Studies on the Isolation of Endophytic Bacteria from Tomato Plants and Their Growth-promoting Activities

[Objective] The study aimed to investigate the growth-promoting activities of endophytic bacteria from tomato plants.[Method]The endophytic bacteria isolated from different tissues of tomato plants were analyzed for the effects of their growth-promoting activities on the germination and growth of tomato plants.The bacteria with growth-promoting activity were preliminarily identified.[Result]Totally 59 endophytic bacterial strains were isolated from roots and stems of tomatoes,of which 4 showed significantly growth-promoting activity to germination and growth of tomato.The results suggest that these strains are endowed with the potential capability of growth-promoting.[Conclusion]The endophytic bacteria with growth-promoting activity were found among the isolates from tomato plants.This provided a good foundation for utilization of these bacteria with growth-promoting activity.

Determination of Growth-promoting and Antagonistic Action of Endophytic Bacteria Strains Itb57 and Itb295 of Tobacco

[ Objective ] The paper was to study the growth-promoting and antagonistic action of endophytic bacteria strains Itb57 and Itb295 of tobacco to explore their functions in biological control. [ Method] The growth-promoting effects of bacterial suspension ~ff endophytic bacteria Itb57 and Itb295 on tobacco seedling un- der different treatment modes were studied using potting method in greenhouse. The antagonistic action of bacterial suspension of endophytic bacteria Itb57 and Itb295 on Phytophthora nicotianae, Alternaria alternata and Botrytis cinerea were measured by duel culture method. [ Result] Bacterial suspensions of enduphytic bacteria Itb57 and Itb295 had certain growth-promoting effects on tobacco seedling, which could significantly increase the fresh weight and dry weight in aerial part; the growth-promoting effect of soaking ＋ spraying and irrigating treatment was the best. Itb57 strain had good antagonistic action against P. nicotianae. A. alterna- ta and B. cinerea, while Itb295 strain only had good antifungal effect against P. nicotianae. [ Conclusion] The results provided basis for the study and application of tobacco endophytic bacteria strains Itb57 and Itb295 in biocontrol of tobacco diseases.

Growth of marine bacteria and ammonium regeneration from substrates in different C:N ratios

Natural assemblages of marine bacteria were chosen in a batch culture experiments. The impact of varying nitrogen substrate concentrations and the substrate C：N ratios （C：Ns） on the bacterial C：N ratio （C：NB）, the bacterial growth efficiency （BGE） and ammonium regeneration was mainly examined. The C：Ns ratios varied from 5：1 （carbon limitation） to 40：1 （nitrogen limitation） with varying combinations of glucose and NO3. The C：NB ratio had positive relationship with the C：Ns ratio （r=0.93, n=8）, whose value was 3.77 when the C：Ns ratio was 5：1 but increased to 6.47 when the C：Ns ratio was 40：1. These results indicate that the C：NB ratio is a potential diagnostic tool for determining the bacterial growth in natural waters controlled by either, carbon or nitrogen. BGE decreased with the declining nitrate concentration and negatively related to C：N8 （r=-0.51, n=8）. The average value of BGE was 0.20. This value was a little lower than other reports, which could be induced by the nitrogen source used in our experiments. Finally, regeneration time of ammonium delayed with the increasing C：Ns ratio, which indicates that there were different metabolism mechanisms when bacterial growth was limited by carbon source and nitrogen source.

Endophytic bacteria associated with endangered plant Ferula sinkiangensis K. M. Shen in an arid land： diversity and plant growth-promoting traits

Ferula spp. are traditional medicinal plants found in arid land. Large-scale excavation for extracting bioactive compounds from the plants in arid regions of Xinjiang over the last few years has, however, significandy decreased their distributions. Due to the urgent need for preservation of these plant resources, along with the need of searching for alternative source of the useful metabolites, it is important to screen the endophytic microbial resources associated with the plant Ferula sinkiangensis K. M. Shen. In the study, a total of 125 endophytic bacteria belonging to 3 phyla, 13 orders, 23 families, and 29 genera were isolated based on 16S rRNA gene sequencing data. Among the different isolates, three strains isolated from roots were potential novel species of the genera Porphyrobacter, Paracoccus and draycofatopsis. In this study, 79.4% and 57.1% of the total isolates were capable of producing indole-3-acetic acid （IAA） and siderophore, respectively. And, 40.6% of the strains inhibit the growth of fungal pathogen Afternaria alternata, 17.2% and 20.2% strains were positive for antagonism against Vertidllium dahlia 991 and V. dahlia 7, respectively. These results demonstrated that E sinkiangensis is a rich reservoir of endophytic bacterial resources with potential for production of biologically important functions such as plant growth-promoting factors.

