胶孢镰刀菌产生串珠镰刀菌素的不稳定性

从陕北克山病病区分离到的两株串珠镰刀菌素产生菌株－胶孢镰刀菌陕－６号和２－１７号进行单孢分离,分别得到２３和１９个单孢分离株。这些单孢菌株可为两种培养型：一种形态上与原始菌株相似,产生串珠镰刀菌素,产色素,具有大、小分生孢子,转管八次产毒量有下降,另一种则不产串珠镰刀菌素和孢子,无色素,后者在二株菌的单孢分离菌中所占比例分别为６０．９％和１５．８％。由此可见,胶孢镰刀菌产毒稳定性受异核体和该菌单     

胶孢镰刀菌产生串珠镰刀菌素的不稳定性

从陕北克山病病区分离到的两株串珠镰刀菌素产生菌株——胶孢镰刀菌(Fusarium subglutinans Wollenw.et Reinking)陕-6号和2-17号进行单孢分离,分别得到23和19个单孢分离株。这些单孢菌株可分为两种培养型:一种形态上与原始菌株相似,产生串珠镰刀菌素,产色素,具有大、小分生孢子,转管八次产毒量有下降;另一种则不产串珠镰刀菌素和孢子,无色素,后者在二株菌的单孢分离菌中所占比例分别为60.9％和15.8％。由此可见,胶孢镰刀菌产毒稳定性受异核体和该菌单核变异性共同影响。     

DON生物合成的亚细胞定位和精准外排研究进展

单端孢霉烯B族毒素脱氧雪腐镰刀烯醇（deoxinivalenol, DON）是产毒镰刀菌在侵染小麦等作物过程中的一类重要的致病因子,可以帮助产毒镰刀菌在麦穗间扩展。DON会抑制蛋白质合成,对动物、微生物和寄主具有毒性（cytotoxicity and phytotoxicity）,然而产毒镰刀菌自身借助何种保护机制免受DON毒害目前研究甚少。DON毒害机制的研究对于镰刀菌毒素的持续防控和粮食安全、人民生命健康保障具有重要意义。综述了产毒镰刀菌DON合成解毒机制的最新研究进展,主要包括DON合成的亚细胞定位、合成基因簇内的外排蛋白和解毒基因作用方式,以期为有针对性地破解其解毒机制,设计研发高效靶向控毒技术的相关研究提供参考。     

球孢白僵菌继代培养中的菌落局变现象

通过球孢白僵菌两个野生型菌株及其单孢株在不同培养基、温度、湿度和光照条件下继代培养,结果产生3种不同类型的菌落局变.局变产生的分离子多表现为菌落瘩薄或气生菌丝陡长、产孢量下降、生长速率增加等现象.培养基、温度、湿度和光照等因素对菌落局变有明显诱导作用.湿度为15℃,相对湿度较低及全光照条件下于SDAY培养基上培养,局变发生频率最低.在实验室继代培养中,野生型菌株在4-14代内即可发生局变而被局变分离子所取代.引人注意的是,单孢株局变产生的分离子同时伴随着棕黄色或红棕色素的分泌,仅以菌落形态和颜色等培养特征作为球孢白僵菌种的划分依据是不可靠的.文中提出了菌落局变发生的遗传变异可能机制.     

禾谷镰孢菌高产毒菌株的构建*

为研究禾谷镰孢菌Fusarium graminearum Schw.单端孢霉烯族毒素生物合成基因（产毒基因）在寄主体内的表达,作者构建了带报告基因GUS（(-葡糖苷酸酶基因）的质粒pGUSTRI6P5,并通过对野生型菌株的转化获得禾谷镰孢高产毒菌株。该质粒含有由TRI5（禾谷镰孢单端孢霉二烯合酶基因）启动子（TRI5 Prom）驱动的GUS基因编码区、潮霉素B抗性基因和拟枝孢镰孢F. sporotrichioides的产毒调控基因TRI6（FSTRI6）。用pGUSTRI6P5转化野生型菌株GZ3639后,在含潮霉素 B的培养基上选取抗性菌落,单孢分离获单孢菌株（转化子）。在GYEP（葡萄糖-酵母粉-蛋白胨）液体培养基上,转化子B4-1和B16-1的GUS比活力强,15-AcDON（15-乙酰脱氧雪腐镰刀菌烯醇）产量高,且两者呈正相关（相关系数（r）分别为0.9839和0.9523）。B4-1和B16-1两个转化子可作为研究禾谷镰孢与其寄主相互作用的工具菌株。     

