Geomicrobiology of deep-sea deposits: estimating community diversity from low-temperature seafloor rocks and minerals

The role of deep‐sea microbial communities in the weathering of hydrothermal vent deposits is assessed using mineralogical and molecular biological techniques. The phylogenetic diversity of varied deep‐sea bare rock habitats associated with the oceanic spreading centre at the Juan de Fuca Ridge was accessed using restriction fragment length polymorphism (RFLP) and rDNA sequencing. The mineralogical composition of the deposits used for phylogenetic analysis was determined by X‐ray diffraction in order to determine the proportion and composition of sulphide minerals, and to determine degree of alteration associated with each sample. RFLP analyses resulted in 15 unique patterns, or Operational Taxonomic Units (OTUs). Most environments examined were dominated by only one or two OTUs, which often comprised approximately 60% of the rDNA clones generated from that environment. Only one environment, the Mound, had a representative rDNA clone from every OTU identified in this study. For one other environment, ODP sediments, rDNA clones were all contained in a single OTU. The diversity of the microbial community is found to decrease with decreasing reactivity of the sulphide component in the samples and with increasing presence of alteration products. Phylogenetic analyses reveal that OTUs contain representatives of the epsilon‐, beta‐ and gamma‐subdivisions of the Proteobacteria. OTU1, which dominates clone libraries from every environment and is increasingly dominant with increasing rock alteration, is closely related to a group of chemolithoautotrophic iron‐oxidizing bacteria that have been recently isolated from the deep sea. The apparent abundance and widespread distribution within the samples examined of the putative iron‐oxidizing bacteria that may be represented by OTU1 suggests that this physiological group could play an important role in rock‐weathering and carbon fixation at the seafloor.     

Functional genes based analysis of sulfur-oxidizing bacteria community in sulfide removing bioreactor

Sulfur-oxidizing bacteria (SOB) are the main microorganisms that participate in the bioremediation of sulfide-rich wastewater. To reveal the SOB community structure and determine which members of SOB contribute to the sulfide oxidation in a sulfide-rich cloth printing and dyeing wastewater treatment plant, specific primer pairs dsrA 625F/877R, soxB 704F/1199R, and sqr 473F/982R based on the SOB functional genes encoding dissimilatory sulfite reductase, sulfate thioesterase/thiohydrolase, and sulfide: quinone oxidoreductase were designed. The restriction fragment length polymorphism analysis showed that the diversity indices and the abundance of each OTU have no significant changes after time, which suggested the SOB community in the sulfide removing bioreactor have high steady phylogenetic analysis of functional gene-based clone libraries detected the SOB from Chlorobia, α-proteobacteria, β-proteobacteria, and γ-proteobacteria. The combined clone library showed the presence of dominant members of the SOB species closely related to families Halothiobacillaceae (17%), Hydrogenophilaceae (14%), and Rhodocyclaceae (13%), which may contribute to the sulfide oxidation in wastewater treatment process. This work provides a precise understanding of SOB microbial community within sulfide removing bioreactor, and the result gives assistance for the optimization of the treatment systems for sulfide biological degradation.     

Microbial diversity and biogeochemistry of the Guaymas Basin deep‐sea hydrothermal plume

Hydrothermal plumes are hot spots of microbial biogeochemistry in the deep ocean, yet little is known about the diversity or ecology of microorganisms inhabiting plumes. Recent biogeochemical evidence shows that Mn(II) oxidation in the Guaymas Basin (GB) hydrothermal plume is microbially mediated and suggests that the plume microbial community is distinct from deep‐sea communities. Here we use a molecular approach to compare microbial diversity in the GB plume and in background deep seawater communities, and cultivation to identify Mn(II)‐oxidizing bacteria from plumes and sediments. Despite dramatic differences in Mn(II) oxidation rates between plumes and background seawater, microbial diversity and membership were remarkably similar. All bacterial clone libraries were dominated by Gammaproteobacteria and archaeal clone libraries were dominated by Crenarchaeota. Two lineages, both phylogenetically related to methanotrophs and/or methylotrophs, were consistently over‐represented in the plume. Eight Mn(II)‐oxidizing bacteria were isolated, but none of these or previously identified Mn(II) oxidizers were abundant in clone libraries. Taken together with Mn(II) oxidation rates measured in laboratory cultures and in the field, these results suggest that Mn(II) oxidation in the GB hydrothermal plume is mediated by genome‐level dynamics (gene content and/or expression) of microorganisms that are indigenous and abundant in the deep sea but have yet to be unidentified as Mn(II) oxidizers.     

