Adaptive response of microbial communities to soluble microbial products

We carried out two experiments to study the influence of soluble microbial products (SMP) on biomass concentration [defined as mixed liquor suspended solids (MLSS)] and removal of soluble biological and chemical oxygen demands (sBOD₅ and sCOD): (1) SMP were allowed to accumulate, and (2) SMP content was artificially reduced by washing the biomass. The daily initial sCOD in both experiments was kept constant at 859±6 mg/l for 16 days. In experiment 1, the highest sCOD removal (80%) occurred during the first day. Thereafter, it decreased successively to 40% [sludge retention time (SRT), 12 days], after which it increased steadily to 50±4%. Variations in residual sCOD were accompanied by variations in sBOD₅, showing that the biodegradability of the accumulated SMP components was changing. MLSS fluctuated within the range 1,200±25–1,993±58 mg/l. We attributed the irregular accumulation of the biomass to variations in the biodegradability of SMP components. The initial sBOD₅/MLSS ratio varied according to variations in initial sBOD₅ and MLSS, whereas the residual ratio was constant at 0.025±0.008. This indicated a direct relationship between the concentrations of biomass and SMP produced. In experiment 2, MLSS increased from 1,200±25 to a constant value (2,810±16 mg/l; SRT, 12 days). After this time, no decrease or increase in MLSS was observed. Correspondingly, sCOD and sBOD₅ removal increased from 80–97 to 84–99%. A stable microbial community that could consume organic matter efficiently was developed under these conditions.     

土壤微生物生态过程与微生物功能基因多样性

土壤微生物在陆地生态系统中具有重要的生态功能,包括参与地球化学物质循环、污染物降解、环境剧烈变化的缓冲等.土壤微生物的生态功能与土壤功能联系密切,微生物群落结构与组成变化会直接影响土壤功能的发挥.土壤微生物通过具有生物活性的酶参与一系列的代谢活动,编码酶的功能基因成为微生物功能标记物.近10年中,以功能基因多样性为核心的分子生态学研究迅速发展,为从功能基因角度了解土壤微生物的生态功能提供了一个新的切入点.本文综述了与土壤微生物生态功能相关的功能基因多样性研究进展,并对该领域的发展前景提出展望.     

Significance of microbial interactions in control of microbial ecosystems

A microbial ecosystem represents a delicately balanced population of microorganisms each interacting with and influencing the other members of the population. An understanding of the nature and effects of these interactions is essential to improving the performance of these ecologies, which are important, in such diverse processes as biological waste treatment procedures, water pollution abatement, industrial fermentations, human or animal digestives processes and in soil. There are several types of mocrobial interactions, such as commensalism, inhibition, food competition, predation, parasitism, and synergism, which either singly or in combination may influence the functioning of the microbial ecology. To understand interactions, it is necessary to perform a detailed study of the physiology of the individual predominating microorganisms to establish their requirements with respect to such environmental factors as nutrients, temperature, pH, oxidation-reduction potential, removal of waste products, or toxic materials which may be involved in control processes and to determine how these factors affect their capabilities. The sum total of this information will indicate the possible interactions between the microorganisms and will form the basis for conducting experiments either in the laboratory or with mathematical models. Such experiments will lead to an understanding of microbial activities and to the formulation of control measures, often using an alteration of the environmental factors for regulation of the microbial ecologies. Extensive research remains to be done on the microbial interact inns in obtain the desired, precise control of these ecological processes.     

The influence of soluble microbial products on microbial community composition: hypothesis of microbial community succession

Soluble microbial products (SMP) are organic compounds produced by activated sludge microorganisms as they degrade substrates. They include by-products of microbial activity, death and lysis. The available literature does not reveal how SMP influence microbial community composition. In this regard, we microscopically studied changes in composition of microbial communities, especially protozoa and metazoa, under the influence of increased as well as reduced levels of SMP. The presence of SMP at high level significantly caused changes in microbial community composition. Microbial species shifted from attached ciliates (12-175 microm) to free-swimming and crawling ciliates (35-330 microm) and then invertebrates, which included rotifers (0.2-1 mm) and nematodes (1-50 mm). The shift of small-size microorganisms to large ones was observed as one of the most significant influences of SMP. Attached ciliates reappeared when we removed the SMP that had accumulated in the bioreactors - we have called this as the resurrection phenomenon of microorganisms. Such rapid changes in microbial community composition were not observed in the experiment with low concentration of SMP. Overall, the results suggest that accumulation of SMP is one of the intrinsic regulatory mechanisms that control viability and dormancy of microbial communities in activated sludge.     

微生物在成矿及矿区环境修复中的应用研究现状

随着近代微生物学与地质学研究的不断发展和深入,微生物在矿业相关领域的基础和应用研究日益受到重视。本文总结了近年来微生物及其技术在找矿、选矿、采矿等方面的应用研究进展情况,并着重对微生物在矿产的成矿以及废弃矿区的环境修复方面的研究进行了详细介绍。     

iNKT cells in microbial immunity: recognition of microbial glycolipids

Natural killer T cells expressing an invariant T cell antigen receptor (iNKT cells) are cells of the innate immune system. After recognizing glycolipid antigens presented by CD1d molecules on antigen presenting cells (APCs), iNKT cells rapidly produce large quantities of cytokines, thereby stimulating many types of cells. Recent studies have described several mechanisms of iNKT cell activation and the contribution of these cells to antimicrobial responses. iNKT cells can be activated by endogenous antigens and/or inflammatory cytokines from APCs. However, iNKT cells also recognize certain microbial glycolipids by their invariant T cell antigen receptor (TCR), and they contribute to pathogen clearance in certain microbial infections. These findings indicate that the iNKT TCR is useful for detecting certain microbial pathogens. Moreover, recent studies suggest that iNKT cell glycolipid antigens may be useful in antimicrobial therapy and vaccines.     

