Research Progress on Biofilms in Pseudomonas aeruginosa

The opportunistic pathogen Pseudomonas aeruginosa is a gram-negative bacteria which can form biofilms.In this review,we summarized the biology mechanism of biofilms in Pseudomonas aeruginosa,including Pseudomonas aeruginosa adhesion,extracellular polysaccharide Psl and Pel,alginate participated in the biofilm maturation,and quorum sensing systems regulated the formation of biofilm in Pseudomonas aeruginosa,and the drug target on biofilm.The bacterial biofilms protected the bacteria from unsuitable environmental conditions.Through researching the structure and the pathogenesis of Pseudomonas aeruginosa,and its resistance molecular mechanisms,we could adjust or regulate the expression of biofilm-associated factors,optimize the anti-infection treatment in Pseudomonas aeruginosa.     

脂多糖对细菌生物被膜形成及厚壳贻贝幼虫变态的影响

为探究脂多糖(LPS)对海洋细菌生物被膜形成、海洋贝类幼虫变态所产生的作用,本研究使用不同浓度的LPS直接刺激厚壳贻贝幼虫,观察其对幼虫附着变态的直接作用;同时在海假交替单胞菌形成生物被膜的过程中添加不同浓度的LPS,通过分析生物被膜生物学特性的变化,及变化后的生物被膜对厚壳贻贝幼虫附着变态的影响。研究结果显示,3种浓度的LPS均可直接诱导厚壳贻贝幼虫的变态;10 mg/L浓度LPS处理后的生物被膜其细菌密度、膜厚明显降低(p<0.05),胞外产物中多糖(如可乐酸)、脂类显著增加(p<0.05),同时其对幼虫变态的诱导作用也显著提高(p<0.05),因此推测,在厚壳贻贝幼虫的附着变态过程中,LPS具有直接诱导作用;除此之外,脂多糖还可以通过调控生物被膜胞外物质,特别是可乐酸的生成,从而间接影响厚壳贻贝幼虫的附着变态。     

Manging contaminated sediments

Management of contaminated sediments, i.e. linking risk assessment and problem solutions, needs both quality criteria respecting recent findings on bioavailability of pollutants and in-depth knowledge on processes controlling their particular hydrological and biogeochemical dynamics. In thefirst part of our review, new insights into ‘diagenetic’ mechanisms on particles including ageing and their effects on biological interactions were presented. These findings clearly indicate the need to refine bioavailability models including equilibrium partitioning. A set of bioassays is a powerful supplement to assess sediment quality. In thesecond part, an interdisciplinary process approach relating to the release of DOC, nutrients and pollutants into the open water is described, which has been derived from the evaluation of the international state-of-the-technology with three major themes: ‘experimental techniques’, ‘processes and properties’ and ‘development and validation of models’. Special study targets are the formation of aggregates in turbulent water, flocs and biofilms from organic reactions, and formation of new surfaces for readsorption of dissolved pollutants. Of greatest importance is the degradation of organic matter, which affects both hydrodynamic processes and geochemical redox cycles, thus providing driving forces, e.g. for metal mobilization. Models for predicting pollutant transport in rivers are still dominated by hydromechanical parameters. A first step for extending these models could involve typical milieu factors such as competing ions, complexing agents, redox conditions and pH-values. The next steps would include binding constants and other factors describing solid/solution interactions of critical chemicals in a multicomponent system. In theforthcoming issues of JSS — J Soils and Sediments, two practical fields of application will be discussed: in-situ sediment treatment — natural attenuation approach (Part III) and subaquous storage/capping of dredged material (Part IV). The abstracts of both parts can be found in the appendix.     

自然环境中的多物种生物膜:研究方法及社群相互作用

自然界中的微生物大多以多物种生物膜的形式存在,这种生命形式可以增加微生物对外界环境胁迫的耐受性。在多物种生物膜中,微生物之间的相互作用包括合作、竞争、信号分子的传递、以及水平基因转移等。研究自然环境中多物种生物膜内部微生物之间的相互作用,不仅对于理解自然生物膜的形成和演替过程具有重要意义,而且也可以为多物种生物膜在环境质量提升、微生物多样性维持等方面提供理论指导。本文主要分为两个部分:第一部分总结了环境中多物种生物膜的研究方法,包括实验室模拟体系下生物膜的构建及其分析检测技术;第二部分论述了天然多物种生物膜内细菌间的相互作用。     

不同浓度吲哚乙酸对周丛生物微生物群落代谢特性的影响

周丛生物是重要的初级生产者和分解者，在生态系统中扮演着重要角色。从碳源利用角度探讨了吲哚乙酸（indole-3-acetic acid，IAA）对周丛生物微生物群落代谢特性的影响。以人工培育的周丛生物为材料，在温室培育20 d后施加不同浓度的吲哚乙酸，使用Biology生态测试板在群落水平上对微生物碳源利用特性进行定量分析，测定平均每孔颜色变化率和多功能指数。结果表明:随着培养时间的增加，25、50、100 mg·L^-1高浓度IAA处理后，平均每孔颜色变化率显著增加，特定的碳源（如碳水化合物）利用能力发生变化，微生物功能多样性指数（Shannon指数、McIntosh指数）显著升高，说明高浓度IAA可以促进周丛生物的碳代谢活性，为探讨周丛生物的扩大培养与富集方法奠定了基础。