混合培养提高菌株解磷解钾能力的探讨

沈阳农业大学的微生物实验室保藏菌种中得到互相不拮抗的根瘤菌S-2、溶磷菌P-3和硅酸盐细菌K-5,对这3株菌进行两两复合及三菌复合,分别测试其溶磷、解钾能力。结果表明:3株菌在第10天时溶磷、解钾能力最强。溶磷能力:两两复合培养的溶磷能力比各菌单独培养溶磷能力要提高25.50%、51.54%、26.99%,并且三菌复合培养具有1+1+13的溶磷效果。解钾能力:两两复合培养时S-2与P-3组合溶解钾长石的能力增强,但S-2与K-5、P-3与K-5的组合并无明显的促进作用,三菌复合虽较各菌株单独培养时高,但未表现出1+1+13解钾效果。     

The mitochondrial genome of the fission yeast Schizosaccharomyces pombe. 3. Gene mapping in strain EF1 (CBS 356) and analysis of hybrids between the strains EF1 and ade7-50h-

The Schizosaccharomyces pombe strain EF1 (CBS 356) is haploid, prototrophic, respiratory competent, and of homothallic mating type. From restriction enzyme analysis the length of the mitochondrial genome is 17.3 kilobase pairs, which is in good agreement with the value of 17.1 kilobase pairs determined by electron microscopy. The mitochondrial genome of strain EF1 is thus about 2.3 kilobase pairs shorter than that of strain ade7-50h- (about 19.4 kilobase pairs). A restriction map was constructed for 11 enzymes: For most, but not all of them, the pattern is nearly identical to that of strain ade7-50h-. The genes for the large ribosomal RNA, the subunits 1, 2, and 3 of cytochrome c oxidase, subunits 6 and 9 of ATP synthetase, and cytochrome b were localized by hybridization with mitochondrial DNA probes from Saccharomyces cerevisiae. The gene order was found to be the same in both yeast strains. From Southern hybridization of strain ade7-50h- with nick-translated mitochondrial DNA from strain EF1 it is evident that strain EF1 does not possess the intron, which is present in the cytochrome b gene of Schizosaccharomyces pombe strain ade7-50h-. Crosses between strain ade7-50h- and EF1 demonstrate that both the nuclear and the mitochondrial genomes are able to recombine. The mitochondrial genomes of 2 out of 30 independently isolated hybrids between the two strains are described as the result of recombination between the two parental mitochondrial genomes.     

Co-Housing Rodents with Different Coat Colours as a Simple,Non-Invasive Means of Individual Identification: Validating Mixed-Strain Housing for C57BL/6 and DBA/2 Mice

Standard practice typically requires the marking of laboratory mice so that they can be individually identified. However, many of the common methods compromise the welfare of the individuals being marked (as well as requiring time, effort, and/or resources on the part of researchers and technicians). Mixing strains of different colour within a cage would allow them to be readily visually identifiable, negating the need for more invasive marking techniques. Here we assess the impact that mixed strain housing has on the phenotypes of female C57BL/6 (black) and DBA/2 (brown) mice, and on the variability in the data obtained from them. Mice were housed in either mixed strain or single strain pairs for 19 weeks, and their phenotypes then assessed using 23 different behavioural, morphological, haematological and physiological measures widely used in research and/or important for assessing mouse welfare. No negative effects of mixed strain housing could be found on the phenotypes of either strain, including variables relevant to welfare. Differences and similarities between the two strains were almost all as expected from previously published studies, and none were affected by whether mice were housed in mixed- or single-strain pairs. Only one significant main effect of housing type was detected: mixed strain pairs had smaller red blood cell distribution widths, a measure suggesting better health (findings that now need replicating in case they were Type 1 errors resulting from our multiplicity of tests). Furthermore, mixed strain housing did not increase the variation in data obtained from the mice: the standard errors for all variables were essentially identical between the two housing conditions. Mixed strain housing also made animals very easy to distinguish while in the home cage. Female DBA/2 and C57BL/6 mice can thus be housed in mixed strain pairs for identification purposes, with no apparent negative effects on their welfare or the data they generate. This suggests that there is much value in exploring other combinations of strains.     

Species of tetrahymena identical by small subunit rRNA gene sequences are discriminated by mitochondrial cytochrome c oxidase I gene sequences

The mitochondrial cytochrome c oxidase 1 (CO1) genes of two isolates of each of the seven mating types of Tetrahymena thermophila were sequenced and found to differ by < 1% in nucleotide sequence and to be identical by putative protein sequence. As this gene was highly conserved in this species, the CO1 gene sequence was determined for four pairs of Tetrahymena species identical in their small subunit rRNA gene sequences. The following pairs of species showed from 1% to 12% divergence at the nucleotide level, enabling discrimination of all these species: (1) Tetrahymena pyriformis strain T and Tetrahymena setosa strain HZ-1; (2) Tetrahymena canadensis strain UM1215 and Tetrahymena rostrata strain ID-3; (3) Tetrahymena pigmentosa strain UM1285 and Tetrahymena hyperangularis strain EN112; and (4) Tetrahymena tropicalis strain TC-105 and Tetrahymena mobilis. However, because of the synonymous nature of the majority of substitutions, the pairs of species were identical based on the putative protein sequence.     

