Chloramphenicol resistant mutants of Bacillus subtilis

Summary Telve chloramphenicol resistant (CM ^r)-mutants were isolated from B. subtilis ATCC 6633 and were classified into the following six groups. Group I. No 50s ribosomal protein change was detectable. Ribosomes did not show alteration of the binding ability to CM or to erythromycin in vitro. Group II. A 50s protein, 50a, was altered. Ribosomes did not show alteration of the binding ability to CM or to erythromycin in vitro. The genes specifying the 50a protein was in the cysA-str region on B. subtilis chromosome. Group III. A 50s protein, 50b, was altered. Biological properties of the ribosomes were the same as Group I or II so fas as examined. The genes for 50b protein was in the cysA-str region. Group IV. A 50s protein, 50c, was altered. Ribosomes showed a definite decrease in ability to bind to CM in vitro. The binding of erythromycin to the ribosomes was not impaired. The chromosomal locus of the CM ^r (and for 50c protein) was in the cysA-str region. Group V. A 50s protein, 50e, was changed. The ability of the ribosomes to bind in vitro both to CM and to erythromycin was greatly reduced. The genetic locus of the CM ^r (and for 50e protein) was in the cysA-str region. Group VI. A 50s protein, 50f, was altered. Ribosomes showed a decrease in ability to bind in vitro both to CM and to erythromycin. The genes for 50f protein was in the cysA-str region.The results suggest that the ribosomal resistance to CM may be caused by an independent change of at least several 50s ribosomal protein species. The genetic data shown here and those reported previously show that at least two 30s and seven 50s ribosomal protein genes are situated in the cysA-str region on B. subtilis chromosome.     

In-vitro evaluation of the antimicrobial activity of Bauhinia variegata,locally known as koiralo

Bauhinia variegata, commonly known as Koiralo is considered as medicinal plant in Nepal and India. The alcoholic extract of this plant was found to have antimicrobial activity against Bacillus subtilis (ATCC 6635) Pseudomonas aeruginosa (ATCC 27853), Salmonella typhi, Shigella dysenteriae, Staphylococcus aureus (ATCC 29213) and Vibrio cholerae. The largest zone of inhibition (18 mm) was found to be exhibited against B. subtilis. For this organism the minimum bactericidal concentration (MBC) of the crude extract was 0.39 mg/ml. The extract was found to be more effective against gram-positive than gram-negative bacteria. The antimicrobial activity of the extract was found to be decreased during purification.     

A review of length–weight relationships of fishes from freshwaters of Turkey

This paper presents 145 length–weight relationships gathered from the literature pertaining to 30 Turkish freshwater fish species belonging to six families. The value of the slope b ranged from 2.04 for Carassius carassius to 3.46 for Scardinus erythroptalmus. The mean value of b was 2.91 (SD = 0.305), which did not differ significantly from 3.0 (t‐test, P > 0.05). The median value of b was 2.95; 50% of the b values ranged from 2.68 to 3.14. The plot of log a vs b was used to detect outliers.     

Determination of the true intraocular pressure and modulus of elasticity of the human cornea in vivo

The purpose of this study was to determine the true intraocular pressure and modulus of elasticity of the human cornea in vivo. The cornea was modeled as a shell, and the equations for the deformations of a shell due to applanating and intraocular pressures were combined to model the behavior of the cornea during applanation tonometry. At certain corneal dimensions called the calibration dimensions, the applanating and intraocular pressures are considered to be equal. This relationship was used to determine the modulus of elasticity of the cornea and the relationship between the applanating and intraocular pressures. The true intraocular pressure (IOPT) was found to be related to Goldmann’s applanating pressure (IOPG) as (IOPT = IOPG/K, where K is a correction factor. For the calibration corneal thickness of 0.52 mm, the modulus of elasticity E in MPa of the human cornea was found to be related to the true intraocular pressure IOPT in mmHg as E = 0.0229IOPT. The generalization of the Imbert—Fick law that takes into account the effect of corneal dimensions and stiffness was found to be given by IOPT = 73.5W/(K A), where W is the applanating weight in gf (gram force) and A is the applanated area in mm². The calculated true intraocular pressure and modulus of elasticity were found to agree with published experimental results. The mathematical model developed may therefore be used to improve results from applanation tonometry and to estimate the mechanical property of the cornea in vivo.     

