二甲戊灵对棉田土壤微生物的影响

以土壤微生物为研究对象,采用平板计数法分别对不同深度土壤细菌、真菌、放线菌数量进行统计,探究二甲戊灵处理后土壤微生物种群变化。结果表明,土壤深度为0~15 cm时,二甲戊灵对细菌、真菌、放线菌多为抑制作用,其中放线菌种群对表现的最为明显,呈持续抑制状态;细菌次之,呈阶段性抑制状态;而真菌对二甲戊灵具有一定抗性,随着时间的推移抑制和激活均不明显。土壤深度为15~20 cm时,二甲戊灵对3种微生物有不同程度激活作用。二甲戊灵对土壤微生物的影响随微生物种类和二甲戊灵浓度和土壤深度而异。正常使用浓度下,对微生物的影响是暂时的,其稳定系统不易破坏,但长期施用二甲戊灵会引起土壤微生物的失衡。     

杀松材线虫海洋细菌HT-11的鉴定及培养条件研究

[目的]从海洋中分离并筛选具有杀松材线虫活性的细菌。[方法]采用稀释涂布平板法对采自青岛近海海域的样品进行细菌分离,采用浸渍法测定菌株的杀线虫活性,并对筛选菌株的形态学、生理生化特性和16S r DNA序列进行测定,通过单因素试验筛选产生杀线虫活性物质的最适培养条件。[结果]共分离到36株海洋细菌,根据杀线虫活性筛选出1株具有高杀线虫活性的细菌HT-11。该菌株分离自牡蛎,其培养滤液处理松材线虫24 h的校正死亡率高达92.41%。根据形态学、生理生化特性和16S r DNA序列测定及其系统发育分析结果,将菌株HT-11鉴定为考克氏菌属(Kocuria)。单因素试验结果表明,该菌株在营养肉汤(NB)培养基中产生杀线虫活性物质的最适培养条件为:海水浓度100%,初始p H 7.0,培养温度25℃,培养时间3 d。[结论]该研究可为海洋微生物资源的开发及其杀松材线虫天然活性物质的利用提供理论依据。     

新疆核桃根际土壤中解钾菌的分离筛选及鉴定

为给核桃专用微生物肥的研制提供菌株材料,通过对解钾菌的分离纯化,筛选对新疆核桃根际土壤具有解钾作用且能在其根际稳定定殖的优质高效菌株。结果表明:从阿克苏、和田、喀什3个新疆核桃主产区的根际土壤中分离出解钾菌27株;采用火焰光度计法对其解钾能力进行测定,选出解钾菌16株;经耐利福平诱导后剩余14株;将其进行大田定殖试验后,最终筛选出10株解钾能力较强的菌株。经16S r DNA进行鉴定,得出这10株解钾菌归属于3个属。分别为假单胞菌属Pseudomonas、芽孢杆菌属Bacillus、微杆菌属Microbacterium,其中假单胞菌属为优势种属。     

Bacterial inoculants for rice: effects on nutrient uptake and growth promotion

Beneficial soil bacteria are able to colonize plant root systems promoting plant growth and increasing crop yield and nutrient uptake through a variety of mechanisms. These bacteria can be an alternative to chemical fertilizers without productivity loss. The objectives of this study were to test bacterial inoculants for their ability to promote nutrient uptake and/or plant growth of rice plants subjected to different rates of chemical fertilizer, and to determine whether inoculants could be an alternative to nitrogen fertilizers. To test the interaction between putatively beneficial bacteria and rice plants, field experiments were conducted with two isolates: AC32 (Herbaspirillum sp.) and UR51 (Rhizobium sp.), and different nitrogen fertilization conditions (0%, 50%, and 100% of urea). Satisfactory results were obtained in relation to the nutrient uptake by plants inoculated with both isolates, principally when the recommended amount of nitrogen fertilizer was 50% reduced. These bacterial strains were unable to increase plant growth and grain yield when plants were subjected to the high level of fertilization. This study indicated that the tested inoculant formulations can provide essential nutrients to plants, especially when the levels of nitrogen fertilizers are reduced.     

纤维素降解细菌的筛选及其酶活测定

为了充分利用植物废渣中丰富的纤维素资源,以羧甲基纤维素钠(CMC-Na)为唯一碳源的培养基和刚果红染色筛选法从朽木周围富含腐殖质的土壤中筛选得到3株活性较高的纤维素降解细菌：ZWY-3、DP-6和DP-8,并分别在不同的培养时间、培养温度、起始pH、碳源下对3株菌株进行酶活测定。结果表明：3株菌株都在接种后24 h、pH 7、30℃、葡萄糖为碳源时达到产酶高峰,其中接种后24 h时DP-6的酶活最高,达144.86 U;ZWY-3在30℃、pH 7时酶活最大,分别达126.74 U和133.82 U;3株菌株在其最适条件下培养,并以葡萄糖为碳源时,DP-6活性最高,可达218.96 U。3株细菌菌株在降解农业纤维工业中具有良好的应用前景。     

马铃薯黑痣病生防菌的筛选和鉴定及其生长条件的研究

从甘肃省景泰县条山农场不同连作年限的马铃薯地块中取根际土样品,分离筛选马铃薯黑痣病病原菌-立枯丝核菌(Rhizoctonia solani)的拮抗菌。采用土壤平板稀释、对峙法筛选拮抗菌;结合形态特征、生理生化及16Sr DNA分子鉴定;采用单因素试验设计对G1菌株的生长条件进行初步试验。通过初筛和复筛,从108株细菌中获得1株对立枯丝核菌拮抗效果稳定、拮抗能力较强的细菌G1。采用平板对峙法测定其拮抗作用,抑菌带宽度达6mm,抑菌圈直径2.5 cm,抑菌率为66.7%。结合形态特征、生理生化及16Sr DNA分子鉴定,G1为类芽孢杆菌(Paenibacillus sp.);采用单因素试验设计对G1菌株的生长条件进行初步试验。结果表明,菌株G1在4℃~45℃,p H 5~10,盐浓度0~50 g·L-1都能生长,碳源、氮源利用广泛,最适条件为:温度37℃,p H 7,蔗糖为碳源,蛋白胨为氮源,盐浓度为10 g·L-1。拮抗菌G1被鉴定为类芽孢杆菌,该菌株抑菌带较宽、抑菌效果稳定,生长条件与马铃薯生长的大田环境基本相符,具有作为一株优良生防菌的必要条件。     

