肺炎链球菌假想蛋白SPD0873的表达纯化及保守性分析

目的 通过构建原核表达载体,获得纯化的肺炎链球菌S.pn重组假想蛋白SPD0873,并制备多克隆抗体,进一步分析其在常见S.pn菌株中的保守性.方法 分离培养D39型肺炎链球菌,获取其基因组DNA.利用PCR方法扩增去除信号肽的spd0873序列,采用基因体外重组法将spd0873序列克隆到原核表达载体pET-32(a)内,测序鉴定.将重组质粒转化到E.coli Rossetta(DE3)中,经IPTG诱导大量表达融合6个组氨酸标签的SPD0873重组蛋白,经Ni-NTA树脂纯化后,获得的重组蛋白用SDS-PAGE和Western 印迹鉴定;将鉴定后纯化的蛋白免疫BALB/C小鼠制备多克隆抗体,并用间接ELISA检测多克隆抗体的效价,Western 印迹方法分析多克隆抗体的特异性,同时,鉴定该蛋白在5种常见肺炎链球菌分离株的保守性.结果 克隆的spd0873序列与GenBank中的数据相符,并实现了SPD0873蛋白高水平的可溶表达.纯化蛋白免疫BALB/C小鼠获得高滴度、高特异性的的多克隆抗体,Western 印迹验证SPD0873蛋白在5株常见肺炎链球菌菌株中均有表达.结论 成功制备了高滴度、高特异性的SPD0873蛋白多克隆抗体,同时,检测到SPD0873蛋白在5种常见的肺炎链球菌菌株中非常保守,为研究该蛋白的生物学功能及肺炎链球菌多肽联合疫苗的研制奠定了基础.     

Molecular cloning and expression analysis of hemocyanin gene from Macrobrachium nipponense

目的 克隆日本沼虾血蓝蛋白基因,进行生物信息学及时空表达分析. 方法 利用cDNA末端快速扩增技术( RACE)从肝胰腺中克隆血蓝蛋白基因cDNA全长序列,用生物学软件对其序列进行生物信息学分析,时空表达分析采用实时荧光定量PCR方法. 结果 日本沼虾血蓝蛋白基因cDNA全长2 151 bp,包含14 bp的5'UTR、148 bp的3'UTR和189 bp的开放阅读框(ORF).ORF编码663个氨基酸,预测分子量为76.65kD,理论等电点为5.42,含有典型的3个血蓝蛋白结构域和2个保守的铜离子结合位点.与淡水螯虾、凡纳滨对虾血蓝蛋白相似性分别为70％和63％.该基因在肝胰腺中的相对表达量最高,肌肉和血细胞表达较弱,大颚器官、表皮和卵巢几乎不表达:肝胰腺血蓝蛋白基因的表达量在蜕皮间期最高,蜕皮后期和蜕皮前期较低;嗜水气单胞菌刺激后肝胰腺中的表达量显著增加. 结论 与其他甲壳动物相似,日本沼虾血蓝蛋白基因具有典型的结构域和保守的铜离子结合位点,在蜕皮间期的肝胰腺中呈高表达,是参与机体免疫防御反应的一种重要分子.     

日本沼虾血蓝蛋白基因cDNA全长克隆及表达分析

目的 克隆日本沼虾血蓝蛋白基因,进行生物信息学及时空表达分析。方法 利用cDNA末端快速扩增技术（RACE ）从肝胰腺中克隆血蓝蛋白基因cDNA全长序列,用生物学软件对其序列进行生物信息学分析,时空表达分析采用实时荧光定量PCR方法。结果 日本沼虾血蓝蛋白基因cDNA全长2 151 bp,包含14 bp的 5′UTR、148 bp的 3′UTR 和189 bp的开放阅读框（ORF）。ORF编码 663 个氨基酸,预测分子量为76.65kD,理论等电点为5.42,含有典型的3个血蓝蛋白结构域和2个保守的铜离子结合位点。与淡水螯虾、凡纳滨对虾血蓝蛋白相似性分别为70%和63%。 该基因在肝胰腺中的相对表达量最高,肌肉和血细胞表达较弱,大颚器官、表皮和卵巢几乎不表达;肝胰腺血蓝蛋白基因的表达量在蜕皮间期最高,蜕皮后期和蜕皮前期较低;嗜水气单胞菌刺激后肝胰腺中的表达量显著增加。结论 与其他甲壳动物相似,日本沼虾血蓝蛋白基因具有典型的结构域和保守的铜离子结合位点,在蜕皮间期的肝胰腺中呈高表达,是参与机体免疫防御反应的一种重要分子。     

