不同富集和分离培养条件下的含酚废水处理生物膜微生物群落结构与活性比较分析

采用Biolog和变性梯度凝胶电泳(DGGE)技术研究了不同苯酚浓度培养对焦化废水处理厂反硝化池生物膜样品中微生物群落结构和代谢类型的影响。DGGE结果表明, 不同浓度苯酚和不同培养方式富集培养后, 细菌16S rDNA的部分条带分布谱形发生改变, 还有部分条带只受到了苯酚浓度变化的影响; 富集培养过程中由于碳源组成相对焦化废水简单, DGGE条带所代表的优势微生物多样性有所降低。Biolog试验结果表明, 生物膜样本的细菌群落代谢能力最强; 低浓度苯酚富集后的样品能利用的底物碳源类型最丰富。对Biolog试验结果的主成分分析显示, 相同浓度苯酚富集培养后的细菌群落代谢功能多样性相似, 但从DGGE结果看出其结构组成产生了变化。富集培养使样品微生物群落的代谢功能发生改变, 低浓度的苯酚富集增加了群落中微生物的代谢类型。而不同条件获得的分离物其苯酚降解能力的初步分析也表明, 富集与分离条件对苯酚降解菌的分离能力和得到的菌株特性具有差别。     

分子生态学方法在微生物肥料质量监测中的应用

应用PCR—DGGE技术对某微生物肥料的质量进行了跟踪监测,并结合分离培养和克隆文库分析对其菌种组成进行了检测。结果表明,同一生产批次3个不同包装样品的细菌和真菌DGGE（denaturing gradient gel eleetrophoresis）图谱相似性为80％-100％,3个不同生产批次之间DGGE图谱相似性为80％-88％,表明该微生物肥料的菌种组成的稳定性较好。但分离培养和克隆文库分析结果显示样品的菌种组成与产品标签说明之间存在较大差异。对于产品标注的6种微生物组成,只有Lactobacillus属的微生物可与之对应,其他检测到的Bacillus、Monascus、Brevibacillus、Psudomonas和Penicillium属的微生物并未包括在产品说明中。研究表明用分子生态学方法可以比较客观准确的对微生物肥料质量进行评估和峪测。     

分子生态学方法在微生物肥料质量监测中的应用*

应用PCR-DGGE技术对某微生物肥料的质量进行了跟踪监测,并结合分离培养和克隆文库分析对其菌种组成进行了检测。结果表明,同一生产批次3个不同包装样品的细菌和真菌DGGE(denaturing grad ient gel electrophoresis)图谱相似性为80%~100%,3个不同生产批次之间DGGE图谱相似性为80%~88%,表明该微生物肥料的菌种组成的稳定性较好。但分离培养和克隆文库分析结果显示样品的菌种组成与产品标签说明之间存在较大差异。对于产品标注的6种微生物组成,只有Lactob     

PCR-DGGE方法分析原油储层微生物群落结构及种群多样性

使用基于 16 S r DNA的 PCR- DGGE(变性梯度凝胶电泳 )图谱分析结合条带割胶回收 DNA进行序列分析 ,对新疆克拉玛依油田一中区注水井 (12 # 9- 11)和与该注水井相应的两个采油井 (12 # 9- 9S、13# 11- 8)井口样品微生物群落的多样性进行了比较并鉴定了部分群落成员。 DGGE图谱聚类分析表明注水井与两油井微生物群落的相似性分别为 30 %和 2 0 % ,而两油井间微生物群落结构的相似性为 5 4 %。DGGE图谱中优势条带序列分析表明注水井样品和油井样品中的优势菌群为未培养的环境微生物 ,它们与数据库中 α、γ、δ、ε变形杆菌 (Proteobacteria)和拟杆菌 (Bacteroidetes)有很近的亲缘关系。 DGGE与分子克隆相结合的分子生物学方法在研究微生物提高原油采收率 (MEOR)机理 ,以及指导 MEOR在油田生产中的应用有着重要的意义     

