滇藏热泉arxA基因型厌氧砷氧化原核微生物多样性及其影响因素

【目的】探究滇藏地区热泉沉积物微生物及arxA基因的多样性及其影响因素。【方法】采用Illumina MiSeq高通量测序技术和统计学的分析方法,针对3个滇藏地热区的22个样点,进行地球化学分析及微生物多样性分析,并分析其与环境因子之间的相关性。【结果】沉积物微生物群落主要门类及其丰度占比为Chloroflexi(21.27%)、Deinococcus-Thermus(17.25%)、Aquificae(13.39%)、Proteobacteria(9.27%)、Acetothermia(8.3%)、Bacteroidetes(4.96%)与Crenarchaeota(4.57%);具有arxA基因的微生物主要门类及其丰度占比分别为Proteobacteria(64.87%)、Bipolaricaulota (9.55%)、Deinococcus-Thermus (6.42%)与Crenarchaeota (4.05%);不同地热区优势种群有所差异,主要受温度、pH值、砷浓度、总溶解固体(TDS)及海拔等因素的影响,Mantel检验呈显著相关性(P<0.001)。【结论】沉积物中...     

Microbial diversity in Tunisian geothermal springs as detected by molecular and culture-based approaches

Prokaryotic diversities of 12 geothermal hot springs located in Northern, Central and Southern Tunisia were investigated by culture-based and molecular approaches. Enrichment cultures for both aerobic and anaerobic microorganisms were successfully obtained at temperatures ranging from 50 to 75°C. Fourteen strains including four novel species were cultivated and assigned to the phyla Firmicutes (9), Thermotogae (2), Betaproteobacteria (1), Synergistetes (1) and Bacteroidetes (1). Archaeal or universal oligonucleotide primer sets were used to generate 16S rRNA gene libraries. Representative groups included Proteobacteria, Firmicutes, Deinococcus-Thermus, Thermotogae, Synergistetes, Bacteroidetes, Aquificae, Chloroflexi, candidate division OP9 in addition to other yet unclassified strains. The archaeal library showed a low diversity of clone sequences belonging to the phyla Euryarchaeota and Crenarchaeota. Furthermore, we confirmed the occurrence of sulfate reducers and methanogens by amplification and sequencing of dissimilatory sulfite reductase (dsrAB) and methyl coenzyme M reductase α-subunit (mcrA) genes. Altogether, we discuss the diverse prokaryotic communities arising from the 12 geothermal hot springs studied and relate these findings to the physico-chemical features of the hot springs.     

A Comprehensive Census of Microbial Diversity in Hot Springs of Tengchong,Yunnan Province China Using 16S rRNA Gene Pyrosequencing

The Rehai and Ruidian geothermal fields, located in Tengchong County, Yunnan Province, China, host a variety of geochemically distinct hot springs. In this study, we report a comprehensive, cultivation-independent census of microbial communities in 37 samples collected from these geothermal fields, encompassing sites ranging in temperature from 55.1 to 93.6°C, in pH from 2.5 to 9.4, and in mineralogy from silicates in Rehai to carbonates in Ruidian. Richness was low in all samples, with 21–123 species-level OTUs detected. The bacterial phylum Aquificae or archaeal phylum Crenarchaeota were dominant in Rehai samples, yet the dominant taxa within those phyla depended on temperature, pH, and geochemistry. Rehai springs with low pH (2.5–2.6), high temperature (85.1–89.1°C), and high sulfur contents favored the crenarchaeal order Sulfolobales, whereas those with low pH (2.6–4.8) and cooler temperature (55.1–64.5°C) favored the Aquificae genus Hydrogenobaculum. Rehai springs with neutral-alkaline pH (7.2–9.4) and high temperature (>80°C) with high concentrations of silica and salt ions (Na, K, and Cl) favored the Aquificae genus Hydrogenobacter and crenarchaeal orders Desulfurococcales and Thermoproteales. Desulfurococcales and Thermoproteales became predominant in springs with pH much higher than the optimum and even the maximum pH known for these orders. Ruidian water samples harbored a single Aquificae genus Hydrogenobacter, whereas microbial communities in Ruidian sediment samples were more diverse at the phylum level and distinctly different from those in Rehai and Ruidian water samples, with a higher abundance of uncultivated lineages, close relatives of the ammonia-oxidizing archaeon “Candidatus Nitrosocaldus yellowstonii”, and candidate division O1aA90 and OP1. These differences between Ruidian sediments and Rehai samples were likely caused by temperature, pH, and sediment mineralogy. The results of this study significantly expand the current understanding of the microbiology in Tengchong hot springs and provide a basis for comparison with other geothermal systems around the world.     