Natural occurrence of microbial sulphur oxidation by long-range electron transport in the seafloor

Recently, a novel mode of sulphur oxidation was described in marine sediments, in which sulphide oxidation in deeper anoxic layers was electrically coupled to oxygen reduction at the sediment surface. Subsequent experimental evidence identified that long filamentous bacteria belonging to the family Desulfobulbaceae likely mediated the electron transport across the centimetre-scale distances. Such long-range electron transfer challenges some long-held views in microbial ecology and could have profound implications for sulphur cycling in marine sediments. But, so far, this process of electrogenic sulphur oxidation has been documented only in laboratory experiments and so its imprint on the seafloor remains unknown. Here we show that the geochemical signature of electrogenic sulphur oxidation occurs in a variety of coastal sediment environments, including a salt marsh, a seasonally hypoxic basin, and a subtidal coastal mud plain. In all cases, electrogenic sulphur oxidation was detected together with an abundance of Desulfobulbaceae filaments. Complementary laboratory experiments in intertidal sands demonstrated that mechanical disturbance by bioturbating fauna destroys the electrogenic sulphur oxidation signal. A survey of published geochemical data and 16S rRNA gene sequences identified that electrogenic sulphide oxidation is likely present in a variety of marine sediments with high sulphide generation and restricted bioturbation, such as mangrove swamps, aquaculture areas, seasonally hypoxic basins, cold sulphide seeps and possibly hydrothermal vent environments. This study shows for the first time that electrogenic sulphur oxidation occurs in a wide range of marine sediments and that bioturbation may exert a dominant control on its natural distribution.     

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.     

Candidatus "Scalindua brodae", sp. nov., Candidatus "Scalindua wagneri", sp. nov., two new species of anaerobic ammonium oxidizing bacteria

Anaerobic ammonium oxidation (anammox) is both a promising process in wastewater treatment and a long overlooked microbial physiology that can contribute significantly to biological nitrogen cycling in the world's oceans. Anammox is mediated by a monophyletic group of bacteria that branches deeply in the Planctomycetales. Here we describe a new genus and species of anaerobic ammonium oxidizing planctomycetes, discovered in a wastewater treatment plant (wwtp) treating landfill leachate in Pitsea, UK. The biomass from this wwtp showed high anammox activity (5.0 +/- 0.5 nmol/mg protein/min) and produced hydrazine from hydroxylamine, one of the unique features of anammox bacteria. Eight new planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass. Four of these were affiliated to known anammox 16S rRNA gene sequences, but branched much closer to the root of the planctomycete line of descent. Fluorescence in situ hybridization (FISH) with oligonucleotide probes specific for these new sequences showed that two species (belonging to the same genus) together made up > 99% of the planctomycete population which constituted 20% of the total microbial community. The identification of these organisms as typical anammox bacteria was confirmed with electron microscopy and lipid analysis. The new species, provisionally named Candidatus "Scalindua brodae" and "Scalindua wagneri" considerably extend the biodiversity of the anammox lineage on the 16S rRNA gene level, but otherwise resemble known anammox bacteria. Simultaneously, another new species of the same genus, Candidatus "Scalindua sorokinii", was detected in the water column of the Black Sea, making this genus the most widespread of all anammox bacteria described so far.     

Sulphur‐oxidizing and sulphate‐reducing communities in Brazilian mangrove sediments

Mangrove soils are anaerobic environments rich in sulphate and organic matter. Although the sulphur cycle is one of the major actors in this ecosystem, little is known regarding the sulphur bacteria communities in mangrove soils. We investigated the abundance, composition and diversity of sulphur‐oxidizing (SOB) and sulphate‐reducing (SRB) bacteria in sediments from three Brazilian mangrove communities: two contaminated, one with oil (OilMgv) and one with urban waste and sludge (AntMgv), and one pristine (PrsMgv). The community structures were assessed using quantitative real‐time polymerase chain reaction (qPCR), polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) and clone libraries, using genes for the enzymes adenosine‐5′‐phosphosulphate reductase (aprA) and sulphite reductase (Dsr) (dsrB). The abundance for qPCR showed the ratio dsrB/aprA to be variable among mangroves and higher according to the gradient observed for oil contamination in the OilMgv. The PCR‐DGGE patterns analysed by Nonmetric Multidimensional Scaling revealed differences among the structures of the three mangrove communities. The clone libraries showed that Betaproteobacteria, Gammaproteobacteria and Deltaproteobacteria were the most abundant groups associated with sulphur cycling in mangrove sediments. We conclude that the microbial SOB and SRB communities in mangrove soils are different in each mangrove forest and that such microbial communities could possibly be used as a proxy for contamination in mangrove forests.     

