Antibacterial activity of leaves extracts of Trifolium alexandrinum Linn,against pathogenic bacteria causing tropical diseases

Objective:To investigate antibacterial potential of Trifolium alexandrinum(T.alexandrinum) Linn,against seven gram positive and eleven gram negative hospital isolated human pathogenic bacterial strains responsible for many tropical diseases.Methods:Non-polar and polar extracts of the leaves of T.alexandrinum i.e.,hexane,dichloromethane(DCM),ethyl acetate(EtOAc), methanol(MeOH) and aqueous(AQ) extracts at five different concentrations(1,2,5,10 and 15 mg/ mL) were prepared to evaluate their antibacterial value.NCCL standards were strictly followed to perform antimicrobial disc susceptibility test using disc diffusion method.Results:Polar extracts demonstrated significant antibacterial activity against tested pathogens.EtOAc and MeOH extracts showed maximum antibacterial activity with higher inhibition zone and were found effective against seventeen of the tested pathogens.While AQ plant extract inhibited the growth of sixteen of the test strains.EtOAc and MeOH plant extracts inhibited the growth of all seven gram positive and ten of the gram negative bacterial strains.Conclusions:The present study strongly confirms the effectiveness of crude leaves extracts against tested human pathogenic bacterial strains causing several tropical diseases.Since Egyptian clover is used as a fodder plant,it could be helpful in controlling various infectious diseases associated with cattle as well.

Studies on the edwardsiellosis and characterization of pathogenic bacteria from diseased flounder (Paralichthys olivaceus L.) and turbot (Scophthalmus maximus L.)

Edwardsiellosis of flounder and turbot occurring in different mariculture farms during 2001～ 2004 was examined, including the conditions of disease occurrence, clinical signs and pathological changes. The results showed that all diseased fishes expressed bacterial septicaemia. A total of 148 strains were identified using a combination of traditional physiological and biochemical tests and partial 16S rRNA gene analysis. In addition, the mole fraction G ＋ C ratio of the DNA of representative strain of isolates and serum homology were detected, and pathogenicity tests of isolates were conducted by experimental infection. The results revealed that 148 strains were identified as E. tarda of genus Edwardsiella, all the isolates are of serologic similarity, and have strong pathogenicity to flounder and turbot.

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.

Modification of total and phosphorus mineralizing bacterial communities associated with Zea mays L.through plant development and fertilization regimes

Harnessing the rhizospheric microbiome,including phosphorus mineralizing bacteria(PMB),is a promising technique for maintaining sustainability and productivity in intensive agricultural systems.However,it is unclear as to which beneficial taxonomic group populations in the rhizosphere are potentially associated with the changes in soil microbiomes shifted by fertilization regimes.Herein,we analyzed the diversity and community structure of total bacteria and PMB in the rhizosphere of maize(Zea mays L.)grown in soils under 25 years of four fertilization regimes(compost,biocompost,chemical,or nonfertilized)via selective culture and Illumina sequencing of the 16S rRNA genes.Plant development explained more variations(29 and 13%,respectively)in the composition of total bacteria and PMB in the rhizosphere of maize than the different fertilization regimes.Among those genera enriched in the rhizosphere of maize,the relative abundances of Oceanobacillus,Bacillus,Achromobacter,Ensifer,Paracoccus,Ramlibacter,and Luteimonas were positively correlated with those in the bulk soil.The relative abundance of Paracoccus was significantly higher in soils fertilized by compost or biocompost than the other soils.Similar results were also observed for PMB affiliated with Ensifer,Bacillus,and Streptomyces.Although plant development was the major factor in shaping the rhizospheric microbiome of maize,fertilization regimes might have modified beneficial rhizospheric microbial taxa such as Bacillus and Ensifer.

