一株产木聚糖酶嗜热菌的鉴定及酶学性质

从云南腾冲热泉水样中分离筛选得到一株产木聚糖酶的菌株。通过细菌形态观察、生理生化特性并结合16S rDNA序列分析,经鉴定,该菌为地芽孢杆菌(Geobacillus sp.),命名为Geobacillus sp.PZH1。对该菌株所产嗜热木聚糖酶及酶学特性进行了初步研究。SDS-PAGE和酶谱分析测得该酶分子量约为69 kD;酶的最适反应pH和最适反应温度分别为7.0和70°C,在pH 5.0-11.0和40°C-100°C范围内均有较高酶活;该酶在pH 5.0-12.0范围内和70°C以内具有较高的稳定性;40°C-100°C范围内,该木聚糖酶没有被检测到纤维素酶活性。     

一小型温泉中降解淀粉细菌的筛选、鉴定与淀粉酶性质初步分析

为筛选耐热淀粉酶产生菌并揭示其在温泉中的分布情况,从腾冲县腊幸村一小型热泉不同部位采集样品进行微生物分离及鉴定。样品在65℃培养,挑选形态有差异的菌落点种淀粉-台盼蓝平板,共获得34株具有淀粉降解能力的细菌。分子鉴定结果显示,从温泉底部沙土中筛选得到细菌具有较高的生物多样性,9株具有淀粉降解能力的细菌分别属于土芽胞杆菌(Geobacillus)、厌氧芽胞杆菌(Anoxybacillus)和芽胞杆菌(Bacillus)3个属、7个种,菌株间16S rDNA序列均有一定的差异。对编号为201(Geobacillus thermoglucosidasius)和208(Anoxybacillus flavithermus)的菌株胞外淀粉酶进行初步分析,其胞外淀粉酶最适温度分别为60和70℃,均高于淀粉糊化温度,具有一定的应用潜力。     

一株耐高温细菌CHB1的分离和产酶特性研究

从土壤中分离到1株耐高温细菌CHB1,经鉴定为嗜热脂肪土芽胞杆菌(Geobacillus stearothermophilus)。通过平板透明圈法研究其产酶特性,结果表明CHB1具有蛋白酶、淀粉酶和纤维素酶活性,产酶最适温度均为60℃;最佳产酶时间因酶的种类而不同,淀粉酶为24 h,蛋白酶和纤维素酶为48 h。培养基厚度对产酶有一定的影响,以每皿20~25 mL为宜。     

粘细菌资源挖掘与多相分类研究进展

粘细菌(Myxobacteria)是一类具有复杂多细胞行为、能够广泛捕食各类细菌和真菌并能产生丰富次级代谢产物的药源微生物,具有重要研究和应用价值。然而,由于资源挖掘困难,多相分类研究进展缓慢,严重阻碍了粘细菌的开发利用。本文对粘细菌的特性、分离和纯化方法、目前存在的不足及改进措施进行阐述,并对粘细菌多相分类研究进展及存在的问题进行解析。另外,结合当前技术手段和发展现状,进一步对粘细菌的未来发展趋势进行展望,以期为相关研究提供参考。     

从球衣细菌中分离提取PHB的研究

球衣细菌发酵56h,PHB含量可占菌体干重的26％,而且营养要求简单,具有潜在的应用价值。本文在球衣细菌的纯培养,生理生化特性、最适生长条件和PHB的提取方面做了初步的研究。     

粘细菌:一类重要的微生物资源

粘细菌 (Myxobacteria)是革兰氏阴性单细胞杆状细菌 ,具有有独特的生活史 ,在细胞分化发育和生物进化研究中占有重要地位。尤为重要的是粘细菌可产生丰富的次级代谢产物 ,是一类具有重要经济价值的微生物资源。本文简单地介绍了粘细菌生物学特性、分离纯化、系统分类、活性物质的研究 ,以推动粘细菌资源的全面研究、开发和利用。     

寡营养细菌及其在环境科学中的应用

寡营养细菌是生存在寡营养环境中的一类细菌,其多样性与生物量在整个生物圈组成中都具有较大的优势,因而在生物地球化学循环中发挥着重要作用.从20世纪80年代开始,寡营养细菌在自然或人为环境中的寡营养机制、对饥饿的生理反应以及在生态系统中的作用一直是微生物生态学研究的前沿领域之一,其理论价值与应用前景已受到各国微生物生态学家与环境科学家们的广泛重视.本文综述了寡营养细菌的基本概念、营养类型、生理生态特性、可能的寡营养机制、主要研究方法以及在医学细菌检测和环境重金属监测中的应用等,并指出了寡营养细菌在环境科学中的应用前景.     

