直投式木葡萄糖醋酸杆菌发酵剂的保护剂筛选研究

利用冷冻干燥技术制备一种直投式木葡萄糖醋酸杆菌的复合保护剂,先采用单因素试验优选出10%脱脂奶粉、5%海藻糖、1%谷氨酸可作为木葡糖醋酸杆菌发酵剂的单一保护剂,然后采用响应面分析法优化了直投式木葡萄糖醋酸杆菌复合保护剂中脱脂奶粉、海藻糖、谷氨酸的浓度和配比。结果表明,当复合冻干保护剂中含脱脂乳6.4%、海藻糖0.075%、谷氨酸0.575%时,木葡萄糖醋酸杆菌冻干后细胞的存活率最高、达93.346%。对比试验表明,添加复合冻干保护剂的发酵剂与同浓度的活菌液体发酵剂的细菌纤维素产率差异不显著。     

Bio-organic Amendment of Udic Ustochrept Soil for Minimizing Yield Decline in Sugarcane Ratoon Crops under Subtropical Conditions

The effects of subsequent sugarcane ratooning on soil quality and the crop yields under four treatments [an absolute control (T0), application of recommended dose of nitrogen (N)–phosphorus (P)–potassium (K) (T1), application of sulfitation press mud (SPM), a sugar factory by-product (T2), and SPM along with Gluconacetobacter diazotrophicus (Gd, T3)] were evaluated for 7 years. In the control (T0) and NPK-fertilized (T1) plots, an increase in soil compaction (5.4%), decrease in infiltration rate (6.04%), lower microbial activities, and increased soil phenolic contents (72.4%) rendered the nutrients unavailable, leading to significant declines in the crop yields at the rate of 5.47 Mg ha^?1 y^?1 and 4.67 Mg ha^?1 y^?1, respectively. The crop yield declined from 53 kg ha^?1 in plant crop to 18 kg ha^?1 in the sixth ratoon crop under the absolute control. The rates of yield decline, however, were minimized in SPM (T2) and SPM + Gd (T3) plots to 3.54 and 3.51 Mg ha^?1 y^?1.     

直投式木葡萄糖醋酸杆菌发酵剂的保护剂筛选研究

利用冷冻干燥技术制备一种直投式木葡萄糖醋酸杆菌的复合保护剂,先采用单因素试验优选出10％脱脂奶粉、5％海藻糖、1％谷氨酸可作为木葡糖醋酸杆菌发酵剂的单一保护剂,然后采用响应面分析法优化了直投式木葡萄糖醋酸杆菌复合保护剂中脱脂奶粉、海藻糖、谷氨酸的浓度和配比.结果表明,当复合冻干保护剂中含脱脂乳6.4％、海藻糖0.075％、谷氨酸0.575％时,木葡萄糖醋酸杆菌冻干后细胞的存活率最高、达93.346％.对比试验表明,添加复合冻干保护剂的发酵剂与同浓度的活菌液体发酵剂的细菌纤维素产率差异不显著.     

Potential of Azotobacter spp. as biocontrol agents against Rhizoctonia solani and Fusarium oxysporum in cotton (Gossypium hirsutum), guar (Cyamopsis tetragonoloba) and tomato (Lycopersicum esculentum)

During the current investigation, 51 bacterial isolates/mutants of Azotobacter chroococcum, Azospirillum spp. and Gluconacetobacter diazotrophicus were tested for antifungal activity against three fungal pathogens, namely Rhizoctonia solani cotton, Rhizoctonia solani rice and Fusarium oxysporum tomato using a dual-culture technique under laboratory conditions. Ten isolates/mutants were found to be inhibitory against R. solani cotton, six against R. solani rice and twelve against F. oxysporum tomato. Nearly 50% of the isolates/mutants were siderophore positive. The antimicrobial substance was found to be extracellular and proteinaceous in nature, but in some strains it was found to be associated with other complex material also. Almost all the positive isolates/mutants showed production of antibiotic and antifungal compounds. On the basis of this study, in vitro results under laboratory conditions were reproduced in pot experiments in the greenhouse and chosen isolates/mutants of A. chroococcum were found to be effective biocontrol agents against R. solani cotton (disease index 16.7%) and R. solani rice (2.5%) in cotton crop, whereas in guar, the crop disease index was 2.5% against R. solani cotton, 13.3% against R. solani rice and 0% against F. oxysporum tomato in tomato crop compared with their respective checks.     

Influence of N fertilisation on the isolation of Acetobacter diazotrophicus and Herbaspirillum spp. from Indian sugarcane varieties

 Observations of newer diazotrophs like Acetobacter diazotrophicus and Herbaspirillum spp. in Indian sugarcane varieties is reported here for the first time. A. diazotrophicus was isolated from sugarcane plants where N fertilisation was nil, and numbers in the Indian cultivars were estimated to be up to 10⁶–10⁷ colony forming units g¹ fresh weight. N fertilisation was the limiting factor for the isolation of A. diazotrophicus, as evidenced by selective growth patterns in different concentrations of N sources, but Herbaspirillum spp. were found to occur both in N fertilised and unfertilised samples. The fact that N is not the limiting factor for Herbaspirillum spp. was evidenced in a similar study of its growth pattern in different N sources. Received: 14 May 1998     

Recycling of Organic Wastes Amended with Trichoderma and Gluconacetobacter for Sustenance in Soil Health and Sugarcane Ratoon Yield in Udic Ustochrept