反硝化反应器喹啉降解相关基因多样性与定量分析

【目的】本文旨在探讨喹啉驯化的反硝化反应器微生物群落中苯甲酰辅酶A还原酶基因(bcrA)和8-羟基-2(1H)喹喏酮基因的加氧酶组分(oxoO)基因的多样性与分布。【方法】根据GenBank数据库oxoO基因序列的保守区设计了oxoO基因专一性引物。扩增采用机械击打与酚-氯仿抽提相结合的方法从反应器生物膜样品中提取微生物总DNA,对oxoO基因和bcrA基因进行基因扩增,并构建oxoO和bcrA基因克隆文库。采用荧光实时定量PCR方法对反应器微生物群落中bcrA和oxoO基因进行定量分析。【结果】定量分析结果表明,在反应器运行过程中,bcrA基因数量逐渐增多,而oxoO基因数量逐渐减少。克隆文库基因序列的系统发育分析表明,bcrA基因克隆文库中部分序列与Thauera等菌株的bcrA基因的相似性为97%以上,其余序列与已知bcrA基因序列的相似性为74%-86%;oxoO基因克隆文库中部分序列与恶臭假单胞菌(Pseudomonas putida)的oxoO基因相似性为99%,而其余序列和已知的oxoO基因的序列相似性较低。【结论】喹啉驯化的反硝化反应器系统中,bcrA和oxoO基因的多样性较丰富,且具有一些新的未知的类型。bcrA和oxoO基因的数量随反应器的运行状况而发生变化,显示出其与反应器中微生物种群构成及功能之间的密切关系。这两个基因可以作为一种潜在的生物分子标记,用于监测含喹啉废水反硝化反应器的运行状态。     

鲎素抗菌肽饲喂小鼠对小鼠肠道微生物菌群的影响

目的应用PCR和DGGE技术分析饲喂鲎素对小鼠粪样细菌区系变化的影响。方法将健康21日龄清洁级KM小鼠,随机分为4个处理,分别饲喂生理盐水、合成鲎素、抗生素和益生菌。粪样细菌16SrDNA的V6-V8可变区经PCR扩增,扩增产物经DGGE电泳后再进行相似性分析。切下9条DGGE胶中特异性条带,PCR扩增,TA克隆,测序,鉴定细菌种属。结果对照组DGGE电泳条带较多,在不同时期肠道菌群相似性均较高,相似性在73.5%～76.7%;灌胃合成鲎素和益生菌悬液组,DGGE电泳条带数和对照组比略有减少,不同处理时期肠道菌群相似性在68.1%～69.4%;灌胃抗生素组,DGGE电泳条带数明显减少,不同处理时期肠道菌群相似性在51.4%～63.0%。结论断奶小鼠在灌胃鲎素和抗生素后,肠道微生物区系和对照比发生了改变,最终形成特定的微生物区系;DGGE中特异条带的鉴定表明,灌胃鲎素可以促进粪链球菌和乳酸杆菌的生长,提高数量。     

DGGE和RFLP方法分析桑粒肩天牛幼虫肠道微生物多样性

昆虫是一个复杂的微生态系统,这些微生物对宿主发育,营养物质的消化吸收和防御方面起着重要的作用。利用DGGE和RFLP指纹图谱的方法初步研究桑粒肩天牛幼虫肠道微生态系统。对肠道微生物16S rDNA V3区进行DGGE分离,得到24个不同位置的条带。DGGE图谱亦显示了肠道微生物的季节变化,夏季较冬季菌群丰富。各月DNA样品混合并扩增16S rDNA全长序列,构建16S rDNA克隆文库。用Msp I、Rsa I对文库中175个随机阳性克隆的质粒DNA进行限制性酶切。酶切图谱聚类分析结果显示175个克隆被归为60个不同的类群,这一结果显示桑粒肩天牛幼虫肠道微生物非常丰富。因此,这2种方法都能有效的反应肠道微生物多样性状况,且RFLP比DGGE具有更好的分辨率。结合使用这2种方法,初步反应了桑天牛肠道微生物多样性信息。     

喹啉降解反应器菌群内整合子检测和菌株耐药性分析

运用PCR技术及克隆文库方法,对一个实验室规模的喹啉降解反应器生物膜系统中的整合子进行了分析。结果表明,在该反硝化喹啉降解反应器的生物膜群落中,整合子携带着丰富多样的基因盒。主要为编码与抗生素耐药性相关的基因盒,如氨基糖苷类耐药基因(aadA基因等),也带有与工业废水环境发现的整合子中可能与芳香族化合物降解有关的基因(如FldF基因)。还有一些功能未知的基因。鉴于耐药性相关基因的广泛存在,对该反应器中分离的优势菌株进行了耐药性分析。结果表明,44.1%的菌株存在耐药性,29.4%的菌株有多重耐药性。它们对4种抗生素的耐药率分别为:氨苄青霉素29.4%、卡那霉素23.5%、氯霉素20.6%、链霉素23.5%。不存在抗生素选择压力环境的微生物群落中分离的群落优势菌株普遍具有抗生素耐药性,而且群落基因组的整合子中携带多种抗生素抗性基因的基因盒。这一现象还未曾见报道,其成因值得进一步研究。     

