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1Introduction The ocean covering more than 70% of theearth’s surface represents a less explored environ-ment for microbial diversity(Yu etal., 2005). As agreat promising source for new natural productswhich have not been observed from terrestrial micro-o… 相似文献
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Wanze Zhu Xiaohu Cai Xingliang Liu Jinxi Wang Song Cheng Xiuyan Zhang Dengyu Li Maihe Li 《山地科学学报》2010,7(4):327-338
Little is known about whether soil microbial population dynamics are correlated with forest succession.To test the hypotheses that(1) soil microbial composition changes over successional stages,and(2) soil microbial diversity is positively correlated with plant species diversity,we determined the soil microbial populations,community composition,and microflora diversity in evergreen broad-leaved forests along a chronosequence of vegetation succession from 5 to 300 years in southwestern China.The soil microbi... 相似文献
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Excessive scum production is a widespread phenomenon in present activated sludge wastewater treatment. The question how foaming is initiated and stabilized is still unanswered. Hydrophobic wastewater ingredients and surface active material such as synthetic surfactants are discussed among others as major causative agents for scum production. Focusing on biological impacts non‐filamentous bacteria isolated from scum turned out to contribute to flotation by both cell surface hydrophobicity and emulsification activity, depending on the prevailing substrate and milieu conditions. The biological characterization of scum based on microscopic sludge investigation of conspicuous microorganisms resulted in a significant shift of filamentous and non‐filamentous organism populations with Gram‐positive bacteria prevailing in present nutrient removal plants as compared to the situation ten years ago. Their hydrophobic cell surface is supposed to support adherence and stabilization of interfaces and thus promote sludge flotation. In scum six types of filamentous bacteria turned out to be numerous: Microthrix parvicella and nocardioform actinomycetes, both of them being enriched in the scum fraction, moreover Nostocoida limicola and Eikelboom types 0041/0675, 1851, and 0092. Possible interactive mechanisms between non‐filamentous and filamentous scum bacteria and their selection factors are discussed in order to contribute to a better understanding of scum formation and to provide efficient troubleshooting measures. 相似文献
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对分离自北冰洋73°N以北海域沉积物中的一株放线菌R-527F进行分子鉴定及生物活性研究.通过对菌株的形态特征、培养性状、生理生化特征以及16S rDNA序列进行综合分析,确定该株菌为链霉菌属,暂定名为Streptomyces sp.R-527F.其含有聚酮类Ⅰ型(PKS Ⅰ)和非核糖体含硫多肽类(nonribosomal peptide synthetase,NRPS)化合物的合成基因.对其抗菌活性及活性物质发酵条件进行了研究,实验结果表明,该菌株所产生的抗菌物质对枯草芽孢杆菌具有显著抑制效果,抑菌圈直径达到18.2 mm.适合其抗菌物质的发酵条件:种子液接种量为4％,培养基初始pH为8.0,培养温度为28℃,培养时间为6d,摇床转速为180 r·min-1,装液量为40％,为该菌株抗菌物质的进一步研究奠定发酵条件参数基础. 相似文献
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Calcitic speleothems from a cave located on the north central coast of Grand Cayman commonly include corrosion surfaces that developed when calcite precipitation ceased and corrosion mediated by condensates became the operative process. Dissolution features associated with these surfaces, including etched crystal surfaces, microcavities, and solution-widened boundaries between crystals, are commonly occupied by microbes and microbial mats that have been replaced by calcium phosphate and/or coated with calcium phosphate. No mineralized microbes were found in the calcite crystals that form the speleothems. The morphology of the mineralized hyphae (eight morphotypes) and spores (nine morphotypes) are indicative of actinomycetes, a group of microbes that are ideally adapted to life in oligotrophic cave environs. Superb preservation of the delicate hyphae, aerial hyphae, and delicate ornamentation on the hyphae and spores indicate that the microbes underwent rapid mineralized while close to their original life positions. Although these actinomycetes were extremely susceptible to replacement by calcium phosphate, there is no evidence that they directly or indirectly controlled precipitation. Nevertheless, the association between the P-rich precipitates and microbes shows that the use of phosphorus as a proxy for seasonal climate changes in paleoclimate analyses must be treated with caution. 相似文献
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Tsunami, the natural disaster, which occurred on December 26, 2004 in the Indian Ocean, caused severe damage to mankind in the coastal areas. Total loss of life and economic loss because of this disaster have been estimated by various agencies but its effect on microbial density has not been probed. With our previous results on microbial populations in four locations of the Chennai coast of the Bay of Bengal, India in the pre‐tsunami period, the change in microbial populations was studied after the tsunami at regular intervals in the same locations. Coastal sediment and seawater samples were collected from four different locations after 5–10 h and thereafter at intervals of every 7 days up to 28 days post‐tsunami. Bacteria, fungi and actinomycetes were isolated from the marine samples by serial dilution on respective media. Before the tsunami, the bacterial population was higher in seawater samples than the sediments, whereas fungi and actinomycetes were recorded only in the sediments. The microbial population remarkably increased 5–10 h post‐tsunami in all the marine samples irrespective of the location. However, it slowly declined in the subsequent days and became similar to that of the population recorded before the tsunami. The population of gram‐positive bacteria increased whereas the gram‐negative bacterial population decreased after the tsunami. Further, populations of pathogenic bacteria such as coliform and vibrios did not increase after the tsunami. It has been observed that the increase in populations of bacteria and actinomycetes even after 28 days of tsunami may be due to the introduction of foreign microorganisms that developed the ability to survive in the extreme environment by exhibiting special characteristics such as pigmentation and production of exopolysaccharides. 相似文献
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