Identification of Growth-promoting Bacteria from Rhizosphere of Pastures and Their Effects on Growth of Lotus corniculatus L.

[Objectives] This study was conducted to explore the interaction between nitrogen-fixing and phosphate-solubilizing strains and the optimal combination of different functional strains,in order to provide a theoretical basis for the development of PGPR compound fertilizers suitable for local environment.[Methods] In this study,16S rDNA gene sequence analysis was used to identify fast-growing and competitive strains from pasture nodules and rhizosphere soils in Guizhou Province,and three representative Rhizobia and phosphorus-solubilizing bacteria were chosen for the test of bacterial combination when reducing 50% of nitrogen and 30% of phosphorus.The effects of different strain combinations on the plant height,root length,aboveground and underground biomass of Lotus corniculatus L.were investigated,and the total nitrogen and total phosphorus contents of the plants were determined.[Results] The mixed bacterial agents could promote the increase of root biomass,and the effects of A1,A3,B3 and C3 were the most obvious.The fresh weight and dry weight of the roots of L.corniculatus increased by 30.35%-168.45% and 26.43%-180.00%,respectively,and A3,B3,B2 and C3 had the best effects.The total phosphorus content of the plants increased by 12.79%-55.25% compared with the CK2;and most of the bacterial agents with significant growth-promoting effects showed decreased total nitrogen contents,while those with non-significant growth-promoting effects showed significantly-increased total nitrogen contents,which were not as much as the CK1.Comprehensively,the most productive combination was C3,namely R27-2 Rhinohizobium fredii and P33-3 Stenotrophomonas rhizophila.[Conclusions] This study can provide a theoretical basis for the production and promotion of bacterial fertilizers.

不同促生菌配合生长调节剂处理对滩涂稻田盐分变化、水稻产量及品质的影响

为了探明促生菌和生长调节剂对滩涂稻田盐分变化、水稻产量及稻米品质的影响,于2020年6—11月,在江苏南通沿海滩涂地区布置水稻种植试验,采用双因素裂区设计,主区为促生菌浸种处理,包括清水(CK)、如东促生菌(RD)和宁波促生菌(NB)浸种,副区为生长调节剂喷施处理,包括喷施清水(W)、碧护(0.136%赤·吲乙·芸苔)(T1)和复硝酚钠(T2)。结果表明,种稻过程中灌溉水盐度变化幅度为0.78~1.12 g·kg^(-1),CK、RD和NB处理水稻生长期间土壤盐分变化幅度为1.11~1.87 g·kg^(-1)。水稻产量在RD和NB下较CK分别增加了4.65%和1.83%;在T1和T2下较W分别增加了5.50%和1.05%;RD-T1下水稻产量较CK-W增加效果最好,达到11.66%(P<0.05),且每穗粒数和实粒数分别增加了13.45%和13.85%(P<0.05)。与CK相比,RD稻米糙米率、直链淀粉和蛋白质含量均显著降低,其他品质指标无显著差异。双因素分析结果表明,生长调节剂对穗长、每穗粒数、实粒数和产量均具有显著影响,促生菌对水稻千粒重具有显著影响,生长调节剂和促生菌仅对水稻千粒重具有显著互作效应。可见,促生菌结合生长调节剂处理对滩涂水稻增产具有明显效果,且生长调节剂主要提高了每穗粒数和实粒数,促生菌主要改善了滩涂水稻千粒重。本研究结果为探索适宜的农艺管理措施以达到滩涂水稻增产目的提供了技术参考。

Plant Growth-Prompting Bacteria Influenced Metabolites of <i>Zea mays var. amylacea </i>and <i>Pennisetum americanum p. </i>in a Species-Specific Manner

