利用葡萄糖发酵产聚β—羟基丁酸菌株的选育

采用常规紫外线诱变处理真养产碱杆菌Ｈ１６,获得高效利用葡萄糖产聚β－羟基丁酸的突变株,摇瓶发酵试验证明,突变株耐糖程度及其程度及其积累ＰＨＢ的能力均优于亲株Ｈ１６。ＰＨＢ积累量达１０ｇ／Ｌ以上。     

利用葡萄糖发酵产聚β－羟基丁酸菌株的选育

采用常规紫外线诱变处理真养产碱杆菌Ｈ１６,获得高效利用葡萄糖产聚β－羟基丁酸（ＰＨＢ）的突变株。摇瓶发酵试验证明,突变株耐糖程度及其积累ＰＨＢ的能力均优于亲株Ｈ１６。ＰＨＢ积累量达１０ｇ／Ｌ以上。     

产灵菌红素沙雷氏菌的诱变育种

通过紫外线—氯化锂复合处理灵菌红素生产菌沙雷氏菌 (Serratiasp )W 0 2 0 6,用高浓度葡萄糖为碳源的选择性平板定向筛选抗葡萄糖分解代谢物阻遏的高产株 ,筛得高产突变株B 2 0 ,相对于原始菌株 ,B 2 0摇瓶发酵灵菌红素产量提高了 3倍 ,5L反应器上的产量提高了 63 %。     

耐高糖、高渗透压D-核糖高产菌株的选育及其发酵培养

以产D-核糖40-45 g.L-1的枯草芽孢杆菌突变株BFD-100810为出发菌株,通过紫外线、硫酸二乙酯等方法诱变处理,获得一株核糖高产突变株BFD-101106。对该突变株的产核糖能力进行了验证,并对发酵条件进行了研究。     

金霉素链霉菌的诱变育种

从金霉素链霉菌(Streptomyces aureofaciens)重组体2U一84经紫外线处理得到A3-32突变株,产量比2U一84提高10．6％以上。A3—32突变株又经紫外线处理,得到一株分泌金黄色色素的突变株5一43,产量为A3-32的60—70％。而5一43突变株经不同诱变因素：紫外线、乙烯亚胺及氮芥处理,均得到色素形成能力消失的突变株,这些菌株的产量均比5—43高,提高的幅度也较大。其中紫外线处理得到的u一42突变株比5—43突变株提高78％,比重组体2u 8{提高21．5％。色素形成能力愈小者,其产量愈高,这说明产量与色素之间存在着一定的相关性。由弱孢子型6—15突变株经乙烯亚胺与紫外线复合处理,得到孢子丰富,产量明显提高的EU-63突变株,比重组体2U一84提高49．6％。     

血红铆钉菇氨基酸缺陷型菌株的紫外诱变选育

通过原生质体去细胞壁技术,以血红铆钉菇原生质体为材料,利用紫外线对其进行诱变处理,筛选出6株氨基酸营养缺陷型突变株,经稳定性试验确认1株突变株性状可以稳定遗传,利用生长谱法对缺陷型进行了鉴定、分析。结果表明,该菌株为L-半胱氨酸缺陷型菌株,为营养缺陷型突变株的筛选奠定了基础。     

D-核糖生产菌的选育

将枯草芽胞杆菌通过紫外线诱变得到了莽草酸缺陷突变株,在２８株突变株中有１０株积累Ｄ－核糖。这些菌株均属戊糖磷酸途径的非氧化支路缺失突变株。对这些菌株的产核糖能力进行了验证、培养基中芳香族氨基酸的浓度影响Ｄ－核糖的积累     

福氏2a志贺氏菌2457T株argT基因突变体的构建

目的：构建福氏2a志贺氏菌2457T株argT基因缺失突变体和ArgT蛋白非降解突变体,以进行后续ArgT功能研究。方法：根据福氏2a志贺氏菌2457T株基因组全序列,采用λ-Red重组系统对argT基因进行缺失,并经PCR验证;采用定点突变的方法构建ArgT非降解株,并经SDS-PAGE验证;对野生株、argT缺失突变株和ArgT非降解突变株37℃时的生长曲线及生化反应进行比较研究。结果：构建了2457T的argT缺失突变株和ArgT非降解突变株;2种突变株初始生长均较慢,但最终和野生株状态一致;2种突变株利用甘露醇的能力都比野生株强,而利用葡萄糖的能力降低。结论：获得了福氏2a志贺氏菌2457T株argT基因缺失突变体和ArgT蛋白非降解突变体。     