血链球菌与nifs、nifu基因同源序列分析

目的对具有一定的特异性和稳定性的血链球菌ＡＴＣＣ１０５５６染色体一８００ｂｐＤＮＡ片段进行基因序列分析。方法采用ＴＡ克隆技术并进行碱基序列测定,通过ＧｅｎｅＢａｎｋ进行同源分析。结果ＡＴＣＣ１０５５６ＤＮＡ片段氨基酸序列含有与固氮酶ｎｉｆｓ、ｎｉｆｕ基因同源序列,同源率分别为７２％,７１％。与非固氮菌中的磷酸吡哆醛依赖性氨基酸转移酶基因也具有同源性,同源率６３％。Ｓｏｕｔｈｅｒｎ杂交表明,与血链球菌ＡＴＣＣ１０５５６相似的另２株血链球菌含有同样的ｎｉｆｓ、ｎｉｆｕ基因,而其它亲源相近的口腔链球菌,如血链球菌ＪＦｒ菌株,变链球菌血清型ｃ、ｄ、ｆ参考菌株及唾液链球菌ＨＨＴ参考株不含有同样ｎｉｆ基因。结论血链球菌ＡＴＣＣ１０５５６含有的ｎｉｆ基因具有一定特异性,其基因结构及其生理性功能尚待深入研究。     

远源链球菌可能与细胞分裂相关的新基因ftsK的克隆与序列分析

目的克隆并分析远源链球菌(S．sobrinus)可能与细胞分裂相关的新基因fisK。方法采用“genome walking system(基因组步移系统)”克隆远源链球菌可能与细胞分裂相关的新基因fisK，与GenBank进行同源性分析，并用蛋白质分析软件分析fisK的氨基酸序列。结果所克隆的新基因由2100个碱基组成，编码699个氨基酸。用GOR4软件对S．sobrinuss ftsK的二级结构预测，显示其主要由a螺旋和无规卷曲组成，另有小部分伸展线，但无β折叠，在其N末端有一跨膜区。对氨基酸序列进行保守区分析，氨基酸335～530序列具有ftsK／SpoⅢE保守序列，同源性分析，除N末端226个氨基酸外，其余氨基酸序列与大肠杆菌细胞分裂蛋白FtsK的C末端2／3序列同源，217～635氨基酸与枯草杆菌SpoⅢE的C末端同源。结论通过“基因组步移系统”克隆出的新基因可能与远源链球菌细胞分裂蛋白FtsK相关。     

副血链球菌fap1-orf4基因座位编码的ORF3调控Fap1糖基化与成熟的研究

目的 研究副血链球菌fap1-orf4基因座位编码的ORF3是否调控Fap1的糖基化与成熟,并探讨其对副血链球菌黏附功能的影响.方法 采用基因置换技术构建副血链球菌orf3等位基因置换突变株,利用瓦补分析和Western blot检测副血链球菌Fap1的表达水平,并采用全唾液包被的羟磷厌石黏附试验检测副血链球菌的黏附能力.结果 (1)副血链球菌orf3基凶置换突变株VT1774未发生极化;(2)Western blot检测菌株VT1774显示成熟的Fap1(Mr约220×103)被不成熟的Fap1(M,约470 × 103)所取代,互补分析显示VT1774的互补株VT1775能恢复表达成熟的Fap1;(3)菌株VT1774黏附能力显著下降.结论 副血链球菌fap1-orf4基因座位编码的ORF3是Fap1糖基化与成熟所必需的,orf3基因置换导致Fap1成熟障碍与菌株黏附力显著下降.     

