摘要:

The effect of applications of γ-benzene hexachloride (γ-BHC) to two submerged tropical soils at rates equivalent to recommended field practice (5 kg/ha) and 10 times this level upon the mineralization of native soil nitrogen was studied. No inhibitory effect on nitrogen mineralization was detected. A significant increase in the amount of nitrogen mineralized was detected in one of the soils over a period of 16 weeks of submergence. Additions of γ-BHC at 6 kg/ha resulted in significant increases in nitrogen fixation in both soils. Populations of anaerobic, phosphate-dissolving bacteria were found to be higher in the two soils when they were treated with γ-BHC at 6 kg/ha.

ISSN:0008-4166    

DOI:10.1139/m67-082

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Aflatoxin G1was removed from liquid cultures by growing and resting cells ofFlavobacterium aurantiacumNRRL B-184. In inoculated culture media containing toxin levels of 7.5 p.p.m. and above, there was a protracted growth lag which was subsequently overcome; toxin removal then occurred, concomitant with growth. Only a few cells demonstrated aberrant morphological forms when cultured in the presence of aflatoxin G1. A comparison of the effects of aflatoxin G1with B1on growth and morphology showed that B1was distinctly more toxic. Three hundred and thirty micrograms of aflatoxin G1was removed per 1 × 1013resting cells during a 4-hour incubation period. Preincubation of resting cells with aflatoxin B1did not interfere with subsequent uptake of G1.

ISSN:0008-4166    

DOI:10.1139/m67-083

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Increases in germination of conidia ofTrichoderma viridein the presence of soil was demonstrated with 5 of 16 amino acids tested. Only slight increases in germination occurred with selected mono-, di-, and tri-saccharides.Fungistasis of the test conidia was partially annulled when the pH of the spore suspension was adjusted to pH 0.3–0.4 and 1.3–1.4 before addition to agar discs over soil. The pH change was transitory and nearly reached an equilibrium with the soil within 6 to 8 h. Significant changes in the effectiveness of nutrients in reversing fungistasis occurred when the pH of the spore suspension was adjusted before addition to soil. Spore germination increased two- to four-fold with alanine, aspartic, and glutamic acids when the pH was adjusted in the range pH 1.3–1.4 to 5.5–6.5. Glucose increased spore germination only slightly, regardless of pH, but enhanced germination when combined with alanine and aspartic acid. In the presence of glucose, the molar concentration of the amino acids necessary to reverse fungistasis completely or partially was reduced.

ISSN:0008-4166    

DOI:10.1139/m67-084

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The effect of oat straw, green bean plants, and cellulose on the infection index and saprophytic activity ofRhizoctonia, and the effect of chitin, N-supplemented oat straw, and green cotton plants on the infection index, saprophytic activity, and soil microflora was tested. A modified method for countingRhizoctonia-antagonistic bacteria, actinomycetes, and fungi was developed. A relationship between efficiency of the amendments in decreasing infection index and in suppressing the saprophytic activity ofRhizoctoniawas observed at the end of the experimental period. Decrease in infection index and saprophytic activity was accompanied by increase in counts of general and antagonistic soil microorganisms. This increase was especially pronounced in chitin-amended soil. The possible mechanism of the biological control ofRhizoctoniaby chitin is discussed.

ISSN:0008-4166    

DOI:10.1139/m67-085

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The isolation of six distinct new plaque variants from pools of S- and M-Mengo (small- and medium-plaque variants respectively) is described. The size of plaques produced in L cell monolayers under nutrient agar by five of the six new variants is strongly inhibited by the addition to the overlay of dextran sulfate of molecular weight 500,000. The sixth, although similar to L-Mengo in its virulence to mice and in having plaques that are almost unaffected by the addition of protamine or dextran sulfate to the overlay, can be distinguished from the latter by the larger and more uniform plaques it produces. The marked heterogeneity in the size of plaques produced by L-Mengo appears to be an inherent property of this variant, since all attempts to isolate other plaque variants from L-Mengo pools have been unsuccessful.The intraperitoneal LD50's of all six new variants in 14- to 16-g mice was determined. There is no complete correlation between the virulence of these variants and their sensitivity to inhibition by dextran sulfate.

ISSN:0008-4166    

DOI:10.1139/m67-086

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The influence of temperature, pH, and sulfur source on arylsulfatase formation inP.rettgeriwas investigated. The highest level of enzyme activity was found when the organism was grown at 28 °C in a glycerol–salts medium (pH 7.0) containing 2.7 mMmethionine. Low levels of enzyme activity were found when the organism was grown in the presence of 0.8 and 1.5 mMsulfate but 3.0 and 9.0 mMsulfate repressed enzyme formation.Conditions optimal for the formation of enzyme active againstp-nitrophenol sulfate were not identical with those optimal for formation of enzyme active against nitrocatechol sulfate.The findings of this work are compared to similar findings in other bacterial systems.