Poor soil is one of the agricultural world’s principal challenges, inciting the use of chemical fertilizer’s to improve overall soil quality. However, the use of chemical fertilizer has significant and cascading environmental consequences. Therefore, the use of beneficial microbes’ inoculation in treating poor soil is a considerably ecofriendly sustainable solution. In the current study, we supplemented nutrient-deprived soil with plant growth promoting bacteria (PGPB), Pseudomonas fluorescens. The bacterial inoculations of Pseudomonas fluorescenswere added to the poor soil following two days post-sowing of Zea mays var. amylacea and Pennisetumamericanum p. seedlings. Metabolite analyses were conducted two months after treatment for both shoots and roots using nuclear magnetic resonance method (NMR). The data indicated significant changes in 19 metabolites relative to control in both plants shoot and roots. Among these metabolites, 7 were upregulated in roots of Zea mays var. amylacea, and 9 metabolites were upregulated in roots of Pennisetum americanum p. The PGPB enhanced sugars (fructose, glucose, sucrose) and amino acids (glutamate, alanine and succinate) in roots, while down regulating in shoots of Pennisetum americanum p. The Pseudomonas fluorescens induced, predominantly,Aminoacyl-tRNA related metabolite, and Alanine, aspartate and glutamate metabolite biosynthesis in Zea mays var. amylacea), whereas PGPB induced metabolites in Pennisetum americanum p., dominated by up regulated carbohydrate related (starch and sucrose) metabolites. The difference in some metabolic response between the two plants indicated that PGPB influence has a species-specific manner.

Nutrient-Induced Growth of Coliform and HPC Bacteria in Drinking-Water Pipes

We conducted a study on a model drinking water distribution system to evaluate the impact of nutrient in the form of sodium acetate on the growth and survival of coliform and heterotrophic plate count (HPC) bacteria for a maximum of 21 days residence time of water in pipes. Our results show that, besides the nutrient added and the absence of any additional source of contamination and additional supply of nutrient, there was significant growth of the above mentioned bacteria in the pipes and bottles for a couple of days, after which the bacterial population began to decrease. The results indicate that the bacteria used the nutrient to grow and multiply until the nutrient was totally consumed and became depleted in the bulk water phase, after which the bacterial population reached a near stationary level and subsequently declined. This suggests the death of some of the bacteria and their dead cells were used by other bacteria for growth and survival. Using a detection limit of 3.3 CFU/100 mL for the coliforms, the study shows that after sometime, no bacteria were found in the water phase of the pipe, however, the biofilm in the pipes still harbored some of the bacteria. The results have revealed that the bacteria also have the tendency to move from the water phase to the biofilm since the latter provides a more suitable environment for bacteria to thrive on and grow, thus prolonging their survival in the system.

Growth Characteristics of <i>Fuirena umbellata</i>in a Surface Flow Constructed Wetland and Its Influence in Nutrients and Faecal Bacteria Removal from Domestic Wastewater in Cameroon

Various configurations of vegetated bed systems with a variety of macrophytes have been tested experimentally in Cameroon, for the treatment of domestic wastewater. The aim of this work was to assess the growth and biomass production of Fuirena umbellata (Cyperaceae) and its potentials in the removal of faecal bacteria and nutrients from primarily treated domestic effluent. A wetland vegetated with this macrophyte and a non-vegetated wetland (control) were continuously fed with primarily treated domestic wastewater at an estimated loading rate of 205 Litres/day in dry and rainy seasons for two consecutive years. Physicochemical and microbiological parameters of the effluent were monitored at the inflow and outflows of the wetlands alongside with the growth and productivity attributes of the young plants during each season. The density of plants ranged in the wetland from 17 - 185 plants/m2 and from 11 - 146 plants/m2 respectively during the first and the second years. More biomasses were instead produced in the dry seasons than in the rainy seasons but with no significant differences observed. As for nutrients removal, higher efficiencies were observed in the vegetated wetland (45% - 73%) compared to the non-vegetated control (17% - 66%). Similar trends were observed for the faecal bacteria but with no significant differences between the seasons. However, the vegetated beds were significantly more efficient than the non-vegetated control in the reduction of many physicochemical parameters and faecal bacteria. This varied with the seasons.