广州地区患儿流感嗜血杆菌分离株荚膜基因分型的研究

目的用PCR方法进行流感嗜血杆菌荚膜编码基因分型,调查儿童急性呼吸道感染患儿流感嗜血杆菌的感染情况。方法以流感嗜血杆菌荚膜编码基因（bexA）和荚膜分型编码基因（Hi-a、Hi-b）作为靶基因设计引物,用PCR方法扩增标准菌株为ATCC9006、ATCC49247、EQA0609的3个编码基因并测序,在此基础上对临床分离的43株流感嗜血杆菌进行荚膜基因分型研究。结果PCR结果显示标准菌株ATCC49247未扩增出bexA编码基因,ATCC9006扩增出bexA和Hi-a编码基因,EQA0609扩增出为bexA和Hi-b编码基因,并且PCR产物序列与GenBank公布的序列一致性高。临床分离菌株Hi未扩增出bexA、Hi-a及Hi-b编码基因。结论本实验研究表明广州地区儿童急性呼吸道感染患儿所分离的流感嗜血杆菌主要是不可分型的无荚膜菌株。     

幽门螺杆菌细胞毒素相关蛋白A的分离纯化

在对Ｈｐ毒力因子进行的研究中 ,发现ＣａｇＡ基因是Ｈｐ高毒力株的标志基因。其编码产物 细胞毒素相关蛋白Ａ(ＣａｇＡ)是引起人类严重胃部疾患的主要因素之一 ,ＣａｇＡ基因并不存在于所有的Ｈｐ菌株中 ,在中国人中约有 90 %感染者含有此基因。该基因已被克隆和测序 ,含有ＣａｇＡ基因与不含ＣａｇＡ基因的菌株在致病能力上存在显著的差异。目前一致认为含ＣａｇＡ基因的Ｈｐ菌株为高毒株 ,与消化性溃疡 ,萎缩性胃炎及胃癌的发生密切相关。ＣａｇＡ蛋白位于细胞表面 ,是一种亲水性免疫显性蛋白 ,可刺激患者机体产生相应的ＩｇＧ和ＩｇＡ抗…     

金黄葡萄球菌蛋白A与SUMO标签的融合表达及应用研究

目的 从金黄葡萄球菌菌株(ATCC6538)中克隆得到蛋白A的全长基因并对其结构及应用进行研究.方法 从该菌株的基因组DNA中克隆得到全长的葡萄球菌蛋白A基因,对其基因结构分析之后,将该基因的成熟区全长片段和抗体结合功能区片段重组到pHisSUMO原核分泌表达载体上与SUMO标签融合表达,通过ELISA的方法来鉴定融合蛋白的抗体结合活性及其稳定性,并将抗体结合功能区片段耦联到CNBr活化的琼脂糖凝胶上进行抗体的纯化.结果 首次获得了此株菌的全长蛋白A基因并发布于GenBank中,登录号为EU695225.蛋白A全长蛋白和功能区蛋白在pHisSUMO载体上得到正确高效表达,通过ELISA鉴定SUMO标签的存在,没有影响全长蛋白和功能区蛋白的抗体结合活性并有效提高了功能区蛋白的稳定性.在抗体纯化实验中,应用表达的蛋白A能够得到浓度和纯度较高的抗体并具有较好的效价.结论 克隆得到一个新的葡萄球菌蛋白A全长基因.蛋白A功能区蛋白与SUMO标签融合表达,在保持抗体结合活性的基础上提高了稳定性,并成功应用于抗体的纯化.     

肺炎链球菌假想蛋白SPD0414的表达纯化及保守性分析

目的:获得纯化的肺炎链球菌(S.pn)重组假想蛋白SPD0414,并分析其在常见S.pn菌株中的保守性。方法:利用PCR方法扩增SPD0414蛋白胞外区核酸序列,将其克隆到原核表达载体ppSUMO内,转化到E.coliBL21(DE3)中,经IPTG诱导表达后Ni-NTA树脂纯化重组蛋白。用SDS-PAGE和Western blot鉴定蛋白特异性及纯度。通过纯化蛋白免疫BALB/c小鼠制备其多克隆抗体,并用间接ELISA检测多克隆抗体的效价,Western blot方法分析多克隆抗体的特异性,同时,鉴定该蛋白在6种常见肺炎链球菌分离株的保守性。结果:克隆的SPD0414序列与Gene Bank中的数据相符,并实现了重组SPD0414蛋白高水平的可溶表达纯化蛋白免疫BALB/c小鼠获得高滴度、高特异性的的多克隆抗体,Western blot验证SPD0414蛋白在6株常见肺炎链球菌菌株中均有表达。结论:成功制备了高滴度、高特异性的SPD0414多克隆抗体,证实了SPD0414在肺炎链球菌不同菌株间保守性较高,为肺炎链球菌多肽联合疫苗的研制奠定了基础。     