Community composition of marine bacterioplankton determined by 16S rRNA gene clone libraries and fluorescence in situ hybridization

We determined the compositions of bacterioplankton communities in surface waters of coastal California using clone libraries of 16S rRNA genes and fluorescence in situ hybridization (FISH) in order to compare the community structures inferred from these two culture-independent approaches. The compositions of two clone libraries were quite similar to those of clone libraries of marine bacterioplankton examined by previous studies. Clones from gamma-proteobacteria comprised ca. 28% of the libraries, while approximately 55% of the clones came from alpha-proteobacteria, which dominated the clone libraries. The Cytophaga-Flavobacter group and three others each comprised 10% or fewer of the clone libraries. The community composition determined by FISH differed substantially from the composition implied by the clone libraries. The Cytophaga-Flavobacter group dominated 8 of the 11 communities assayed by FISH, including the two communities assayed using clone libraries. On average only 10% of DAPI (4', 6'-diamidino-2-phenylindole)-stained bacteria were detected by FISH with a probe for alpha-proteobacteria, but 30% of DAPI-stained bacteria appeared to be in the Cytophaga-Flavobacter group as determined by FISH. alpha-Proteobacteria were greatly overrepresented in clone libraries compared to their relative abundance determined by FISH, while the Cytophaga-Flavobacter group was underrepresented in clone libraries. Our data show that the Cytophaga-Flavobacter group can be a numerically dominant component of coastal marine bacterioplankton communities.     

长庆油田延9低渗透油藏微生物群落研究

目的:研究长庆油田延9低渗透油藏微生物群落,为实施微生物提高原油采收率提供指导和依据。方法:长庆油田延9油藏三口不同油井(柳28-46、柳28-47和柳27-45)的油水样品建立16S rDNA克隆文库进行研究。结果:构建了柳28-46、柳28-47和柳27-45油井样品的微生物基因克隆文库,其分类操作单元(OUT)数分别为21、20和20个;序列分析比对表明,3口井的共同的优势微生物菌群为铜绿假单胞菌(Pseudomonas aeruginos),分别占各文库的32.8%、32%和42.9%,它是最常见最主要的采油功能菌之一。此外硫酸盐还原菌(SRB)和铁细菌也处于优势地位,它们是原油开采中的有害菌。结论:延9低渗透油藏微生物群落和其潜在功能的分析为开展微生物提高石油采收率应用提供了良好的基础资料。     

Phylogenetic analysis of a microbial community involved in anaerobic oxidation of ammonium nitrogen

The phylogenetic diversity of a microbial community involved in anaerobic oxidation of ammonium nitrogen in the DEAMOX process was studied. Analysis of clone libraries containing 16S rRNA gene inserts of Bacteria, (including Planctomycetes) and Archaea revealed the presence of nucleotide sequences of the microorganisms involved in the main reactions of the carbon, nitrogen, and sulfur cycles, including nitrifying, denitrifying, and ANAMMOX bacteria. In the bacterial clone library, 16S rRNA gene sequences of representatives of the phyla Proteobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Verrucomicrobia, Lentisphaerae, Spirochaetales, and Planctomycetes, as well as of some new groups, were detected. In the archaeal clone library, nucleotide sequences of methanogens belonging to the orders Methanomicrobiales, Methanobacteriales, and Methanosarcinales were found. It is possible that both ANAMMOX bacteria and bacteria of the genus Nitrosomonas are involved in anaerobic ammonium oxidation in the DEAMOX reactor. Many sequences were similar to those from the clone libraries obtained previously from the ANAMMOX community of marine sediments. It is also probable that the DEAMOX reactions occur in natural ecosystems (in marine and freshwater sediments and the oceanic water column), thereby providing for the coupling of the nitrogen and sulfur cycles.     

