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91.
Summary Field experiments were conducted to investigate the effect of organic mulching on the nutrient status, microbiological properties and the yield of maize and green gram crops. Soil organic carbon and humin and humus carbon of the fallow and the cropped soils were augmented by mulching. More of nitrogen, available phosphorus and ammoniacal and nitrate nitrogen were found in mulched soils. Soil reaction was not affected by mulching. Mulched treatments maintained more of soil moisture and soil temperature lowered during summer and rainy seasons. Population of bacteria, fungi, actinomycetes and Azotobacter were augmented in mulched treatments at all the stages of sampling. Mulching significantly increased the grain and straw yield of both the crops. The nitrogen uptake by grain was higher in mulched than in the unmulched treatments. 相似文献
92.
Summary An all glass tight growth chamber, entirely sterilizable, has been constructed to carry out axenic and gnotobiotic cultures
of rice plants (Oryza sativa L.). When grown in liquid medium and in the absence of combined nitrogen but in the presence of the diazotrophsAzotobacter vinelandii andRhodopseudomonas capsulata, rice plants exhibited a complete biological cycle from germination up to ear stage, during a period of time similar to the
one encountered in french paddy soil of Camargue. In one experiment, mannitol was given to rice culture medium together withAzotobacter vinelandii andRhodopseudomonas capsulata. In another experiment, mannitol was not given together with Rhodopseudomonas, and still positive nitrogen gain was obtained,
although it was less than culture with mannitol.
When15N labeled cells of Rhodopseudomonas were added in rice culture medium,15N was partly transferred to rice plant. Among the nitrogen substances excreted from the bacteria in the rhizosphere medium,
large organic molecules were shown to be the most abundant in our experimental conditions. Moreover, the concentration of
free ammonia or aminoacids present in the rice rhizosphere were always compatible with a bacterial nitrogenase activity. 相似文献
93.
Superoxide dismutase and catalase activities were studied in Azotobacter vinelandii grown diazotrophically at different ambient oxygen concentrations in continuous culture. Activities were expressed either as specific activity or activity per cell. Specific superoxide dismutase activity increased by a factor of 1.6 with increasing oxygen concentration from about 1% to 90% air saturation of the growth medium whereas specific catalase activity increased only slightly, if at all. Since cell volumes increased in parallel to increases in the oxygen concentration cellular superoxide dismutase activities increased by a factor of 4.3 while cellular catalase activities increased by a factor of 3.3. Under all conditions only the Fe-containing form of superoxide dismutase was detected. The possible function of these enzymes in the protection nitrogenase from oxygen damage is discussed.Abbreviation SOD
superoxide dismutase 相似文献
94.
Summary A study was conducted to know the effect of four common herbicidesviz, Lasso, Nitrofen, Propinol, and Simazine on soil microorganisms in Red Sandy soil. In general the application of different herbicides did not adversely affect the microbial population. The bacterial population was decreased by the application of propinol and nitrofen. Simazine and lasso stimulated the fungal population. The stimulation in Azotobacter population was observed in lasso, nitrofen and simazine treated soil. 相似文献
95.
AIMS: The ability of Azotobacter vinelandii, a N(2)-fixing bacterium, to biodegrade tetracyanonickelate (TCN) was evaluated. METHODS AND RESULTS: The amounts of TCN were measured spectrophotometrically. Ammonia was determined colorimetrically by the indophenol method. The produced methane from TCN conversion by A. vinelandii was detected by gas chromatography. Results showed that A. vinelandii was able to biodegrade 1 mmol l(-1) of TCN. Ammonia and methane were detected during the process of TCN degradation. Effects of exogenous nitrogen sources on TCN degradation were addressed in this study. Results revealed that the addition of ammonia (1, 5 and 10 mmol l(-1)) into the reaction mixtures caused decrease of TCN degradation rate during a 24-h incubation period. This inhibition was also observed when nitrite (5 and 10 mmol l(-1)) was added, whereas TCN degradation still proceeded after the addition of nitrate at the same concentrations. Furthermore, the rate of TCN utilization was strikingly enhanced when 0.8% of glucose was added. CONCLUSIONS: Azotobacter vinelandii can degrade 1 mmol l(-1) of TCN into ammonia and methane. However, the inhibitory effects of exogenous ammonia and nitrite on TCN degradation by this bacterium were found in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report defining the capability of A. vinelandii to degrade TCN. This bacterium might have potential value in applied strategies for removing metal-cyano wastes. Furthermore, these findings would be helpful in designing a practical system inoculated with A. vinelandii for the treatment of TCN. 相似文献
96.