Identification of Streptococcus sanguinis with a PCR-generated species-specific DNA probe

The objective of the present study was to design a PCR-generated DNA probe and determine the specificity of the probe for the identification of clinical isolates of Streptococcus sanguinis. To do this, we examined over 200 arbitrarily primed PCR (AP-PCR) amplicon patterns obtained with DNA from clinical isolates of S. sanguinis. A 1.6-kb DNA amplicon that was common to all AP-PCR profiles was extracted from agarose gels and then cloned and sequenced. A search for a similar sequence in the GenBank database with the BLASTN program revealed that the 1.6-kb DNA fragment comprised an intergenic region between two housekeeping genes, uncC (proton-translocating ATPase) and murA (UDP-N-acetylglucosamine enolpyruvyl transferase). Three digoxigenin-labeled DNA probes were synthesized on the basis of the sequence of the 1.6-kb fragment: the sequence of probe SSA-1 contained the proton-translocating ATPase (uncC) and the entire intergenic region, the sequence of probe SSA-2 contained only the intergenic region, and the sequence of probe SSA-3 contained an internal region of the murA gene. Dot blot hybridization showed that the three probes displayed signals for hybridization to both S. sanguinis strain ATCC 10556 and the S. sanguinis clinical isolates. Probe SSA-1, however, hybridized to DNA from S. oralis and S. mitis. Probe SSA-3 hybridized to DNA from S. gordonii, S. mitis, S. oralis, S. parasanguinis, and S. vestibularis. The probe SSA-2-specific intergenic region appeared to be specific for S. sanguinis. The results from this study suggest that probe SSA-2 may serve as a species-specific DNA probe for the identification of clinical isolates of S. sanguinis.     

Cloning of the gene encoding streptococcal immunoglobulin A protease and its expression in Escherichia coli.

We have identified and cloned a 6-kilobase-pair segment of chromosomal DNA from Streptococcus sanguis ATCC 10556 that encodes immunoglobulin A (IgA) protease activity when cloned into Escherichia coli. The enzyme specified by the iga gene in plasmid pJG1 accumulates in the periplasm of E. coli MM294 cells and has a substrate specificity for human IgA1 identical to that of native S. sanguis protease. Hybridization experiments with probes from within the encoding DNA showed no detectable homology at the nucleotide sequence level with chromosomal DNA of gram-negative bacteria that excrete IgA protease. Moreover, the S. sanguis iga gene probes showed no detectable hybridization with chromosomal DNA of S. pneumoniae, although the IgA proteases of these two streptococcal species cleaved the identical peptide bond in the human IgA1 heavy-chain hinge region.     

Lactose transport in Streptococcus mutans: isolation and characterization of factor IIIlac, a specific protein component of the phosphoenolpyruvate-lactose phosphotransferase system.

The transport of lactose in Streptococcus mutans is mediated via an inducible phosphoenolpyruvate-lactose phosphotransferase system. This system requires for catalytic activity a membrane fraction (enzyme II), two general proteins called enzyme I and HPr, and a soluble specific protein termed factor IIIlac. This protein factor was purified from S. mutans ATCC 27352 by chromatographies on DEAE-cellulose, hydroxylapatite, Ultrogel AcA 34, and phosphocellulose. The purified protein migrated as a single band with a molecular weight of 10,000 on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and urea. The molecular weight calculated from the amino acid composition was 10,541. Gel filtration of the native protein gave a molecular weight of 41,500. Its isoelectric point was ca. 4.70. A specific antiserum was prepared against purified factor IIIlac. Immunodiffusion experiments revealed that only cellular extracts from lactose-grown cells contained factor IIIlac. A cross-reaction was observed with all of the S. mutans strains tested as well as with Streptococcus sanguis 10556, Streptococcus lactis 11454, and Staphylococcus aureus 6538. No precipitin band was observed with extracts of Streptococcus salivarius, Streptococcus faecalis, Lactobacillus casei, and Bacillus subtilis.     