红树林土壤细菌群落16S rDNA V3片段PCR产物的DGGE分析

从土壤中抽提微生物总DNA ,直接扩增 16SrDNAV3片段 ,应用变性梯度凝胶电泳 (DGGE)和分子克隆技术分析 16SrDNAV3片段的多态性 ,发现地域因素和红树品种都是影响土壤细菌群落结构的因素。通过对杯萼海桑土壤 16SrDNAV3片段PCR产物两个DGGE条带进行分子克隆、序列测定和Blast分析 ,发现每个DGGE条带包含着许多不同的 16SrDNAV3片段 ,并且其中多数为NCBI未收录的序列。这表明DGGE和克隆技术相结合的方法是研究土壤微生物群落结构的一种可行方法。     

喹啉与吲哚驯化的反硝化反应器的微生物群落结构分析比较

[目的]本研究旨在比较分析分别以喹啉和吲哚为底物,在相同条件下驯化的两个反硝化生物反应器的微生物群落结构.[方法]采用相同的种子污泥和相同的驯化条件,经过大约6周的驯化后,两个反应器均达到稳定而高效的污染物去除能力,通过16S rDNA克隆文库技术对两个反应器的微生物群落结构进行研究.[结果]研究发现,微生物群落结构表现出很大的差异.喹啉驯化的群落中所有的OTU都属于Betaproteobacteria,而吲哚驯化的群落中Betaproteobacteria占56.3%,吲哚驯化的群落具有更高的多样性.两个群落的优势OTU也不同,喹啉驯化群落中Thauera及其它Rhodocyclaceae科的微生物占整个群落的73%,而吲哚驯化群落中优势OTU为Comamonadaceae科、Alcaligenaceae科和Rhodocyclaceae科等类型的微生物,其中Comamonadaceae科的一个OTU占整个群落的28.7%.[结论]不同的驯化底物对微生物群落的组成具有较强的选择作用.首次报道并比较了可高效降解喹啉和吲哚的反硝化生物反应器的微生物群落结构.     

Characterization of sulfate-reducing bacteria dominated surface communities during start-up of a down-flow fluidized bed reactor

An anaerobic down-flow fluidized bed reactor was inoculated with granular sludge and started-up with sulfate containing synthetic wastewater to promote the formation of a biofilm enriched in sulfate-reducing bacteria (SRB), to produce biogenic sulfide. The start-up was done in two stages operating the reactor in batch for 45 days followed by 85 days of continuous operation. Low-density polyethylene was used as support. The biofilm formation was followed up by biochemical and electron microscopy analyses and the composition of the community was examined by 16S rDNA sequence analysis. Maximum immobilized volatile solids (1.2 g IVS/L_support) were obtained after 14 days in batch regime. During the 85 days of continuous operation, the reactor removed up to 80% of chemical oxygen demand (COD), up to 28% of the supplied sulfate and acetate was present in the effluent. Sulfate-reducing activity determined in the biofilm with ethanol or lactate as substrate was 11.7 and 15.3 g COD/g IVS per day, respectively. These results suggested the immobilization of sulfate reducers that incompletely oxidize the substrate to acetate; the phylogenetic analysis of the cloned 16S rDNA gene sequences showed high identity to the genus Desulfovibrio that oxidizes the substrates incompletely. In contrast, in the granular sludge used as inoculum a considerable number of clones showed homology to Methanobacterium and just few clones were close to SRB. The starting-up approach allowed the enrichment of SRB within the diverse community developed over the polyethylene support.     

