Antimicrobial effect of Malaysian vegetables against enteric bacteria

Objective: To investigate the antibacterial activities of green vegetables(pennywort,mint, garlic, parsley and celery) against four common enteric bacteria [Salmonella enterica(ATCC 25957)(S. enterica), Shigella flexneri(ATCC 12022)(S. flexneri),Escherichia coli(ATCC 43889)(E. coli) and Enterobacter cloacae(ATCC 13047)(E. cloacae)] as an alternative medicine for controlling food borne diarrhea disease and the synergistic effect of green vegetables against those bacteria.Methods: Five common vegetables(pennywort, mint, garlic, parsley and celery) were purchased and extracted. The antimicrobial activities of these extracts were tested against four common enteric bacteria(S. enterica, S. flexneri, E. coli and E. cloacae). Ten different concentrations of the extracts(from 640 to 1.25 mg/m L) were prepared and used for the study. The minimal inhibitory concentration(MIC) was determined by the broth dilution method. The antimicrobial activities were assessed by using both well diffusion and disc diffusion methods.Results: Garlic extract showed excellent inhibitory effects on all enteric bacteria. Other plants(parsley, celery, mint and pennywort) were not effective against enteric bacteria.The MIC of garlic against S. flexneri and E. cloacae was 40 mg/m L. The MIC of S. enterica and E. coli were 20 and 10 mg/m L, respectively. The performance of the well diffusion method was better than that of the disc diffusion method with clear and sharp inhibition zones of tested bacteria against plant extracts.Conclusions: Garlic had excellent antimicrobial effects against enteric bacteria and was recommended to be given to patients with gastroenteritis. The other vegetables(pennywort, mint, parsley and celery) showed no inhibitory effects on enteric bacteria but still can be used for its richness in vitamins and fibers. The performance of the well diffusion method was better than that of the disc diffusion method in detecting the antibacterial effects of green vegetables.

Effect of Mineral Dusts on the Growth of Silicate Bacteria S35

In order to compare the chemical compositions and physical properities of dusts on silicate bacteria S35, the chemical compositions of six kinds of mineral dusts have been analyzed and the changes of pH value, glucose （GLU）, electrolyte and Mn, Si, Fe before and after the dusts reacted with silicate bacteria S35 have been measured. The SEM analysis has been used to study the bacterial form and interface action status in the course of reaction between dusts and bacteria. The results show that these mineral dusts have different effects on experiment bacteria. Therefore, it is concluded that the effect of mineral dusts on silicate bacteria has correlation with the chemical compositions and physical properities of dusts.

Algicidal effect of bacterial isolates of Pedobacter sp. against cyanobacterium Microcystis aeruginosa

The aim of this study was to isolate algicidal bacteria so as to control harmful cyanobacterium Microcystis aeruginosa （M. aeruginosa） blooms using biological methods. Nine bacterial strains were isolated to inhibit the growth ofM. aeruginosa, among which the Mail 1-5 bacterial strain exhibited remarkable algicidal activity against M. aeruginosa cells during the test. Based on the 16S rDNA analysis, the isolated Mail 1-5 was identified as Pedobacter sp. through morphology and homology research. The results of cocultivation of the cyanobacteria with MaI 11-5 algicidal isolates showed obvious algicidal activity against cyanobacterial cells. The algicidal effect of Mail 1-5 exceeded 50% after two days, exceeded 70% after four days, and reached 80% after seven days. The observation results with a scanning electron microscope showed that the cyanobacterial cells aggregated and produced mucous-like substances when cocultivated with the algicidal bacteria. The results indicated that the Mail 1-5 bacterial strain may possess a novel function for controlling harmful blooms and further studies will provide new insights into its role in water environment.

Clear felling and burning effects on soil nitrogen transforming bacteria and actinomycetes population in Chittagong University campus, Bangladesh

The effect of forests clear felling and associated burning on the population of soil nitrogen transforming bacteria and actinomycetes are reported at three pair sites of Chittagong University campus, Bangla- desh in monsoon tropical climate. Clear felled area or burnt site and 15-21 year mixed plantation of native and exotic species, situated side by side on low hill having Typic Dystrochrepts soil was represented at each pair site. At all the three pair sites, clear felled area or burnt site showed very significantly （p~_0.001） lower population of actinomycetes, Rhizobium, Nitrosomonas, Nitrobacter and ammonifying as well as deni- trifying bacteria compared to their adjacent mixed plantation. From en- vironmental consideration, this finding has implication in managing natural ecosystem.