核桃根际耐旱促生菌的分离筛选及其促生作用研究

为获得高效促生的核桃根际菌株,研制微生物菌肥,改善土壤肥力,促进植株生长发育,提升核桃品质奠定理论基础。以核桃根际土壤为材料,分离筛选具有固N、溶P、解K、分泌生长素和产胞外多糖能力的菌株,通过16S rDNA测序鉴定菌属。按照功能叠加增效、功能互补的原则,人工构建合成菌群,采用盆栽试验验证菌群对核桃幼苗的促生效果。结果表明,共筛选出9株耐旱促生菌株,其中5株具有溶P能力,溶P量为2.28~61.63μg·mL^(-1),4株具有分泌IAA能力,分泌IAA量为2.32~9.44μg·mL^(-1),4株具有产胞外多糖的能力,产胞外多糖量为37.69~112.84μg·mL^(-1)。经鉴定分别属于节杆菌属、肠杆菌属、剑菌属、中华根瘤菌属、假单胞菌属和鞘氨醇杆菌属。盆栽试验表明,4种菌群均能显著促进核桃幼苗的生长,株高、生物量和净光合速率,与对照相比,分别增加了32.3%~64.2%、37.6%~52.6%和47.4%~68.5%。此外,复合菌群的施用还显著提高了土壤β-葡萄糖苷酶(BG)、β-N-乙酰葡糖胺糖苷酶(NAG)和碱性磷酸酶(AP)活性,增加了速效P、硝态N及铵态N含量(P<0.05),其中以复合菌群T4效果最佳。研究结果可为研制适合干旱半干旱区的微生物肥料提供菌种资源。

2株有效抑制剑麻斑马纹病菌的生防细菌鉴定

剑麻斑马纹病是一种由烟草疫霉(Phytophthoranicotianae)引起的传染性病害,导致剑麻出现叶斑、茎腐和轴腐的症状,对剑麻纤维的产量和质量造成严重影响。目前,剑麻斑马纹病的防治主要采取以农业栽培措施为主,抗病育种和化学药剂防治相结合的综合防治策略,但是农业防治人工成本高,工人操作技术参差不齐;抗病育种难度大,周期长;化学防治受剑麻叶片表面带有蜡质层的影响,存在药液不易吸附的问题,而且大量施药也容易造成病原抗药性提高和环境污染。因此,开发防治剑麻斑马纹病的生防菌资源,探索综合防控新途径显得尤为重要。本研究以烟草疫霉菌为靶标菌,通过五点对峙法筛选,获得2株生防菌PpHyHNCJ2和PpHyHNCJ5,其菌丝生长抑制率分别为85.92%和83.10%。通过对烟草疫霉菌菌丝显微结构进行观察发现,菌株PpHyHNCJ2和PpHyHNCJ5均抑制了烟草疫霉菌菌丝的生长,生防菌对峙的烟草疫霉菌出现菌丝体膨大增粗、分枝畸形、缠绕等现象。基于细胞形态、生理生化反应以及16S rDNA基因序列比对分析,菌株PpHyHNCJ2和PpHyHNCJ5鉴定为多粘类芽孢杆菌(Paenibacillus polymyxa)。进一步研究显示菌株PpHyHNCJ2和PpHyHNCJ5均具有广谱拮抗作用,能够很好地抑制辣椒疫霉菌(Phytophthora capsica)、大豆疫霉菌(P.sojae)、瓜疫霉菌(P.melonis)、棕榈疫霉菌(P.palmivora)、豇豆疫霉菌(P.vignae)、尖孢镰刀菌(Fusarium oxysporum)、黑曲霉菌(Aspergillus niger)、暹罗刺盘孢菌(Colletotrichum siamense)等11种病原菌的生长。此外,菌株PpHyHNCJ2和PpHyHNCJ5具有解有机磷能力、解无机磷能力、解钾能力、固氮能力和产铁能力,可为作物的良好生长提供条件。结果表明,菌株PpHyHNCJ2和PpHyHNCJ5对剑麻斑马纹病的防治具有良好的潜力,可为剑麻斑马纹病的生物防治提供基础材料。