Microbial Composition and Structure of a Rotating Biological Contactor Biofilm Treating Ammonium-Rich Wastewater without Organic Carbon

High nitrogen losses were observed in a rotating biological contactor (RBC) treating ammonium-rich (up to 500 mg NH4(+)-N/L) but organic-carbon-poor leachate from a hazardous waste landfill in K?lliken, Switzerland. The composition and spatial structure of the microbial community in the biofilm on the RBC was analyzed with specific attention for the presence of aerobic ammonium and nitrite oxidizing bacteria and anaerobic ammonium oxidizers. Anaerobic ammonium oxidation (anammox) involves the oxidation of ammonium with nitrite to N2. First the diversity of the biofilm community was determined from sequencing cloned PCR-amplified 16S rDNA fragments. This revealed the presence of a number of very unusual 16S rDNA sequences, but very few sequences related to known ammonium or nitrite oxidizing bacteria. From analysis of biofilm samples by fluorescence in situ hybridization with known phylogenetic probes and by dot-blot hybridization of the same probes to total RNA purified from biofilm samples, the main groups of microorganisms constituting the biofilm were found to be ammonium-oxidizing bacteria from the Nitrosomonas europaea/eutropha group, anaerobic ammonium-oxidizing bacteria of the "Candidatus Kuenenia stuttgartiensis" type, filamentous bacteria from the phylum Bacteroidetes, and nitrite-oxidizing bacteria from the genus Nitrospira. Aerobic and anaerobic ammonium-oxidizing bacteria were present in similar amounts of around 20 to 30% of the biomass, whereas members of the CFB phylum were present at around 7%. Nitrite oxidizing bacteria were only present in relatively low amounts (less than 5% determined with fluorescence in situ hybridization). Data from 16S rRNA dot-blot and in situ hybridization were not in all cases congruent. FISH analysis of thin-sliced and fixed biofilm samples clearly showed that the aerobic nitrifiers were located at the top of the biofilm in an extremely high density and in alternating clusters. Anammox bacteria were exclusively present in the lower half of the biofilm, whereas CFB-type filamentous bacteria were present throughout the biofilm. The structure and composition of these biofilms correlated very nicely with the proposed physiological functional separations in ammonium conversion.     

Discovery and characterization of a new bacterial candidate division by an anaerobic sludge digester metagenomic approach

We have constructed a large fosmid library from a mesophilic anaerobic digester and explored its 16S rDNA diversity using a high-density filter DNA–DNA hybridization procedure. We identified a group of 16S rDNA sequences forming a new bacterial lineage named WWE3 (Waste Water of Evry 3). Only one sequence from the public databases shares a sequence identity above 80% with the WWE3 group which hence cannot be affiliated to any known or candidate prokaryotic division. Despite representing a non-negligible fraction (5% of the 16S rDNA sequences) of the bacterial population of this digester, the WWE3 bacteria could not have been retrieved using the conventional 16S rDNA amplification procedure due to their unusual 16S rDNA gene sequence. WWE3 bacteria were detected by polymerase chain reaction (PCR) in various environments (anaerobic digesters, swine lagoon slurries and freshwater biofilms) using newly designed specific PCR primer sets. Fluorescence in situ hybridization (FISH) analysis of sludge samples showed that WWE3 microorganisms are oval-shaped and located deep inside sludge flocs. Detailed phylogenetic analysis showed that WWE3 bacteria form a distinct monophyletic group deeply branching apart from all known bacterial divisions. A new bacterial candidate division status is proposed for this group.     

Molecular evidence for genus level diversity of bacteria capable of catalyzing anaerobic ammonium oxidation

Recently, a bacterium capable to oxidize ammonium anaerobically at a high rate was identified as novel member of the Planctomycetales (Strous, M., Fuersi, J. A., Kramer, E. H. M., Logemann, S., Muyzer, G., van de Pas-Schoonen, K. T., Webb, R. I., Kufnen, J. G., and Jetten, M. S. M.: Nature 400, 446-449, 1999). Here we investigated the microbial community structure of a trickling filter biofilm with a high anaerobic ammonium oxidation activity. Fluorescence in situ hybridization (FISH) with a set of nine probes designed for specific identification of the recently described anaerobic ammonium oxidizer demonstrated that only one probe hybridized to bacteria within the biofilm. For phylogenetic characterization of putative biofilm anaerobic ammonium oxidizers a full-cycle 16S rDNA approach was performed by using a Planctomycetales-specific forward primer for PCR amplification. Of the twenty-five 16S rDNA fragments (1364 bp in length) amplified from the biofilm, nine were affiliated to the Planctomycetales. Comparative analysis showed that these sequences were more than 98.9% similar to each other but only distantly related to the previously recognized anaerobic ammonium oxidizer (below 91% similarity) and all other organisms represented in public 16S rRNA databases (similarities of below 79%). The retrieved sequences and the previously recognized anaerobic ammonium oxidizer represent two well-separated groups of a deep-branching lineage within the Planctomycetales. Quantitative FISH analysis with a newly designed specific probe showed that the novel bacterium, provisionally classified as "Candidatus Kuenenia stuttgartiensis" constituted the dominant fraction of the biofilm bacteria. In situ probing revealed that ammonia-oxidizing bacteria of the beta-subclass of Proteobacteria were also present, albeit in significant smaller amounts, within the anoxic biofilm. Comparative sequence analysis of a stretch of the gene encoding ammonia-monooxygenase (amoA) demonstrated the occurrence of the DNA of at least three different populations of beta-subclass ammonia oxidizers within the biofilm.     