The B-Z transition in supercoiled DNA depends on sequence beyond nearest-neighbors.

In order to examine sequence-dependent structural effects in DNA, the ability of alternating purine-pyrimidine fragments to undergo a B-Z transition when cloned in a supercoiled plasmid was determined solely as a function of sequence, with base and nearest-neighbor composition held constant. Sequences of 22 GC and 2 AT base pairs were synthesized such that the AT base pairs varied between contiguous placement and separation by eight GC base pairs. Results show, surprisingly, that the ease of the B-Z transition varies with the position of the two AT base pairs, occurring at lower superhelical densities when AT base pairs are contiguous, and at higher torsional strain when the AT base pairs are moved further apart.     

Biological and Molecular Categorization of Strains of Banana bunchy top virus

Banana bunchy top virus (BBTV), a complex circular single‐stranded DNA virus with multiple genomic components, is a destructive pathogen in banana‐cultivating areas worldwide. Based on symptoms (such as vein clearing, green streak on pseudostem, leaf atrophy, bunchy top and stunting) as well as polymerase chain reaction (PCR) amplification patterns with different primer pairs, all BBTV isolates collected from Taiwan and other countries can be divided into five distinctive strains. Three primer pairs, C1, stem‐loop common region (CR‐SL) and TS were used for PCR amplifications. Strain 1, which induces conspicuous symptoms, is a common severe strain; it reacted positively with C1 and CR‐SL but negatively with TS in the PCR assays, so its PCR pattern was indicated as ‘+/+/?’ for C1, CR‐SL and TS primer pairs, respectively. Strain 2 seemed to be a Taiwan‐specific severe strain which induced severe symptoms, and its PCR pattern was ‘+/+/+’ as it showed positive reactions with all three primer pairs. Strain 3, causing the most severe symptoms, is a Malaysia‐specific severe strain whose PCR pattern is ‘?/+/?’. Strain 4 induced moderately severe symptoms and is an intermediate strain whose PCR pattern is ‘?/+/?’. Strain 5 is a mild strain; it did not induce symptoms in banana and it reacted positively with C1, CR‐SL and TS primer pairs. Interestingly, an additional 537‐bp fragment was amplified from Strain 5 with the CR‐SL primer pair. The PCR pattern of Strain 5 is therefore indicated as ‘+/++/+’. This study demonstrates that various BBTV strains exist in nature and they differ biologically and also molecularly.     

An amicronucleate mutant of Tetrahymena thermophila

A stable amicronucleate strain of Tetrahymena thermophila was isolated following nitrosoguanidine mutagenesis. The mutant has the same growth rate and viability as the micronucleate parent strain, and has no micronucleus detectable by chromatin-specific staining in vegetative growth or during conjugation. The mutant pairs with normal efficiency with cells of complementary mating type. Matings of the mutant with aneuploid strains which lose their micronucleus during meiosis produced cell pairs yielding one viable and one inviable cell. The mutant receives a micronucleus from a normal mating partner, but this micronucleus is lost by the mutant cells within two hundred generations.     

淡色库蚊抗药性相关胰蛋白酶基因cDNA全长克隆与序列分析

用逆Northern印迹和Northern印迹法进一步鉴定淡色库蚊对溴氰菊酯抗药性和敏感性品系胰蛋白酶的表达差异 ,结果显示 ,胰蛋白酶基因在抗药性品系中的表达量分别是敏感性品系的 4.3和 3.9倍。采用RACE法筛选cDNA文库 ,获得总长度为 90 9bp的淡色库蚊胰蛋白酶基因的全长序列 ,其中开放阅读框为 786bp ,推导出编码 2 6 1个氨基酸的蛋白质 (GenBank/NCBIAY0 34 0 6 0 ) ,其与冈比亚按蚊胰蛋白酶同源性最高 ,为 5 5 %     

Analysis of plasmid deoxyribonucleic acid in a cariogenic strain of Streptococcus faecalis: an approach to identifying genetic determinants on cryptic plasmids.

Streptococcus faecalis strains ND539 and OG1 have been previously shown to be cariogenic in gnotobiotic animals. Deoxyribonucleic acid analyses have revealed the presence of a single 26-megadalton plasmid designated pAM539 in the former strain, whereas the latter strain was found to be plasmid-free. By gene transfer experiments, it was possible to construct isogenic pairs of strains that differed only with regard to the presence or absence of pAM539. Comparative studies of isogenic pairs showed that the presence of pAM539 conferred bacterial sensitivity to a bacteriocin produced by S. faecalis strain 5952.     