Selection and characterisation of lactic acid bacteria isolated from different origins for ensiling Robinia pseudoacacia and Morus alba L.leaves

The objective of this study was to isolate lactic acid bacteria（LAB） strains from different origins and to select the best strains for ensiling Robinia pseudoacacia（RB） and Morus alba L.（MB）leaves. The LAB strains were inoculated into the extracted liquid obtained from RB and MB leaves to evaluate the fermentation products. 11 LAB strains were selected for further experiments based on the highest products of lactic or acetic acid, including 1 strain of Weissella confusa, 2 of Lactobacillus reuteri and 8 of Lactobacillus plantarum.The API 50 CH fermentation experiment indicated that all of the selected 11 LAB strains utilised most of the carbohydrates. All the strains grew at temperatures between 10 and 45℃ and at a p H of 3.5 to 4.5; however, L. reuteri F7 and F8 tolerated a p H as low as 3.0. All 11 LAB strains showed antibacterial activity against Listeria monocytogens, Escherichia coil, Salmonella sp. and Acetobacter pasteurianus; however, after excluding the effect of organic acids, only F7 and F8 still exhibited antibacterial activity. The present study indicated that the selected 11 LAB strains could be used to prepare silages of RB and MB leaves, especially L. reuteri F7 and F8.

Corrosion and Electrochemical Behavior of 316L Stainless Steel in Sulfate-reducing and Iron-oxidizing Bacteria Solutions

Corrosion and electrochemical behavior of 316L stainless steel was investigated in the presence of aerobic iron-oxidizing bacteria IOB and anaerobic sulfate-reducing bacteria SRB isolated from cooling water systems in an oil refinery using electrochemical measurement, scanning electron microscopy SEM and energy dispersive atom X-ray analysisEDAX. The results show the corrosion potential and pitting potential of 316L stainless steel decrease distinctly in the presence of bacteria, in comparison with those observed in sterile medium under the same exposure time. SEM morphologies have shown that 316L stainless steel reveals no signs of pitting attack in the sterile medium. However, micrometer-scale corrosion pits were observed on 316L stainless steel sur- face in the presence of bacteria. The presence of SRB leads to higher corrosion rates than IOB. The interactions between the stainless steel surface, abiotic corrosion products, and bacterial cells and their metabolic products in- creased the corrosion damage degree of the passive film and accelerated pitting propagation.

Functional identification of phenazine biosynthesis genes in plant pathogenic bacteria Pseudomonas syringae pv. tomato and Xanthomonas oryzae pv. oryzae

Phenazines are secondary metabolites with broad spectrum antibiotic activity and thus show high potential in biological control of pathogens. In this study, we identified phenazine biosynthesis （phz） genes in two genome-completed plant pathogenic bacteria Pseudomonas syringae pv. tomato （Pst） DC3000 and Xanthomonas oryzae pv. oryzae （Xoo） PXO99A. Unlike the phz genes in typical phenazine-producing pseudomonads, phz homologs in Pst DC3000 and Xoo PXO99A consisted of phzC/D/E/F/G and phzC/E1/E2/F/G, respectively, and the both were not organized into an operon. Detection experiments demonstrated that phenazine-l-carboxylic acid （PCA） of Pst DC3000 accumulated to 13.4 IJg L-1, while that of Xoo PXO99A was almost undetectable. Moreover, Pst DC3000 was resistant to 1 mg mL-1 PCA, while Xoo PXO99A was sensitive to 50 IJg mL ~ PCA. Furthermore, mutation of phzF blocked the PCA production and significantly reduced the pathogenicity of Pst DC3000 in tomato, while the complementary strains restored these phenotypes. These results revealed that Pst DC3000 produces low level of and is resistant to phenazines and thus is unable to be biologically controlled by phenazines. Additionally, phz-mediated PCA production is required for full pathogenicity of Pst DC3000. To our knowledge, this is the first report of PCA production and its function in pathogenicity of a plant pathogenic P. syringae strain.