Linking Microbial Community Structure to S,N and Fe Biogeochemical Cycling in the Hot Springs at the Tengchong Geothermal Fields,Southwest China

Sediment and water samples collected from one acidic and three alkaline high temperature hot springs at the Tengchong terrestrial geothermal field, Southwest China, were examined using mineralogical, geochemical, and molecular biological techniques. The mineralogical and geochemical analyses suggested that these hot springs contained relatively high concentrations of S, Fe and N chemical species. Specifically, the acidic water was rich in Fe²⁺, SO₄^2? and NH₄⁺, while the alkaline waters were high in NO₃^?, H₂S and S₂O₃^?. Analyses of 16S rRNA gene sequences showed their bacterial communities were dominated by phyla Aquificae, Cyanobacteria, Deinococci-Thermus, Firmicutes, Proteobacteria, and Thermodesulfobacteria, while the archaeal clone libraries were dominated by orders Desulfurococcales, Sulfolobales, and Thermoproteales. Potential S-, N- and Fe-metabolizing prokaryotes were present at a relatively high proportion, but with large differences in the diversity and metabolic functions of each sample. These findings provide implications for uncovering microbial functions in elemental biogeochemical cycles within the Tengchong geothermal environments: i). the distinct differences in abundance and diversity of microbial communities in geothermal sediments were related to different in situ physicochemical conditions; ii). the S-, N- and Fe-related prokaryotes would take advantage of the strong chemical disequilibria in the hot springs; and iii). in return, their metabolic activities could promote the transformation of the S, Fe and N chemical species, thereby forming the basis of biogeochemical cycles in the terrestrial geothermal environments.     

Diversity and abundance of the arsenite oxidase gene aioA in geothermal areas of Tengchong, Yunnan, China

A total of 12 samples were collected from the Tengchong geothermal areas of Yunnan, China, with the goal to assess the arsenite (AsIII) oxidation potential of the extant microbial communities as inferred by the abundance and diversity of the AsIII oxidase large subunit gene aioA relative to geochemical context. Arsenic concentrations were higher (on average 251.68 μg/L) in neutral or alkaline springs than in acidic springs (on average 30.88 μg/L). aioA abundance ranged from 1.63 × 10¹ to 7.08 × 10³ per ng of DNA and positively correlated with sulfide and the ratios of arsenate (AsV):total dissolved arsenic (As_Tot). Based on qPCR estimates of bacterial and archaeal 16S rRNA gene abundance, aioA-harboring organisms comprised as much as ~15 % of the total community. Phylogenetically, the major aioA sequences (270 total) in the acidic hot springs (pH 3.3–4.4) were affiliated with Aquificales and Rhizobiales, while those in neutral or alkaline springs (pH 6.6–9.1) were inferred to be primarily bacteria related to Thermales and Burkholderiales. Interestingly, aioA abundance at one site greatly exceeded bacterial 16S rRNA gene abundance, suggesting these aioA genes were archaeal even though phylogenetically these aioA sequences were most similar to the Aquificales. In summary, this study described novel aioA sequences in geothermal features geographically far removed from those in the heavily studied Yellowstone geothermal complex.     

