采用未培养技术对荷斯坦奶牛瘤胃细菌多样性进行初步分析

采用未培养(Culture independent)技术直接从荷斯坦奶牛瘤胃液中提取瘤胃细菌微生物混合DNA(也叫元基因组DNA),利用细菌16SrDNA通用引物27F与1492R,扩增瘤胃混合微生物的16SrDNA,根据16SrDNA序列对瘤胃细菌多样性进行初步分析。通过16SrDNA序列同源性分析,发现有多于一半以上的序列与可培养的菌株的同源性小于90%,属于不可培养的菌株。选用45条测得序列与已知序列构建系统发育树,分析结果表明,它们分属于两大类LGCGPB(the lowG CGram positivebac teria)和CFB(Cytophaga_Flexibacter $CBacteroides group),剩下的克隆尚难确定其分类地位,可能是代表新属和种的序列,这些序列已向GenBank提交并得到序列号(AY986777_AY986791)。     

筛选鉴定一株产生抑菌活性物质的海洋放线菌

目的：分离筛选能够产生抑菌活性物质的海洋放线茵,并进行生理生化和16SrDNA鉴定。方法：用分离培养基培养海洋放线菌,并筛选出能够产生抑菌活性物质的菌株,对所筛选菌株的形态特征、生理生化特性进行鉴定分析;采用通用引物27F、1492R扩增该菌株的16SrDNA,对测序结果进行分析;采用Neighbor—Joining（N—J）法构建系统发育进化树。结果：筛选到一株对金黄色葡萄球菌、大肠杆菌、白色念珠菌具有较强抗性的海洋放线菌F1,该菌株好氧,中度嗜盐,在高氏I号培养基上呈白色绒粉状,16SrDNA序列比对表明该菌株与田无链霉菌（Streptomyces tanashiensis）NR043369的相似度为99％。结论：筛选到的菌株F1是一株海洋来源的放线菌,与田无链霉菌NR043369的同源性较高,可能属海洋链霉菌属,对金黄色葡萄球菌等病原菌具有较强的抑菌活性。     

一株产纤维素酶细菌的筛选、鉴定及其纤维素酶的部分特性

目的:分离堆肥中具有产纤维素酶酶活的菌株并进行鉴定,同时进行该菌株纤维素酶酶特性的研究.方法:采用刚果红平板法进行筛选得到菌株,利用16SrDNA通用引物对其基因组DNA进行扩增,测序得到CCH-1的部分16SrDNA序列,经Blastn调出与菌株16SrDNA同源的序列,用软件MEGA 4.0按照Neighbor-Joining方法构建16SrDNA系统发育树,并采用DNS法测定所产纤维素酶酶活.结果:GCH-1的生理生化指标与蜡质芽胞杆菌理化指标相符,与Bacillus cereus IAM 12605(T)处于同一分支,相似性为99.8%.CCH-1菌株发酵48h能达到最大产酶量,所产纤维素酶在40℃有最高酶活力,酶活力分别为0.581μ/mL,GCH-1菌株产生的纤维素酶酶系在pH 7.0～9.0能够保持较高的相对酶活力,超过85%相对活力.结论:GCH-1初步鉴定为蜡质芽孢杆菌(Bacillus cereus),能够产胞外纤维素酶.     

一株产天然蓝色素海洋链霉菌的筛选鉴定

从胶州湾附近海域水样中分离筛选到一株可产生天然蓝色素的链霉菌。采用通用引物16F27/16R1492扩增该菌株的16SrDNA,对测序结果进行序列分析,采用Neighbor-Joining(N-J)法构建系统发育进化树,同时结合链霉菌的传统形态学和生理生化特性对菌株进行鉴定。16SrDNA序列分析表明菌株与Streptomyces violaceolatus KCTC 9772相近,相似率为99%。在Neighbour-Joining法构建的系统发育进化树中,该菌株与Streptomyces violaceolatus聚类在同一分枝上。因此将该菌株鉴定为紫边链霉菌Streptomyces violaceolatus。     

厚荚相思树根瘤菌HJ06菌株的16S rDNA全序列和nifA基因片段分析

对厚荚相思(Acaciacrassicarpa)根瘤菌HJ06菌株的16SrDNA全序列和nifA基因片段进行了测定。结果表明,HJ06菌株在以16SrDNA序列构建的系统发育树状图中位于根瘤菌属(Rhizobium)分支中,与根瘤菌属各个种的相似性达95%以上;从HJ06菌株克隆出的585bpnifA基因片段与Klebsiellapneumoniae的同源性达到99.3%,与Klebsiellaoxytoca的NifF,NifL,NifA,NifB蛋白基因的同源性为97.8%。     