极耐热α-L-鼠李糖苷酶的性质及其在异槲皮素制备中的应用研究

L-鼠李糖苷酶可特异性切除糖苷类化合物上连接的α-L-鼠李糖基,已被广泛用于食品、医药等工业领域。作者旨在获得耐受高温的α-L-鼠李糖苷酶,提高工业生产的效率和降低使用成本。首先对嗜热菌Sulfolobus islandicus来源的α-L-鼠李糖苷酶基因进行克隆及大肠杆菌的异源表达,随后测定了系列酶学性质,接着优化了该酶制备异槲皮素的酶法制备工艺。结果表明:重组酶SisRha在90℃下酶活力最佳,具有极好的热稳定性,其在80℃下孵育120 min后酶活力几乎没有损失;最适反应pH为5.5,在pH 4.5~7.0时,pH稳定性良好;重组酶SisRha对人工底物对硝基苯酚鼠李糖糖苷(p NPR)的Km值为(0.15±0.03) mmol/L,Vmax值为(6.26±0.51)U/mg,k_(cat)值为(10.48±0.86) s^(-1);对底物p NPR、芦丁、朝藿定C、柚皮苷、橘皮苷和淫羊藿苷的比活力分别为25.06、11.89、6.74、3.14、2.77、0.42 U/mg。重组酶SisRha转化芦丁生成异槲皮素的适宜工艺为:用酶量0.40 U/mL,在85℃、pH 5.0的条件下反应1 h,可将2 mmol/L芦丁几乎全部转化,摩尔转化率高达98.56%。本研究丰富了现有的α-L-鼠李糖苷酶资源,为嗜热菌来源的α-L-鼠李糖苷酶的研究奠定了基础,同时提供了一种高温转化芦丁制备异槲皮素的方法。

聚维酮碘诱导与杀灭铜绿假单胞菌L型的实验观察

[目的]了解聚维酮碘诱导与杀灭铜绿假单胞菌L型的效果。[方法]用悬液法进行L型菌诱导与杀灭试验。[结果]以含500mg/L有效碘的聚维酮碘作用1min～5min、1000mg/L有效碘的聚维酮碘作用1min可诱导铜绿假单胞菌形成L型;对原菌株与L型的最小抑菌浓度分别为62.500mg/L与125.000mg/L。[结论]消毒应用的聚维酮碘剂量应高于用铜绿假单胞菌原菌株测得的杀灭合格的剂量。

苯唑西林诱导金黄色葡萄球菌形成L型研究

目的用苯唑西林(青霉素类抗生素)诱导金黄色葡萄球菌形成L型。方法用抗生素诱导法(液体法),用高渗培养进行金黄色葡萄球菌L型的诱导,用含药平板法进行细菌L型的筛选及菌落计数。对细菌L型的培养物进行革兰和细胞壁染色;对金黄色葡萄球菌原型及回复型菌进行MIC测定。结果与结论苯唑西林在50μg.mL-1时,可诱导金黄色葡萄球菌形成L型。

谷氨酰胺和L-肉碱对低温下肉羊瘤胃纤维分解菌的影响

本试验研究了饲粮中添加谷氨酰胺和L-肉碱对低温下肉羊瘤胃纤维素分解菌的影响,旨在了解谷氨酰胺和L-肉碱在减缓低温应激中的作用,为生产实践中应用抗应激剂提供理论依据和参考。试验选用9只健康东北细毛羊×德国肉用美利奴杂交肉羊,采用L9(34)正交试验设计,设3个谷氨酰胺水平(0、0.6%、1.2%)与3个L-肉碱水平(0、75、150m g/kg)。试验羊在低于正常饲养温度(由10℃降至0℃)条件下,饲喂添加不同水平谷氨酰胺和L-肉碱的饲粮。结果表明,谷氨酰胺有降低瘤胃白色瘤胃球菌相对含量的趋势(P>0.05),L-肉碱能显著降低瘤胃白色瘤胃球菌的相对含量(P<0.05),二者复合使用有缓解瘤胃白色瘤胃球菌相对含量下降的趋势;谷氨酰胺能显著提高瘤胃黄化瘤胃球菌相对含量(P<0.05),L-肉碱有提高瘤胃黄化瘤胃球菌相对含量的趋势(P>0.05),二者复合使用能进一步提高瘤胃黄化瘤胃球菌的相对含量(P>0.05);谷氨酰胺和L-肉碱有降低瘤胃产琥珀酸丝状杆菌相对含量的趋势(P>0.05),但二者复合使用有缓解瘤胃产琥珀酸丝状杆菌相对含量下降的趋势。结果提示:谷氨酰胺和L-肉碱在低温下复合使用能缓解瘤胃白色瘤胃球菌、产琥珀酸丝状杆菌相对含量的下降,提高瘤胃黄化瘤胃球菌相对含量。经比较分析,低温环境下肉羊饲粮谷氨酰胺和L-肉碱的添加量分别为1.2%和75mg/kg时可有效改变瘤胃微生物菌群,提高机体抵抗冷应激的能力。