Cloning and characterization of the Azotobacter vinelandii recA gene and construction of a recA deletion mutant

Summary The recA gene of Azotobacter vinelandii was isolated from a genomic library by heterologous complementation of an Escherichia coli recA mutation for resistance to UV radiation. The A. vinelandii recA gene was localized on adjacent PstI fragments of 1.3 and 1.7 kb. The cloned A. vinelandii recA gene was functionally analogous to the E. coli recA gene. It was also able to complement the E. coli recA mutation for homologous recombination. A recA deletion mutant of A. vinelandii was constructed. This mutant was sensitive to DNA-damaging agents like UV rays, methyl methane sulfonate (MMS) and nalidixic acid and was deficient in homologous recombination.     

Extracellular Production of Yeast Protease

The groEL gene of the alkaliphilic Bacillus sp. strain C-125 was cloned in Escherichia coli and sequenced. The groEL gene encoded a polypeptide of 544 amino acids and was preceded by the incomplete groES gene, lacking its 5′-end. The sequence of the derived amino acids was 87.5% identical to that of B. subtilis, 85.4% identical to that of B. stearothemophilus, and 60.9% identical to that of E. coli. The GroEL protein was expressed in E. coli. Purified GroEL protected yeast a-glucosidase from irreversible aggregation at a high temperature and the addition of Mg-ATP was essential for reactivation of the a-glucosidase. The addition of E. coli GroES increased recovery of the enzyme activity, indicating that C-125 GroEL could function in coordination with E. coli GroES.     

八仙山不同类型松栎林群落主要特征分析

为探究八仙山保护区不同类型森林群落的更新潜力、多样性程度以及稳定性水平,阐明三者间的关系,该文以保护区内油松林、蒙古栎林和油松-栓皮栎混交林(松栎混交林)3种不同类型天然次生林为对象,调查建群种径级结构和更新潜力,计算不同层次群落多样性,测定M.Godron稳定性,并采用主成分法建立评价模型.结果表明:(1)油松种群径...     

The Structure of Graphinone

A microorganism M–2 was isolated as a strain capable of converting (—)-menthone to other compounds. The strain was identified as Pseudomonas fluorescens by taxonomical investigation. The conversion products of (—)-menthone were determined to be (—)-t-4-isopropyl-3-oxo-r-l-cyclohexanecarboxylic acid,* (+)-c-4-isopropyl-3-oxo-r-1-cyclohexane-carboxylic acid* and (+)-t-3-hydroxy-t-4-isopropyI-r-l-cyclohexanecarboxylic acid.* As the main pathway, it was proposed that (—)-menthone was oxidized to a keto acid which was successively reduced to a hydroxy acid.     

Characterization of CalS9 in the biosynthesis of UDP-xylose and the production of xylosyl-attached hybrid compound

The gene cluster of calicheamicin contains calS9, which encodes UDP-GlcA decarboxylase that converts UDP-GlcA to UDP-xylose. calS9 was cloned in pET32a(+) and expressed in Escherichia coli BL21 (DE3) to characterize its putative function. The reaction product was analyzed by high-performance liquid chromatography (HPLC) and electrospray ionization-mass spectrometry. The deoxysugar biosynthesis of Streptomyces sp. KCTC 0041BP was inactivated by gene replacement to generate Streptomyces sp. GerSM2 mutant, which was unable to produce dihydrochalcomycin. calS7, calS8, and calS9 UDP-xylose biosynthetic genes were cloned in an integrative plasmid pSET152 to generate pBPDS, which was heterologously expressed in Streptomyces sp. GerSM2. Finally, novel glycosylated product, 5-O-xylosyl-chalconolide derivative, in the conjugal transformants was isolated and analyzed by HPLC and liquid chromatography–mass spectrometry.     