半嵌套式PCR技术区别检测犬细小病毒疫苗株和强毒株的研究

Two pairs of PCR primers were designed according to the sequances of the vaccine strain and virulent strain of CPV. Heminested PCR method was established. Result of the first PCR amplification showed the same amplified products of 574bp length, after the second PCR amplification, the virulent strain produced the length 364bp fragment, but the vaccine strain couldn' t produce that. The products of PCR were examined by electrophoresis and restriction enzyme digestion. The result showed the length of the fragment and enzyme sites were as the same as those designed. The PCR assay of CPV was proved to be specific and sensitive. It shows that this method may be used in discriminating the vaccine strain and virulent strain of CPV or monitoring the vaccinated canine in order to aviod disease and financial losing.     

Escherichia coli JA221 can suppress the UAG stop signal

The Escherichia coli strain JA221 can suppress the UAG stop codon, although the existence of an amber suppressor tRNA has not previously been described for this strain. When using a plasmid to express α-sarcin, which has TAG as its stop signal, two proteins were obtained: a smaller protein corresponding in size to that of the expected protein, and a larger protein, which could be accounted for by the presence of a second stop codon (TGA) 18 base pairs downstream of the original. This feature of strain JA221 must therefore be considered when using this strain as a host for the production of recombinant proteins.     

Separation of Prodigiosenes and Identification as Prodigiosin Syntrophic Pigment from Mutant Pairs of Serratia marcescens

Countercurrent distribution is capable of resolving mixtures of closely related prodigiosene pigments. Syntrophic pigment produced by several pairs of Serratia marcescens color mutants was identified as prodigiosin (2-methyl-3-amyl-6-methoxyprodigiosene) by countercurrent distribution, soda lime pyrolysis, and other techniques. The metabolic block of mutant strain H-462, derived from parent strain HY, was located between the blocks of mutant strains OF and WF, both derived from parent strain Nima.     

Phototactic responses of Chlamydomonas eugametos gametes before and after fusion

The phototactic behavior of Chlamydomonas eugametos gametes and vis-à-vis pairs was quantitated using a fully automated, computer-controlled microvideo image analysis system. Two different mt- (mating type minus) and one mt+ (mating type plus) strain, together with the two combinations of pairs were studied. One mt- strain of dark-adapted gametes was non-phototactic while the others were positively phototactic at all effective intensities of white light. The mt+ strain exhibited one of the strongest positive responses that has so far been reported in algae (r-values greater than 0.7). After sexual fusion, the mt+ cell powers the swimming vis-à-vis pair. Its phototactic behavior reversed on fusion, with the pairs swimming away from all effective light intensities, irrespective of whether its partner was formerly phototactic or not. However, when adapted to the dark for an hour or more, vis-à-vis pairs swam positively to the light. The ecological consequence could be that pairs settle and develop into zygotes under intermediate light intensities or at light-dark interfaces.     

The Host Genotype and Environment Affect Strain Types of Bifidobacterium longum subsp. longum Inhabiting the Intestinal Tracts of Twins

To investigate the influences of host genotype and environment on Bifidobacterium longum subsp. longum inhabiting human intestines at the strain level, six pairs of twins, divided into two groups (children and adults), were recruited. Each group consisted of two monozygotic (MZ) twin pairs and one dizygotic (DZ) twin pair. Child twins had been living together from birth, while adult twins had been living separately for 5 to 10 years. A total of 345 B. longum subsp. longum isolates obtained from 60 fecal samples from these twins were analyzed by multilocus sequence typing (MLST), and 35 sequence types (STs) were finally acquired. Comparison of strains within and between the twin pairs showed that no strains with identical STs were observed between unrelated individuals or within adult DZ twin pairs. Eight STs were found to be monophyletic, existing within MZ twins and child DZ twins. The similarity of strain types within child cotwins was significantly higher than that within adult cotwins, which indicated that environment was one of the important determinants in B. longum subsp. longum strain types inhabiting human intestines. However, although these differences between MZ and DZ twins were observed, it is still difficult to reach an exact conclusion about the impact of host genotype. This is mainly because of the limited number of subjects tested in the present study and the lack of strain types tracing in the same twin pairs from birth until adulthood.     