Distribution of ether lipids and composition of the archaeal community in terrestrial geothermal springs: impact of environmental variables

Archaea can respond to changes in the environment by altering the composition of their membrane lipids, for example, by modification of the abundance and composition of glycerol dialkyl glycerol tetraethers (GDGTs). Here, we investigated the abundance and proportions of polar GDGTs (P‐GDGTs) and core GDGTs (C‐GDGTs) sampled in different seasons from Tengchong hot springs (Yunnan, China), which encompassed a pH range of 2.5–10.1 and a temperature range of 43.7–93.6°C. The phylogenetic composition of the archaeal community (reanalysed from published work) divided the Archaea in spring sediment samples into three major groups that corresponded with spring pH: acidic, circumneutral and alkaline. Cluster analysis showed correlation between spring pH and the composition of P‐ and C‐GDGTs and archaeal 16S rRNA genes, indicating an intimate link between resident Archaea and the distribution of P‐ and C‐GDGTs in Tengchong hot springs. The distribution of GDGTs in Tengchong springs was also significantly affected by temperature; however, the relationship was weaker than with pH. Analysis of published datasets including samples from Tibet, Yellowstone and the US Great Basin hot springs revealed a similar relationship between pH and GDGT content. Specifically, low pH springs had higher concentrations of GDGTs with high numbers of cyclopentyl rings than neutral and alkaline springs, which is consistent with the predominance of high cyclopentyl ring‐characterized Sulfolobales and Thermoplasmatales present in some of the low pH springs. Our study suggests that the resident Archaea in these hot springs are acclimated if not adapted to low pH by their genetic capacity to effect the packing density of their membranes by increasing cyclopentyl rings in GDGTs at the rank of community.     

Hydrogen production potential of fermentative microorganisms from the Sargasso Sea

Mounting evidence suggests that ammonia-oxidizing archaea (AOA) may play important roles in nitrogen cycling in geothermal environments. In this study, the diversity, distribution and ecological significance of AOA in terrestrial hot springs in Kamchatka (Far East Russia) were explored using amoA genes complemented by analysis of glycerol dialkyl glycerol tetraethers (GDGTs) of archaea. PCR amplification of functional genes (amoA) from AOA and ammonia-oxidizing bacteria (AOB) was performed on microbial mats/streamers and sediments collected from three hot springs (42°C to 87°C and pH 5.5-7.0). No amoA genes of AOB were detected. The amoA genes of AOA formed three distinct phylogenetic clusters with Cluster 3 representing the majority (～59%) of OTUs. Some of the sequences from Cluster 3 were closely related to those from acidic soil environments, which is consistent with the predominance of low pH (<7.0) in these hot springs. Species richness (estimated by Chao1) was more frequently higher at temperatures below 75°C than above it, indicating that AOA may be favored in the moderately high temperature environments. Quantitative PCR of 16S rRNA genes showed that crenarchaeota counted for up to 80% of total archaea. S-LIBSHUFF separated all samples into two phylogenetic groups. The profiles of GDGTs were well separated among the studied springs, suggesting a spatial patterning of archaeal lipid biomarkers. However, this patterning did not correlate significantly with variation in archaeal amoA, suggesting that AOA are not the predominant archaeal group in these springs producing the observed GDGTs.     

Linking microbial oxidation of arsenic with detection and phylogenetic analysis of arsenite oxidase genes in diverse geothermal environments

The identification and characterization of genes involved in the microbial oxidation of arsenite will contribute to our understanding of factors controlling As cycling in natural systems. Towards this goal, we recently characterized the widespread occurrence of aerobic arsenite oxidase genes (aroA‐like) from pure‐culture bacterial isolates, soils, sediments and geothermal mats, but were unable to detect these genes in all geothermal systems where we have observed microbial arsenite oxidation. Consequently, the objectives of the current study were to measure arsenite‐oxidation rates in geochemically diverse thermal habitats in Yellowstone National Park (YNP) ranging in pH from 2.6 to 8, and to identify corresponding 16S rRNA and aroA genotypes associated with these arsenite‐oxidizing environments. Geochemical analyses, including measurement of arsenite‐oxidation rates within geothermal outflow channels, were combined with 16S rRNA gene and aroA functional gene analysis using newly designed primers to capture previously undescribed aroA‐like arsenite oxidase gene diversity. The majority of bacterial 16S rRNA gene sequences found in acidic (pH 2.6–3.6) Fe‐oxyhydroxide microbial mats were closely related to Hydrogenobaculum spp. (members of the bacterial order Aquificales), while the predominant sequences from near‐neutral (pH 6.2–8) springs were affiliated with other Aquificales including Sulfurihydrogenibium spp., Thermocrinis spp. and Hydrogenobacter spp., as well as members of the Deinococci, Thermodesulfobacteria and β‐Proteobacteria. Modified primers designed around previously characterized and newly identified aroA‐like genes successfully amplified new lineages of aroA‐like genes associated with members of the Aquificales across all geothermal systems examined. The expression of Aquificales aroA‐like genes was also confirmed in situ, and the resultant cDNA sequences were consistent with aroA genotypes identified in the same environments. The aroA sequences identified in the current study expand the phylogenetic distribution of known Mo‐pterin arsenite oxidase genes, and suggest the importance of three prominent genera of the order Aquificales in arsenite oxidation across geochemically distinct geothermal habitats ranging in pH from 2.6 to 8.     