Fusarium verticillioides is the most important seed transmitted pathogen that infects maize. It produces fumonisins, toxins that have potential toxicity for humans and animals. Control of F. verticillioides colonisation and systemic contamination of maize has become a priority area in food safety research. The aims of this research were (1) to characterise the maize endorhizosphere and rhizoplane inhabitant bacteria and Fusarium spp., (2) to select bacterial strains with impact on F. verticillioides growth and fumonisin B1 production in vitro, (3) to examine the effects of bacterial inoculum levels on F. verticillioides root colonisation under greenhouse conditions. Arthrobacter spp. and Azotobacter spp. were the predominant genera isolated from maize endorhizosphere and rhizoplane at the first sampling period, whilst F. verticillioides strains showed the greatest counts at the same isolation period. All F. verticillioides strains were able to produce fumonisin B1 in maize cultures. Arthrobacter globiformis RC5 and Azotobacter armeniacus RC2, used alone or in a mix, demonstrated important effects on F. verticillioides growth and fumonisin B1 suppression in vitro. Only Azotobacter armeniacus RC2 significantly reduced the F. verticillioides root colonisation at 106 and 107 CFU g–1 levels under greenhouse conditions. 相似文献
97.
当尿素浓度高于0.5 m oL/L时,棕色固氮菌(Azotobactervinelandii)固氮酶钼铁蛋白的乙炔还原活性呈指数下降;而经厌氧缓冲系统稀释并保温后,又可得到明显恢复。尿素对邻菲口罗啉从还原的或部分缺失P-cluster 的MoFe 蛋白中螯合金属原子簇的Fe 原子均有较大的促进作用。还原MoFe 蛋白在尿素梯度凝胶电泳中的迁移率:在0~1.5 m ol/L内,无明显变化;在1.5~5.0 m ol/L内,线性变小;在5.0~8.0 m ol/L内,则呈平缓状态。结果表明:(1)尿素对不同状态的MoFe 蛋白金属原子簇的影响程度不尽相同,而对蛋白质的变构作用是尿素影响MoFe 蛋白的活性和金属原子簇稳定性的主要原因;(2)MoFe 蛋白的构象与金属原子簇密切相关;(3)MoFe 蛋白在变性过程中,活性下降可能先于分子整体构象的变化 相似文献
98.
99.
棕色固氮菌(Azotobactervinelandi)钼铁蛋白经邻菲口罗啉和O2处理后,缺失一部分FeMoco和Pcluster,并失去大部分活性。高柠檬酸铁、Na2S和二硫苏糖醇(DTT)分别与K2CrO4、KMnO4和Na2MoO4按一定比例混合的具有不同颜色的重组液,均可显著激活失活的钼铁蛋白;然而,除DTT可略提高失活蛋白的活性外,其它化合物或缺一、二种化合物的混合液均无激活能力。含99Mo重组液与失活蛋白重组后的微分扰动角关联测定显示,该蛋白中的41%的99Mo的状态与克氏肺炎杆菌99MoFe蛋白中的99Mo相似,表明这种激活主要是以金属原子簇含量恢复为基础的。由此可推论出,含Mn或Cr的重组液,通过与失活钼铁蛋白重组得到含Mn或Cr的固氮酶是可能的。 相似文献
100.
Karl H. Tibelius Robert L. Robson M. G. Yates 《Molecular & general genetics : MGG》1987,206(2):285-290
Summary Genomic DNA from Azotobacter chroococcum was shown by DNA hybridization to contain sequences homologous to Rhizobium japonicum H2-uptake (hup) hydrogenase genes carried on the plasmid pHU1. Two recombinant cosmid clones, pACD101 and pACD102, were isolated from a gene library of A. chroococcum by colony hybridization and physically mapped. Each contained approximately 42 kb of insert DNA with approximately 27 kb of overlapping DNA. Further hybridization studies using three fragments from pHU1 (6 kb HindIII, 6.4 kb BglII and 5 kb EcoRI) showed that the hup-specific regions of R. japonicum and A. chroococcum are probably highly conserved. Weak homology to the hydrogenase structural genes from Desulfovibrio vulgaris (Hildenborough) was also observed. A 24 kb BamHI fragment from pACD102 subcloned into a broad host-range vector restored hydrogenase activity to several Hup- mutants of A. chroococcum. 相似文献