粘细菌生物活性产物及其应用研究进展

粘细菌(myxobacteria)是一类具有多细胞群体行为特征的药源微生物类群。粘细菌能通过次级代谢产生大量结构新颖并具有生物活性的小分子天然产物,还能分泌种类、功能丰富多样的酶类。这些生物活性产物使粘细菌不仅具有重要的研究价值,还有广泛的应用前景。然而,资源挖掘困难、次级代谢产物得率低等制约因素的存在严重阻碍了粘细菌的研究和应用。本文主要对粘细菌的生物学特征、生物活性产物、生物合成调控及在医疗、农业和食品上的应用进行归纳总结,并结合已有成果对粘细菌研究存在的问题提出可能的对策和展望,为今后粘细菌的深入研究和资源开发利用提供参考。     

野生冬虫夏草伴生细菌群落结构及多样性分析

采用基于PCR扩增的变性梯度凝胶电泳(PCR-DGGE)技术,研究8种不同地理来源野生冬夏草中伴生细菌的群落结构,通过优势条带切胶测序分析,确定了不同来源冬虫夏草伴生优势细菌的种属信息,分析结果表明冬虫夏草中细菌群落多样性丰富,不同来源冬虫夏草的细菌多样性指数(H’)、丰度(D)和均匀度(J)均有所不同,且伴生细菌群落相似性与样品产地间的距离远近呈一定的正相关。本研究还发现了冬虫夏草样品中的4种共有细菌Flavihumibacter petaseus、Sphingomonas aestuarii、Geobacillus pallidus和Methylovirgula ligni,为进一步研究伴生细菌在冬虫夏草生长发育中所起的作用奠定了基础。     

多种微生物搭载返回式卫星的试验研究

利用我国发射的科学返回式卫星,对４ 种具有实际应用价值的真菌、１ 种细菌和３ 种动物病毒的生长及某些特性如产酶、毒力及免疫学等进行了初步研究。结果表明,从４ 株真菌所选育的变异株产酶活性都得到不同程度的提高,但生长速度有的加快,有的则变慢; １ 种动物病毒和１ 种细菌的毒力降低,并能产生较好的免疫原性。     

A polyphasic taxonomic study of thermophilic bacilli from shallow, marine vents

Eighty-seven thermophilic, aerobic, spore-forming bacteria were isolated from shallow, marine, thermal vents of the Eolian Islands (Italy) and tested for a broad spectrum of phenotypic characteristics. A numerical taxonomy study was performed on these isolates and 8 thermophilic Bacillus and Geobacillus reference strains by 89 selected features. Results from cluster analysis showed the formation of nine clusters. Most of the isolates (83%) fell into several phenetically well distinguished clusters, loosely related to Geobacillus thermodenitrificans. The remaining isolates grouped together with different reference strains. Eighteen isolates, representative of the different clusters, were selected for subsequent genotypic characterisation, including partial 16S rDNA sequence analysis of 18 strains and almost complete 16S rDNA sequences of 9 strains. Subsequent DNA/DNA reassociation studies and determination of the base composition of DNA identified seven isolates as Geobacillus thermodenitrificans, two isolates as G. thermoleovorans and one isolate as Bacillus pallidus. Four isolates represented two novel species of Bacillus. The remaining four represented novel Geobacillus species, one of which has recently been described as Bacillus vulcani DSMZ 13174 T.     

Cadmium ion biosorption by the thermophilic bacteria Geobacillus stearothermophilus and G. thermocatenulatus

This study reports surface complexation models (SCMs) for quantifying metal ion adsorption by thermophilic microorganisms. In initial cadmium ion toxicity tests, members of the genus Geobacillus displayed the highest tolerance to CdCl2 (as high as 400 to 3,200 microM). The thermophilic, gram-positive bacteria Geobacillus stearothermophilus and G. thermocatenulatus were selected for further electrophoretic mobility, potentiometric titration, and Cd2+ adsorption experiments to characterize Cd2+ complexation by functional groups within and on the cell wall. Distinct one-site SCMs described the extent of cadmium ion adsorption by both studied Geobacillus sp. strains over a range of pH values and metal/bacteria concentration ratios. The results indicate that a functional group with a deprotonation constant pK value of approximately 3.8 accounts for 66% and 80% of all titratable sites for G. thermocatenulatus and G. stearothermophilus, respectively, and is dominant in Cd2+ adsorption reactions. The results suggest a different type of functional group may be involved in cadmium biosorption for both thermophilic strains investigated here, compared to previous reports for mesophilic bacteria.     