单端孢霉烯族毒素的产生及分子调控机制

禾谷镰刀菌复合种(Fusarium graminearum species complex,FGSC)引起的赤霉病是小麦生产上危害最为严重的病害之一。赤霉病除了造成减产外,感病籽粒中含有多种镰刀菌毒素,如单端孢霉烯族的呕吐毒素,可引起人畜中毒和重大疾病,给食品安全构成严重威胁。过去20年,随着禾谷镰刀菌全基因组序列的公布和遗传转化体系的成熟,禾谷镰刀菌Fusarium graminearum的功能基因组学的研究取得了较大进展,单端孢霉烯族毒素的产生、调控机制及网络研究成为热点。本文综述国内外单端孢霉烯族毒素的生物合成和分子调控机制,包括合成基因簇及决定不同产毒化学型的基因、产毒调控元件、环境因子调控产毒的分子机制,可为小麦抗赤霉病的育种提供新思路,为新型药剂的研发提供分子靶标,为赤霉病的持续防控和毒素污染的有效治理提供理论依据。     

球孢白僵菌继代培养中菌落局变现象及环境影响因素的研究

球孢白僵菌野生型多孢标以及从其上分离的单孢株在不同培养基,光照,温度和湿度条件下继代培养。结果显示：无论是多孢株还是单孢株。在传代中均发生显著的菌落局变,并产生形态各异的分离子,多表现为菌苔瘠薄或气生菌丝徒长,肉眼可见产孢量减少,尤其是单孢株菌落局变产生的分离子往往伴随着棕黄色或红棕色色素的分泌。培养基、温度、湿度和光照等环境因素对菌落局变产生具明显诱导作用,以ＳＤＡＹ培养基、偏低的温湿度和全光照     

球孢白僵菌继代培养中菌落局变现象及环境影响因素的研究

球孢白僵菌[Beauveria bassiana(Bals.)Vuill.]野生型多孢株以及从其上分离的单孢株在不同培养基、光照、温度和湿度条件下继代培养,结果显示:无沦是多孢株还是单孢株,在传代中均发生显著的菌落局变,并产生形态各异的分离子,多表现为菌苔瘠薄或气生菌丝徒长,肉眼可见产孢量减少;尤其是单孢株菌落局变产生的分离子往往伴随着棕黄色或红棕色色素的分泌。培养基、温度、湿度和光照等环境因素对菌落局变产生具明显诱导作用。以SDAY培养基、偏低的温湿度和全光照条件下产生局变频率较低。大批量生产中以麦麸作原料较适宜。提出了菌落局变发生的几种可能的遗传机制。     

尖孢镰刀菌(Fusarium oxysporum)诱导矿化回收稀土离子La(Ⅲ)

[目的] 从罗源湾红树林浅滩土壤中筛选出产脲酶真菌,研究其对镧La（Ⅲ）的最大耐受浓度,利用其吸附和产脲酶作用诱导矿化回收稀土离子La（Ⅲ）,以期为稀土离子La（Ⅲ）的资源回收提供菌种资源和应用技术指导。[方法] 从罗源湾红树林浅滩土壤中分离、筛选、纯化出可产脲酶及耐La（Ⅲ）真菌,通过ITS rDNA基因序列分析对其进行鉴定;同时,利用XRD、SEM-Mapping及FT-IR分析探讨菌株回收La（Ⅲ）的机理。[结果] 经分离、纯化得到一株可产脲酶及耐受高浓度La（Ⅲ）的真菌FZU-07,鉴定为尖孢镰刀菌（Fusarium oxysporum）,其具有较强诱导矿化回收La（Ⅲ）的能力,对La（Ⅲ）的最大耐受浓度为400 mg/L。菌株FZU-07单独对La（Ⅲ）吸附回收效率为46.19%;在诱导矿化条件下回收效率可提高到99.16%。FT-IR和SEM-Mapping分析表明,尖孢镰刀菌吸附La（Ⅲ）与菌丝体表面的氨基、羟基、羰基和磷酸基团相关;XRD和SEM-Mapping结果表明诱导矿化是通过该菌的产脲酶特性,使尿素分解产生碳酸,并与钙离子结合生成球霰石晶型的碳酸钙,La（Ⅲ）被捕获在球霰石晶格中,形成La（Ⅲ）和碳酸钙的混合固相,以共沉淀的形式被回收。[结论] 菌株FZU-07,是一株具有产脲酶特性的尖孢镰刀菌（Fusarium oxysporum）,且具有较强的诱导矿化回收La（Ⅲ）能力。表明微生物诱导碳酸钙沉淀是一种可行且生态友好的回收稀土离子的方法。     