Distribution of Arsenite-Oxidizing Bacteria and its Correlation with Temperature in Hot Springs of the Tibetan-Yunnan Geothermal Zone in Western China

The distribution of arsenite-oxidizing bacteria in response to temperature is of great importance to an understanding of biogeochemical cycling of arsenic in geothermal features. The abundance and diversity of arsenite-oxidizing bacteria were investigated in the geothermal features of Tengchong County of Yunnan Province, Dachaidan County of Qinghai Province, and Tibet. The abundance of aioA genes, which encode the large subunit of arsenite oxidase, was determined by quantitative polymerase chain reactions. The diversity of aioA genes was studied by PCR-cloning-based phylogenetic analyses. The results showed that the aioA gene abundance increased as temperature decreased, whereas its diversity at the OTU level (97% cutoff) increased with increasing temperature. This suggests that temperature played an important role in affecting aioA gene distribution and thus arsenic speciation. The aioA gene population (at OTU level) differed among the studied regions, indicating geographic isolation may be an important factor controlling aioA gene distribution in hot springs.     

Abundance and diversity of archaeal accA gene in hot springs in Yunnan Province, China

It has been suggested that archaea carrying the accA gene, encoding the alpha subunit of the acetyl CoA carboxylase, autotrophically fix CO₂ using the 3-hydroxypropionate/4-hydroxybutyrate pathway in low-temperature environments (e.g., soils, oceans). However, little new information has come to light regarding the occurrence of archaeal accA genes in high-temperature ecosystems. In this study, we investigated the abundance and diversity of archaeal accA gene in hot springs in Yunnan Province, China, using DNA- and RNA-based phylogenetic analyses and quantitative polymerase chain reaction. The results showed that archaeal accA genes were present and expressed in the investigated Yunnan hot springs with a wide range of temperatures (66–96 °C) and pH (4.3–9.0). The majority of the amplified archaeal accA gene sequences were affiliated with the ThAOA/HWCG III [thermophilic ammonia-oxidizing archaea (AOA)/hot water crenarchaeotic group III]. The archaeal accA gene abundance was very close to that of AOA amoA gene, encoding the alpha subunit of ammonia monooxygenase. These data suggest that AOA in terrestrial hot springs might acquire energy from ammonia oxidation coupled with CO₂ fixation using the 3-hydroxypropionate/4-hydroxybutyrate pathway.     

冰川生态系统固碳微生物研究进展

[目的] 海南海口含有丰富的温泉资源,对温泉微生物多样性进行研究,有助于进一步开发和利用海南温泉微生物资源。[方法] 本文采用Illumina HiSeq高通量测序技术对海口3个温泉[海甸岛荣域温泉（S1）、火山口开心农场温泉（S2）和西海岸海长流温泉（S3）] 水样中微生物ITS序列和16S rRNA基因V3-V4区进行测序及生物信息学分析,探究海口市3个不同区域的温泉真菌多样性与细菌多样性。[结果] （1）α多样性分析表明,真菌群落中,S3 > S1 > S2,而在细菌群落中,S2 > S1 > S3。β多样性分析表明,3个温泉真菌群落和细菌群落组成差异皆显著。（2）分类分析表明,温泉真菌群落优势菌门为子囊菌门（Ascomycota）和担子菌门（Basidiomycota）,细菌群落优势菌门为变形菌门（Proteobacteria）、拟杆菌门（Bacteroidetes）、Thermi、硝化螺旋菌门（Nitrospirae）、绿菌门（Chlorobi）、厚壁菌门（Firmicutes）、绿弯菌门（Chloroflexi）、放线菌门（Actinobacteria）。（3）CCA（Canonical correspondence analysis）分析表明,3个温泉的真菌群落主要影响因子是温度,细菌群落主要影响因子是总磷。[结论] 海南省海口市温泉中含有丰富的微生物资源,其微生物群落组成受多种环境因子影响,且影响真菌和细菌的主要环境因子不同。     