蔗糖异构酶催化生产异麦芽酮糖研究进展

作为蔗糖的一种异构体,异麦芽酮糖具有许多独特的生理功能,例如非致龋齿性、益生元特性、适合糖尿病人使用以及对大多数细菌和酵母的抗性等,因而受到广泛关注。异麦芽酮糖主要是通过蔗糖异构酶催化蔗糖转化形成,反应中同时生成的海藻酮糖以及少量的葡萄糖和果糖,给工业生产带来困扰。简要论述异麦芽酮糖的特性、生理功能及其生产中存在的问题,重点论述蔗糖异构酶催化蔗糖转化的机理,为异麦芽酮糖在食品工业中的开发利用提供参考。     

Geobacillus jurassicus sp. nov., a new thermophilic bacterium isolated from a high-temperature petroleum reservoir, and the validation of the Geobacillus species

Four thermophilic, spore-forming bacterial strains, DS1(T), DS2, 46 and 49, were isolated from the high-temperature Dagang oilfield, located in China. The strains were identified by using the polyphasic taxonomy approach. These were aerobic, gram-positive, rod-shaped, moderately thermophilic (with an optimum growth temperature of 60-65 degrees C), chemoorganotrophic bacteria capable of growing on various sugars, carboxylic acids and crude oil. Two strains, DS1(T) and DS2, were capable of growing on individual saturated hydrocarbons. The G + C content of the DNA of strains DS1(T) and DS2 was 54.5 and 53.8 mol%, respectively. The phylogenetic analysis of the 16S rDNA of strains DS1(T) and DS2 showed that they form a separate cluster within the genus Geobacillus. The cellular fatty acids of the isolates were dominated by iso-15:0, iso-16:0 and iso-17:0 acids, which are the typical fatty acids of bacteria from the genus Geobacillus. The DNA-DNA hybridization study and the comparative analysis of the morphological and chemotaxonomic characteristics of strains DS1(T) and DS2 showed that they differ from the previously described Geobacillus species and belong to a new species, which was called Geobacillus jurassicus. DS1(T) (=VKM B2301(T), = DSM 15726(T)) is the type strain of this species. According to both DNA-DNA reassociation studies and 16S rDNA sequence analysis, two other strains, 46 and 49, were assigned to the species G. stearothermophilus. In this paper, we provide evidence that the new combinations G. stearothermophilus, G. thermoleovorans, G. kaustophilus, G. thermoglucosidasius and G. thermodenitrificans may be considered to be valid.     

The phylogenetic diversity of aerobic organotrophic bacteria from the Dagan high-temperature oil field

The distribution and species diversity of aerobic organotrophic bacteria in the Dagan high-temperature oil field (China), which is exploited via flooding, have been studied. Twenty-two strains of the most characteristic thermophilic and mesophilic aerobic organotrophic bacteria have been isolated from the oil stratum. It has been found that, in a laboratory, the mesophilic and thermophilic isolates grow in the temperature, pH, and salinity ranges characteristic of the injection well near-bottom zones or of the oil stratum, respectively, and assimilate a wide range of hydrocarbons, fatty acids, lower alcohols, and crude oil, thus exhibiting adaptation to the environment. Using comparative phylogenetic 16S rRNA analysis, the taxonomic affiliation of the isolates has been established. The aerobic microbial community includes gram-positive bacteria with a high and low G+C content of DNA, and gamma and beta subclasses of Proteobacteria. The thermophilic bacteria belong to the genera Geobacillus and Thermoactinomyces, and the mesophilic strains belong to the genera Bacillus, Micrococcus, Cellulomonas, Pseudomonas, and Acinetobacter. The microbial community of the oil stratum is dominated by known species of the genus Geobacillus (G. subterraneus, G. stearothermophilus, and G. thermoglucosidasius) and a novel species "Geobacillus jurassicus." A number of novel thermophilic oil-oxidizing bacilli have been isolated.     