Thauera and Azoarcus as functionally important genera in a denitrifying quinoline-removal bioreactor as revealed by microbial community structure comparison

Structural shifts associated with functional dynamics in a bacterial community may provide clues for identifying the most valuable members in an ecosystem. A laboratory-scale denitrifying reactor was adapted from use of non-efficient seeding sludge and was utilized to degrade quinoline and remove the chemical oxygen demand. Stable removal efficiencies were achieved after an adaptation period of six weeks. Both denaturing gradient gel electrophoresis profiling of the 16S rRNA gene V3 region and comparison of the 16S rRNA gene sequence clone libraries (LIBSHUFF analysis) demonstrated that microbial communities in the denitrifying reactor and seeding sludge were significantly distinct. The percentage of the clones affiliated with the genera Thauera and Azoarcus was 74% in the denitrifying reactor and 4% in the seeding sludge. Real-time quantitative PCR also indicated that species of the genera Thauera and Azoarcus increased in abundance by about one order of magnitude during the period of adaptation. The greater abundance of Thauera and Azoarcus in association with higher efficiency after adaptation suggested that these phylotypes might play an important role for quinoline and chemical oxygen demand removal under denitrifying conditions.     

Quantification of Hyphomicrobium populations in activated sludge from an industrial wastewater treatment system as determined by 16S rRNA analysis

The bacterial community structure of the activated sludge from a 25 million-gal-per-day industrial wastewater treatment plant was investigated using rRNA analysis. 16S ribosomal DNA (rDNA) libraries were created from three sludge samples taken on different dates. Partial rRNA gene sequences were obtained for 46 rDNA clones, and nearly complete 16S rRNA sequences were obtained for 18 clones. Seventeen of these clones were members of the beta subdivision, and their sequences showed high homology to sequences of known bacterial species as well as published 16S rDNA sequences from other activated sludge sources. Sixteen clones belonged to the alpha subdivision, 7 of which showed similarity to Hyphomicrobium species. This cluster was chosen for further studies due to earlier work on Hyphomicrobium sp. strain M3 isolated from this treatment plant. A nearly full-length 16S rDNA sequence was obtained from Hyphomicrobium sp. strain M3. Phylogenetic analysis revealed that Hyphomicrobium sp. strain M3 was 99% similar to Hyphomicrobium denitrificans DSM 1869(T) in Hyphomicrobium cluster II. Three of the cloned sequences from the activated sludge samples also grouped with those of Hyphomicrobium cluster II, with a 96% sequence similarity to that of Hyphomicrobium sp. strain M3. The other four cloned sequences from the activated sludge sample were more closely related to those of the Hyphomicrobium cluster I organisms (95 to 97% similarity). Whole-cell fluorescence hybridization of microorganisms in the activated sludge with genus-specific Hyphomicrobium probe S-G-Hypho-1241-a-A-19 enhanced the visualization of Hyphomicrobium and revealed that Hyphomicrobium appears to be abundant both on the outside of flocs and within the floc structure. Dot blot hybridization of activated sludge samples from 1995 with probes designed for Hyphomicrobium cluster I and Hyphomicrobium cluster II indicated that Hyphomicrobium cluster II-positive 16S rRNA dominated over Hyphomicrobium cluster I-positive 16S rRNA by 3- to 12-fold. Hyphomicrobium 16S rRNA comprised approximately 5% of the 16S rRNA in the activated sludge.     