Purification and biochemical properties of a bacteriocin from Actinobacillus actinomycetemcomitans.

Extracts of certain strains of Actinobacillus actinomycetemcomitans are inhibitory to strains of Streptococcus sanguis such as S. sanguis ATCC 10556. The isolation of a protein from an A. actinomycetemcomitans sonic extract which copurified with the inhibitory activity was accomplished by preparative isoelectric focusing, Sephadex G-100 gel filtration chromatography, and preparative polyacrylamide gel electrophoresis (PAGE). The resulting isolated protein, which focused at a pH of 6.1 to 6.3, appeared as a single band in anionic nondissociating PAGE analysis. This protein could be dissociated into two subunits with molecular weights of 50,000 and 70,000, which were resolvable by PAGE analysis. A 1,758-fold increase in specific activity was seen in the purified inhibitory protein compared with the crude sonic extract starting material. The properties of the inhibitory activity in the A. actinomycetemcomitans extract are characteristic of a bacteriocin. Accordingly, we propose the name actinobacillicin for the inhibitory protein.     

Identification of the gene encoding a 38-kilodalton immunogenic and protective antigen of Streptococcus suis

In our continued effort to search for a Streptococcus suis protein(s) that can serve as a vaccine candidate or a diagnostic reagent, we constructed and screened a gene library with a polyclonal antibody raised against the whole-cell protein of S. suis type 2. A clone that reacted with the antibody was identified and characterized. Analysis revealed that the gene encoding the protein is localized within a 2.0-kbp EcoRI DNA fragment. The nucleotide sequence contained an open reading frame that encoded a polypeptide of 445 amino acid residues with a calculated molecular mass of 46.4 kDa. By in vitro protein synthesis and Western blot experiments, the protein exhibited an electrophoretic mobility of approximately 38 kDa. At the amino acid level the deduced primary sequence shared homology with sequences of unknown function from Streptococcus pneumoniae (89%), Streptococcus mutans (86%), Lactococcus lactis (80%), Listeria monocytogenes (74%), and Clostridium perfringens (64%). Except for strains of serotypes 20, 26, 32, and 33, Southern hybridization analysis revealed the presence of the gene in strains of other S. suis serotypes and demonstrated restriction fragment length differences caused by a point mutation in the EcoRI recognition sequence. We confirmed expression of the 38-kDa protein in the hybridization-positive isolates using specific antiserum against the purified protein. The recombinant protein was reactive with serum from pigs experimentally infected with virulent strains of S. suis type 2, suggesting that the protein is immunogenic and may serve as an antigen of diagnostic importance for the detection of most S. suis infections. Pigs immunized with the recombinant 38-kDa protein mounted antibody responses to the protein and were completely protected against challenge with a strain of a homologous serotype, the wild-type virulent strain of S. suis type 2, suggesting that it may be a good candidate for the development of a vaccine that can be used as protection against S. suis infection. Analysis of the cellular fractions of the bacterium by Western blotting revealed that the protein was present in the surface and cell wall extracts. The functional role of the protein with respect to pathogenesis and whether antibodies against the antigen confer protective immunity against diseases caused by strains of other pathogenic S. suis capsular types remains to be determined.     

Natural history of Streptococcus sanguinis in the oral cavity of infants: evidence for a discrete window of infectivity