盐胁迫下植物促生菌和2,4-表油菜素内酯对月季幼苗光合生理及离子转运的影响

以月季品种巴西诺幼苗为试验材料,采用室内盆栽试验,探究不同盐质量分数(0、0.3%、0.6%、0.9%)胁迫下根际施用2,4-表油菜素内酯(EBR,1μmol/L)、接种植物促生菌(PGPB)普罗维登斯菌(Providencia vermicola,1×10^(7)cfu/mL)及其复合处理对月季幼苗生长、光合和叶绿素荧光参数、离子转运及抗氧化系统的影响,以探明两者缓解月季盐胁迫的机制。结果表明,不同质量分数盐胁迫下月季幼苗生长受到抑制,株高、叶片厚度以及地上部和根系生物量等显著下降,施用EBR或者PGPB可以缓解月季受到的生长抑制程度。0.9%盐胁迫下,与对照(不喷施EBR,不接种PGPB)相比,EBR+PGPB处理的叶绿素a、叶绿素b含量分别增加13.1%和32.3%;叶绿素荧光参数中PSⅡ最大光化学效率(Fv/Fm)与对照无显著差异,PSⅡ潜在活性(Fv/Fo)增加8.8%,净光合速率(Pn)增加53.7%,蒸腾速率(Tr)和气孔导度(Gs)与对照相比无显著变化,胞间二氧化碳浓度(Ci)降低6.0%。0.9%盐胁迫下,与对照相比,EBR+PGPB处理后月季地上部和根系Na+含量分别降低21.1%和26.6%,地上部和根系K^(+)含量则分别增加73.7%和70.4%,地上部和根系中K^(+)/Na^(+)值分别增加116.7%和135.1%;同时EBR+PGPB处理能够激活超氧化物岐化酶(SOD)、过氧化氢酶(CAT)活性,降低超氧阴离子自由基产生速率和H_(2)O_(2)累积,与对照差异显著。综上,添加EBR、接种PGPB或者EBR+PGPB处理均可以不同程度地提高月季叶绿素含量,保护叶绿素荧光系统,维持植物Na^(+)和K^(+)的平衡,激活SOD、CAT等抗氧化酶活性以及降低细胞膜脂过氧化和H2O2累积,以减轻盐胁迫对月季幼苗的伤害程度,促进月季生长,其中以EBR+PGPB处理下月季幼苗的抗盐性效果更佳。

生物法修复盐渍化土壤研究进展

我国盐渍化土壤面积大,已严重制约了农业的发展和土壤的循环利用,修复盐渍化土壤有利于增加我国耕地面积、提高粮食产量。盐渍化土壤通常采用物理、化学和生物3种方法进行修复。相比于化学和物理修复法,生物修复法利用生物的生命代谢活动降低土壤的盐分,更经济、环保和高效,因此已在盐渍化土壤修复中得到广泛应用。文章总结了土地盐渍化危害及我国土地盐渍化现状,论述了植物、微生物和微生物-植物联合修复盐渍化土壤的机制和研究现状,并展望了生物法修复盐渍化土壤的应用前景。

一株旱稻联合固氮菌株的分离鉴定及促生作用

[目的]旱稻是一种重要的种质资源,对成熟期旱稻根系内生固氮菌进行筛选与鉴定,以获得对旱稻有较好促生作用的菌株。[方法]采用联合固氮固体培养基培养方法,从成熟期旱稻根系中分离出内生固氮菌,通过扩增固氮酶nifH基因和16S rRNA基因进行分子鉴定和系统进化分析生化指标测定和形态学鉴定;采用透明圈法进行溶磷、产铁载体能力验证;以褐球固氮菌为阳性对照,利用ELISA测定试剂盒测定菌株分泌固氮酶活性、1-氨基环丙烷-1-羧酸(ACC)脱氨酶,采用Salkowski比色法测定生长素(IAA)含量,并研究其生长特征。将分离的固氮菌株以1%浓度(约8×10~7CFU/mL)浸泡旱稻谷种进行催芽,研究其促生效果。[结果]分离的菌株URR45为固氮菌,属于嗜温型微生物,最适生长温度为32~50℃,最适pH为6.0~6.5,不耐盐。其分泌的固氮酶含量为220.15 U/L,ACC含量为898.69 ng/mL,生长素含量为14.91 mg/L,固氮酶含量和ACC含量显著高于对照组褐球固氮菌。该菌株能够利用葡萄糖、麦芽糖等碳源,属于发酵型细菌,具有水解明胶、溶磷和产铁载体特性。该菌株经16S rRNA基因测序后通过NCBI BLAST比对,鉴定为Herbaspirillum seropedicae,隶属于Pseudomonadota门、Betaproteobacteria纲、Burkholderiale目、Oxalobacteraceae科、Herbaspirillum属,革兰氏染色呈阴性。促生试验结果表明,在主根长度、侧根长度以及测根数方面均显著高于对照组。[结论]该菌株对旱稻幼苗具有一定的促生作用,在农业上产上可作为功能性内生固氮菌开发利用。