产胞外黑色素菌株的鉴定及发酵条件优化

从重庆不同区域收集土壤,分离到一株高产黑色素的菌株(H4),通过16Sr DNA序列测定,菌株与Streptomyces puniciscabiei序列相似性为99%,该菌产生的胞外黑色素在可见-紫外光区均有吸收,紫外区光吸收强,随着波长的减小,吸收增强,在210 nm左右有1个吸收高峰。采用响应面法对其发酵条件进行了优化,结果表明该菌株在L-酪氨酸的含量为0.73 g/L,p H值为6.05,温度28℃的条件下,菌株黑色素实际产量达2.49 g/L。     

兼性厌氧纤维素菌的分离与系统发育分析

从四川卧龙中国保护大熊猫研究中心提供的野外放归大熊猫“祥祥”的粪样中,分离到一株产纤维素酶的兼性厌氧菌株。该菌株经初步生理生化鉴定为肠杆菌科沙雷氏菌（Serratia）,命名为Serratia JF-1116。用PCR技术扩增了该菌的16S rDNA全序列,并对其进行了克隆和测序,对该序列在GenBank中的BLAST结果表明,所有与该序列高度同源的序列均为肠杆菌科的16SrDNA基因序列,选取同源性高的菌株的16SrDNA基因序列进行系统发育分析,菌株与3株Serratia聚类在一起。     

华重楼内生菌SS02的分离与抗菌活性的初步研究*

从华重楼(Parispolyphyllavar·ChinensisFranch)的地下块茎中分离到一株内生细菌(SS02),试验表明其发酵液对13种作物致病菌的生长有抑制作用。形态和生理生化特征表明SS02属于芽孢杆菌属(Bacillus sp·)细菌。扩增、测序得到SS02的部分16SrDNA序列,GenBank接收号AY842144。用Blastn调出与菌株16SrDNA同源的序列,用Clustalw进行多重序列对比,用Phylip按Neighbor-Joining法构建1     

细菌群体感应抑制活性微生物Zou 03的筛选与鉴定

从近海区生态环境中分离纯化98株海洋菌株,以根癌农杆菌WCF47为敏感检测菌株,筛选出1株具细菌群体感应抑制活性的菌株Zou03,对其进行形态、生理生化特征鉴定和16S rDNA分子鉴定。结果显示,Zou03具枯草芽胞杆菌(Bacillus subtilis)的典型特征,其16S rDNA序列通过对比分析,与GenBank中枯草芽胞杆菌16SrDNA的部分序列同源性为100%。综合形态、生化特征及16S rDNA序列对比分分析,鉴定菌株Zou03为枯草芽胞杆菌。表明近海区生态环境中存在具有抑制细菌群体感应活性的微生物,有利于海洋微生物资源开发,为以致病菌群体感应系统为靶点的新型疗法提供新技术。     

海南温泉嗜热菌的16S rDNA分析

目的:确定24株海南温泉嗜热菌菌株的分类地位。方法:Blastn分析菌株16S rDNA序列同源性;邻接法构建菌株16SrDNA序列系统发育进化树并分析菌株的进化位置;Clustax比对分析菌株的相似度和进化距离。结果:菌株LY5和LY4的16SrDNA序列与Geobacillus pallidus strain B1,partial sequence(GenBank:HM030740.1)的16S rDNA序列同源性分别为98%和97%,其他菌株的16S rDNA序列与Geobacillus subterraneus,strain R-35641(GenBank:FN428689.1)的16S rDNA序列的同源性均大于96%。Clustax比对分析表明26株菌16S rDNA序列前段(1～70bp)、中段(70bp～1 420bp)、后段(1 420～1 484bp)的相似度分别为40%、100%和60%,进化距离分析表明菌株GT7、LY4和LY5与其他菌株进化距离较远,其余菌株之间进化距离差异不明显。综上所述,初步将24株温泉嗜热菌鉴定为土芽孢杆菌属(Geobacillus sp.)。结论:16S rDNA序列分析可用于温泉嗜热菌的鉴定。     

Heating of a Local Region of a Branching Streamer as a Starting Point of a Space Leader and a Negative-Leader Step

Plasma Physics Reports - Localized plasma formations called space leaders are observed in streamer coronas of negative leaders of long laboratory sparks. The main leader completes a step when the...     

Geminiviruses: a tale of a plasmid becoming a virus

Background  

Geminiviruses (family Geminiviridae) are small single-stranded (ss) DNA viruses infecting plants. Their virion morphology is unique in the known viral world – two incomplete T = 1 icosahedra are joined together to form twinned particles. Geminiviruses utilize a rolling-circle mode to replicate their genomes. A limited sequence similarity between the three conserved motifs of the rolling-circle replication initiation proteins (RCR Reps) of geminiviruses and plasmids of Gram-positive bacteria allowed Koonin and Ilyina to propose that geminiviruses descend from bacterial replicons.     