The heterogeneous group of oral bacteria within the sanguinis (sanguis) streptococci comprise members of the indigenous biota of the human oral cavity. While the association of Streptococcus sanguinis with bacterial endocarditis is well described in the literature, S. sanguinis is thought to play a benign, if not a beneficial, role in the oral cavity. Little is known, however, about the natural history of S. sanguinis and its specific relationship with other oral bacteria. As part of a longitudinal study concerning the transmission and acquisition of oral bacteria within mother-infant pairs, we examined the initial acquisition of S. sanguinis and described its colonization relative to tooth emergence and its proportions in plaque and saliva as a function of other biological events, including subsequent colonization with mutans streptococci. A second cohort of infants was recruited to define the taxonomic affiliation of S. sanguinis. We found that the colonization of the S. sanguinis occurs during a discrete "window of infectivity" at a median age of 9 months in the infants. Its colonization is tooth dependent and correlated to the time of tooth emergence; its proportions in saliva increase as new teeth emerge. In addition, early colonization of S. sanguinis and its elevated levels in the oral cavity were correlated to a significant delay in the colonization of mutans streptococci. Underpinning this apparent antagonism between S. sanguinis and mutans streptococci is the observation that after mutans streptococci colonize the infant, the levels of S. sanguinis decrease. Children who do not harbor detectable levels of mutans streptococci have significantly higher levels of S. sanguinis in their saliva than do children colonized with mutans streptococci. Collectively, these findings suggest that the colonization of S. sanguinis may influence the subsequent colonization of mutans streptococci, and this in turn may suggest several ecological approaches toward controlling dental caries.     

Transfection of Streptococcus sanguis by phage deoxyribonucleic acid isolated from Streptococcus mutans.

Streptococcus sanguis ATCC 10556 cells were infected with free phage DNA of S, mutans strain PK 1. Two transformants were isolated which made colonies with large mucoid forms on mitis-salivarius agar. Both transformants had an increased ability to synthesize insoluble glucan and showed an adhesive nature on glass surfaces. These characteristics of the transformants bear a resemblance to S. mutans. These transformants had many physiological characteristics by which they could be recognized as S. sanguis. However, they resembled S. salivarius in forming a large amount of soluble fructan. Furthermore, the transformant cells did not produce ammonia from arginine, whereas their parent cells did.     

Differentiation of Streptococcus uberis from Streptococcus parauberis by polymerase chain reaction and restriction fragment length polymorphism analysis of 16S ribosomal DNA.

Streptococcus uberis type II has been proposed recently as a separate species designated Streptococcus parauberis (A. M. Williams and M. D. Collins, J. Appl. Bacteriol. 68:485-490, 1990). Differentiation of S. parauberis from S. uberis has been possible only by DNA-DNA hybridization or 16S rRNA sequencing, since the biochemical and serological characteristics of the two species are indistinguishable. A simple and reliable technique was developed for differentiating S. parauberis (S. uberis type II [ATCC 13386]) from S. uberis (S. uberis type I [ATCC 9927, ATCC 13387, and ATCC 27958]) by restriction fragment length polymorphism (RFLP) analysis of 1.4-kb 16S ribosomal DNA (rDNA). Oligonucleotide primers complementary to 16S rRNA genes were used to amplify 16S ribosomal gene fragments from genomic DNA by polymerase chain reaction. The 1.4-kb 16S rDNA fragment was digested with ScaI, NspI, DdeI, and AvaII restriction endonucleases. Restriction fragments produced by all four restriction endonucleases were characteristic for each species. RFLP analysis of 16S rDNA from 24 "S. uberis" isolates obtained from mammary secretions of dairy cows indicated that all 24 isolates were indeed S. uberis.     

Development of PCR-based hybridization protocol for identification of streptococcal species.

16S rRNA of Streptococcus agalactiae, S. uberis, and S. parauberis was bound to streptavidin-coated magnetic beads by using a biotinylated oligonucleotide probe complementary to a highly conserved region of the molecule. In-solution hybridization of radiolabelled oligonucleotide probes to immobilized 16S rRNA allowed the specific identification of S. agalactiae and S. parauberis but not S. uberis. PCR was used to amplify a species-specific region of the 16S rRNA gene from these species. One of the PCR primers was biotinylated at the 5' end to allow purification of the amplified product on streptavidin-coated magnetic beads and subsequent denaturation to yield immobilized single-stranded DNA. Radiolabelled oligonucleotide probes were hybridized in solution to the single-stranded target molecule and enabled species-specific identification of the target organism. This protocol overcame problems associated with hybridization of the S. uberis-specific probe to 16S rRNA in solution. A similar procedure may enable the specific detection of other streptococci which exhibit a species-specific sequence in this region of the gene.