Algae-lysing Effect of Algicidal Bacteria on Microcystis in Bloom Water

The Microcystis sample was selected from natural bloom water,then the algicidal effects of the bacterial strain fluid of the two algicidal bacteria,supernatant and bacterial liquid were studied. Moreover,the changes of microalgae colony and morphology in the process of algae-lysing were observed using neutral red staining and scanning electron microscope. It showed that AA06 bacteria had certain algicidal effect while AA10 bacteria had no effect. All the supernatants of the two bacterial strains had obvious algicidal effects,and the algicidal effects between the bacterial liquid and supernatant had no significant differences( P < 0. 05). The effects of algae-lysing mainly owed to the chemical substances secreted by algicidal bacteria. During the algae-lysing process,the algae colony did not disperse into individual cells. The segments of the dead cells still aggregated together.

Effect of the Suppression of Cariesitic Bacterial Growth and Biofilm Formation Using Hydrogen/Free Chlorine Mixed Water Produced by an Electrolysis-Type Hydrogen Generator

OBJECTS: Hydrogen has been shown to possess antibacterial effects at high concentrations. In addition, chlorine has a strong bactericidal effect even at low concentrations. Electrolysis is a way to simultaneously generate these two components. However, the concentration of hydrogen/free chlorine mixed water generated through electrolysis decreases quickly. It is predicted that the concentration of hydrogen/free chlorine mixed water will vary depending on the quality of water used. After investigating the optimum generation conditions, the effects of the most stable concentration of hydrogen/free chlorine mixed water on carious tooth fungus were evaluated in vitro. Thus, in this experiment, our goal was to evaluate the effects of hydrogen/free chlorine mixed water on oral bacteria. MATERIALS AND METHODS: Using a device that generates hydrogen/free chlorine through electrolysis, the differences in the concentrations of hydrogen and free chlorine based on electrolysis time were evaluated using tap water. Additionally, various concentration changes due to electrolysis time on the hydrogen/free chlorine mixed water were evaluated. Distilled tap water as a control group, hydrogen/free chlorine mixed water, and commercially available mouthwash were added for 1 minute to cultured Streptococcus mutans and then rinsed out with the culture medium. Bacterial growth (600 nm) and biofilm formation (590 nm) were measured at 3 and 6 hours after the addition of the medium. RESULTS: The concentration of hydrogen/chlorine mixed water produced by electrolysis varied depending on electrolysis time and the water used. The inhibitory effect of bacterial growth was enhanced depending on the chlorine concentration. Regarding the inhibitory effect on biofilm formation, only the mixed water of hydrogen/free chlorine concentration (500 ppb - 1.0 mg/L) had a suppressing effect after 6 hours. CONCLUSION: It was suggested that hydrogen/chlorine mixed water can be easily produced by electrolysis and has the effect of suppressing the growth of dental caries;therefore, it could be used as a cleaning agent in oral care products.

Synergistic Effect of Combined Antibiotics against Some Selected Multidrug Resistant Human Pathogenic Bacteria Isolated from Poultry Droppings in Akure, Nigeria

Antibiotic resistant bacteria pass between humans, between animals and between humans and animals in both directions, the use of antibiotics in poultry has contributed to multiple antibiotic resistant in pathogenic bacteria and use of two antibiotics might prevent the emergence of resistance to either. In this study, synergistic effect of combined antibiotics against multidrug resistant human pathogenic bacterial isolates from poultry droppings in Akure, Nigeria was examined. Collection of samples, isolation and identification of bacteria were carried out using standard microbiological method, antibiotic sensitivity test was performed by disc diffusion method and zone of inhibition was used to interpret the sensitivity test as resistant, susceptible or intermediate while combined effects of two antibiotics were investigated by macrobroth dilution and checkerboard assay methods while the synergetic effects of combined antibiotics were calculated using Fractional Inhibitory Concentration (FIC) and percentage synergistic interaction was calculated. All the ten (10) species of bacterial isolates were multidrug resistant and are less resistant to ofloxacin. The highest percentage synergistic interactions observed were Ofloxacin + Amoxicillin (90%), Ciprofloxacin + Amoxicillin (90%), Tetracycline + Amoxicillin (70%), Tetracycline + Augmentin (80%), Cotrimoxazol + Amoxicillin (50%), Cotrimoxazol + Augmentin (70%), Chloramphenicol + Amoxicillin (70%) and Chloramphenicol + Augmentin (80%). Poultry droppings is a potential source of human pathogenic bacteria, high frequency of multiple antibiotic resistance bacteria observed in this study is of great treat to man as this may cause the treatment of infection caused by these bacteria to be difficult. Combination of beta-lactam antibiotic with fluoroqunolones, tetracycline, Chloramphenicol and Cotrimoxazole was synergetic and this will reduce dose related toxicity and prevent resistance to single antibiotic.