Archaeal and bacterial diversity in hot springs on the Tibetan Plateau, China

The diversity of archaea and bacteria was investigated in ten hot springs (elevation >4600 m above sea level) in Central and Central-Eastern Tibet using 16S rRNA gene phylogenetic analysis. The temperature and pH of these hot springs were 26-81°C and close to neutral, respectively. A total of 959 (415 and 544 for bacteria and archaea, respectively) clone sequences were obtained. Phylogenetic analysis showed that bacteria were more diverse than archaea and that these clone sequences were classified into 82 bacterial and 41 archaeal operational taxonomic units (OTUs), respectively. The retrieved bacterial clones were mainly affiliated with four known groups (i.e., Firmicutes, Proteobacteria, Cyanobacteria, Chloroflexi), which were similar to those in other neutral-pH hot springs at low elevations. In contrast, most of the archaeal clones from the Tibetan hot springs were affiliated with Thaumarchaeota, a newly proposed archaeal phylum. The dominance of Thaumarchaeota in the archaeal community of the Tibetan hot springs appears to be unique, although the exact reasons are not yet known. Statistical analysis showed that diversity indices of both archaea and bacteria were not statistically correlated with temperature, which is consistent with previous studies.     

Geochemistry and microbial ecology in alkaline hot springs of Ambitle Island,Papua New Guinea

The availability of microbiological and geochemical data from island-based and high-arsenic hydrothermal systems is limited. Here, the microbial diversity in island-based hot springs on Ambitle Island (Papua New Guinea) was investigated using culture-dependent and -independent methods. Waramung and Kapkai are alkaline springs high in sulfide and arsenic, related hydrologically to previously described hydrothermal vents in nearby Tutum Bay. Enrichments were carried out at 24 conditions with varying temperature (45, 80 °C), pH (6.5, 8.5), terminal electron acceptors (O₂, SO₄ ^2?, S⁰, NO₃ ^?), and electron donors (organic carbon, H₂, As^III). Growth was observed in 20 of 72 tubes, with media targeting heterotrophic metabolisms the most successful. 16S ribosomal RNA gene surveys of environmental samples revealed representatives in 15 bacterial phyla and 8 archaeal orders. While the Kapkai 4 bacterial clone library is primarily made up of Thermodesulfobacteria (74 %), no bacterial taxon represents a majority in the Kapkai 3 and Waramung samples (40 % Proteobacteria and 39 % Aquificae, respectively). Deinococcus/Thermus and Thermotogae are observed in all samples. The Thermococcales dominate the archaeal clone libraries (65–85 %). Thermoproteales, Desulfurococcales, and uncultured Eury- and Crenarchaeota make up the remaining archaeal taxonomic diversity. The culturing and phylogenetic results are consistent with the geochemistry of the alkaline, saline, and sulfide-rich fluids. When compared to other alkaline, island-based, high-arsenic, or shallow-sea hydrothermal communities, the Ambitle Island archaeal communities are unique in geochemical conditions, and in taxonomic diversity, richness, and evenness.     

In-depth Characterization via Complementing Culture-Independent Approaches of the Microbial Community in an Acidic Hot Spring of the Colombian Andes

The microbial community of a Colombian high mountain hot spring, El Coquito, was analyzed using three different culture-independent assessments of 16S ribosomal RNA genes: clone libraries, pyrosequencing of the V5–V6 hypervariable region, and microarray. This acidic spring had a diverse community composed mainly of Bacteria that shared characteristics with those from other hot springs and extreme acidic environments. The microbial community was dominated by Proteobacteria, Firmicutes, and Planctomycetes and contained chemotrophic bacteria potentially involved in cycling of ferrous and sulfur-containing minerals and phototrophic organisms, most of which were eukaryotic micro-algae. