Isolation and characterization of phosphate-solubilizing bacteria from seagrass rhizosphere soil

Phosphate-solubilizing bacterial strains(6 Nos.) were isolated from the rhizosphere soils of two seagrasses(Halophila ovalis(R.Br.) Hook and Halodule pinifolia(Miki) Hartog) in the Vellar estuary.Experimental studies found that the strain PSSG6 was effective in phosphate solubilization with Phosphate Solubilization efficiency index E = 375 ± 8.54,followed by the strain PSSG5 with Phosphate Solubilization efficiency index E = 275 ± 27.3.Of the 6 strains isolated,the strains PSSG4 and PSSG5 be-longed to the genus Bacillus,and PSSG1,PSSG2 and PSSG3 were identified as Citrobacter sp.,Shigella sp.,and Klebsiella sp.,respectively,by conventional method,and PSSG6 was identified as Bacillus circulans using conventional and molecular methods.     

一种新型功能性海带豆酱的制备工艺研究

为了探究一种新型纳豆菌发酵食品的最佳工艺,利用纳豆菌发酵大豆和海带,以发酵物中游离氨基酸态氮含量和纳豆激酶活性为评价指标,通过单因素试验和正交试验确定最佳发酵条件。结果表明,发酵温度42℃、发酵时间54 h、接种量1%、料水比(m/v)1︰4、配料比(大豆︰海带)2︰1时发酵产物中游离氨基酸态氮含量最高(0.041%);发酵温度40℃、发酵时间48 h、接种量3%、料水比(m/V)1︰2,配料比(大豆︰海带)3︰1时发酵产物中纳豆激酶活性最高(可达1426.53IU/g)。     

海绵共附生微生物基因多态性的RAPD-PCR分析

采用传统分离手段对中国南海海域的细薄星芒海绵（Stelletta tenui（Lindgren,1897）1、皱皮软海绵（Halichondria rugosa（Ridley＆Dendy））、澳大利亚厚皮海绵（Craniella australiensis（Carter））、贪婪倔海绵（Dysidea avara（Schmidt））4种海绵体内的微生物进行了分离培养,随机挑选64株芽孢杆菌属细菌（每种海绵16株）进行了RAPD-PCR基因多态性分析。研究表明,一些海绵微生物是可以通过传统分离手段得到的,来自同一或者不同海绵的微生物均具有丰富的基因多态性。     

碳酸钙颗粒的细菌诱导形成

为研究胶质芽孢杆菌（Bacillus mucilaginosus）在特定条件下能否诱导合成碳酸钙,作者采用胶质芽孢杆菌两种常用 基本培养基（有氮培养基和无氮培养基）,以磷灰石矿物为钙源,进行了利用胶质芽孢杆菌促进碳酸钙形成的实验,借助扫 描电镜（SEM）、能谱定量分析（EDS）和X-射线衍射（XRD）等手段观察分析形成碳酸钙的晶体结构和化学组成。结果表 明,胶质芽孢杆菌能促进碳酸钙晶体的形成,在有氮加磷矿粉的细菌培养液中形成的碳酸钙多于无氮加磷矿粉的细菌培养 液,在有氮加磷矿粉的细菌培养液中观察到柱状碳酸钙的形成。作者认为,胶质芽孢杆菌通过其风化作用及较强的吸附功能, 利用其分泌的碳酸酐酶（CA）和溶解CO2在分解磷灰石的过程中促进了碳酸钙的形成。     

含钾矿粉对胶质芽孢杆菌分泌胞外多糖的影响

研究了不同实验条件下,含钾矿粉对胶质芽孢杆菌（Bacillus mucilaginosus）分泌胞外多糖的影响,以进一步揭示细 菌与矿物的相互作用机理。实验分别采用无矿（不加含钾矿粉）无钾（不含可溶性钾）、无矿有钾（有可溶性钾）、有矿（100 mL培养液加0.3 g含钾矿粉）无钾及有矿有钾4组培养基培养胶质芽孢杆菌,进行产胞外多糖的分析比较。研究发现,在有 钾长石粉但不含钾离子的培养条件下,胶质芽孢杆菌产生的多糖和蛋白质含量最高;在既有钾矿粉又有可溶性钾离子存在 的培养条件下,菌体产生的蛋白质和胞外多糖含量稍低;在无钾矿粉的条件下,无论有没有钾离子的两种培养基中,蛋白 质和多糖含量都很低。研究结果表明,有无钾矿粉的不同培养条件能够引起胶质芽孢杆菌分泌胞外多糖的单糖组成成分产 生明显差异,胶质芽孢杆菌胞外分泌物与细菌对含钾矿粉中钾的利用密切相关。     

Influence of Probiotics on the Growth and Digestive Enzyme Activity of White Pacific Shrimp （Litopenaeus vannamel）

The influence of Bacillus probiotics on the digestive enzyme activity and the growth of Litopenaeus vannamei were de-termined in this study. The shrimp was treated with five percentages (1.5, 3.0, 4.5, 6.0 and 7.5) of probiotics (Bacillus spp.) supple-mented to the feed and cultured for 45d. The growth measured as the weight gain at the end of culturing was significantly (P<0.05) higher in probiotic-treated shrimps than that of the control (without receiving probiotics). Activities of protease and amylase, two digestive enzymes of the midgut gland and the intestine were significantly (P<0.05) higher in probiotic-treated shrimp than in the control.     

Interactions of uranium with bacteria and kaolinite clay

We assessed the accumulation of uranium (VI) by a bacterium, Bacillus subtilis, suspended in a slurry of kaolinite clay, to elucidate the role of microbes on the mobility of U(VI). Various mixtures of bacteria and the koalinite were exposed to solutions of 8 × 10^− 6 M- and 4 × 10^− 4 M-U(VI) in 0.01 M NaCl at pH 4.7. After 48 h, the mixtures were separated from the solutions by centrifugation, and treated with a 1 M CH₃COOK for 24 h to determine the associations of U within the mixture. The mixture exposed to 4 × 10^− 4 M U was analyzed by transmission electron microscope (TEM) equipped with EDS. The accumulation of U by the mixture increased with an increase in the amount of B. subtilis cells present at both U concentrations. Treatment of kaolinite with CH₃COOK, removed approximately 80% of the associated uranium. However, in the presence of B. subtilis the amount of U removed was much less. TEM–EDS analysis confirmed that most of the U removed from solution was associated with B. subtilis. XANES analysis of the oxidation state of uranium associated with B. subtilis, kaolinite, and with the mixture containing both revealed that it was present as U(VI). These results suggest that the bacteria have a higher affinity for U than the kaolinite clay mineral under the experimental conditions tested, and that they can immobilize significant amount of uranium.     

The effect of cadmium on fulvic acid adsorption to Bacillus subtilis

The effects of Cd on the adsorption of an aquatic fulvic acid (FA) to the surface of Bacillus subtilis were investigated from pH 2.5 to 7.0, at fixed ionic strength (0.1 M NaClO₄) and at ambient temperature (22 °C). Cd (14 mg/l) had no effect on FA adsorption at pH<5 but increased FA adsorption at pH>6. The effects of Cd (0, 14 mg/l) on FA adsorption to B. subtilis were further examined as a function of initial FA concentration (0–45 mg C/l) at pH 6.5. FA adsorption isotherms also were measured at pH 6.5 as a function of dissolved Cd concentration (0–14 mg/l) at three initial FA concentrations (4, 8, 22 mg C/l). At all FA concentrations studied at pH 6.5, FA adsorption increased with increasing initial total Cd concentration.

Under all studied conditions, preferential adsorption of high- to intermediate-molecular-weight FA components to B. subtilis resulted in a fractionation of the FA pool, with lower-molecular-weight components remaining in solution. At pH>6, Cd further enhanced the adsorption of high- to intermediate-molecular-weight FA components but did not significantly enhance the adsorption of lower-molecular-weight components. Hence, the overall process of adsorptive fractionation was not altered significantly by the presence of Cd.

Overall, the results of this study (1) demonstrate that FA adsorption to bacterial surfaces can be altered by the presence of a metal cation, and (2) provide further evidence that microbe–metal–ligand interactions may significantly affect the mobility and fate of natural organic matter in the subsurface.     

Conversion and degradation of crude oil by Bacillus SP3

The objective of this study is to demonstrate the basic characteristics of Bacillus SP3 and evaluate its effect on different crude oils. Strain SP3 is a motile, gram-positive, spore-producing rod that was isolated from a reservoir of the Shengli oil field in East China. The cells of strain SP3 grew at high temperatures up to 58℃ at the pH range of 5.5–8.5. Strain SP3 grew facultatively and could use different organic substrates, and produce some metabolites such as 4-hydroxy-4-methyl-2-pentanone, methyl-2-nitrogen benzene and 1, 2-benzenedicarboxylic acid bis ester. Laboratory studies have demonstrated that the strain converted and degraded different components and changed the physical and chemical properties of crude oils. Strain SP3 degraded crude oil and the growth of bacteria on crude oil resulted in loss of aromatic hydrocarbons, resins and asphaltenes. The bioconversion of crude oils would lead to an enrichment in lighter hydrocarbons and an overall redistribution of saturate hydrocarbons. The interactions of microorganisms with crude oils are variable, depending on the microbial species and the chemical compositions of crude oils.     

一株引起清溪乌鳖(Pelodiscus sinensis nigrum)“摇头病”致病菌的分离鉴定与药敏分析

从患"摇头病"清溪乌鳖(Pelodiscus sinensis nigrum)的肝脏、脾脏、肾脏、肺组织中分离得到1株细菌。菌落为圆形乳白色凸起,融蜡状,表面光滑,边缘清晰整齐;对该菌进行染色镜检可见其为革兰氏阳性杆菌,呈单个或链状排列。结合生理生化检测结果、16S rDNA基因和gyrB基因和rpoB基因序列分析以及系统进化树结果,该菌株为蜡样芽孢杆菌群(Bacillus cereus group)内新种。用不同浓度的分离菌腹腔注射感染健康的清溪乌鳖,观察发现死亡的清溪乌鳖出现与自然发病鳖相似的症状且从病鳖内脏中可分离得到同样的菌;经统计和计算,其LD₅₀为2.42×10⁵ CFU/kg体重。应用纸片扩散法对14种常用抗菌药物进行药敏试验,结果显示,分离菌对头孢氨苄、氟苯尼考、强力霉素、恩诺沙星、氧氟沙星五种药物敏感;对利福平、头孢他啶则耐药。本研究为清溪乌鳖细菌性病原的报道,旨在为该病的确诊与防治提供科学依据和参考。