Antimicrobial activity against periodontopathogenic bacteria,antioxidant and cytotoxic effects of various extracts from endemic Thermopsis turcica

Objective:To investigate the in vitro antimicrobial potential of Thermopsis turcica Kit Tan,Vural&Kckdk against periodoutopathogenie bacteria,its antioxidant activity and cytotoxic effect on various cancer cell lines.Methods:In vitro antimicrobial activities of elhanol.methanol,ethyl acetate(ElAc,n-hexane and water extracts of Thermopsis turcica herb against periodontopathogenic bacteria,Aggregatibacter actinnmycelemconilans ATCC 29523 and Porphyromonas gingivalis ATCC 33277 were tested by agar well diffusion,minimum inhibitory concentration(MIC)and minimal bactericidal concentration(MBC),Antioxidant properties of the extracts were evaluatod by 1,1-diphenyl-2-picryl-hydrazyl radical scavenging activity and p-carotene bleaching methods.Amounts of phenolic contents of the extracts were also analysed by using the Folin-Ciocalteu reagent.Additionally,cytotoxic activity of the extracts on androgcn-insensilivc prostate cancer,androgen—sensitive prostate cancer,chronic myelogenous leukemia and acute promyelocytic leukemia bunian cancer cell lines were determined by 3-4,5-dimelhylthiazol-2-yh-2,5-diphenyltclrazolium bromide assay.Human gingival fibroblast cells were used as a control.Results:Our data showed that ELAc extract had the highest antimicrobial effect on Aggregatibacter actinomycetemitans(MIC:1.562 mg/ml_MHC:3.124 mg/ml.)and Porph yromonas gingiralis(MIC:0.781 mg/mL,MBC:1.562 mg/mL).In antioxidant assays.ElAc extract exhibited also the highest radical scavenging activity[IC_(50)=(30.0±0.3)μg/ml.]and the highest inhibition[(74.35±0.30)%]|against lineloic acide oxidation.The amount of phenolic content of it was also the highest[(l62.5±l.2)μg/mg gallic acid].In cytotoxic assay,only etbanol[IC_(50)=(80.00±1.21)μg/ml.]and EtAc extract[IC_(50)=(70.0±0.9)μg/ml]were toxic on acute promyeloeytic leukemia cells at 20—100μg/mL.P<0.05>.However,no toxic effect was observed on human gingival fibroblast cells.Cunclusions:According to our findings,owing to its antioxidant and cytotoxic potential,EtAc exlrael might include anticancer agents for acute promyelocytic leukemia.

Synergistic effect between cryptotanshinone and antibiotics in oral pathogenic bacteria

Cryptotanshinone (CT), a major tanshinone of medicinal plant Salvia miltiorrhiza Bunge, demonstrated effective in vitro antibacterial activity against all oral bacteria tested in this experiment. The antibacterial activities of CT against oral bacteria were assessed using the checkerboard and time-kill methods to evaluate the synergistic effects of treatment with ampicillin or gentamicin. The CT was determined against oral pathogenic bacteria with MIC and MBC values ranging from 0.5 to 16 and 1 to 64 μg/mL;for am- picillin from 0.0313 to 16 and 0.125 to 32 μg/mL;for gentamicin from 2 to 256 and 4 to 512 μg/mL respectively. The range of MIC50 and MIC90 were 0.0625 - 8 μg/mL and 1 - 64 μg/mL, respectively. The combination effects of CT with antibiotics were synergistic (FIC index < 0.5) against tested oral bacteria except additive, Streptococcus sobrinus, S. criceti, and Actinobacillus actinomycetemcomitans (FIC index < 0.75 - 1.0). The MBCs were shown reducing ≥4 - 8-fold, indicating a synergistic effect as defined by a FBCI of ≤0.5. Furthermore, a time-kill study showed that the growth of the tested bacteria was completely attenuated after 3 - 6 h of treatment with the 1/2 MIC of CT, regardless of whether it was administered alone or with ampicillin or gentamicin. The results suggest that CT could be employed as a natural antibacterial agent against cariogenic and periodontopathogenic bac- teria.