大肠杆菌氮代谢调节蛋白GlnG与固氮施氏假单胞菌氮代谢调节蛋白NtrC的功能互补研究

旨在围绕大肠杆菌DH10B(Escherichia coli DH10B)中氮代谢调节蛋白GlnG与施氏假单胞菌A1501(Pseudomonas stutzeriA1501)中氮代谢调节蛋白NtrC在一般氮代谢调控网络中是否存在功能互补展开研究。利用DH10B菌的glnG基因回补A1501菌的ntrC突变株,以及A1501菌的ntrC基因回补DH10B菌的glnG突变株,对所获得的功能互补株分别展开生理生化表型测定。结果表明,在以硝酸钾或尿素为唯一氮源的培养条件下,DH10B glnG基因可以回补A1501ntrC突变株的氮源利用能力,并且部分恢复ntrC突变株的固氮酶活性(约为野生型A1501固氮酶活性的45%);与DH10B glnG突变株相比,A1501菌的ntrC基因回补了DH10B glnG突变株以精氨酸为唯一氮源的生长能力。以上结果说明DH10B菌的GlnG蛋白与A1501菌的NtrC蛋白不仅在进化关系上紧密联系而且在所测试的氮代谢途径中存在功能互补。     

高生物量草分枝杆菌突变株诱变选育的研究

目的:为了获得具有提高人体免疫力的草分支杆菌菌株的生长量。方法:采用紫外线和硫酸二乙酯两种方法,对其原始菌株进行复合诱变,筛选生长能力强的突变菌株。结果:实验结果表明紫外线诱变最佳处理时间为90 s,硫酸二乙酯诱变最佳处理时间为50 min,筛选出生长能力强的3株突变株(50min-1、50min-4和50min-7),其生长能力较原菌株分别提高了62%、57%和59%。通过方差分析来检测这3株突变菌株的遗传稳定性,结果显示传代次数对突变株50min-1和50min-4的生长量影响不显著,而对50min-7的生长量的影响显著,因此50min-1和50min-4具有遗传稳定性。结论:研究结果为草分支杆菌的发酵研究提供了优良菌株。     

Mutant Bac. subtilis A2 with an enhanced capacity to induce an adaptive response

Mutant A2 with increased ability to induce adaptive response was isolated in Bac. subtilis and its properties studied. Mutant A2 was shown to be more resistant to mutagenic action of MNNG, EMS, UV light. It was also discovered that A2 was more sensitive to the lethal action of MNNG and UV light than parent strain 103. It was shown by clonal analysis of mutant colonies, formed by mutant cells A2 and 103 that A2 strain had increased ability to form complete mutants. Properties of A2 mutant suggest that in the process adaptive response induction were is expression of both adaptive response enzymes and some other which are necessary for reparation of premutagenic UV lesions.     

不同添加物对D-核糖产量的影响

采用短小芽孢杆菌转酮酶缺陷突变株 ,通过先后向培养基中添加适量的葡萄糖酸钠、Mn2 + ,直接或间接地影响D 核糖的生物合成途径 ,最终影响D 核糖的产量。此外向培养基中添加芳香族氨基酸中的酪氨酸 ,有机酸中的山梨酸可以促进D 核糖的生物合成 ,使其产量达 6 4.2 g/L。     

Association between M. pneumoniae hemolysis, attachment, and pulmonary pathogenicity

Three different groups of hemolysis mutants were produced by treatment of the M. pneumoniae FH-P24 strain with N-methyl-N-nitro-nitrosoguanidine. The first group of mutants, strains P24-L1, L2, and L11, showed wide and clear hemolytic zones, and attaching ability to erythrocytes and to hamster lung cells were the same as the properties of the parent strain and produced significant microscopic lung lesions. Mutant P24-S1 showed non-hemolysis and non-hemadsorption, yet retained the attaching ability to lung cells and produced milder lung lesions. Mutant P24-S11 showed none of those activities, did not cause any lung lesion, and was never recovered from the lungs of hamsters. A close relationship between the hemolytic ability of M. pneumoniae and the histopathogenicity in the hamster lung is suggested in this study. The attaching ability of organisms seems to be an important factor at the initial stage of infection.     

