Sulfate reduction and trichloroethylene biodegradation by a marine microbial community from hydrothermal vents sediments

Sulfate reduction (SR) and trichloroethylene (TCE) biodegradation at two different temperatures (37 and 70 °C) were investigated in enrichment cultures prepared with two different samples of sediments collected from hydrothermal vents. The unadapted sediments were incubated with sulfate (4 g L⁻¹) as the electron acceptor before TCE addition to enrich them in biomass and to establish a constant sulfate reduction (SR, 87% sulfate conversion and specific H₂S concentration of 90.81 ± 8.19 mg H₂S g VSS⁻¹), afterwards TCE was added at an initial concentration of 300 ??mol L⁻¹. The best results for TCE biodegradation were obtained at 37 °C. At this temperature, SR was up to 92%, whereas TCE biodegradation reached 75% and ethane was detected as the main degradation product. Under thermophilic conditions (70 °C) TCE biodegradation reached up to approximately 60% and the SR was 30% in 30 days of incubation with the chlorinated solvent. Along with these results, the 16S rDNA analysis from samples at 37 °C showed the presence of bacteria belonging to the genera: Clostridium, Bacillus and Desulfuromonas. The overall results on TCE degradation and SR suggest that cometabolic TCE degradation is carried out by sulfate or sulfur reducers and fermentative bacteria at mesophilic conditions.     

河北承德地区两个温泉中细菌的多样性分析

通过构建16S rDNA克隆文库,对承德地区两温泉中的细菌多样性水平及系统发育关系进行了初步研究。研究表明:68°C的A11文库中阳性克隆的16S rDNA序列分属5个细菌类群,分别为Firmicutes(6.25%)、Deinococcus-Thermus(25.0%)、Gammaproteobacteria(12.5%)、Betaproteobacteria(50.0%)、Alphaproteobacteria(6.25%);而74.5°C的A12文库仅属于一个细菌类群:厚壁菌门(Firmicutes)。两温泉中细菌多样性的差异表明,温度是影响温泉中细菌多样性水平的重要因素。此外,A11文库中克隆的16S rDNA序列与许多已知的可产色素的好氧菌相似性很高,而A12文库中的细菌多数为专性厌氧或兼性厌氧型,其中厌氧芽孢杆菌属(Anoxybacillus)中的Anoxybacillus flavithermus可以作为研究泉华形成的理想材料。     

Organic sulfur removal from coal by microorganisms from extreme environments

Abstract: Microbial samples were collected from sulfurous, near neutral pH, thermal waters of Yellowstone Park. Thermophilic mixed cultures were identified that removed 90% of pyritic and sulfate sulfur and 33% of the organic sulfur from North Dakota lignite. The 30–40% organic desulfurization barrier was studied for possible inhibitors to organic sulfur removal from coal.     

Bacterial community composition in thermophilic microbial mats from five hot springs in central Tibet

Despite detailed study of selected thermophilic taxa, overall community diversity of bacteria in thermophilic mats remains relatively poorly understood. A sequence-based survey of bacterial communities from several hot spring locations in central Tibet was undertaken. Diversity and frequency of occurrence for 140 unique 16S rRNA gene phylotypes were identified in clone libraries constructed from environmental samples. A lineage-per-time plot revealed that individual locations have evolved to support relatively large numbers of phylogenetically closely related phylotypes. Application of the F _ST statistic and P test to community data was used to demonstrate that phylogenetic divergence between locations was significant, thus emphasizing the status of hot springs as isolated habitats. Among phylotypes, only the Chlorobi were ubiquitous to all mats, other phototrophs (Cyanobacteria and Chloroflexi) occurred in most but not all samples and generally accounted for a large number of recovered phylotypes. Phylogenetic analyses of phototrophic phylotypes revealed support for location-specific lineages. The alpha, beta and gamma proteobacteria were also frequently recovered phyla, suggesting they may be abundant phylotypes in mats, a hitherto unappreciated aspect of thermophilic mat biodiversity. Samples from one location indicated that where phototrophic bacteria were rare or absent due to niche disturbance, the relative frequency of proteobacterial phylotypes increased. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Bacterial reduction of hexavalent chromium