Microbial community analysis and performance of a phosphate-removing activated sludge

The microbial community of a phosphate-removing activated sludge was analyzed according to the extracted 16S rDNA sequences. The sludge, which accumulated 5.6% P by weight, was obtained from a sequencing batch reactor treating a fatty-acid rich wastewater containing 108 mg l(-1) total organic carbon (TOC), 14.0 mg l(-1) N and 16.2 mg l(-1) P. The reactor at 25 degrees C and pH 7.6 removed over 96% TOC and 99.9% P from the wastewater. According to the 16S rDNA analysis of the 114 clones developed, the sludge had a diverse population, mainly comprising Proteobacteria (71.0%) and the Cytophaga Flavobacterium Bacteroides group (23.7%), plus a few species of Planctomycetales (2.6%), Verrucomicrobiales (1.8%) and Firmicutes (0.9%). Of the 114 clones, 36 (31.6%) were closely affiliated with Acinetobacter. However, Acinetobacter did not accumulate phosphate judging from the images of sludge samples hybridized with an Acinetobacter-specific probe and stained with a phosphate-specific dye. The identities of the phosphate-removing bacteria remain unclear.     

Identification of anammox bacteria in a full-scale deammonification plant making use of anaerobic ammonia oxidation

The existence of anaerobic ammonia-oxidizing (anammox) bacteria was postulated in the late 1970s. Approximately 20 years later, these lithotrophic members of the nitrogen cycle were identified as deep-branching members of the planctomycetes. Recently, full-scale implementation of biological deammonification was successfully achieved in the DEMON reactor at the wastewater treatment plant in Strass, Austria. The sludge of this reactor contains red granules and brownish flocs that can be physically separated. The two fractions yielded different banding patterns in denaturing gradient gel electrophoresis of PCR products obtained with primer sets targeting the 16S rRNA genes of planctomycetes. Comparative analysis of partial sequences of almost full-length 16S rRNA gene clones obtained from the granules and flocs confirms the differences in the community composition of the two fractions. The sequences retrieved from the red granules were 93% similar to those of Candidatus Brocadia anammoxidans, a bacterium known to catalyze the anaerobic ammonia oxidation.     

Diversity of the archaeal community in 44 anaerobic digesters as determined by single strand conformation polymorphism analysis and 16S rDNA sequencing

The diversity of Archaea in anaerobic digesters was characterized by strand conformation polymorphism (SSCP) analysis and the sequencing of 16S rDNA genes. The 44 digesters sampled, located in eight different countries, treated effluents from agriculture, the food processing and petro-chemical industries, pulp and paper plant, breweries, slaughterhouses and municipal waste. All the existing processes were represented among the samples (fixed-film, fluidized bed, stirred-tank, UASB, sequential batch reactor, lagoon). Single strand conformation polymorphism analysis targeting the V3 region of 16S rDNA revealed between four to six distinct archaeal peaks per digester. The diversity of dominant Archaea in the 44 digesters was estimated as 23 different 16S rDNA sequences. Cloning of archaeal 16S rRNA genes from 11 distinct total genomic DNA, screening of clones by SSCP and the sequencing of 170 of them made it possible to characterize these SSCP peaks. All the sequences retrieved were members of the Euryarchaeaota subdomain. Furthermore, most of the sequences retrieved were very close to already known and cultivated strains or to environmental clones. The most frequent archaeal sequences were close to Methanosaeta concilii and to a 16S rDNA clone vadinDC06 located in the Methanobacterium clade (84% and 73% of digesters respectively). The other sequences were members of the Methanobacteriales and the Methanomicrobiales families. Only one sequence was far from any sequence of the database and it could be grouped with several sequences of environmental clones. Each digester harboured between two to nine archaeal sequences with only one of them corresponding to a putative acetate-utilizing species. Furthermore, the process in the digesters appeared to play a part in the distribution of archaeal diversity.     

Rarity associated with specific ecological niches in the bacterial world: the 'Synergistes' example

The 'Synergistes' group, which apparently represents an as yet unnamed division of the bacteria, was explored in 93 anaerobic environments (guts, soils, digestors, etc.). From 16S rDNA gene-targeted polymerase chain reaction (PCR) assays, this group appeared to be present in 90% of the anaerobic microbial ecosystems analysed. The phylogeny of 103 16S rDNA sequences from 30 ecosystems showed a strong link between 16S rDNA sequences and given ecosystems. 'Synergistes' 16S rDNA sequences from animal sources (termites, guinea pigs, pigs, birds, etc.) formed clustered phylogenetical groups. 'Synergistes' groups were also associated either with anaerobic digestors and soils or with thermophilic conditions. Sequences available from the DNA database were consistent with the results. These results show the wide diversity of the 'Synergistes' division as well as the specific ecological niche of each 16S rDNA sequences.