Life history adaptations and stress tolerance of four domestic species of Drosophila

Life history traits and stress tolerance were studied in four domestic species of Drosophila–D. melanogaster, D. simulans, D. auraria and D. immigrans– to understand how they adapt to their environments. In all species, larval weight approximately doubled in 1 day. The relative egg weight (egg weight : pupal weight) was smaller and the larval period was longer in D. immigrans than in the other three species. The pupal period was the longest in D. auraria. However, the adaptive significance of these differences in larval and pupal periods was not clear. The pupal case was generally thicker in the larger species, probably to support the larger pupal body. The start of oviposition was earliest and reproductive effort was greatest in female D. simulans, followed by female D. melanogaster. In contrast, starvation tolerance and the increase in bodyweight after eclosion was greater in D. immigrans and D. auraria than in the other two species. Pupal desiccation tolerance was greatest in D. melanogaster and lowest in D. auraria, and the less tolerant species seemed to select more humid sites for pupation. Adult tolerance to desiccation was greatest in D. melanogaster and lowest in D. simulans. In contrast, adult cold tolerance was greater in D. auraria and adult heat tolerance was lower in D. immigrans than in the other species. These differences in life history traits and stress tolerance represent the Drosophila species differential adaptations, and are assumed to allow coexistence of the species.     

Efficient expression of mosquito-larvicidal proteins in a gram-negative bacterium capable of recolonization in the guts of Anopheles dirus larva

The gram-negative bacterium, An11/2 G1, isolated from the guts of Anopheles dirus mosquito larvae, was identified as Enterobacter amnigenus. The E. amnigenus was able to recolonize in the gut of An. dirus larva but not in those of Aedes aegypti and Culex quinquefasciatus larvae. It was able to float in water for a longer period than Bacillus thuringiensis subsp. israelensis and Bacillus sphaericus. These are desirable characteristics for a delivery vehicle of mosquito-larvicidal toxins for the control of mosquito larvae, and E. amnigenus was therefore used as a host to express the cryIVB gene of B. thuringiensis subsp. israelensis and the binary toxin genes of B. sphaericus. The recombinant E. amnigenus produced a high level of CryIVB protein, which was toxic to larvae of Ae. aegypti and An. dirus. Another E. amnigenus producing the 51-kDa protein of B. sphaericus was toxic to larvae of An. dirus and Cx. quinquefasciatus. The recombinant plasmids were stable in E. amnigenus without the presence of selective pressure for at least 23 generations. The recombinant E. amnigenus should represent a desirable biological agent for controlling mosquito larvae. Received: 20 February 1998 / Received last revision: 5 October 1998 / Accepted: 11 October 1998     

Occurrence of Ochratoxin A-Producing Fungi in Commercial Corn Kernels in Argentina

Potentially ochratoxigenic Aspergillus and Penicillium species were identified and the natural occurrence of ochratoxin A (OTA) in corn kernels was evaluated. Likewise, the capacity to produce OTA by Aspergillus section Nigri and Circumdati was investigated. A total of 50 corn samples for human consumption was collected in the south of Córdoba Province. The surface-disinfected method for mycobiota determination was used. The OTA detection was performed by HPLC. OTA production was tested in strains belonging to section Nigri and Circumdati. Statistical analysis demonstrated that the specie A. flavus was isolated in higher frequency (p<0.01) from corn kernels in DRBC and DG18 media. The percentage of corn kernels contaminated by A. niger var. niger was similar in DRBC and DG18 media. The frequency of grains contaminated by A. flavus and A. niger var. awamori was higher than A. niger var. niger and A. japonicus var. japonicus (p<0.01) in DG18 media. The other potentially ochratoxigenic species, A. ochraceus, was isolated between 5% and 10% of the corn kernels in DG18 and DRBC media, respectively. The OTA producing species P. verrucosum was not isolated. All samples of corn were OTA negative (<1 ng g⁻¹). Thirty strains (25%) of the black Aspergillus were OTA producers. From four strains of A. ochraceus isolated, only one produced OTA. Due to the storage variable conditions could not be adequate in this substrate, the presence of ochratoxigenic strains of section Nigri and OTA needs to be evaluated for a longer time to establish the toxicological risk for human beings. The contamination of stored corn kernels with A. flavus and Aspergillus section Nigri was significant.     