Summary Cr(VI)-reducing bacteria are widespread and Cr(VI) reduction occurs under both aerobic and anaerobic conditions. Under aerobic conditions, both NADH and endogenous cell reserves may serve as the electron donor for Cr(VI) reduction. Under anaerobic conditions, electron transport systems containing cytochromes appear to be involved in Cr(VI) reduction. High cell densities are necessary to obtain a significant rate of Cr(VI) reduction. Cr(VI) reduction by bacteria may be inhibited by Cr(VI), oxygen, heavy metals, and phenolic compounds. The optimum pH and temperature observed for Cr(VI) reduction generally coincide with the optimal growth conditions of cells. The optimum redox potential for Cr(VI) reduction has not yet been established.     

Proteinoid microspheres more stable in hot than in cold water

The occurrence of organisms of primitive appearance near submarine hydrothermal vents has indicated sea-floor conditions that are like those under which proteinoid microspheres are produced in the laboratory. Experimental examination of the question of whether some proteinoid microspheres might be stable in hot water has revealed proteinoids that are soluble in cold water but precipitate on heating. Unanswered questions are discussed.     

Anaerobic growth on elemental sulfur using dissimilar iron reduction by autotrophic Thiobacillus ferrooxidans

Abstract Anaerobic growth on elemental sulfur using dissimilar iron reduction by Thiobacillus ferrooxidans has been demonstrated. The ferric ion reducing activity (FIR) of the anaerobic cells was double that of the aerobic cells. Significant differences in inhibition of FIR by respiratory inhibitors were observed between aerobic and anaerobic cells. A higher amount of cytochrome was detected in anaerobic cells compared to aerobic cells. Absorption minima developed with the addition of ferric sulfate in the dithionite reduced cell suspension demonstrated that the ferric ion could accept electrons from the cytochrome system of this bacterium. The possibility of two different electron transport chains in ferric ion reduction is discussed.     

Spatial patterns of Aquificales in deep-sea vents along the Eastern Lau Spreading Center (SW Pacific)

The microbial diversity associated with actively venting deep-sea hydrothermal deposits is tightly connected to the geochemistry of the hydrothermal fluids. Although the dominant members of these deposits drive the structure of the microbial communities, it is less well understood whether the lower abundance groups are as closely connected to the geochemical milieu, or driven perhaps by biotic factors such as microbial community interactions. We used the natural geochemical gradients that exist in the back-arc basin, Eastern Lau Spreading Center and Valu-Fa Ridge (ELSC/VFR) in the Southwestern Pacific, to explore whether the chemolithotrophic Aquificales are influenced by geographical location, host-rock of the vent field or deposit type. Using a combination of cloning, DNA fingerprinting (DGGE) and enrichment culturing approaches, all genera of this order previously described at marine vents were detected, i.e., Desulfurobacterium, Thermovibrio, Aquifex, Hydrogenivirga, Persephonella and Hydrogenothermus. The comparison between clone libraries and DGGE showed similar patterns of distribution of different Aquificales whereas results differed for the enrichment cultures that were retrieved. However, the use of cultivation-based and -independent methods did provide complementary phylogenetic diversity overview of the Aquificales in these systems. Together, this survey revealed that the ELSC/VFR contains some of the largest diversity of Aquificales ever reported at a deep-sea vent area, that the diversity patterns are tied to the geography and geochemistry of the system, and that this geochemical diverse back-arc basin may harbor new members of the Aquificales.     

