【作者】 刘彩霞；

【导师】 黄为一；

【作者基本信息】 南京农业大学 ， 微生物学， 2009， 硕士

【摘要】 耐盐碱微生物是盐碱土生态系统中的一类重要的土壤微生物,了解耐盐碱微生物在盐碱土中的分布特征及其在盐碱土改良中的作用具有重要意义。本文从新疆、江苏盐碱土地区采集植物根际、非根际土样,分析不同盐含量及不同粒径团聚体中微生物区系分布规律,结果表明,以氯化物为主要成分的盐碱土,肥力水平低下,盐分抑制土壤蔗糖酶、脲酶、过氧化物酶的活性,盐碱土中真菌、放线菌的数量较少,细菌是其中的优势种群,在各级团聚体及不同盐化程度的盐碱土中细菌分布都比较均匀。从以上盐碱土土样中分离到耐盐碱细菌120株。以分解秸秆和产胞外多糖能力为指标,筛选出秸秆5天降解率达30%以上菌株3株,分别为J2、X4、M5；筛选出胞外多糖产量在4 g·L-1以上的细菌3株,分别为：DF-2、A17、M6。筛选过程中发现,分解秸秆细菌一般耐盐性较强,在盐碱土中分布广泛。但产胞外多糖细菌在尚未开垦的滩涂重盐碱土中较难分离到,大部分产胞外多糖细菌耐盐性差,主要分布在已开垦盐碱土的植物根际。分离得到的六株细菌与促进盐碱土改良及盐碱环境中植物生长相关的生物学特性研究结果表明：菌株M5、A17、M6、J2及X4具有精氨酸脱羧酶活性；6株细菌均能产生铁载体,产IAA,菌株DF-2产IAA能力较强；菌株J2、M6和DF-2对油菜的促生效果较好。对促生能力较强的菌株J2、DF-2、M6进行了初步鉴定：菌株J2为短小芽孢杆菌(Bacillus pumilus),菌株DF-2为中华根瘤菌属(Sinorhizobium),菌株M6为枯草芽孢杆菌(Bacillus subtilis).菌株J2分解秸秆,不产胞外多糖,耐盐碱能力较强;菌株M6既分解秸秆又产胞外多糖,耐盐碱能力较强；菌株DF-2产胞外多糖,不分解秸秆,耐盐性差,但耐碱性较好,在pH 8-10范围,胞外多糖产量可达pH 7情况下的5-11倍。通过土柱试验研究了菌株J2、M6与外源有机物相互作用对盐碱土物理、生物性状的影响。结果表明,施用未腐熟玉米秸秆处理>2mm大团聚体含量显著高于施加已腐熟的有机肥的处理,与空白对照相比,施加玉米秸秆处理接种菌株J2、M6大团聚体含量增加40%以上,接种菌株M6处理最显著,大团聚体形成量达60%以上,即既分解秸秆又产胞外多糖的耐盐碱细菌菌株M6配施未腐熟玉米秸秆,使其在土壤中腐熟,对盐碱土团聚体形成的促进作用最显著,可作为改良滩涂盐碱土的有效措施。团聚体形成的动态跟踪发现,土壤团聚体形成过程与细菌活性密切相关,团聚体含量与细菌数量相关性均达(+)90%以上。玉米盆栽试验发现,在施加玉米秸秆的盐碱土中,供试菌株能在玉米根际较好定殖。菌株M6使玉米根际土中可溶性糖含量明显增加,对玉米植株生物量有显著促进作用,而菌株J2与对照相比促进作用不显著。通过油菜盆栽试验,研究了菌株J2、DF-2、M6对油菜生长与耐盐性的影响,结果表明,细菌胞外多糖有利于团聚体和油菜生物量的增加。腐熟秸秆或未腐熟秸秆均可提高油菜根际可溶性糖含量及土壤>0.25mm团聚体含量,提高土壤的保水能力,促进油菜生长。既产胞外多糖又分解秸秆细菌菌株M6对团聚体形成及油菜生长均有显著促进作用,有望开发为滩涂盐碱土改良的微生物菌剂。更多还原