Methoxyhydroquinone, a Growth Inhibitor of Ophiobolus graminis, in Leaves of Oat Seedlings

A methanol extract of leaves of oat seedlings grown in sand cultures in the dark contained a compound which inhibited the growth of Ophiobolus graminis. The inhibitory factor was isolated and proved to be present in the plant as methoxyhydroquinone glucoside. The glucoside was readily hydrolysed to the corresponding aglucone. The methoxyhydroquinone, or possibly its oxydation product, methoxy-P-benzoquinone, was inhibitory to both Ophiobolus graminis var. graminis and Ophiobolus graminis var. avenae, whereas Fusarmm oxysporum var. lycopcrsici was not affected. Synthetic methoxyhydroquinone at 80 mg/l gave a 100% inhibition of Ophiobolus graminis var. graminis. After being exposed to 80 mg/l of the inhibitor for 24 h the mycelium was unable to initiate growth when transferred to a fresh nutrient solution. Only extracts from young leaves showed inhibitory activity, extracts from mature leaves giving no inhibition. The hydroquinone, or its glucoside, was not detected in roots of young seedlings, where avenacin was the only antifungal compound present.     

小蓬NeMT2基因的克隆及其植物表达载体的构建

该研究利用RACE ( Rapid amplification of cDNA ends)技术从小蓬中成功分离编码金属硫蛋白( Metal-lothionein,MT)的cDNA序列,命名为NeMT2,在GenBank中登录号为KT835290。该基因全长590 bp,开放阅读框为237 bp,编码78个氨基酸,编码的氨基酸序列中含有14个半胱氨酸残基( Cys,C),呈C-C,C-X-C,C-X-X-C排列,集中分布在肽链的N端和C端,基因编码蛋白的分子量为7.6036 kD,等电点为4.71。系统发育分析表明,小蓬金属硫蛋白NeMT2与藜科的海蓬子( AEF01492)和盐穗木( AHI62953)同源性最高,其次是甜菜( XP 010667708.1)。生物信息学分析表明,金属硫蛋白NeMT2无信号肽结构,属于非跨膜亲水性蛋白;疏水性分析表明,NeMT2蛋白的35~45个氨基酸之间有较强的疏水性,其中第41位Asp具最强的疏水性(1.444);结构预测分析该蛋白质二级结构的主要元件是无规则卷曲。通过RT-PCR对NeMT2基因的表达分析发现, NeMT2基因在铜矿区和非铜矿区的小蓬叶片中均有表达,但该基因在铜矿区小蓬叶片的表达量明显高于非铜矿区。将小蓬NeMT2基因定向克隆到植物表达载体pCAMBIA1300的35S 启动子下游,构建该基因的植物超表达载体pCAMBIA1300＋NeMT2。该研究结果为进一步研究该基因的功能和小蓬响应重金属胁迫的分子机制提供了一定基础。     

Effects of weather conditions on selected airborne fungal spores in the southern part of the state of Enugu,Nigeria

A study of airborne fungal spore was carried out at nine locations in the southern part of the state of Enugu, Nigeria, from March 2005 to February 2006. The aim of the study was to ascertain the variations in selected fungal spore types at the sites owing to weather conditions. The variation in airborne fungal spores of 14 taxa was studied using modified Tauber pollen traps including Alternaria, Corynespora, Curvularia, Drechslera type, Endophragmiella, Botryodiplodia, Ganoderma, Gliomastrix, Nigrospora, Pithomyces, Spegazzinia, Sporidesmium, Tetraploa and Ustilago. The frequency of the spore types recorded showed considerable variation. The highest spore counts were recorded in July, June and October. The highest numbers of fungal spores were recorded during the rainy season (June–October) to early dry season (November–December). The peak of occurrence of most selected fungal spore types was July. The highest percentages of fungal spores were documented at the recording stations Mgbowo Junction, UNTH Ituku Ozalla and Oji River Express Junction. Spearman’s correlation analyses were performed for the monthly amounts of the fungal spore types and monthly meteorological factors. The numbers of Curvularia, Nigrospora and Sporidesmium was significantly correlated with relative humidity, while those of Endophragmiella, Pithomyces and Nigrospora were significantly correlated with temperature. A significant correlation was also found between the number of Nigrospora spores and light intensity and Sporidesmium spores and wind velocity. Relative humidity and temperature seem to be the most important weather conditions affecting the frequency of the selected spore types in the atmosphere.     