Microbiology and geochemistry of great boiling and mud hot springs in the United States Great Basin

A coordinated study of water chemistry, sediment mineralogy, and sediment microbial community was conducted on four >73°C springs in the northwestern Great Basin. Despite generally similar chemistry and mineralogy, springs with short residence time (~5–20 min) were rich in reduced chemistry, whereas springs with long residence time (>1 day) accumulated oxygen and oxidized nitrogen species. The presence of oxygen suggested that aerobic metabolisms prevail in the water and surface sediment. However, Gibbs free energy calculations using empirical chemistry data suggested that several inorganic electron donors were similarly favorable. Analysis of 298 bacterial 16S rDNAs identified 36 species-level phylotypes, 14 of which failed to affiliate with cultivated phyla. Highly represented phylotypes included Thermus, Thermotoga, a member of candidate phylum OP1, and two deeply branching Chloroflexi. The 276 archaeal 16S rDNAs represented 28 phylotypes, most of which were Crenarchaeota unrelated to the Thermoprotei. The most abundant archaeal phylotype was closely related to “Candidatus Nitrosocaldus yellowstonii”, suggesting a role for ammonia oxidation in primary production; however, few other phylotypes could be linked with energy calculations because phylotypes were either related to chemoorganotrophs or were unrelated to known organisms. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Bacterial community structure analysis of a hot spring soil by next generation sequencing of ribosomal RNA

In the present study the whole bacterial community structure of Tapovan hot spring soil located in the state of Uttarakhand, India was analysed through next generation sequencing. The hot spring soil is slightly alkaline in nature with abundance of sulphur. The spring soil was rich in various metallic and non-metallic elements required for bacterial survival. The community was found to comprise of 14 bacterial phyla with representation of members belonging to Firmicutes, Proteobacteria, Thermi, Bacteroidetes, Aquificae, Actinobacteria, chloroflexi, TM7, Fusobacteria etc. At the genus level Bacillus, Pseudomonas, Symbiobacterium, Thermus, Geobacillus, Anoxybacillus were found in abundance as compared to other genera like Flavobacterium, Ureibacillus, Clostridium, Meiothermus, Acinetobacter, Desulfotomaculum and Rheinheimera.     

Recent developments in the thermophilic microbiology of deep-sea hydrothermal vents

The diversity of thermophilic prokaryotes inhabiting deep-sea hot vents was actively studied over the last two decades. The ever growing interest is reflected in the exponentially increasing number of novel thermophilic genera described. The goal of this paper is to survey the progress in this field made in the years 2000–2005. In this period, representatives of several new taxa of hyperthermophilic archaea were obtained from deep-sea environments. Two of these isolates had phenotypic features new for this group of organisms: the presence of an outer cell membrane (the genus Ignicoccus) and the ability to grow anaerobically with acetate and ferric iron (the genus Geoglobus). Also, our knowledge on the diversity of thermophilic bacteria from deep-sea thermal environments extended significantly. The new bacterial isolates represented diverse bacterial divisions: the phylum Aquificae, the subclass Epsilonproteobacteria, the order Thermotogales, the families Thermodesulfobacteriaceae, Deferribacteraceae, and Thermaceae, and a novel bacterial phylum represented by the genus Caldithrix. Most of these isolates are obligate or facultative lithotrophs, oxidizing molecular hydrogen in the course of different types of anaerobic respiration or microaerobic growth. The existence and significant ecological role of some of new bacterial thermophilic isolates was initially established by molecular methods.     

Carrier of reduced sulfur is a possible role for thiotaurine in symbiotic species from hydrothermal vents with thiotrophic symbionts

Experiments supporting the possible role of the free sulfur-containing amino acid thiotaurine, as a transport and storage compound for sulfide in invertebrates with thiotrophic symbionts are described. The free-living chemotrophic sulfur-oxidising bacterium, Thiobacillus hydrothermalis (strain DSMZ 7121), was used as a model for the symbionts as the actual symbionts have not been obtained in culture.Thiotaurine contains two sulfur atoms, namely the inner sulfone and the outer sulfane sulfur; the latter presents a potential source of reducing equivalents for the symbiont. Nevertheless, we observed no oxidation of thiotaurine when this compound was added to a culture of T. hydrothermalis pre-grown on sulfide. In contrast, when thiotaurine was added to the culture together with an extract of the trophosome of a vestimentiferan tubeworm from the Manus basin, we observed that thiotaurine was oxidised to hypotaurine with concomitant acidification and formation of bacterial biomass. Thus, the trophosome contains an unknown catalytic factor. We suggest that thiotaurine requires reduction prior to oxidation by T. hydrothermalisand that the host may catalyse the conversion of thiotaurine through the glutathione redox couple. This way, the host can accurately control energy delivery (as reduced sulfur) to the symbionts and can therefore control their symbiont biomass.     