Glycolate Uptake by Mutant Strains of Escherichia coli K-12

Mutant strains of Escherichia coli K-12 were shown to be impaired in their ability to assimilate glycolate-2-(14)C. One strain (Glc-103) has lost the ability to oxidize glycolate; another strain (Glc-102) was relatively impermeable to the compound. A third strain (Glc-104) had undergone a similar loss in permeability, and, in addition, was deranged in the synthesis of either glyoxylate reductase or malate synthase G.     

Isolation and characterization of nitrogenase-derepressed mutant strains of cyanobacterium Anabaena variabilis.

A positive selection method for isolation of nitrogenase-derepressed mutant strains of a filamentous cyanobacterium, Anabaena variabilis, is described. Mutant strains that are resistant to a glutamate analog, L-methionine-D,L-sulfoximine, were screened for their ability to produce and excrete NH4+ into medium. Mutant strains capable of producing nitrogenase in the presence of NH4+ were selected from a population of NH4+-excreting mutants. One of the mutant strains (SA-1) studied in detail was found to be a conditional glutamine auxotroph requiring glutamine for growth in media containing N2, NO3-, or low concentrations of NH4+ (less than 0.5 mM). This glutamine requirement is a consequence of a block in the assimilation of NH4+ produced by an enzyme system like nitrogenase. Glutamate and aspartate failed to substitute for glutamine because of a defect in the transport and utilization of these amino acids. Strain SA-1 assimilated NH4+ when the concentration in the medium reached about 0.5 mM, and under these conditions the growth rate was similar to that of the parent. Mutant strain SA-1 produced L-methionine-D,L-sulfoximine-resistant glutamine synthetase activity. Kinetic properties of the enzyme from the parent and mutant were similar. Mutant strain SA-1 can potentially serve as a source of fertilizer nitrogen to support growth of crop plants, since the NH4+ produced by nitrogenase, utilizing sunlight and water as sources of energy and reductant, respectively, is excreted into the environment.     

Physiological and structural analysis of light-harvesting mutants of Rhodobacter sphaeroides.

Two mutants of Rhodobacter sphaeroides defective in formation of light-harvesting spectral complexes were examined in detail. Mutant RS103 lacked the B875 spectral complex despite the fact that substantial levels of the B875-alpha polypeptide (and presumably the beta polypeptide) were present. The B800-850 spectral complex was derepressed in RS103, even at high light intensities, and the growth rate was near normal at high light intensity but decreased relative to the wild type as the light intensity used for growth decreased. Mutant RS104 lacked colored carotenoids and the B800-850 spectral complex, as well as the cognate apoproteins. This strain grew normally at high light intensity and, as with RS103, the growth rate decreased as the light intensity used for growth decreased. At very low light intensities, however, RS104 would grow, whereas RS103 would not. Structural analysis of these mutants as well as others revealed that the morphology of the intracytoplasmic membrane invaginations is associated with the presence or absence of the B800-850 complex as well as of carotenoids. A low-molecular-weight intracytoplasmic membrane polypeptide, which may play a role in B800-850 complex formation, is described, as is a 62,000-dalton polypeptide whose abundance is directly related to light intensity as well as the absence of either of the light-harvesting spectral complexes. These data, obtained from studies of mutant strains and the wild type, are discussed in light of photosynthetic membrane formation and the abundance of spectral complexes per unit area of membrane. Finally, a method for the bulk preparation of the B875 complex from wild-type strain 2.4.1 is reported.     