4种消毒剂对规模化奶牛场常见病原菌消毒效果的评价

试验旨在探讨常见消毒剂对规模化奶牛场环境气载和动物体表优势病原菌的杀灭效果,为进一步制定科学合理的消毒技术规范提供参考。研究以优势病原菌(金黄色葡萄球菌、大肠杆菌、产气荚膜梭菌)为指示菌,通过悬液定性和定量试验探讨常见消毒剂(安灭杀、辉胜-30、过硫酸氢钾、聚维酮碘)对细菌繁殖体的杀灭效果。结果显示,1∶100倍稀释的安灭杀消毒液作用1、20及5 min能够有效杀灭金黄色葡萄球菌、产气荚膜梭菌和大肠杆菌;1∶200倍稀释的辉胜-30消毒液作用10、20及15 min能够有效杀灭金黄色葡萄球菌、产气荚膜梭菌和大肠杆菌;1∶200倍稀释的过硫酸氢钾消毒液作用3、5、5 min能够有效杀灭金黄色葡萄球菌、产气荚膜梭菌和大肠杆菌;1∶400倍稀释的聚维酮碘消毒液作用15、20、20 min能够有效杀灭金黄色葡萄球菌、产气荚膜梭菌和大肠杆菌。研究表明,金黄色葡萄球菌和大肠杆菌对安灭杀消毒液敏感,产气荚膜梭菌对过硫酸氢钾复合物粉较敏感,4种消毒剂宜交替使用可避免耐药性菌株的产生。

不同有机废弃物载体对Bacillus megaterium有效性的影响

为了给Bacillus megaterium选择理想的吸附载体。测定了草炭、金针菇渣、腐熟鸡粪、牛粪、羊粪的吸菌量及其载体菌剂的有效活菌数、胞外多糖(EPS)含量和发芽指数。草炭的吸菌量最高为1.64 mL/g,但随存放时间延长,草炭载体菌剂的有效活菌数和EPS含量急剧降低,且38 d内的发芽指数均小于80%,表现植物毒性。鸡粪和金针菇渣的吸菌量虽小于草炭,但随存放时间延长,鸡粪载体菌剂的有效活菌数和EPS含量逐渐增大,金针菇渣载体菌剂的EPS含量逐渐增加、有效活菌数降低幅度缓慢,且存放7 d后发芽指数均大于80%,表现植物无毒性。第38天时鸡粪和金针菇渣载体菌剂的有效活菌数分别为1.29×10^(9)CFU/g和6.20×10^(8)CFU/g,EPS含量分别为535.29 mg/kg和559.34 mg/kg,均显著高于其他载体菌剂。鸡粪和金针菇渣是B.megaterium较为理想的吸附载体。

10种药剂处理对杨梅凋萎病的防控效果评价

为有效控制杨梅凋萎病发生,减少农残,保证果品安全,在湖南省通道县杨梅基地设置4月25日和5月10日(采果前)喷施0.5%小檗碱水剂500倍液等5种药剂各1次+7月5日(采果后)30%苯甲·咪鲜胺悬浮剂3000倍液等2种药剂1次,共10个药剂组合处理,比较不同药剂处理的病枝减退率、病情指数减退率和相对防效。结果表明,不同药剂处理的杨梅凋萎病的病枝减退率为15.29%~74.07%,相对防效为22.23%~80.00%。其中,杨梅成熟前喷施0.5%小檗碱水剂500倍液2次+采果后喷施30%苯甲·咪鲜胺悬浮剂3000倍液1次处理的防控效果最佳,其病枝减退率达到74.07%,相对防效达到80.00%;杨梅成熟前喷施0.5%小檗碱水剂500倍液2次+采果后喷施40%吡醚·戊唑醇悬浮剂3000倍液,防控效果次之,其病枝减退率为65.35%、相对防效为75.56%;其他处理的相对防效均低于55%。因此,杨梅生产上推荐在杨梅成熟前喷施0.5%小檗碱水剂500倍液,采果后喷施30%苯甲·咪鲜胺3000倍液防控杨梅凋萎病,以避免杨梅果实农残超标且达到较好防控效果。