Allele intersection analysis: a novel tool for multi locus sequence assignment in multiply infected hosts

Wolbachia are wide-spread, endogenous α-Proteobacteria of arthropods and filarial nematodes. 15-75% of all insect species are infected with these endosymbionts that alter their host's reproduction to facilitate their spread. In recent years, many insect species infected with multiple Wolbachia strains have been identified. As the endosymbionts are not cultivable outside living cells, strain typing relies on molecular methods. A Multi Locus Sequence Typing (MLST) system was established for standardizing Wolbachia strain identification. However, MLST requires hosts to harbour individual and not multiple strains of supergroups without recombination. This study revisits the applicability of the current MLST protocols and introduces Allele Intersection Analysis (AIA) as a novel approach. AIA utilizes natural variations in infection patterns and allows correct strain assignment of MLST alleles in multiply infected host species without the need of artificial strain segregation. AIA identifies pairs of multiply infected individuals that share Wolbachia and differ in only one strain. In such pairs, the shared MLST sequences can be used to assign alleles to distinct strains. Furthermore, AIA is a powerful tool to detect recombination events. The underlying principle of AIA may easily be adopted for MLST approaches in other uncultivable bacterial genera that occur as multiple strain infections and the concept may find application in metagenomic high-throughput parallel sequencing projects.     

Construction and characterization of an Escherichia coli strain with a uncI mutation.

A strain of Escherichia coli with a mutation in the promoter proximal gene ( uncI ) of the unc operon has been constructed by using a new gene replacement method. The mutation is a deletion of a defined sequence of 196 base pairs. It was constructed by homologous integration and segregation of a ColE1-derived recombinant plasmid containing the mutation, in a temperature-sensitive polA strain. The mutant strain is phenotypically unc+ but has a reduced growth yield compared to a normal sibling strain.     

Plasmid pCBI carries genes for anaerobic benzoate catabolism in Alcaligenes xylosoxidans subsp. denitrificans PN-1

Pseudomonas sp. strain PN-1 is reclassified as Alcaligenes xylosoxidans subsp. denitrificans PN-1. Strain PN-1 is a gram-negative, rod-shaped organism, is motile by means of lateral flagella, is oxidase positive, and does not ferment sugars. Plasmid pCBI, carrying genes for the anaerobic degradation of benzoate in strain PN-1, is 17.4 kilobase pairs in length and is transmissible to a number of denitrifying Pseudomonas aeruginosa and Pseudomonas stutzeri strains. A restriction endonuclease map was constructed.     

Isolation and genetic analysis of an Agrobacterium tumefaciens avirulent mutant with a chromosomal mutation produced by transposon mutagenesis.

A transposon 5 (Tn5) insertion was introduced into the genome of A. tumefaciens (A-208 strain harboring a nopaline type Ti-plasmid) using a conjugative pJB4JI plasmid containing Tn5. Five thousand transconjugants were assayed for virulence on carrot (Daucus carota L.) disks; 54 isolates were avirulent or very attenuated. The cellular localization (plasmid or chromosome) of the Tn5 insertion in those isolates were identified by Southern hybridization analysis. An avirulent mutant (B-90 strain) with the Tn5 insertion in the chromosome was selected and characterized. The mutant had the same growth rate as that of the parent strain in L-broth. The mutant and the parent strain had similar attachment ability to carrot root cells. Tn5 was inserted into one site of the chromosome. The wild-type target chromosomal region (1281 base pairs) was cloned and sequenced. An open reading frame (ORF) consisting of 395 base pairs was identified. The wild-type DNA fragment (1.6 kb) containing the ORF introduced into B-90 strain complemented the avirulent phenotype of the strain. A soluble protein was predicted from the ORF. The Tn5 was inserted near the 3'-terminal of the ORF. Homology search of this ORF found no significant homology to known genes and proteins. Thus, the ORF identified in this paper seems to be a new chromosomal virulence gene of A. tumefaciens.     

DA大鼠的繁殖性能及部分生物学特性参数的测定

目的建立我国新的近交系品系DA种群,观察其生长繁殖性能及部分生物学特性。方法从丹麦M＆B公司引进近交系大鼠DA,建立种群,从其扩大群中随机抽取15对鼠,统计其繁殖率;抽取50只DA鼠（雌雄各半）测其部分血液生化。结果近交系种群扩大成功,DA大鼠平均产仔数为5．5,成活率为90.8％,所测生理生化值接近Wistar大鼠。结论DA大鼠已适应我国环境,种群引进成功;性别对脏器重量、系数和血生化影响显著。     

4株SARS冠状病毒基因组5’端序列的分析与比较

利用5′RACE试剂盒对从中国不同地区、不同SARS患者体中分离的SARS-CoV基因组5′端序列进行RT-PCR扩增,并将扩增产物克隆至T easy vector。扩增片段的序列测定结果表明:所分离的4株SARS-CoV基因组5′端非编码区的核苷酸序列和其他国家和地区报道的序列基本一致,而且所形成二级结构也完全相同,但与已知普通冠状病毒的差别较大。同时发现在依赖于RNA的RNA聚合酶起始密码子上游-197 nt处有冠状病毒典型的转录调控核心保守序列5′-CUAAAC-3′。