Bacillus subtilis mutant with altered ability for heterologous transformation]

Mutant strain of Bacillus subtilis, which produced in certain conditions significantly reduced quantity of trnasformants during transformation by homologous DNA, as compared with transformation by heterologous DNA from Bac. aterrimus, is isolated. The ability to transfection by phage SPO1 DNA and the efficiency of infection of the mutant by this phage are also decreased. The causes of such alterated properties are discussed.     

Effect of lectin on nodulation by wild-type Bradyrhizobium japonicum and a nodulation-defective mutant.

The nodulation characteristics of wild-type Bradyrhizobium japonicum USDA 110 and mutant strain HS111 were examined. Mutant strain HS111 exhibits a delayed-nodulation phenotype, a result of its inability to initiate successful nodulation promptly following inoculation of the soybean root. Previously, we showed that the defect in initiation of infection leading to subsequent nodulation which is found in HS111 can be phenotypically reversed by pretreatment with soybean root exudate or soybean seed lectin. This effect is not seen after pretreatment with root exudates and lectins obtained from other plant species. Treatment of strain HS111 with as little as 10 soybean seed lectin molecules per bacterium (3.3 X 10 (-12) M) resulted in enhancement of nodule formation. Pretreatment of wild-type B. japonicum USDA 110 with soybean root exudate or seed lectin increased nodule numbers twofold on 6-week-old plants. Wild-type strain USDA 110 cells inoculated at 10(4) cells per seedling exhibited a delay in initiation of infection leading to subsequent nodulation. Wild-type cells pretreated in soybean root exudates or seed lectin did not exhibit a delay in nodulation at this cell concentration. Mutant strain HS111 pretreated in seed lectin for 0 or 1 h, followed by washing with the hapten D-galactose to remove the lectin, exhibited a delay in initiation of nodulation. Phenotypic reversal of the delayed-nodulation phenotype exhibited by strain HS111 was seen if incubation was continued for an additional 71 h in plant nutrient solution following 1 h of lectin pretreatment. Reversal of the delayed-nodulation phenotype of HS111 through lectin pretreatment was prevented by chloramphenicol or rifampin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Deletion of exon I of SMAD7 in mice results in altered B cell responses

The members of the TGF-beta superfamily, i.e., TGF-beta isoforms, activins, and bone morphogenetic proteins, regulate growth, differentiation, and apoptosis, both during embryonic development and during postnatal life. Smad7 is induced by the TGF-beta superfamily members and negatively modulates their signaling, thus acting in a negative, autocrine feedback manner. In addition, Smad7 is induced by other stimuli. Thus, it can fine-tune and integrate TGF-beta signaling with other signaling pathways. To investigate the functional role(s) of Smad7 in vivo, we generated mice deficient in exon I of Smad7, leading to a partial loss of Smad7 function. Mutant animals are viable, but significantly smaller on the outbred CD-1 mouse strain background. Mutant B cells showed an overactive TGF-beta signaling measured as increase of phosphorylated Smad2-positive B cells compared with B cells from wild-type mice. In agreement with this expected increase in TGF-beta signaling, several changes in B cell responses were observed. Mutant B cells exhibited increased Ig class switch recombination to IgA, significantly enhanced spontaneous apoptosis in B cells, and a markedly reduced proliferative response to LPS stimulation. Interestingly, LPS treatment reverted the apoptotic phenotype in the mutant cells. Taken together, the observed phenotype highlights a prominent role for Smad7 in development and in regulating the immune system's response to TGF-beta.     

Characterization of a Schizosaccharomyces pombe morphological mutant altered in the galactomannan content

In a search for Schizosaccharomyces pombe mutants resistant to the antifungal agent papulacandin B, a morphological mutant was isolated. The mutant is round shaped in contrast to the rod shaped parental strain. This morphological defect segregated as a recessive Mendelian character and was not observed in other papulacandin B resistant mutants belonging to the same complementation group. The mutation mapped in the right arm of S. pombe chromosome III very close to pap1 marker. Mutant cell walls were more susceptible to alkali extraction and Novozyme degradation than those from the wild-type. A specific reduction in the cell wall galactomannan fraction was the only significant difference detected as compared to the wild-type strain. Levels of beta (1,3)-glucan and mannan synthases as well as other enzymic periplasmic mannoproteins were very similar in wild type and mutant strains.