L-天冬酰胺酶Ⅱ基因工程菌的培养

为提高L 天冬酰胺酶Ⅱ基因工程菌EscherichiacolipKA/CPU2 10 0 0 9的产酶量 ,采用正交试验法确定了较佳培养条件 ,并优化了发酵工艺。工程菌摇瓶产酶稳定在 190U/ml。 2 5L发酵罐产酶亦高达 180U/ml,发酵周期大大缩短 ,仅 9～ 10h。产酶量比原工艺提高 1倍以上 ,具有较好的工业生产前景。

胆囊细菌L型

用非高渗透压培养基培养法从常规细菌学检查阴性的慢性胆囊炎胆囊组织、胆汁及胆石中分离细菌Ｌ型，获得了８６．０２～１００％的检出率。胆囊检出的细菌Ｌ型绝大多数是稳定Ｌ型，在常规细菌学培养基或Ｌ型高渗透压琼脂培养基上不能形成可见的生长现象。沸水浴１０分钟可杀死胆囊或胆结石中的细菌Ｌ型，多种抗生素能抑制胆囊细菌Ｌ型的生长。细菌稳定Ｌ型在胆囊中如此广泛存在，可能是慢性胆囊炎与胆囊结石的重要病因。

高效转化L-谷氨酸为γ-氨基丁酸菌株的筛选、鉴定及初步优化

从发酵食品及自然界中筛选出能利用L-谷氨酸生产γ-氨基丁酸的菌株,并对转化条件进行初步优化。采用乳酸菌分离纯化的方法分离出乳酸菌,再通过初筛、复筛挑选出高产γ-氨基丁酸的菌株,并对其进行形态学、常规生理生化鉴定及16S rDNA基因分析,随后对菌株产γ-氨基丁酸的转化条件进行初步优化。根据常见细菌系统鉴定手册,所筛菌株初步确定为植物乳杆菌(Lactobacillus plantarum)。优化后的最佳转化条件为:菌株菌龄为36 h、缓冲液初始pH为4.8、缓冲液浓度为0.2 mol/L。在优化后的转化条件下,添加5 g/dL底物转化24 h,转化率最高可达97.81%,转化液中γ-氨基丁酸的质量浓度达34.26 g/L,该菌种可作为γ-氨基丁酸产生菌,具有较好的γ-氨基丁酸生产潜力。

天冬氨酸酶基因工程菌固定化细胞制备L-天冬氨酸合成条件优化

以反丁烯二酸和氨水为原料,采用天冬氨酸酶基因工程菌固定化细胞生物催化法合成L-天冬氨酸。通过响应面法考察反丁烯二酸浓度、温度、p H对合成L-天冬氨酸的影响。结果表明,固定化天冬氨酸酶基因工程菌合成L-天冬氨酸最佳条件为:底物反丁烯二酸的质量浓度为300 g/L,反应温度为37℃,底物p H为7.5,L-天冬氨酸的产率为96.7%。固定化细胞可连续使用10批次。通过电镜观察发现天冬氨酸酶基因工程菌均匀分布于载体,天冬氨酸酶基因工程菌固定化细胞具有良好的稳定性。