Bacterial and archaeal populations at two shallow hydrothermal vents off Panarea Island (Eolian Islands, Italy)

The aim of this study was to investigate the microbial community thriving at two shallow hydrothermal vents off Panarea Island (Italy). Physico-chemical characteristics of thermal waters were examined in order to establish the effect of the vents on biodiversity of both Bacteria and Archaea. Water and adjacent sediment samples were collected at different times from two vents, characterised by different depth and temperature, and analysed to evaluate total microbial abundances, sulphur-oxidising and thermophilic aerobic bacteria. Total microbial abundances were on average of the order of 10⁵ cells ml⁻¹, expressed as picoplanktonic size fraction. Picophytoplanktonic cells accounted for 0.77–3.83% of the total picoplanktonic cells. The contribution of bacterial and archaeal taxa to prokaryotic community diversity was investigated by PCR–DGGE fingerprinting method. The number of bands derived from bacterial DNA was highest in the DGGE profiles of water sample from the warmest and deepest site (site 2). In contrast, archaeal richness was highest in the water of the coldest and shallowest site (site 1). Sulphur-oxidising bacteria were detected by both culture-dependent and -independent methods. The primary production at the shallow hydrothermal system of Panarea is supported by a complex microbial community composed by phototrophs and chemolithotrophs.     

Stable sulfur isotopic distributions and sulfate reduction in lake sediments of the Adirondack Mountains,New York

Cores from five lakes of the Adirondack Mountains, New York, were analyzed for sedimentary sulfur concentrations and stable sulfur isotopic compositions. Isotopic values of total sedimentary sulfur were as much as 6 to 8 lower than isotopic values of sulfur sources (soils, tree leaves and lake water sulfate) which showed little isotopic variation in the Adirondacks. The low isotopic values of recent sediments indicate increased sulfate reduction, probably in response to increased sulfate loading and acid deposition. Detailed historical reconstruction of sulfate loading histories from sedimentary sulfur profiles is premature, however, since model calculations indicate that sulfur can be added to deeper older sediments by ongoing, contemporary sulfate reduction.     

Bacterial endosymbionts: genome reduction in a hot spot

Prokaryotic symbionts are common in invertebrates and play an essential metabolic role in deep-sea hydrothermal vent communities. Complete genome sequences of bacterial endosymbionts of two deep-sea clams are providing new insights into evolutionary genome reduction.     

Assimilation of sulfur from alkyl- and arylsulfonates by Clostridium spp.

Organisms able to utilize one of several alkyl- and arylsulfonates as sole source of sulfur under anoxic conditions were enriched. Three fermenting bacteria, all putative Clostridium spp., were isolated in pure culture. All three organisms had wide substrate ranges for alkylsulfonates, taurine and arylsulfonates, presumably due to three different enzyme systems. One organism, strain KNNDS (DSM 10612) was selected for further characterization. The organism was possibly a new Clostridium sp., with Clostidium intestinalis as its nearest neighbor (97.6% similarity of rDNA). Strain KNNDS catalyzed complete sulfonate utilization concomitant with growth. Growth yields of approximtely 3 kg protein/mol sulfur were observed, independent of the sulfur source [e.g. sulfate, sulfide, 4-(phenyl)butyl-1-sulfonate, 2,6-naphthyldisulfonate or 4-nitrocatechol sulfate]. We failed to detect significant amounts of either an arylsulfonatase or an arylsulfatase, and we hypothesize different arylsulfatases [EC 3.1.6.1] in aerobes and in Clostridium spp. Received: 15 October / Accepted: 29 November 1996     