链格孢霉醇和链格孢霉醇单甲醚产生菌株的筛选

本文对分离自小麦、马铃薯、番茄和茄子上链格孢霉属２个种的９６个菌珠,用枯草杆菌生长抑制试验筛选链格孢霉醇（ＡＯＨ）和链格孢霉醇单甲醚（ＡＭＥ）的产生菌株,有４８株产生毒性作用。１８株产强、中毒性菌用高效液相色谱分析,有１３株产ＡＯＨ和ＡＭＥ。链格孢的产毒素菌株率比茄链格孢低,但产毒素含量却是前者明显高于后者。其中产ＡＯＨ和ＡＭＥ的最高含量,链格孢菌株ＸＡ－８分别为２８０和５１４０ｍｇ／ｋｇ,而茄链     

Differential Mitotic Stability of Yeast Disomes Derived from Triploid Meiosis

The frequencies of recovered disomy among the meiotic segregants of yeast (Saccharomyces cerevisiae) triploids were assessed under conditions in which all 17 yeast chromosomes were monitored simultaneously. The studies employed inbred triploids, in which all homologous centromeres were identical by descent, and single haploid testers carrying genetic markers for all 17 linkage groups. The principal results include: (1) Ascospores from triploid meiosis germinate at frequencies comparable to those from normal diploids, but most fail to produce visible colonies due to the growth-retarding effects of high multiple disomy. (2) The probability of disome formation during triploid meiosis is the same for all chromosomes; disomy for any given chromosome does not exclude simultaneous disomy for any other chromosome. (3) The 17 yeast chromosomes fall into three frequency classes in terms of disome recovery. The results support the idea that multiply disomic meiotic segregants of the triploid experience repeated, nonrandom, post-germination mitotic chromosome losses (N + 1 leads to N) and that the observed variations in individual disome recovery are wholly attributable to inherent differences in disome mitotic stability.     

Otolith microstructure during the pelagic, settlement and benthic phases in burbot

During the pelagic larval phase of burbot Lota lota L., the pattern of otolith increments changes, showing three, clearly distinguishable growth sectors: a first sector with faint increments, difficult to enumerate, comprising an average (±S.D.) of 17˙5±6˙7 increments, a second sector with distinct increments comprising an average of 33˙1±7˙6 increments and a third sector where increments again become faint and difficult to enumerate. Laboratory experiments conducted in parallel to the field investigation showed that settlement occurs after the formation of this third, faint sector and is marked by the formation of numerous accessory growth centres within the range of three to five daily increments. There was a strong linear relationship between sagittal width and total length of the burbot (r²=0˙928) over the range examined. Significantly different growth rates were calculated for the three otolith sectors (faint, distinct, faint) in burbot larvae, indicating large environmental changes during their pelagic larval phase in Lake Constance. These results suggest that inshore migration of burbot larvae does not take place in the warm epilimnetic surface waters but via an alternative pathway, the cold hypolimnion or profundal zone.     