Mechanisms of coexistence of a bacteria and a bacteriophage in a spatially homogeneous environment

When bacteriophage are added to laboratory bacteria populations, bacteria mutants that are resistant to the phage quickly dominate the population. The phage will only persist in the long‐term if there are sufficient bacteria in the population that show susceptibility to the phage. We investigated the mechanisms allowing for coexistence by adding the virulent bacteriophage φ6 to cultures of the bacterium Pseudomonas syringae pv. phaseolicola in a spatially homogeneous environment. We saw large differences between replicate cultures, in particular when one or both of the species persisted. These differences can be explained by variation in the timing of the appearance of various resistant phenotypes in the bacteria populations before the phage were added, which determines their relative frequencies within the populations. Although these resistant phenotypes have similar fitnesses in the presence and in the absence of the phage, they have a profound effect on the persistence of the phage. Our results give a clearer understanding of the ecological mechanisms that lead to the coexistence of bacteria and virulent phage in environments where there are no spatial refuges available to the bacteria population.     

Effects of a disease affecting a predator on the dynamics of a predator-prey system

We study the effects of a disease affecting a predator on the dynamics of a predator-prey system. We couple an SIRS model applied to the predator population, to a Lotka-Volterra model. The SIRS model describes the spread of the disease in a predator population subdivided into susceptible, infected and removed individuals. The Lotka-Volterra model describes the predator-prey interactions. We consider two time scales, a fast one for the disease and a comparatively slow one for predator-prey interactions and for predator mortality. We use the classical “aggregation method” in order to obtain a reduced equivalent model. We show that there are two possible asymptotic behaviors: either the predator population dies out and the prey tends to its carrying capacity, or the predator and prey coexist. In this latter case, the predator population tends either to a “disease-free” or to a “disease-endemic” state. Moreover, the total predator density in the disease-endemic state is greater than the predator density in the “disease-free” equilibrium (DFE).     

Facile synthesis of a D-galactono-1,6-lactone derivative, a precursor of a copolyester

2,3,4,6-Tetra-O-methyl-d-galactonic acid (5) was readily prepared from d-galactono-1,4-lactone (1) in 47% yield. The sequence involves tritylation of HO-6 of 1, followed by O-permethylation and deprotection. Lactonization of 5 led to the per-O-methyl-d-galactono-1,6-lactone, which was copolymerized with epsilon-caprolactone by ring-opening polymerization catalyzed by scandium triflate. The incorporation of the sugar comonomer into the polyester chain was about 10%.     

Glycan expression as a tool for a deeper understanding of a reproductive gland in a skate of economic importance

Atlantoraja platana is an oviparous skate endemic to the south-west Atlantic Ocean, and is one of the skate species most exploited by local industrial bottom trawl fisheries. Oviparous elasmobranchs encapsulate their eggs in complex egg cases produced by the oviductal gland (OG). This organ is exclusively present in these fishes and comprises four distinct zones: club, baffle, papillary and terminal. The relative size and structural complexity of these zones correlate with mode of reproduction. Glycans are known to play major roles in reproduction so their distribution in each zone of the OG could explain the functional multiplicity of the gland in skates, but this topic has not been previously investigated. In this study, morphological, histochemical and lectin-histochemical analysis revealed various novel aspects of A. platana's OG. The club, papillary and terminal zones positively stained for periodic acid Schiff's reagent (PAS) and Alcian Blue (AB), indicating the presence of neutral and acid mucopolysaccharides. However, the buffle zone was negative for PAS and AB stains, but was positive for all the lectins used. Each zone of the OG had a characteristic pattern of glycan expression. Finally, we confirmed the presence of sperm but not sperm storage. This is the first lectin-histochemical study of the OG in chondrichtyan fish and it has proven to be an important tool to understand some of the mechanisms of fertility and reproductive success in economic important species such as A. platana.     

Characterization of a protease of a feather-degrading Microbacterium species

AIMS: To characterize a new feather-degrading bacterium. METHODS AND RESULTS: The strain kr10 producing a high keratinolytic activity when cultured on native feather broth was identified as Microbacterium sp., based on phenotypical characteristics and 16S rDNA sequence. The bacterium presented optimum growth and feather-degrading activity at pH 7.0 and 30 degrees C. Complete feather degradation was achieved during cultivation. The keratinase was partially purified by gel filtration chromatography. It was optimally active at pH 7.0 and 55 degrees C. The enzyme was inhibited by 1,10-phenanthroline, EDTA, p-chloromercuribenzoic acid, 2-mercaptoethanol and metal ions like Hg(2+), Cu(2+) and Zn(2+). SIGNIFICANCE AND IMPACT OF THE STUDY: A new Microbacterium sp. strain was characterized presenting high feather-degrading activity, which appears to be associated to a metalloprotease-type keratinase. This micro-organism has enormous potential for use in biotechnological processes involving keratin hydrolysis.