Sulfate reduction and S-oxidation in a moorland pool sediment

In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO₄ ^2– reduction rates in the sediment, (2) depletion of SO₄ ^2– in the overlying water column and (3) release of³⁵S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO₄ ^2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core³⁵SO₄ ^2– injection. Rates of SO₄ ^2– consumption in the overlying water were estimated by changes in SO₄ ^2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m^–2 d^–1. Rates of SO₄ ^2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m^–2 d^–1 (November) to 0.43–1.81 mmol m^–2 d^–1 (July, August and April). Maximum rates of oxidation to SO₄ ^2– in July 1990 estimated by combination of SO₄ ^2– reduction rates and rates of in situ SO₄ ^2– uptake in the enclosed water column were 10.3 and 10.5 mmol m^–2 d^–1 at an organic rich and at a sandy site respectively.Experiments with³⁵S^2– and³⁵SO₄ ^2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO₄ ^2– and (2) the presence of mainly non SO₄ ^2–-S derived from reduced S transported from the sediment into the overlying water. A³⁵S^2– tracer experiment showed that about 7% of³⁵S^2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author     

Temperature-dependent enumeration and characterization of anaerobic, thermophilic xylan-degrading bacteria present in two Icelandic hot springs

Abstract Anaerobic thermophilic xylan-degrading bacteria present in unenriched and enriched 70°C samples from two Icelandic hot springs were enumerated at 68, 78, 90 and 99°C by the use of the Most-Probable-Number method. Xylan was used as substrate. From the samples taken at 70°C and incubated at the temperatures previously described no growth was observed above 78°C. A total of ten strains were isolated and characterized from the positive MPN enrichment cultures from the MPN experiments. A higher number of different strains could be isolated in the enriched samples compared with the unenriched, control samples from the same hot spring. Introduction of xylan, i.e., in situ enrichment, into one of the hot springs changed the bacterial population, as none of the bacteria isolated from the unenriched samples were isolated from the enriched samples. All the isolated bacteria were asporogenous, non-motile and gram-negative rods. One long thin rod had morphological similarities to members of the genus Dictyoglomus and was found in both hot spring samples.     

Inorganic sulfur turnover in oligohaline estuarine sediments

Inorganic sulfur turnover was examined in oligohaline (salinity < 2 g kg^-1) Chesapeake Bay sediments during the summer. Cores incubated for < 3 hr exhibited higher sulfate reduction (SR) rates (13–58 mmol m^-2 d^-1) than those incubated for 3–8 hr (3–8 mmol m^-2 d^-1). SR rates (determined with³⁵SO ₄ ^2- ) increased with depth over the top few cm to a maximum at 5 cm, just beneath the boundary between brown and black sediment. SR rates decreased below 5 cm, probably due to sulfate limitation (sulfate < 25 μM). Kinetic experiments yielded an apparent half-saturating sulfate concentration (K_s) of 34 μM, ≈ 20-fold lower than that determined for sediments from the mesohaline region of the estuary. Sulfate loss from water overlying intact cores, predicted on the basis of measured SR rates, was not observed over a 28-hr incubation period. Reduction of³⁵SO ₄ ^2- during diffusion experiments with intact core segments from 0–4 and 5–9 cm horizons was less than predicted by non-steady state diagenetic models based on³⁵SO ₄ ^2- reduction in whole core injection experiments. The results indicate that net sulfate flux into sediments was an order of magnitude lower than the gross sulfur turnover rate. Solid phase reduced inorganic sulfur concentrations were only 2–3 times less than those in sediments from the mesohaline region of the Bay, despite the fact that oligohaline bottom water sulfate concentrations were 10-fold lower. Our results demonstrate the potential for rapid SR in low salinity estuarine sediments, which are inhabited by sulfate-reducing bacteria with a high affinity for sulfate, and in which sulfide oxidation processes replenish the pore water sulfate pool on a time scale of hours.