Molecular characterization of subject-specific oral microflora during initial colonization of enamel

The initial microbial colonization of tooth surfaces is a repeatable and selective process, with certain bacterial species predominating in the nascent biofilm. Characterization of the initial microflora is the first step in understanding interactions among community members that shape ensuing biofilm development. Using molecular methods and a retrievable enamel chip model, we characterized the microbial diversity of early dental biofilms in three subjects. A total of 531 16S rRNA gene sequences were analyzed, and 97 distinct phylotypes were identified. Microbial community composition was shown to be statistically different among subjects. In all subjects, however, 4-h and 8-h communities were dominated by Streptococcus spp. belonging to the Streptococcus oralis/Streptococcus mitis group. Other frequently observed genera (comprising at least 5% of clone sequences in at least one of the six clone libraries) were Actinomyces, Gemella, Granulicatella, Neisseria, Prevotella, Rothia, and Veillonella. Fluorescence in situ hybridization (FISH) confirmed that the proportion of Streptococcus sp. sequences in the clone libraries coincided with the proportion of streptococcus probe-positive organisms on the chip. FISH also revealed that, in the undisturbed plaque, not only Streptococcus spp. but also the rarer Prevotella spp. were usually seen in small multigeneric clusters of cells. This study shows that the initial dental plaque community of each subject is unique in terms of diversity and composition. Repetitive and distinctive community composition within subjects suggests that the spatiotemporal interactions and ecological shifts that accompany biofilm maturation also occur in a subject-dependent manner.     

OLAND生物脱氮系统中硝化菌群16S rDNA的DGGE分析

为了考察生物脱氮系统中硝化菌群（氨氧化菌和亚硝酸氧化菌）的种群多样性及硝化菌群随溶解氧降低的种群变化规律,并建立一套行之有效的用于自养生物脱氮系统中功能微生物菌群的快速分子检测技术,采用DGGE（变性梯度凝胶电泳）分子检测技术对硝化菌群的16SrDNA的特异性PCR扩增产物进行了分析,结果表明：OLAND生物脱氮系统中氨氧化菌和亚硝酸氧化菌随溶解氧的降低表现出了不同的种群变化规律,氨氧化菌种群多样性受溶解氧的影响非常大,而非亚硝酸氧化菌的种群多样性比较单一,且不受溶解氧的影响。结合FISH（全细胞荧光原位杂交）分析结果表明,在OLAND限氧稳定运行后期,亚硝化单胞菌属（Nitrosomonas）是主要的氨氧化菌,占OLAND限氧亚硝化阶段反应器中总细菌数的72.5%左右。     

Bacterial diversity of metagenomic and PCR libraries from the Delaware River

To determine whether metagenomic libraries sample adequately the dominant bacteria in aquatic environments, we examined the phylogenetic make-up of a large insert metagenomic library constructed with bacterial DNA from the Delaware River, a polymerase chain reaction (PCR) library of 16S rRNA genes, and community structure determined by fluorescence in situ hybridization (FISH). The composition of the libraries and community structure determined by FISH differed for the major bacterial groups in the river, which included Actinobacteria, beta-proteobacteria and Cytophaga-like bacteria. Beta-proteobacteria were underrepresented in the metagenomic library compared with the PCR library and FISH, while Cytophaga-like bacteria were more abundant in the metagenomic library than in the PCR library and in the actual community according to FISH. The Delaware River libraries contained bacteria belonging to several widespread freshwater clusters, including clusters of Polynucleobacter necessarius, Rhodoferax sp. Bal47 and LD28 beta-proteobacteria, the ACK-m1 and STA2-30 clusters of Actinobacteria, and the PRD01a001B Cytophaga-like bacteria cluster. Coverage of bacteria with > 97% sequence identity was 65% and 50% for the metagenomic and PCR libraries respectively. Rarefaction analysis of replicate PCR libraries and of a library constructed with re-conditioned amplicons indicated that heteroduplex formation did not substantially impact the composition of the PCR library. This study suggests that although it may miss some bacterial groups, the metagenomic approach can sample other groups (e.g. Cytophaga-like bacteria) that are potentially underrepresented by other culture-independent approaches.     