基于环境RNA研究海山效应对浮游细菌多样性和分布的影响

研究采用环境RNA技术探究西太平洋M4海山区细菌多样性,并与基于环境DNA技术的研究结果进行比较,解析细菌代谢活性特征。结果表明基于环境RNA和DNA技术检获的物种构成相似,但真光层中蓝细菌在RNA中的占比明显高于DNA,显示其高代谢活性;而α变形菌在RNA中的占比明显小于DNA,代谢活性低;γ变形菌在RNA中占比更大且随水层加深而增加。物种间关系网络复杂度随着水深的增加呈先升高后下降的趋势。基于RNA数据构建的网络较DNA数据网络简单,且随着水深增加变化趋势更加显著,去除蓝细菌后网络变化剧烈,而去除α变形菌对网络影响小。综上,研究基于环境RNA技术提供了海山区浮游细菌多样性及分布更加完整的认知,α变形菌在海山区多样性占比和其在群落中作用可能被高估。

DHA单酰基甘油酯型藻油对小鼠急性酒精性肝损伤的保护作用

研究DHA单酰基甘油酯对小鼠急性酒精性肝损伤的保肝作用及机制。将雄性小鼠随机分为正常组、模型组、实验组(DHA单酰基甘油酯组)、阳性对照组(DHA三酰基甘油酯组和DHA乙酯组)5组。给药15 d后,检测血清丙氨酸氨基转移酶(ALT)、天冬氨酸氨基转移酶(AST)、碱性磷酸酶(ALP)、甘油三脂(TG)、总胆固醇(TC)、高密度脂蛋白(HDL)和低密度脂蛋白(LDL)含量,肝组织Toll样受体4(TLR 4)、髓样分化因子(MyD88)、核转录因子κB(NF-κB)基因表达水平。观察肝组织病理性改变;分析小鼠粪便细菌多样性。DHA单酰基甘油酯能显著降低急性酒精肝损伤小鼠血清ALT、AST、ALP、TG、TC和LDL浓度,而显著增加HDL浓度,改善酒精引起的肝组织病理性改变,而且DHA单酰基甘油酯对小鼠肝损伤改善效果优于DHA三酰基甘油酯和DHA乙酯。此外,DHA单酰基甘油酯能显著抑制酒精肝损伤小鼠肝组织TLR 4、MyD88、NF-κB基因表达,对酒精引起的肠道菌群紊乱具有一定恢复作用。DHA单酰基甘油酯对酒精诱导小鼠肝损伤具有一定保护作用,其机制可能与抑制TLR 4/NF-κB通路和改善肠道菌群有关。

绿原酸抗菌作用及机制的研究进展

绿原酸是植物体在有氧呼吸过程中经莽草酸途径合成的一种苯丙素类物质,自然存在于多种中药材和食物中,杜仲、金银花和咖啡等植物中含量较高,具有抗菌、抗炎、抗氧化、抗癌和免疫调节等多种药理活性。近年来,绿原酸作为研究活性物质的焦点之一,因其抗菌谱广,对多种细菌和真菌均有较好的抗菌活性,故绿原酸对临床菌株的抗菌作用逐渐被重视和研究。本文综述了近年来国内外关于绿原酸对多种致病菌的抗菌作用及机制的研究进展,旨在为绿原酸抗菌作用的深入研究提供参考,为临床抗感染治疗和控制带来新思路,有助于绿原酸在医药领域的开发。

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。

生防菌对芒果叶部炭疽病的生防效果研究

生物防治是芒果胶孢炭疽病防控的主要措施之一。为了系统性评价生防菌的防控效果,为生防菌剂的生产应用提供指导,本文采用离体叶片针刺法,室内评价了18种生防菌对‘贵妃’‘台农1号’两个芒果主栽品种叶部炭疽病的防护、治疗和兼防兼治效果。结果表明,生防菌对两个主栽品种的芒果叶部病害的防效具有一致性,18种生防菌均具有防护、治疗和兼防兼治的作用,其中对‘贵妃’芒果效果较好的是S8(蜡质芽孢杆菌菌剂)、S3(枯草芽孢杆菌菌剂),对‘台农1号’芒果效果最好的是S3;田间防治芒果叶部炭疽病试验表明,S8、S9(枯草·纳豆·地衣芽孢杆菌·硝化细菌)效果较好,防效超过90%,可以应用于芒果叶部胶孢炭疽病的生物防治中。

