other studies for which a homogenous protoplast suspension is required. The procedure was also successful forAspergillus niger.

ISSN:0008-4166    

DOI:10.1139/m81-061

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Heat activation (70 °C for 20 min) resulted in alteration in structural proteins and enzymes found inBacillus cereusspore coats. The three notable changes were increased glycosylation of coat proteins, alteration in polypeptide pattern on sodium dodecyl sulfate – polyacrylamide gels, and an increase in free SH groups of proteins. About three polypeptides leaked out in small quantities from the spore coats during heat activation.The extraction of five spore coat associated enzyme activities was followed during the coat stripping procedures, which left the cortex and core intact. Two of these activities,L-alanine dehydrogenase and purine nucleoside hydrolase, were solubilized when the undercoat was extracted by 1,4-dithioerythritol (DTE) at pH 9.8. Three other activities, a protease, a corticolytic enzyme, and purine nucleoside phosphorylase, were solubilized by both DTE alone and DTE plus urea at pH 9.8. The DTE plus urea extraction removed the two more insoluble coat layers, the outer cross-patch, and the inner pitted layers. Mutants deficient in the cross-patch layer contained normal amounts of the protease, corticolytic, and purine nucleoside phosphorylase activities suggesting their association with the pitted layer.In intact spores all five enzymes were found to be stable to the heat activation treatment. However, extracted and partially purified preparations of protease, purine nucleoside phosphorylase, andL-alanine dehydrogenase were heat sensitive. Similar preparations of corticolytic enzyme and purine nucleoside hydrolase were stable to the heat activation conditions.

ISSN:0008-4166    

DOI:10.1139/m81-062

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Viruses were isolated from every sample of raw (100 L) and treated (1000 L) water collected at a water treatment plant drawing sewage-contaminated river water. Few plaque-forming isolates were found but cytopathogenic viruses were isolated as frequently in drinking water as in raw water. In drinking water some samples contained more than 1 cytopathogenic unit per litre, but most contained 1–10/100 L. These viruses had not been inactivated or removed by prechlorination, flocculation, filtration, ozonation, and postchlorination. There were no coliforms present and a residual chlorine level had been maintained. Poliovirus type 1 was a frequent isolate but many isolates were nonpoliovirus. The presence of these viruses in drinking water raises questions about the efficacy of some water treatment processes to remove viruses from polluted water.

ISSN:0008-4166    

DOI:10.1139/m81-063

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Micrococcus roseusforms bicyclic keto-carotenoids. The effects of nicotine, piperonyl butoxide, and 2-(4-chlorophenylthio)triethylamine hydrochloride (CPTA) were studied with regard to their ability to selectively inhibit carotenogenesis in the organism. Nicotine caused accumulation of β-zeacarotene; piperonyl butoxide caused accumulation of phytoene and traces of phytofluene, ζ-carotene, and β-zeacarotene. In both cases canthaxanthin biosynthesis was inhibited. CPTA inhibited canthaxanthin synthesis and caused accumulation of β-zeacarotene and γ-carotene and their mono- and di-hydroxy derivatives. Regardless of the inhibitor used, canthaxanthin was the major colored carotenoid biosynthesized. The expected precursors of carotenoid cyclization, neurosporene and (or) lycopene, were not detected in CPTA- or nicotine-inhibited cultures. Therefore, carotenoid cyclization inM.roseusdoes not involve neurosporene or lycopene and must occur early in carotene biosynthesis, prior to the formation of β-zeacarotene. ζ-Carotene is proposed as the cyclization substrate and β-zeacarotene as the substrate for oxygen insertion.

ISSN:0008-4166    

DOI:10.1139/m81-064

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Polygalacturonic acid transeliminase (PATE) was produced by all of sixAzospirillumstrains studied. Characteristics were similar to those of PATE from other bacteria: activity was maximal at pH 8.0 and was stimulated by CaCl2. Polygalacturonic acid was used more readily than pectin as a substrate. Polygalacturonic acid in the medium stimulated PATE production by several but not all strains. In all cases some of the PATE produced in cultures remained bound to cell walls. In one strain, most remained cell wall bound. When nitrogen was supplied as amino acids rather than ammonium salts, the ratio of free to bound enzyme was increased. The strains studied varied considerably in response to nutrient amendments and in maximum PATE activity.