Novel streptococcal mutants defective in the regulation of H+-ATPase biosynthesis and in F0 complex

In Streptococcus faecalis (faecium), the cytoplasmic pH is regulated by proton extrusion via a proton translocating F1F0-ATPase; the level of this enzyme increases in response to cytoplasmic acidification (Kobayashi, H., Suzuki, T., and Unemoto, T. (1986) J. Biol. Chem. 261, 627-630). We describe here two novel acid-sensitive mutants, designated AS8 and AS17, that contain ATPase activity but fail to grow on acid media. Our data suggested that in mutant AS17, acidification of the cytoplasm stimulates synthesis of the F0 sector of the ATPase but not the F1 sector. The accumulation in the plasma membrane of F0 sectors devoid of F1 results in enhanced proton permeability, and as a consequence mutant AS17 is unable to regulate the cytoplasmic pH in acid media. The genetic defect may reside in a gene that regulates expression of the F1F0-ATPase. Mutant AS8 does not generate a proton motive force. Our results suggest that the F1F0-ATPase can hydrolyze ATP but fails to translocate protons due to a defect in one of the subunits of the F0 sector.     

胶质芽孢杆菌突变株021120的培养条件及发酵工艺优化

对离子束诱变所获得的突变菌株021120进行了培养条件和发酵工艺研究。单因子及正交试验结果表明,碳源对生物量和芽孢形成的影响最大,其次是氮源,磷和钾的影响较小;添加CaCO3和增加氧通量显著促进芽孢的形成。发酵培养基的理想配方为：2%淀粉、0.4% 酵母、0.1% K2HPO4、0.1％ MgSO4·7H20、0.5 ％CaCO3,pH 7.5。种子菌经二级扩大培养后,按6％的接种量接入70 L发酵罐,在32℃进行发酵,氧通量2.0-2.5 vvm,培养周期38-42 h,芽孢量达到9.80×108 cfu ml-1。通过以上培养基和发酵条件的优化,有效控制了多糖荚膜的产生,并促进了芽孢的形成,获得合格产品。     

The phenomenon of predetermination of the cytoplasm upon interaction between alleles of the ADE2 and ADE13 in the yeast Saccharomyces cerevisiae

Our previous data showed that mutation ade13-1, blocking steps 8 and 12 of purine biosynthesis in the yeast Saccharomyces cerevisiae, caused the inability of strains manifesting this activity to grow on the complete nutrient medium with glucose in addition to the loss of adenylosuccinate lyase activity. It was also determined that the ade2-D mutation, inactivating aminoimidasole ribonucleotide carboxylase (the enzyme of step 6), suppressed this phenotypic manifestation of ade13-1; i.e., the ade2-D mutation restores the ability to grow on this medium. When spores of a hybrid that contained both mutations in the heterozygote were germinated on the YEPD medium, almost complete viability of segregants with genotypes ADE2 ADE13 and ade2-D ADE13 and the absence of ADE2 ade13-1 growth were observed. The number of growing segregants ade2-D ade13-1 amounted to approximately half of the possible number. In this work, a decrease in the proportion of segregants with this genotype was shown to occur only when they were obtained as a result of the segregation of hybrids with the normal allele (ADE2) in the heterozygote. The proportion of segregants with genotype ade2-D ade13-1 did not decrease upon segregation of hybrids similar in the genetic background and containing the ade2-D mutation in the homozygote and ade13-1 in the heterozygote. Spores with this genotype formed in the diheterozygous diploid were able to germinate on a medium containing glycerol and to further grow on a medium with glucose. The data suggest that, when a product of the normal ADE2 allele or of another gene, the synthesis of which is stimulated in the presence of this allele, enters spores with genotype ade2-D ade13-1 during meiosis, some of these spores lose their ability to grow on the medium with glucose; i.e., the ADE2 allele can be phenotypically expressed in the spores that did not contain this allele. This phenomenon is similar to the maternal effect known in some species of animals from various systematic groups.     