【Abstract】 Saline-alkali-tolerant microbes are one kind of soil microbes in saline-alkali soil ecosystem. Thus, to understand the distribution characteristics of saline-alkali-tolerant microbes in saline-alkali soil ecosystem and their effect on improving saline-alkali soil is of great importance.Through collecting rhizosphere and non-rhizosphere soil samples of plant from the saline-alkali soil of xinjiang and Jiangsu province respectively, analyzing the distribution of Microbial flora in saline-alkali soil with different salt content and aggregate with different size, result shows that bacteria is the dominate population and distribute evenly in saline-alkali soil with different salt content and aggregate with different size. Salinity has a greater impact on fungi and there was fewer number of fungi in saline-alkali soil, which chloride was the dominate salt, with a low level of soil fertility. Soil salinity also inhibits the activity of invertase, urease and peroxidase in soil.One hundred and twenty saline-alkali-tolerant bacteria were isolated from saline-alkali soil said upsid. To take the capacity to decomposing straw and producing exopolysaccharides as an index of screening, three strains of bacteria with a 30% degradation rate of straw in five days were selected, named J2、X4、M5. three strains of bacteria with 4 g·L-1 exopolysaccharides production or more in three days were selected, named DF-2、A17、M6. Straw decomposing bacteria mainly have a better resistance to salt stress, and exist extensively in saline-alkali soil. Exopolysaccharides producing bacteria were hard to be found in tidal flat soils with heavy salt content, and were mainly habitated in the rhizosphere of plants in the light salt content soil which has been farmed.The characteristics of isolated bacteria were studied about plant growth-promoting and saline-alkali soil improvement in this paper. The results showed that test strains M5、A17、M6、J2 and X4 have arginine decarboxylase activity; All the strains can produce siderophore and indole acetic acid (IAA), of which DF-2 has a better IAA secretion ability. Strain J2、M6 and DF-2 hold more growth-promoting properties than other strains.The strains were respectively identified as Sinorhizobium sp. DF-2, Bacillus pumilus J2, Bacillus subtilis M6, based on their physio-biochemical characteristics and 16S rDNA sequence analysis. Strain J2 and M6 have a better saline-alkali resistance. Strain J2 has a high decomposing rate of corn straw, but can not produce Exopolysaccharides. Strain M6 can decompose corn straw and produce exopolysaccharides. Strain DF-2 do not decompose straw, has a high production of exopolysaccharides. Strain DF-2 have a poor salt resistance, and a good alkali resistance, production of exopolysaccharides with pH values under eight toten is five to eleven times compares with pH values under seven.Column experiments were carried out to study effects of strain J2、M6 and DF-2 screened from coastal saline-alkali soil, and combined with organic matter on the physical and biological property of saline-alkali soil. Results show that, compared with organic fertilizer, none-decomposed straw has a better effect on the forming of saline-alkali soil macroaggregates bigger than 2 mm. Strain M6、J2 combined with none-decomposed straw have good effects on the forming of soil aggregates, macroaggregates increased to more than 40% compared with control, in which the percent of macroaggregates of soil column inoculated with strain M6 reached to 60%. The inoculation with bacterial strain M6 that can decompose straw and secrete extracellular polymer substances, combining with straw that decomposed in soil, has best effect on the forming of saline-alkali soil aggregates, and is will be a good way to improve saline-alkali soil. The dynamic tracking of the aggregates formation shows that, the formation of soil aggregates is closely related to the bacterial activity, the relevance of the aggregates content and bacteria amount is more than (+)90%.Pot culture experiments of maize were carried out to study effects of strain J2 and M6 combined with none-decomposed straw on the growth of plant. Results show that, strain M6、J2 can colonize well in maize rhizosphere of saline-alkali soil. Inoculation of strain M6 can improve the concentration of soluble sugars significantly in rhizosphere soil and also can increase the plant biomass of maize. However the effects of inoculation of strain J2 is not significant.Pot culture experiments of rape were carried out to study effects of strain J2 and M6 promoting the growth of plant, and improving its resistance to salt. Results show that, Exopolysaccharides conduce to the forming of aggregates and the growth of rape. Straw fermented or not can improve the concentration of soluble sugars, the forming of aggregates bigger than 0.25 mm and water holding ability of soil. Either bacteria cell under logarithm growth period, metabolize by-product (exopolysaccharides) or ferment by-products of maize straw of strain M6 can improve the forming of aggregates and the growth of rape. The inoculation with bacterial strain M6 that can decompose straw and secrete extracellular polymer substances, has best effect on the forming of saline-alkali soil aggregates and the growth of rape, and is can be a good microbial agent to improve saline-alkali soil.更多还原