降解水稻秸秆的复合菌系及其微生物群落结构演替北大核心CSCD

【目的】比较和分析从堆肥中富集的水稻秸秆降解菌系F1和F2的纤维素分解能力、微生物群落结构及其在秸秆降解过程中的演替,从而探究微生物群落结构与秸秆降解效率的相关性。【方法】采用DNS(3,5-二硝基水杨酸,3,5-dinitrosalicylic acid)定糖法测定发酵液中的外切纤维素酶活;采用范氏(Van Soest)洗涤纤维分析法测定发酵前与发酵后的秸秆纤维素、半纤维素、木质素的含量,并计算降解率;采用16S r RNA基因序列分析和实时荧光定量PCR(Quantitative real-time PCR,Q-PCR)对秸秆降解过程中的微生物物种组成及特定的功能微生物进行定性和定量分析。【结果】复合菌系F1的水稻秸秆总降解率、纤维素降解率、半纤维素降解率显著高于复合菌系F2;2种复合菌系的外切纤维素酶活性与cel48基因的拷贝数变化趋势一致;复合菌系F1的物种较丰富,优势物种是好氧细菌,复合菌系F2的物种组成较单一,培养后期具有较高比例的厌氧纤维素分解菌;培养前4天,复合菌系F1和F2的优势物种均为Unclassified Bacillales和Bacillus;第4天之后,不同复合菌系的优势物种及丰度出现差异,F1的优势物种主要属于Bacteroidetes,F2的优势物种主要属于Firmicutes;虽然Petrimonas和Pusillimonas是培养后期的共有优势物种,但是Petrimonas在复合菌系F2中的相对丰度(38.30%)显著高于F1(9.47%),且培养第8天的F2中的Clostridiales OPB54增加至14.85%。【结论】cel48基因拷贝数变化与秸秆纤维素的降解效率、外切纤维素酶活性变化具有一定的相关性,cel48基因可作为潜在的生物分子标记监测秸秆纤维素的降解过程;微生物群落结构对秸秆纤维素的降解效率具有显著影响,Unclassified Bacillales,Bacillus,Petrimonas,Pusillimonas是复合菌系F1和F2降解秸秆纤维素过程中的重要物种。     

微生物多样性保护与病原微生物资源保藏

本文从微生物物种的多样性保护以及病原微生物资源的保藏等方面详细阐述了微生物资源保护与保藏的相互关系与重要性,介绍了微生物多样性保护及其研究进展和意义,病原微生物保藏的概述、资源的收集与共享,以及保藏机构相关信息。     

The microbial pan-genome

A decade after the beginning of the genomic era, the question of how genomics can describe a bacterial species has not been fully addressed. Experimental data have shown that in some species new genes are discovered even after sequencing the genomes of several strains. Mathematical modeling predicts that new genes will be discovered even after sequencing hundreds of genomes per species. Therefore, a bacterial species can be described by its pan-genome, which is composed of a "core genome" containing genes present in all strains, and a "dispensable genome" containing genes present in two or more strains and genes unique to single strains. Given that the number of unique genes is vast, the pan-genome of a bacterial species might be orders of magnitude larger than any single genome.     

Ediacaran microbial colonies

Enigmatic discoidal fossils are common in Neoproterozoic sedimentary sequences and in the stratigraphic record pre-date the first appearance of diverse Ediacaran fossil assemblages. Termed 'medusoids', these Neoproterozoic discoidal fossils have generally been interpreted as coelenterate-grade organisms implying a radially symmetrical body plan for ancestral eumetazoans. Analysis of exceptionally preserved discoidal fossils from the White Sea area, however, indicates that most of these discoidal forms represent colonial microbes. Localized pyritization, for example, reveals the presence of a conspicuous filamentous substructure in Ediacaria , whereas concentric rings, radial sectors and central structures in Cyclomedusa and Paliella compare directly with Recent microbial colonies growing in a nutritionally heterogeneous environment. At least some Ediacaran discoids can be compared with extant concentric ring-shaped microbial colonies that grow in hypersaline microbial mats. Insofar as most of the remaining record of Ediacaran discoids can be attributed to the holdfast structures of non-radiate modular organisms, there is no support from the fossil record for identifying a radiate ancestry for the Metazoa.     

Bayesian-integrated microbial forensics

In the aftermath of the 2001 anthrax letters, researchers have been exploring ways to predict the production environment of unknown-source microorganisms. Culture medium, presence of agar, culturing temperature, and drying method are just some of the broad spectrum of characteristics an investigator might like to infer. The effects of many of these factors on microorganisms are not well understood, but the complex way in which microbes interact with their environments suggests that numerous analytical techniques measuring different properties will eventually be needed for complete characterization. In this work, we present a Bayesian statistical framework for integrating disparate analytical measurements. We illustrate its application to the problem of characterizing the culture medium of Bacillus spores using three different mass spectral techniques. The results of our study suggest that integrating data in this way significantly improves the accuracy and robustness of the analyses.