Degradative pathway of p-aminoazobenzene by Bacillus subtilis

Summary p-Aminoazobenzene was degraded by Bacillus subtilis to aniline and p-phenylenediamine by reductive fission of an azo bond. The aniline was then acetylated to acetanilide while the p-phenylenediamine underwent 2 successive acetylations to yield p-aminoacetanilide and p-phenylenediacetanilide. In addition, another pathway was found in Bacillus subtilis in which p-aminoazobenzene was metabolised to p-acetamidoazobenzene.     

幽门螺杆菌黏附素保守区蛋白的免疫原性、安全性和黏附作用的体外评价

探讨幽门螺杆菌（Hp）保守区（AB）蛋白的体外安全性、免疫原性和黏附作用,以确定AB在Hp疫苗研制中的应用价值.ELISA法测定Hp感染者血清中抗AB抗体,四唑盐比色法（MTT）测定T细胞对AB的增殖反应,流式细胞术检测AB致T细胞表达FasL的作用,二苯胺（DPA）法测定AB致T细胞凋亡率,光镜计数法研究AB抗体对Hp与胃癌细胞黏附的影响.ELISA法共检测了55份血清,以快速尿素酶实验(RUT)作为平行对照,两法的评价判断一致性程度的指标卡帕系数为0.76. 同时,低剂量AB即可刺激Hp⁺T细胞的增殖.体外安全性实验表明,AB无明显调节T细胞表达FasL的作用以及无明显致Hp^－T细胞凋亡的作用. AB抗血清能部分阻断Hp与胃癌细胞系的黏附,在光镜下表现为经抗AB兔血清预处理后,每细胞周围黏附的细菌数较免疫前兔血清预处理组显著减少（P＜0.05）.研究表明AB是安全的、具有免疫原性的Hp菌体成分,既可以刺激体液免疫,又能够提高细胞免疫,并且其抗体还可防止Hp与胃上皮细胞的黏附.     

加勒比松种源苗期DNA甲基化多样性分析

为了解加勒比松(Pinus caribaea)种源的遗传多样性,利用甲基化敏感扩增多态性技术对加勒比松3个变种17个种源的DNA甲基化多样性进行了研究。结果表明,56对引物组合共扩增出425条谱带,其中多态性谱带422条,多态性百分率为99.25%。加勒比松种源幼苗半甲基化比率比全甲基化比率稍高,洪都拉斯加勒比松、古巴加勒比松和巴哈马加勒比松的DNA甲基化率分别为22.39%、22.29%和22.35%,差异不显著。加勒比松的DNA序列遗传多样性(H=0.4376)高于DNA甲基化多样性(H=0.3274),Mantel检验表明,基因组遗传变异与表观遗传变异不存在相关性(r=-0.171,P=0.16)。表观聚类与遗传聚类间存在较大差异,两种聚类分析结果均未将3个加勒比松变种分开。这表明加勒比松变种间的表观遗传变异极为丰富,能为加勒比松遗传改良提供优良种质资源。     

Direct observation of toxic effects of cyanobacterial extracellular products on Daphnia

The filtrate from a suspension of the cyanobacterium Anabaena minutissima var. attenuata depressed thoracic limb beat frequency of Daphnia carinata by 38–45% in a food-free medium. Repeated exposure to the filtrate produced a similar depression of activity with full or neary full recovery. Response time to the filtrate was 5–8 min and recovery time was 8–12 min. The dose effect on limb beat frequency was continuous, linear, correlated with increased concentration and with no threshold. There was no relationship between body length and limb beat frequency.The interaction between toxicity and food concentration was tested using the diatom Cyclotella suspended in Anabaena filtrate. Daphnia limb beat frequency was depressed by 62%.