牙鲆(Paralichthys olivaceus)细菌败血感染症及病原检验与分析

采用调查统计、剖检病变、病原分离鉴定与人工感染健康鱼致病作用试验的方法 ,对自然发生的养殖牙鲆细菌败血感染症病例 ,进行了发病情况、临床表现及病理变化等方面的检验 ,同时取病 (死 )牙鲆的肝、腹水、腐烂肌肉组织为材料进行细菌分离 ,对分离于 1 0尾鱼 2 0株纯培养菌的形态特征、理化特性等进行鉴定。结果表明 ,分离出来的两种细菌 ,一种是弧菌属(VibrioPacini 1 85 4 )细菌的一个新种 (sp .nov .)并定名为牙鲆弧菌 (Vibrioolivaceussp .nov .) ;另一种是气单胞菌属 (AeromonasKluyverandvanNiel 1 936)的嗜水气单胞菌 (A .hydrophila)。通过人工感染试验等表明该两种分离菌为相应感染症的致病菌。

离子注入诱变筛选高产L-乳酸菌及其发酵条件的初步研究

研究了不同于常见的以根霉为菌株发酵生产L-乳酸的乳酸细菌发酵模式。采用新的物理诱变源———N+离子注入诱变菌株LB1,最终筛选出一株L-乳酸产量比出发菌株高2倍多的突变株LB1-1。通过对LB1-1的培养条件进行了初步研究,确定了突变株LB1-1合成L-乳酸的最优碳氮源及其浓度等培养条件,并对发酵过程的pH值调控、供氧对发酵的影响等主要影响细菌L-乳酸发酵的因素进行了较细致的研究,为下一步原位分离技术的研究提供了依据。

427株细菌L型医院感染与耐药分析

目的 为提高医院感染细菌培养阳性率及抗菌药物的有效使用。方法 对我院 1995年 1月～ 1997年 12月从 1870例住院患者采取血、尿、脑脊液、胸腹水、胆汁等标本进行了常规与高渗同步培养的结果进行了对照分析。结果 分离出 L型细菌 4 2 7株 ,而普通培养均为阴性 ,阳性率提高了 2 2 .8% ,分离菌种达 11种之多 ;以金黄色葡萄球菌在各类标本中感染率占首位 ,19.4 4% ;大肠埃希菌占第 2位 ,16.4 % ,凝固酶阴性葡萄球菌、D群肠球菌、酵母菌占第 3位 ,分别为 11%、10 .77%、10 .3 % ;其它各菌属均占有一定比例。对青霉素、头孢类抗生素高度耐药 ,对红霉素、氯霉素、庆大霉素、林可霉素呈低度耐药。结论 采取同步培养可提高阳性率 ,为临床感染性疾病诊断和抗生素的合理使用提供了重要依据。

包埋法固定化色氨酸合成酶基因工程菌合成L-色氨酸的研究

以海藻酸钠作为包埋剂、戊二醛作为交联剂和氯化钙作为填充剂对色氨酸合成酶基因工程菌进行固定化,同时探究3种物质和菌体负载量对固定化菌影响,响应面法优化色氨酸合成酶基因工程菌合成L-色氨酸。固定化色氨酸合成酶基因工程菌最优制备条件为:海藻酸钠28.92 g/L、戊二醛0.95 g/L、氯化钙19.82 g/L、菌体负载量25 g/L,底物L-丝氨酸质量浓度为10 g/L、固定化菌8 g,L-色氨酸产率为28.16%,固定化菌可连续使用15批次。

细菌L型尿路感染及耐药性研究

目的 研究我院细菌L型尿路感染现状及耐药性。方法 对尿路感染标本采用常规与高渗同步培养 ,返祖后原菌应用VITEK -AMS的GP1、GN1卡进行鉴定。结果 从 5 74份尿标本中分离出细菌L型 14 2株 ,而常规培养均为阴性 ,阳性率提高了 2 4 .7% ,其中以凝固酶阴性葡萄球菌 (CNS)占首位 2 6.8% ,其次大肠埃希菌 2 4 .0 % ,肠球菌、金黄色葡萄球菌 (S .A)各占 18.3 %、14 .8%。细菌L型对青霉素呈高度耐药 ,头孢菌素类中度耐药 ,而对红霉素、氯霉素、庆大霉素、环丙沙星、克林霉素呈较低耐药性。结论 采用同步培养法可提高尿路感染阳性率 ,为临床尿路感染诊断及合理使用抗生素提供了重要依据。