In vitro evaluation of antioxidant and radioprotective properties of a novel extremophile from mud volcano: implications for management of radiation emergencies

A thermophilic bacterium, designated as RH 127, was isolated from mud volcano (Baratang Islands) of Andaman region, India (12°07'N 92°47'E/12.117°N 92.783°E) for the first time. Biochemical tests and 16S rRNA gene sequencing indicate that it belongs to the genus Geobacillus. The strain showed 98% confirmed 16S rRNA gene sequence homology with Geobacillus toebii. The bacteria was extracted in various solvent systems and three different fractions prepared. In the present study, antioxidant and radioprotective activity of extracts (INM-7860, INM-7861, and INM-7862) of bacterium G. toebii (strain RH 127) were evaluated. The fractions were evaluated for their introspective comparison of the relative antioxidant efficiency. The antioxidative activities, DPPH radical scavenging effects, hydroxyl radical scavenging effects, membrane protection, antihemolytic activity, and linoleic acid degradation efficacies were assayed. INM-7861 and INM-7862 activated NF-κB expression, as evidenced by reporter assay studies, and thereby contributed to overall radioprotective effect. INM-7862 exhibited best results. This study explicitly shows that the extracts of G. toebii have immense potential as a radiation countermeasure agent.     

Three novel halotolerant and thermophilic Geobacillus strains from shallow marine vents

During a polyphasic taxonomic analysis performed on isolates from shallow marine hydrothermal vents of Eolian Islands (Italy), three thermophilic, halotolerant bacilli, designated as strain 1bw, strain 5-2 and strain 10-1, could not be affiliated to any described species. Physiological and biochemical characteristics, membrane lipids composition, mol % G+C content, and phylogenetic relationships determined on the basis of the 16S rRNA gene sequence analysis, placed these strains within the genus Geobacillus. The three strains were only moderately related to species of Geobacillus and their relatives, members of Saccharococcus. Determination of the relatedness among each other at a higher taxonomic level by DNA-DNA reassociation experiments demonstrated the three isolates to represent three different novel Geobacillus genomospecies. The taxonomic novelty of these three marine strains was substantiated by their physiological properties and by fatty acid patterns that did not match closely those of any Geobacillus type strain. These three novel strains could be of interest to biotechnology because of their ability to produce exopolysaccharides and to adhere on polystirene, characteristics undescribed so far for other Geobacillus species. They are also able to utilise hydrocarbons such as gas oil, kerosene and mineral lubricating oil. Strain 5-2 is tolerant to zinc.     

Abiotic and Microbiotic Factors Controlling Biofilm Formation by Thermophilic Sporeformers

One of the major concerns in the production of dairy concentrates is the risk of contamination by heat-resistant spores from thermophilic bacteria. In order to acquire more insight in the composition of microbial communities occurring in the dairy concentrate industry, a bar-coded 16S amplicon sequencing analysis was carried out on milk, final products, and fouling samples taken from dairy concentrate production lines. The analysis of these samples revealed the presence of DNA from a broad range of bacterial taxa, including a majority of mesophiles and a minority of (thermophilic) spore-forming bacteria. Enrichments of fouling samples at 55°C showed the accumulation of predominantly Brevibacillus and Bacillus, whereas enrichments at 65°C led to the accumulation of Anoxybacillus and Geobacillus species. Bacterial population analysis of biofilms grown using fouling samples as an inoculum indicated that both Anoxybacillus and Geobacillus preferentially form biofilms on surfaces at air-liquid interfaces rather than on submerged surfaces. Three of the most potent biofilm-forming strains isolated from the dairy factory industrial samples, including Geobacillus thermoglucosidans, Geobacillus stearothermophilus, and Anoxybacillus flavithermus, have been characterized in detail with respect to their growth conditions and spore resistance. Strikingly, Geobacillus thermoglucosidans, which forms the most thermostable spores of these three species, is not able to grow in dairy intermediates as a pure culture but appears to be dependent for growth on other spoilage organisms present, probably as a result of their proteolytic activity. These results underscore the importance of abiotic and microbiotic factors in niche colonization in dairy factories, where the presence of thermophilic sporeformers can affect the quality of end products.     

Heterogeneous Properties of Individual Molecules of β-Galactosidase from the Thermophilic Bacteria <Emphasis Type="Italic">Geobacillus stearothermophilus</Emphasis>

Single enzyme molecule assays were performed on β-galactosidase from the thermophilic bacteria Geobacillus stearothermophilus using a capillary electrophoresis-based continuous flow assay and the substrate DDAO-β-d-galactoside. The enzyme was found to be heterogeneous with respect to catalytic rate, electrophoretic mobility and activation energy of catalysis. Catalytic rate was also found to vary over time for individual molecules at elevated temperature. Comparison with β-galactosidase from the mesophilic bacteria Escherichia coli showed that the variation in activity over time was less pronounced and the average activation energy of catalysis was lower for the Geobacillus stearothermophilus enzyme. Attempts to measure the properties of individual β-galactosidase molecules from the thermophilic bacteria Thermus thermophilus and the cold-adapted bacteria Pseudoalteromas haloplanktis using this assay were unsuccessful.