ISSN:0008-4166    

DOI:10.1139/m81-065

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Water samples obtained from three different marine environments (including a commercial harbor, a pristine area, and an oil tanker dock area) from the coast of Washington State were challenged with Prudhoe Bay crude oil under shake-flask conditions at 8 °C. Replicate cultures were grown with and without nitrogen (NO3−, NH4+) and phosphate supplementation. After varying incubation periods, the residual oil was extracted and separated on silica gel columns into saturate and aromatic fractions and these were analyzed by glass capillary gas chromatography to detect the degradation of various compounds. After 27 days of incubation, both the aromatic and saturate fractions were extensively degraded by the microorganisms from these environments when supplemented with nitrogen and phosphorus. Without nutrient supplementation, the aromatics were more readily attacked than the saturates by the populations from the pristine environment and from the commercial harbor area. Under these limited nutrient conditions, samples from near oil tanker docks showed moderate degradation of both the saturate and aromatic fractions. Time course studies, using nutrient-supplemented marine samples, showed that the simple aromatics (e.g., naphthalene and 2-methylnaphthalene) were more readily degraded than then-alkanes. However, once the breakdown of these saturates commenced, these were quickly removed from the oil. The aromatic degradation continued to progress from lower molecular weight, less complex molecules to larger, more complex molecules in the approximate series C2naphthalenes; phenanthrene and dibenzothiophene; C3naphthalenes and methylphenathrenes; C2phenanthrenes.

ISSN:0008-4166    

DOI:10.1139/m81-066

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The K+, Na+, and Mg2+contents ofMethanospirillum hungateiand of the thermophileMethanobacterium thermoautotrophicumwere determined at various phases of growth. The intracellular K+content of exponential phase cells ofM.thermoautotrophicum(approximately 780 mM) was 5.4-fold higher than inM.hungatei, and decreased gradually as the culture entered the stationary phase. Both methanogens concentrated Mg2+, exhibiting an increased content as the cultures aged. Comparisons among extraction methods showed that most of the internal K+was readily released, but a minimum of half of the Mg2+inM.hungatei, and most of the Mg2+inM.thermoautotrophicum, was in a bound form. Exponential phase cells ofM.hungateiestablished an intracellular level of Na+lower than the outside medium, but the thermophile concentrated Na+.Dextran, inulin, sucrose, and glucose penetrated cell pellets to varying degrees and could be used to measure the space corresponding to cytoplasm and to cell wall permeability barriers.L-Phenylalanine penetrated fully and acetate accumulated in both methanogens. Acetate uptake in cell suspensions ofM.hungateiwas fully inhibited by oxygen,N-ethylmaleimide, orN,N′-dicyclohexylcarbodiimide, but was not affected by the proton conductor carbonylcyanidep-trifluoromethoxyphenylhydrazone.L-Malate, which penetratedM.hungateicells poorly, was metabolized to glutamate, indicating the presence of an incomplete reductive carboxylic acid cycle.

ISSN:0008-4166    

DOI:10.1139/m81-067

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Conventional mice fed commercially prepared pelleted food, or a laboratory-prepared food consisting of casein, cornflour, bran, vitamins, and minerals, harboured a layer of lactobacilli on the nonsecretory epithelium of the stomach. In contrast, the majority of mice fed the laboratory-prepared diet to which corn, sunflower seed, or codliver oil had been added lacked a iactobacillus layer in the stomach. Analysis of the fatty acid content of the various diets, and feeding mice diets of known fatty acid composition, led to the conclusion that the relative amounts of palmitic and oleic acid in the food can influence the number of tissue-associated lactobacilli in the mouse stomach.

ISSN:0008-4166    

DOI:10.1139/m81-068

出版商:NRC Research Press    

年代:1981

数据来源: NRC