PGPR调控植物响应逆境胁迫的作用机制

盐碱、干旱等非生物胁迫是限制植物生长和产量的重要环境因子。植物根际促生菌(PGPR)是一类定殖于植物根系的有益微生物,利用其生物学功能制成的生物菌剂具有低成本、高效和环保等优点,不仅可促进植物生长与作物产量,还能提高植物对非生物胁迫的耐受性。本研究对PGPR定义和种类、生物学功能及其在植物响应盐碱、干旱、高低温及重金属等非生物胁迫中的作用加以综述,并对其未来研究方向进行展望,以期为今后PGPR介导植物抗逆性的研究与生物菌剂的开发和应用提供理论支撑。

复合菌制剂对麻羽肉鸡性能和肠道微生物的影响

研究饲粮中添加不同水平复合菌制剂对麻羽肉鸡血清代谢、生长、消化、免疫性能和肠道微生物的影响,选取240只体况健康的1日龄麻羽肉鸡(公、母鸡比例为1∶1),随机分为4组,每组6个重复,每个重复10只,分别在基础饲粮中添加0(对照),0.05%,0.1%和0.2%的复合菌制剂,试验期共90 d.结果表明:与对照相比,0.1%复合菌制剂组显著提高了麻羽肉鸡平均日增质量、采食量、胸腺、法氏囊、胰腺、空肠、回肠器官指数以及血清总蛋白、高密度脂蛋白、免疫球蛋白G(IgG)和溶菌酶水平(p<0.05),显著降低了血清碱性磷酸酶活性(p<0.05);0.05%和0.2%复合菌制剂组显著降低了血清谷草转氨酶活性(p<0.05);不同水平复合菌制剂均显著提高了钙和磷消化率,0.1%复合菌制剂组显著提高了肠道绒毛高度和黏膜厚度(p<0.05).回归分析显示回肠绒毛高度、IgG和甘油三酯水平与复合菌制剂添加量呈显著二项式关系(p≤0.05),且0.1%复合菌制剂组达到最优.此外,复合菌制剂显著改变了麻羽肉鸡盲肠微生物的β多样性(p<0.05),门水平上,主要由拟杆菌门(Bacteroidetes),厚壁菌门(Firmicutes),变形杆菌门(Proteobacteria)组成;属水平上,相对丰度占比超过1%的共有菌有Bacteroides,Mucispirillum,Desulfovibrio等6种;0.2%复合菌制剂组显著提高了疣微菌门(Verrucomicrobia)和帕拉普氏菌属(Paraprevotella)的相对丰度(p<0.05),显著降低了普拉梭菌属(Faecalibacterium)的相对丰度(p<0.05).复合菌制剂可不同程度地改善麻羽肉鸡血清代谢、生长、消化和免疫性能,并对肠道菌群结构产生影响,其中0.1%为适宜添加量.

EM菌发酵兔粪浸出液对小球藻生长及生化成分的影响

研究了EM厨余堆肥菌发酵处理的兔粪浸出液对小球藻(Chlorella vulgaris)的生长及蛋白质、可溶性糖、叶绿素等生化成分的影响。结果表明,兔粪浸出液处理组中,7%浓度组小球藻在第12天时达到最大现存量,为1.06×10^(7)个/mL,而对照组最大现存量只有6.45×10^(6)个/mL;7%浓度组的小球藻与对照组相比生长差异表现明显。5%、7%浓度组在第8天时其藻细胞密度已接近对照组的最大现存量,分别为6.02×10^(6)个/mL和6.80×10^(6)个/mL,表明适宜浓度的兔粪浸出液处理对小球藻的生长有刺激作用。低浓度组中3%浓度组的小球藻生长不理想,但蛋白质积累最高,含量达到17.31 mg/L,与对照组相比差异显著(P<0.05)。6%浓度组的可溶性糖含量最高,为332.7 mg/L,其叶绿素a、叶绿素b和类胡萝卜素含量分别为3.19、1.58 mg/L和0.57 mg/L,与对照组相比差异显著。

