Effects of the detergent Tween 80 on Thermomonospora curvata

Tween 80 (0.1%, v/v) added to Thermomonospora curvata growing in minimal medium caused a transient lowering of the dry cell mass, decreased the optimal growth temperature of the thermophile from 62 to 54°C, and increased extracellular esterase activity. Cells grown in the presence of Tween 80 had decreased concentrations of branched chain fatty acids and increased concentrations of oleic acid. The detergent removed surface protuberances from mycelia and increased the liberation of enzymes active against crystalline cellulose, but did not stimulate liberation of enzymes active against carboxymethylcellulose, starch or pectin.     

Modulation of glycogen and trehalose levels in Micromonospora echinospora (ATCC 15837)

The growth of Micromonospora echinospora was studied in high and low C/N ratio medium using both batch and continuous culture. Asparagine was consumed rapidly in batch cultures where it served as both a nitrogen and carbon source. Glucose consumption was low suggesting that asparagine functions as the major carbon source under these conditions. The effect of nutrient limitation on the accumulation of storage carbohydrate in batch culture revealed an intimate association between nitrogen limitation and the accumulation of carbonaceous reserves. This study revealed that glycogen constituted the major carbohydrate reserve associated with the onset of sporulation. Intracellular trehalose levels were found to be relatively low and may have been affected by the availability of carbon. Continuous culture studies revealed a correlation between glycogen accumulation and increasing growth rate. It was also found that elevated cellular ATP levels correlated with the increase in glycogen, and reduced glycolytic activity. At the higher growth rates cellular ATP levels were elevated and coincided with reduced activity of the key glycolytic enzyme, phosphofructokinase, suggesting that glycogen can act as a convenient energy reservoir when excess carbon flux dictates.     

云南土壤放线菌生态分布的研究

云南具有极为复杂的地理气候。根据云南省不同的地质、地理、土壤、气候、植被特点选择样区,采集土壤样品,研究了云南不同地区、不同生态环境放线菌的生态分布与植被的关系。将云南土壤放线菌区系划分为热带区系、亚热带高原区系、滇西北高山区系和雪山区系四种类型。对云南土壤放线菌区系的特点进行了讨论。     

Development of a 16S rRNA gene-based prototype microarray for the detection of selected actinomycetes genera

Actinomycetes are known for their secondary metabolites, which have been successfully used as drugs in human and veterinary medicines. However, information on the distribution of this group of Gram-positive bacteria in diverse ecosystems and a comprehension of their activities in ecosystem processes are still scarce. We have developed a 16S rRNA-based taxonomic microarray that targets key actinomycetes at the genus level. In total, 113 actinomycete 16S rRNA probes, corresponding to 55 of the 202 described genera, were designed. The microarray accuracy was evaluated by comparing signal intensities with probe/target-weighted mismatch values and the Gibbs energy of the probe/target duplex formation by hybridizing 17 non-actinomycete and 29 actinomycete strains/clones with the probe set. The validation proved that the probe set was specific, with only 1.3% of false results. The incomplete coverage of actinomycetes by a genus-specific probe was caused by the limited number of 16S rRNA gene sequences in databases or insufficient 16S rRNA gene polymorphism. The microarray enabled discrimination between actinomycete communities from three forest soil samples collected at one site. Cloning and sequencing of 16S rRNA genes from one of the soil samples confirmed the microarray results. We propose that this newly constructed microarray will be a valuable tool for genus-level comparisons of actinomycete communities in various ecological conditions.     

Evaluation of Streptomyces sp. strain g10 for suppression of Fusarium wilt and rhizosphere colonization in pot-grown banana plantlets

Streptomyces sp. strain g10 exhibited strong antagonism towards Fusarium oxysporum f.sp. cubense (Foc) races 1, 2 and 4 in plate assays by producing extracellular antifungal metabolites. Treating the planting hole and roots of 4-week-old tissue-culture-derived Novaria banana plantlets with strain g10 suspension (10⁸ cfu/ml), significantly (P<0.05) reduced wilt severity when the plantlets were inoculated with 10⁴ spores/ml Foc race 4. The final disease severity index for leaf symptom (LSI) and rhizome discoloration (RDI) was reduced about 47 and 53%, respectively, in strain g10-treated plantlets compared to untreated plantlets. Reduction in disease incidence was not significant (P<0.05) when plantlets were inoculated with a higher concentration (10⁶ spores/ml) of Foc race 4. Rhizosphere population of strain g10 showed significant (P=0.05) increase of more than 2-fold at the end of the 3rd week compared to the 2nd week after soil amendment with the antagonist. Although the level dropped, the rhizosphere population at the end of the 6th week was still nearly 2-fold higher than the level detected after 2 weeks. In contrast, the root-free population declined significantly (P=0.05), nearly 4-fold after 6 weeks when compared to the level detected after 2 weeks. Neither growth-inhibiting nor growth-stimulating effects were observed in plantlets grown in strain g10-amended soil.     

一株南海红树林底泥抗真菌放线菌(No.H74-18)的化学成分研究

对我国南海红树林底泥中分离的一株放线菌(No.H74-18)的发酵菌丝体采用95%乙醇提取,并对具有抗真菌活性的乙酸乙酯部位进行研究,通过硅胶开放柱色谱分离得到了一个结晶样品。通过制备型反相高效液相色谱分离,从此结晶样品中分离纯化出3个化合物,经NMR、MS等光谱学方法分别鉴定为抗霉素A1(1)、抗霉素A2a(2)、抗霉素A3(3),这些化合物都是抗霉素类化合物。采用LC-MS联用技术分析了此结晶样品中存在的抗霉素类的可能组份。     

一株放线菌次生代谢产物化学成分的研究

目的：研究放线菌这类重要的可再生资源的次生代谢产物的化学成分。方法：通过对一株采集于云南西部土壤放线菌的发酵培养,发酵液经TLC分离纯化、高效液相分析检测、核磁共振和质谱测定。结果：从其次生代谢产物中分离获取了8个化合物,其中4个化合物的结构已经初步确定。结论：4个化合物中两个具有抗肿瘤活性,两个具有抑菌活性。     

Actinomycetous root nodules in angiosperms of Pakistan

Summary In a survey, out of the nineteen genera of non-leguminous angiosperms that are already reported to bear actinomycete-induced nitrogen-fixing root nodules from various parts of the world, the species of seven genera (Alnus, Elaeagnus, Hippophaë, Coriaria, Datisca, Rubus and Casuarina) have been located in Pakistan and checked for nodulation. All the investigated species of the these genera, except those of Rubus and some of the introduced species of Casuarina, were found to bear nodules. In all 12 species belonging to six genera of five families have been recorded to bear actinorhizal nodules in Pakistan.     

链霉菌基因组中放线菌型整合性接合元件的识别

【目的】链霉菌染色体重组和外源DNA片段插入是影响其遗传多样性的主要因素。旨在考察放线菌型整合性接合元件(AICE)在链霉菌遗传多样性中所发挥的作用。【方法】基于AICE的特征性模块, 采用隐马尔科夫模型预测链霉菌基因组序列中的AICEs。【结果】在已全测序的12条链霉菌染色体和35个质粒中, 共识别出29个AICEs, 其中12个为首次报道。Streptomyces coelicolor基因组中发现了4个AICEs, 而其近缘的Streptomyces lividans却没有。【结论】AICEs都整合在链霉菌染色体的核心区, 且都具有典型的整合环出、复制和接合转移等核心模块, 这些可自行转移的元件在链霉菌基因组可塑性中扮演了重要角色。