大港孔店油田水驱油藏微生物群落的分子分析

通过多聚酶链式反应温度梯度凝胶电泳（PCRTGGE）和构建16S rRNA基因克隆文库两种方法对比研究了大港油田孔二北断块注水井和采油井的微生物群落结构。16S rDNA V3区PCR扩增产物的TGGE图谱分析表明,这两个油井的微生物群落结构差异很大。注水井样品的TGGE图谱中有6条主要条带,而采油井样品中只有一个条带占绝对优势。同时,建立了两个样品的16S rRNA基因克隆文库,从中分别挑选了108和50个克隆进行限制性酶切片段长度多样性分析（ARDRA）。注水井样品有33个操作分类单元（OUT）,其中6个OUT是优势类型;而采油井样品只有8个OUT,有1个OUT在文库中占绝对优势。克隆文库和TGGE的研究结果一致,均表明注水井样品的微生物多样性比采油井丰富很多。每个OUT的代表克隆序列分析结果表明,注水井样品中的细菌主要属于α、β、γ变形菌纲和放线菌纲,尤其是红细菌亚纲（47%）。采油井样品的细菌主要属于α、β、γ变形菌纲,尤其是假单胞菌属（62%）。油藏微生物多样性的分子分析可为开展微生物采油技术研究奠定基础。     

Identification, detection, and spatial resolution of Clostridium populations responsible for cellulose degradation in a methanogenic landfill leachate bioreactor

An anaerobic landfill leachate bioreactor was operated with crystalline cellulose and sterile landfill leachate until a steady state was reached. Cellulose hydrolysis, acidogenesis, and methanogenesis were measured. Microorganisms attached to the cellulose surfaces were hypothesized to be the cellulose hydrolyzers. 16S rRNA gene clone libraries were prepared from this attached fraction and also from the mixed fraction (biomass associated with cellulose particles and in the planktonic phase). Both clone libraries were dominated by Firmicutes phylum sequences (100% of the attached library and 90% of the mixed library), and the majority fell into one of five lineages of the clostridia. Clone group 1 (most closely related to Clostridium stercorarium), clone group 2 (most closely related to Clostridium thermocellum), and clone group 5 (most closely related to Bacteroides cellulosolvens) comprised sequences in Clostridium group III. Clone group 3 sequences were in Clostridium group XIVa (most closely related to Clostridium sp. strain XB90). Clone group 4 sequences were affiliated with a deeply branching clostridial lineage peripherally associated with Clostridium group VI. This monophyletic group comprises a new Clostridium cluster, designated cluster VIa. Specific fluorescence in situ hybridization (FISH) probes for the five groups were designed and synthesized, and it was demonstrated in FISH experiments that bacteria targeted by the probes for clone groups 1, 2, 4, and 5 were very abundant on the surfaces of the cellulose particles and likely the key cellulolytic microorganisms in the landfill bioreactor. The FISH probe for clone group 3 targeted cells in the planktonic phase, and these organisms were hypothesized to be glucose fermenters.     

Community Composition of Marine Bacterioplankton Determined by 16S rRNA Gene Clone Libraries and Fluorescence In Situ Hybridization

We determined the compositions of bacterioplankton communities in surface waters of coastal California using clone libraries of 16S rRNA genes and fluorescence in situ hybridization (FISH) in order to compare the community structures inferred from these two culture-independent approaches. The compositions of two clone libraries were quite similar to those of clone libraries of marine bacterioplankton examined by previous studies. Clones from γ-proteobacteria comprised ca. 28% of the libraries, while approximately 55% of the clones came from α-proteobacteria, which dominated the clone libraries. The Cytophaga-Flavobacter group and three others each comprised 10% or fewer of the clone libraries. The community composition determined by FISH differed substantially from the composition implied by the clone libraries. The Cytophaga-Flavobacter group dominated 8 of the 11 communities assayed by FISH, including the two communities assayed using clone libraries. On average only 10% of DAPI (4′,6′-diamidino-2-phenylindole)-stained bacteria were detected by FISH with a probe for α-proteobacteria, but 30% of DAPI-stained bacteria appeared to be in the Cytophaga-Flavobacter group as determined by FISH. α-Proteobacteria were greatly overrepresented in clone libraries compared to their relative abundance determined by FISH, while the Cytophaga-Flavobacter group was underrepresented in clone libraries. Our data show that the Cytophaga-Flavobacter group can be a numerically dominant component of coastal marine bacterioplankton communities.     