豇豆单孢锈菌中病毒样颗粒中双链RNA的存在

从北京西郊清华园附近田间豇豆上采集的豇豆单孢锈菌(Uormyces vignal Barcl)夏孢子。萌发后提取双链RNA,电泳分析可测出300—8000碱基对的三组双链RNA。从萌发的孢子中通过差迷离心提取病毒样颗粒,可获得二种类型的病毒样颗粒,一种直径为35—40nm的等轴颗粒。另一种为长短不等的棒状颗粒,用提纯物提取核酸电泳分析与直接从孢子中提取的双链RNA有相同的核酸带,从而证明这些双链RNA存在于病毒样颗粒中。     

Isolation and some properties of phospholipase D from Bacillus subtilis G-22]

A method of isolating highly purified phospholipase D from Bac. subtilis G-22 is described. It includes ammonium sulphate fractionation, thermal denaturation, chromatography on lipoprotein bound with sepharose 6B and AH-sepharose 4B. The enzyme is 130-fold purified, its yield exceeds 90.0%, its specific activity is 164 units per mg of protein. The homogeneity of the enzyme is demonstrated by polyacrylamide gel electrophoresis, ultracentrifugation, isoelectric focusing and N-terminal amino acid determination by means of dinitrophenylation and dancylation. Proline is found to be N-terminal amino acid. The molecular weight of the enzyme, as determined from gel filtration through Sephadex G-100, is 21500 +/- 300, its sedimentation constant is 1.4S, isoelectric point is at pH 4.2. The molecular weight calculated from amino acid composition, is 21000--22000. Polypeptide chain contains of 196--205 amino acid residues. Phospholipase D develops its maximal activity at pH 8.5 and does not contain free SH-groups. Benzylsulphofluoride does not inhibit the enzyme activity. Phospholipase D is activated by Cd2+, Co2+, Zn2+, Ca2+ and is inhibited by EDTA, pIi50 being about 2.6.     

Occurrence of GTP cyclohydrolase I in Bacillus stearothermophilus

A GTP cyclohydrolase which catalyzes the removal of carbon 8 of GTP as formic acid to yield a single pteridine compound occurs in an obligate thermophile Bacillus stearothermophilus ATCC 8005. The enzyme was purified 5.5-fold. Its molecular weight and Stoke's radius were estimated as 105,000 and 45.3 A, respectively. The Km for GTP was 0.98 microM. The temperature and pH optima for activity were 60-65 degrees C and 8.0-8.4, respectively. No divalent cation was required for the reaction. The pteridine product was 3'-triphosphate of 2-amino-4-hydroxy-6-(D-erythro-1',2',3'-trihydroxypropyl)-7,8-dihydropteridine (dihydroneopterin triphosphate), identified by isolating its immediate derivative, 2',3'-cyclic phosphate of 2-amino-4-hydroxy-6-(D-erythro-1',2',3'-trihydroxypropyl)pteridine (neopterin cyclic phosphate). The radioactive product from [8-14C]GTP agreed with 14C-formate. Molar ratio of formate release to pteridine formation was 1.0.     

The combined effect of sub-optimal temperature and sub-optimal pH on growth and toxin formation from spores of Clostridium botulinum

Low-acid foods (pH greater than or equal to 4.5) are not sufficiently acidic to prevent growth of Clostridium botulinum in otherwise optimal conditions. The combination of sub-optimal pH and sub-optimal temperature may, however, result in a very significant reduction in the risk of growth of this bacterium compared with the risk in optimal conditions. The combined effect of incubation temperatures of 12 degrees and 16 degrees C and pH values between 5.2 and 5.5 on growth and toxin production from spores of Cl. botulinum during incubation for 28 d has been investigated. Growth and formation of toxin (type B) were detected only in medium at pH 5.5 and incubated at 16 degrees C, corresponding to a probability of growth from a single spore within 14 d of 1.6 x 10(-5). The probability of growth in 28 d in the remaining conditions was less than 9 x 10(-6). After transfer of inoculated media from 12 degrees to 30 degrees C growth occurred at pH 5.2-5.5 within 19 d. After transfer of inoculated media from 12 degrees to 20 degrees C growth occurred at pH 5.5 and 5.4 but not at pH 5.3 or 5.2 in 40 d. Growth at pH 5.2-5.5 was accompanied by formation of toxin, in most cases of types A or B. In addition to the effect of sub-optimal temperature and pH, chelation of divalent metal ions by citrate may have contributed to inhibition.