蜜蜂肠道菌群的调节作用及影响因素

近年来, 蜜蜂数量的大量减少导致全球养蜂业面临重要的经济损失,并对农业各个方面造成了严重后果。最新的研究表明肠道菌群与宿主的健康息息相关。综述了肠道菌群的种类和特性,阐述了肠道菌群在蜜蜂等昆虫健康中的调节作用及影响肠道菌群的因素,并对今后的研究方向进行了展望。     

蒙古马肠道细菌总DNA提取方法的比较

本试验采集蒙古马新鲜粪便样品,采用酚－氯仿抽提法和2种细菌基因组DNA提取试剂盒法进行样品中细菌基因组DNA的提取。通过DNA浓度和纯度的测定,并将其作为模板扩增细菌16S rDNA V3区特异性片段对提取效果进行比较,从而找出更适合蒙古马粪便中细菌基因组DNA的提取方法。结果显示,3种提取方法得到的基因组DNA均能用于PCR扩增的模板,其中B试剂盒法提取的DNA数量较多,且纯度高,更适合用于提取蒙古马肠道微生物细菌基因组DNA及后续的蒙古马肠道微生物多样性等分子生物学试验。     

乳酸菌培养物对肉鸡生长性能及免疫功能的影响

试验旨在研究灭活乳酸菌培养物对肉鸡生长性能及免疫功能的影响。选择300只体重相近的健康1日龄AA肉仔鸡,随机分为5组,每组6个重复,每个重复10只鸡,雌、雄各半。其中对照组饲喂基础日粮,抗生素组在基础日粮中添加0.01%金霉素,乳酸菌培养物组分别在基础日粮中添加0.16%乳酸菌培养物L1、L2、L3。试验期42 d,分1~21日龄(前期)和22~42日龄(后期)2个阶段。结果显示,1~21日龄时,乳酸菌培养物L1组肉鸡平均日采食量极显著高于对照组和抗生素组(P<0.01),血清中白介素-2(IL-2)含量显著低于对照组(P<0.05),脾脏指数、胸腺指数、法氏囊指数均显著高于对照组(P<0.05);乳酸菌培养物L2组肉鸡脾脏指数、胸腺指数显著高于对照组(P<0.05);乳酸菌培养物L3组肉鸡平均日增重极显著高于对照组和抗生素组(P<0.01);抗生素组肉鸡血清中γ-干扰素(IFN-γ)含量显著高于乳酸菌培养物组(P<0.05)。22~42日龄时,乳酸菌培养物L1、L2组肉鸡平均日增重极显著高于对照组和抗生素组(P<0.01);乳酸菌培养物L2组肉鸡血清中免疫球蛋白G(IgG)含量显著高于抗生素组(P<0.05),血清新城疫抗体效价及脾脏指数、胸腺指数、法氏囊指数均显著高于对照组(P<0.05);乳酸菌培养物L3组肉鸡血清中免疫球蛋白A(IgA)含量及胸腺指数显著高于对照组(P<0.05)。由此可知,在肉鸡日粮中添加一定量的灭活乳酸菌培养物可在一定程度上提高肉鸡的生长性能、增强其免疫功能,其中,对于提高肉鸡的生长性能,试验前期添加L3效果较好,试验后期添加L1和L2效果较好;对于增强肉鸡的免疫功能,试验前期添加L1效果较好,试验后期添加L2效果较好。     

Marine-Derived Quorum-Sensing Inhibitory Activities Enhance the Antibacterial Efficacy of Tobramycin against Pseudomonas aeruginosa

Bacterial epiphytes isolated from marine eukaryotes were screened for the production of quorum sensing inhibitory compounds (QSIs). Marine isolate KS8, identified as a Pseudoalteromonas sp., was found to display strong quorum sensing inhibitory (QSI) activity against acyl homoserine lactone (AHL)-based reporter strains Chromobacterium violaceum ATCC 12472 and CV026. KS8 supernatant significantly reduced biofilm biomass during biofilm formation (−63%) and in pre-established, mature P. aeruginosa PAO1 biofilms (−33%). KS8 supernatant also caused a 0.97-log reduction (−89%) and a 2-log reduction (−99%) in PAO1 biofilm viable counts in the biofilm formation assay and the biofilm eradication assay respectively. The crude organic extract of KS8 had a minimum inhibitory concentration (MIC) of 2 mg/mL against PAO1 but no minimum bactericidal concentration (MBC) was observed over the concentration range tested (MBC > 16 mg/mL). Sub-MIC concentrations (1 mg/mL) of KS8 crude organic extract significantly reduced the quorum sensing (QS)-dependent production of both pyoverdin and pyocyanin in P. aeruginosa PAO1 without affecting growth. A combinatorial approach using tobramycin and the crude organic extract at 1 mg/mL against planktonic P. aeruginosa PAO1 was found to increase the efficacy of tobramycin ten-fold, decreasing the MIC from 0.75 to 0.075 µg/mL. These data support the validity of approaches combining conventional antibiotic therapy with non-antibiotic compounds to improve the efficacy of current treatments.