辉腾锡勒草原干涸湖泊中氨氧化微生物群落结构分析

【目的】以内蒙古辉腾锡勒草原九十九泉湿地为对象,研究湖泊干涸过程中氨氧化微生物的群落结构及其变化。【方法】通过MPN-PCR定量测定氨氧化古菌(AOA)和氨氧化细菌(AOB)的数量;构建amoA基因克隆文库,进行系统发育分析;结合土壤环境因子,探讨湿地退化过程中影响氨氧化微生物的潜在因素。【结果】依湖泊湿地退水梯度的不同样点中,有75%的样点AOB的数量高于AOA,AOB与AOA的数量比率为0.3-18.1。从湖心到湖岸草原带,AOA和AOB的数量有明显增加,但生物多样性呈降低趋势,二者没有呈现正相关。研究发现,AOB的数量与土壤中NH 4+-N的变化存在良好响应。系统发育分析显示,退化湖泊湿地AOA克隆序列均来自于泉古菌门(Crenarchaeota);AOB的amoA基因的克隆序列大部分与亚硝化单胞菌属(Nitrosomonas)有一定同源性,较少部分与亚硝化螺菌属(Nitrosospira)有一定同源性。【结论】湖泊退水过程增加了湿地土壤氨氧化微生物的数量,而氨氧化微生物的种群丰度有所降低。AOA和AOB群落对湖泊湿地的退化过程做出了响应,其中AOB的响应较为明显,氧化条件和土壤铵浓度的改变可能是促成这种响应的重要原因。     

Analysis of bacterial community structure in the natural circulation system wastewater bioreactor by using a 16S rRNA gene clone library

A variety of physical and chemical parameters are routinely monitored during operation of the Natural Circulation System, a wastewater purification bioreactor in which only natural materials and no synthetic chemicals are used. However, the microbial community structures existing in the Natural Circulation System have not been well characterized. Thus, bacterial community structure and composition in this system were studied using clone library analysis of 16S ribosomal RNA genes amplified using PCR with universal bacterial primer sets. The PCR products were then subcloned into the pGEM-T vector. Each unique restriction fragment length polymorphism pattern, created by using two pairs of restriction endonucleases, was designated as an operational taxonomic unit (OTU). The Natural Circulation System comprises five tanks, the second and third of which play a major role in the bioreactor. Clone library pro-files and principal component analysis revealed differences in the bacterial community structures of the second (anaerobic chamber) and the third (aerobic chamber) tanks. However, the beta-proteobacteria, Bacteroidetes/ Chlorobi and gamma-proteobacteria groups were dominant in both tanks. Bacterial composition was more complex in the second tank (107 OTUs) than in the third tank (68 OTUs). Of a total of 154 OTUs in the clone libraries, only 21 were common to the two tanks. The results obtained in this study should provide important information for future research into and management of the Natural Circulation System wastewater bioreactor.     

A case study for late Archean and Proterozoic biogeochemical iron‐ and sulphur cycling in a modern habitat—the Arvadi Spring

As a consequence of Earth's surface oxygenation, ocean geochemistry changed from ferruginous (iron(II)‐rich) into more complex ferro‐euxinic (iron(II)‐sulphide‐rich) conditions during the Paleoproterozoic. This transition must have had profound implications for the Proterozoic microbial community that existed within the ocean water and bottom sediment; in particular, iron‐oxidizing bacteria likely had to compete with emerging sulphur‐metabolizers. However, the nature of their coexistence and interaction remains speculative. Here, we present geochemical and microbiological data from the Arvadi Spring in the eastern Swiss Alps, a modern model habitat for ferro‐euxinic transition zones in late Archean and Proterozoic oceans during high‐oxygen intervals, which enables us to reconstruct the microbial community structure in respective settings for this geological era. The spring water is oxygen‐saturated but still contains relatively elevated concentrations of dissolved iron(II) (17.2 ± 2.8 μM) and sulphide (2.5 ± 0.2 μM) with simultaneously high concentrations of sulphate (8.3 ± 0.04 mM). Solids consisting of quartz, calcite, dolomite and iron(III) oxyhydroxide minerals as well as sulphur‐containing particles, presumably elemental S⁰, cover the spring sediment. Cultivation‐based most probable number counts revealed microaerophilic iron(II)‐oxidizers and sulphide‐oxidizers to represent the largest fraction of iron‐ and sulphur‐metabolizers in the spring, coexisting with less abundant iron(III)‐reducers, sulphate‐reducers and phototrophic and nitrate‐reducing iron(II)‐oxidizers. 16S rRNA gene 454 pyrosequencing showed sulphide‐oxidizing Thiothrix species to be the dominating genus, supporting the results from our cultivation‐based assessment. Collectively, our results suggest that anaerobic and microaerophilic iron‐ and sulphur‐metabolizers could have coexisted in oxygenated ferro‐sulphidic transition zones of late Archean and Proterozoic oceans, where they would have sustained continuous cycling of iron and sulphur compounds.