A field experiment was conducted with the objectives to relate the changes in the physical properties, soil organic carbon (SOC), nutrient availability, and uptake and output input ratios for sustaining sugarcane ratoon growth and yield in an Udic ustochrept. Eight combinations of trash and farmyard manure (FYM) with and without Trichoderma viride and Gluconacetobacter diazotrophicus were applied in two sugarcane ratoon (first and second ratoon in succession) crops. Application of Trichoderma-enriched trash showed the lowest bulk density (1.36 Mg m^?3) and the greatest infiltration rate (4.5 mm h^?1). Greater rate of increase in SOC was observed under inoculation of Trichoderma with FYM compared to trash mulch. The output/input ratios were greater in plots having trash-based treatments compared to FYM and inorganic fertilizers. Bioagent-inoculated FYM produced greater mean sugar yield (8.89 t ha^?1) compared to bioagent-inoculated trash (7.97 t ha^?1).     

<Emphasis Type="Italic"> Gluconacetobacter diazotrophicus</Emphasis>: a natural endophytic diazotroph of Nile Delta sugarcane capable of establishing an endophytic association with wheat

Gluconacetobacter- like diazotrophs were encountered as dense populations inside the root and stem tissues of sugarcane cultivated in ancient agricultural fields of the Nile Delta. Counts of >10⁵ cells g^-1 were recorded in root and stem samples. The leaves contained a smaller population (<10³ g^-1). The typical dark-orange colonies which developed on LGIP agar plates were purified. Identification was performed with the API microtube systems: API 20E for Enterobacteriaceae and API 20NE for non-Enterobacteriaceae. API profiles of the local isolates were closely related to those of the type culture Gluconacetobacter diazotrophicus (ATTC 49037). The isolates successfully reduced C₂H₂ and produced appreciable amounts of ethylene in the presence of cane juice. This suggested that the local isolates are closely related to the type strain G. diazotrophicus. Wheat seedlings were inoculated with a number of isolates under gnotobiotic conditions. Both optical and scanning electron microscopy showed that endophytic Gluconacetobacter spp. were present in all the samples tested. They were observed in apparently intact and enlarged epidermal root cells, and also in stem tissues, indicating that the bacterium was able to migrate upward into the shoot tissues. Although Gluconacetobacter inoculation did not stimulate the growth of the cereal plant, the results obtained are particularly interesting because this bacterial species was capable of colonizing the internal tissues of wheat, not considered a natural host until now.     

Hydrolytic enzyme activities in maize (Zea mays) and sorghum (Sorghum bicolor) roots inoculated with Gluconacetobacter diazotrophicus and Glomus intraradices

Two strains of Gluconacetobacter diazotrophicus (Pal 5, UAP5541) and the arbuscular mycorrhizal fungus Glomus intraradices increased both the shoot and root dry weight of sorghum 45 days after inoculation, whereas they had no effect on the shoot and root dry weight of maize. Co-inoculation (Gluconacetobacter diazotrophicus plus Glomus mosseae) did not increase the shoot and root dry weight of either plant. There was a synergistic effect of Gluconacetobacter diazotrophicus on root colonization of maize by Glomus intraradices, whereas an antagonistic interaction was observed in the sorghum root where the number of Gluconacetobacter diazotrophicus and the colonization by Glomus intraradices were reduced. Plant roots inoculated with Gluconacetobacter diazotrophicus and Glomus intraradices, either separately or together, significantly increased root endoglucanase, endopolymethylgalacturonase and endoxyloglucanase activities. The increase varied according to the plant. For example, in comparison with non-inoculated plants, there were higher endoglucanase (+328%), endopolymethylgalacturonase (+180%) and endoxyloglucanase (+125%) activities in 45-day old co-inoculated maize, but not in 45-day old sorghum. The possibility is discussed that hydrolytic enzyme activities were increased as a result of inoculation with Gluconacetobacter diazotrophicus, considering this to be one of the mechanisms by which these bacteria may increase root colonization by AM fungi.     

接种重氮营养醋杆菌对植物生长的影响

采用盆栽方法通过对甘蔗、甘薯组培苗和玉米幼苗进行重氮营养醋杆菌的接种，研究了重氮营养醋杆菌对这3种植物生长的影响。试验设置4种处理，即接种细菌 正常供氮，不接种细菌 正常供氮，接种细菌 供低氮(正常供氮量的1／4)，不接种细菌 供低氮。结果表明：(1)接种细菌能够在接种植物体内定殖，从接种处理的玉米、甘蔗和甘薯植株体内均可以分离到接种的细菌菌株。(2)两种供氮水平下，均为接种细菌显著促进了玉米、甘蔗和甘薯的生长，3种植物的生物量、植株高度、茎粗和叶片叶绿素都显著高于不接种细菌的处理，且正常供氮下的促进作用更为明显。     

细菌纤维素产生菌双向凝胶电泳分析技术

对细菌纤维素产生菌株———葡糖酸醋杆菌菌体蛋白的提取过程、等电点的分布及纯化方法等方面进行了探索和优化。结果表明:葡糖酸醋杆菌蛋白主要分布在pI 4~7的范围内;采用超滤浓缩后进行2D Clean-up试剂盒纯化,可以获得更优的蛋白分离效果;在考马斯亮蓝G250染色条件下,有效分离出(1037±65)个蛋白点;建立了高质量葡糖酸醋杆菌蛋白的双向凝胶电泳分析技术。