花生白绢病菌拮抗细菌的分离鉴定及其温室抑菌促生效果

由齐整小核菌Sclerotium rolfsii Sacc.侵染引起的土传真菌性病害——花生白绢病,严重威胁花生的生产。为挖掘对花生白绢病有较好防治效果的拮抗细菌,利用稀释涂布法从感染S.rolfsii的植株根际土壤中分离得到570株细菌,采用平板对峙法筛选出32株S.rolfsii拮抗细菌,结合16S rRNA基因序列、形态学及生理生化特征,确定细菌的分类学地位。通过S.rolfsii与拮抗细菌的发酵液共培养和盆栽试验结果表明:在所筛选的32株拮抗细菌中,4株细菌HNZZ23、HNKF5、HNXX14和HNXX169对S.rolfsii的抑制时间长,抑制效果好,其发酵液对S.rolfsii菌丝生长的抑制率分别为85.30%、85.88%、85.16%和91.00%,对S.rolfsii菌核萌发的最大抑制率分别为100%、85.33%、82.67%和93.33%。菌株HNZZ23和HNXX14的发酵液对盆栽花生白绢病的防治效果分别为30.50%和25.73%,且菌株HNZZ23对花生植株的生长具有显著的促进作用。经分类学鉴定,菌株HNZZ23、HNKF5、HNXX14和HNXX169分别为萎缩芽孢杆菌Bacillus atrophaeuse、短小芽孢杆菌B.pumilus、铜绿假单胞菌Pseudomonas aeruginosa和枯草芽孢杆菌B.subtilis。本研究结果表明,感病花生根际细菌HNZZ23、HNKF5、HNXX14和HNXX169对花生白绢病原菌S.rolfsii具有良好的拮抗作用和生防潜力,可为花生白绢病的生物防治提供优质菌种资源。

2株青贮玉米根际固氮菌的筛选鉴定及促生作用研究

为了获得优良的固氮菌,并评价其对青贮玉米的促生效果,本研究采用稀释涂布平板法,利用阿须贝氏固体培养基从青贮玉米根际土壤中分离筛选到10株固氮菌,对其固氮能力进行分析,结果表明,菌株ZL-2和ZL^(-1)3的固氮能力较强,菌株ZL-2的固氮量为1.07μg·mL^(-1),ZL^(-1)3的固氮量为0.95μg·mL^(-1)。通过细菌形态学、16S rDNA序列分析和生理生化特征,确定菌株ZL-2为生癌肠杆菌和ZL^(-1)3为成团泛菌。对2株固氮菌的促生特性进行分析,结果表明,2个菌株具有泌铵能力、溶磷能力、产嗜铁素能力和合成吲哚-3-乙酸(IAA)的能力。盆栽试验结果表明,接种固氮菌ZL-2和ZL^(-1)3能够显著提高青贮玉米的株高、根长、地上和地下干、鲜重(P<0.05)。田间试验结果表明,2株固氮菌单接种和双接种均能提高青贮玉米的株高、茎粗、产量、粗蛋白含量和全磷含量(P<0.05)。接种2株固氮菌的青贮玉米,其氮代谢和氨同化相关基因(ZmAMT-4、ZmAMTB、ZmGOGAT2和ZmGS1-3)的表达量显著提高(P<0.05)。因此,2株固氮菌具有较好的促生特性,在提高青贮玉米的产量和品质方面发挥了重要作用,是开发微生物菌剂的优质菌种资源。

饲料中添加高硒光合细菌对中华绒螯蟹抗氧化能力和食味品质的影响

试验旨在探究高硒光合细菌在中华绒螯蟹(Eriocheir sinensis)池塘养殖中的应用效果。试验选用设施条件一致的养殖池6个,随机分为3组,试验蟹规格为(165±20) g/只。对照组投喂普通商品饲料,试验1组投喂1轮拌有高硒光合细菌培养物的试验饲料,试验2组投喂两轮含硒试验饲料,每轮连续4 d,有机硒日投喂量为130μg/kg蟹。结果显示,与对照组相比,两个试验组中华绒螯蟹肥满度、背甲红绿值(a*值)显著提高(P<0.05),血清、肝胰腺总抗氧化能力(T-AOC)显著提高(P<0.05),肝胰腺丙二醛(MDA)含量显著下降(P<0.05),肌肉和肝胰腺土腥味均显著减弱(P<0.05),肌肉鲜味显著增强(P<0.05)。与对照组相比,试验2组中华绒螯蟹肝胰腺和肌肉硒含量显著升高(P<0.05),肝胰腺a*值、黄蓝值(b*值)均显著升高(P<0.05);血清、肝胰腺超氧化物歧化酶(SOD)活性、谷胱甘肽(GSH)含量显著提高(P<0.05),血清MDA含量显著下降(P<0.05)。研究表明,投喂2轮试验饲料可显著提高中华绒螯蟹生长性能、肝胰腺与肌肉硒含量,提高机体抗氧化能力,改善色泽和可食部分风味。