ISSN:0008-4166    

DOI:10.1139/m67-087

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The survival of mutant and wild type macroconidia ofNeurosporawas compared after the conida, in the "air dry" state, had been frozen rapidly to −196 °C in liquid nitrogen and thawed rapidly. The 16 isolates ofNeurosporawere compared after 3 months' storage in liquid nitrogen with 7-day-old control cultures. Eleven of the 16 isolates showed no significant difference from 7-day-old controls in the pattern of germination after 8 hours' incubation. In the remainder, those spores germinating did so at a rate comparable to that of the controls, but the final proportion germinating was 5.0–19.0% lower.

ISSN:0008-4166    

DOI:10.1139/m67-088

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Preparations of ballistically disintegratedBacillus subtilisspores have been shown to possess proteinase in addition to esterase activities. Both proteinase and esterase activities have been suggested as trigger for the initiation of germination, but information on these two activities in bacterial endospores is scant. Since some proteinases catalyze the hydrolysis of esters, there exists a possible identity of some esterases with proteinases. To get information on the esterase and proteinase activities ofB.subtilisspores, the sensitivity to heat and to inhibitors was explored. The thermal effect and the effect of certain inhibitors on esterase activities towards several esters suggested that an unspecific esterase was responsible for these activities.Differential effects of heat, pH, and inhibitors on esterase and proteinase activities indicated the dual nature of these two activities. In absence of convincing experimental evidence to the contrary, the present indication seems to be that the esterase activities observed inB.subtilisspores were dissociated from the activity which hydrolyzes casein. The esterase activity was readily inhibited by diethylp-nitrophenyl phosphate, diisopropylphosphofluoridate, eserine, sodium fluoride, and Zn ions, and possessed properties of a B-esterase. The proteinase activity was inhibited only by diisopropylphosphofluoridate showing properties, so far studied, similar to subtilopeptidase.

ISSN:0008-4166    

DOI:10.1139/m67-089

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Decomposition of 2,4-dichlorophenoxyacetate (2,4-D) by a soil arthrobacter was studied using the technique of sequential induction. Compounds oxidized rapidly and without a lag by 2,4-D-grown cells, but slowly or not at all by citrate-grown cells, included 2,4-D, 2- and 4-chlorophenoxyacetate, 3,5-dichloro- and 4-chloro-catechol, catechol, 2,4-dichlorophenol, and 2- and 4-chlorophenol. The manometric data suggested that phenols and catechols were intermediates in the degradation of phenoxyacetates. Resting cells failed to accumulate chlorine-substituted phenols during the metabolism of halogenated phenoxyacetates, apparently because the phenols were oxidized as readily as they were formed. However, 2,4-D-induced cells contained enzymes which acted upon phenoxyacetate and 4-hydroxyphenoxyacetate, but these cells did not metabolize phenol and hydroquinone. Suspensions of such bacteria, but not citrate-grown cells, converted phenoxyacetate and 4-hydroxyphenoxyacetate almost completely to phenol and hydroquinone, respectively. The results indicate that theArthrobactersp. degrades 2,4-D via 2,4-dichlorophenol, and 2- and 4-chlorophenoxyacetate via 2- and 4-chlorophenol, respectively. The results also demonstrate a new technique for obtaining high yields of an intermediate in a metabolic sequence.

ISSN:0008-4166    

DOI:10.1139/m67-090

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Low concentrations of a phenolic metabolite accumulated in the medium during the early stages of growth of anArthrobactersp. in a medium containing 2,4-dichlorophenoxyacetate (2,4-D). The metabolite was identified by gas chromatography, ultraviolet and infrared absorption analysis, and paper chromatography of a nitro-derivative as 2,4-dichlorophenol, thus providing direct evidence that 2,4-D was degraded by the bacterium via its corresponding phenol. A second metabolite, identified by its retention time in the gas chromatograph and its reaction with HI as 2,4-dichloroanisole, was also produced. However, 2,4-D-grown cells, which converted 4-hydroxyphenoxyacetate to hydroquinone, failed to produce hydroquinone during the metabolism of 4-hydroxyanisole, suggesting that the conversion of phenoxyacetates to their corresponding phenols by the bacterium did not proceed via the corresponding anisoles. The role of 2,4-dichloroanisole in the metabolism of 2,4-D by this organism remains unknown.

ISSN:0008-4166    

DOI:10.1139/m67-091

出版商:NRC Research Press    

年代:1967

数据来源: NRC