昆虫病原线虫共生菌及代谢产物对根结线虫的防治作用

为探讨不同种昆虫病原线虫(EPN)共生菌对根结线虫病的防治效果,开展了温室盆栽定量接种试验;为明确EPN共生菌的代谢产物对根结线虫卵孵化和二龄幼虫活性的影响,进行了室内生测试验。结果表明,Meloidogyne incognita(M.incognita)在中蔬4号番茄上接种剂量为1000、2000和5000个卵·株^(−1)时,昆虫病原线虫共生菌Xb-IGA和Pl-IGA对M.incognita卵的繁殖均有较好的抑制效果,抑制效果为59.4%~73.9%。Meloidogyne hapla(M.hapla)在VFNT番茄上接种剂量为2000个卵·株^(−1)时,昆虫病原线虫共生菌Pl-IGA对M.hapla卵的繁殖抑制效果最好,可达74.5%,与常规药剂阿维菌素(82.2%)差异不显著。4种EPN共生菌均能有效降低M.incognita和M.hapla侵染后的发病程度,对番茄根部生长有不同程度的促进作用。在生测试验7 d时,4种昆虫病原线虫共生菌代谢产物的2倍稀释液和5倍稀释液对M.incognita和M.hapla卵孵化抑制率为55.1%~94.8%,对M.incognita二龄幼虫校正死亡率为34.2%~47.8%,对M.hapla二龄幼虫校正死亡率为59.6%~79.9%。因此,昆虫病原线虫共生菌及其代谢产物对根结线虫是非常有潜力的生物杀线虫资源。

寡营养细菌(Oligographic bacteria)及其固沙作用的研究

从新疆古尔班通古特沙漠生物结皮的下层（沙物质层）分离到一株寡营养细菌,G＋;细胞大小在0.328-0.746×0.171-0.240μm;菌落圆形;直径5 mm,白色光滑,隆起明显;兼性好氧;该菌可在含碳量1-15 mg.L-1培养基、10-70℃、pH值5~11的环境中生长,较适宜生长温度范围为15-37℃;最适pH值范围为8-9;该菌在生长过程中分泌大量的黏多糖,室内培养72 h黏度可达9 000 mPa.S。将黏度为1 500 mPa.S的菌体培养液喷洒在流沙表面后,能够形成可以粘连沙粒约6 mm厚的寡营养细菌结皮层,该结皮层不仅能够固沙而且具有一定的减缓土壤中水分蒸发的效果。

PGPR微胶囊菌剂研发及其对玉米的促生效果评价

【目的】为了提高植物根际促生菌(Plant growth-promoting rhizobacteria,PGPR)对作物促生作用的稳定性,研制出以PGPR复合菌液为原料的微胶囊菌剂,探究其对玉米的促生效果。【方法】从玉米根际土壤中分离得到2株PGPR菌株并制备成复合液体菌液。分别用海藻酸钠(SA)和CaCl2作为包埋剂和交联剂,对复合菌液进行包埋以制备微胶囊菌剂。以复合微胶囊菌剂制备的难易程度和菌株包埋率、增殖前活菌数及增殖后活菌数为评价指标,确定微胶囊菌剂制备的最优条件。通过分析微胶囊菌剂在不同聚乙二醇含量、温度、pH、存储时间以及盐含量下的菌株生长及其对玉米生长和根系形态的影响确定PGPR微胶囊菌剂的特性。【结果】分离得到了2株PGPR菌株,具有多种植物促生功能。使用质量分数为1%SA-3%CaCl2制备的微胶囊菌剂稳定性较好,包埋率达91.27%,增殖后的微胶囊活菌数达到8.73×10^(9)cfu·g^(-1),增殖7.79倍。微胶囊菌剂在不同干旱、温度、pH、存储时间和盐浓度条件下对PGPR菌株具有较好的保护作用。PGPR微胶囊菌剂对玉米有显著的促生作用,施用微胶囊菌剂使玉米株高、苗干重和根干重分别增加91.83%、81.82%和29.57%。同时微胶囊菌剂也显著提高了玉米总根长、根表面积、根平均直径、根体积和根尖数。【结论】探明了一种PGPR微胶囊菌剂的制备方法,施用该PGPR微胶囊剂能够显著促进玉米生长、改善玉米根系形态,对玉米的促生效果优于液体菌剂。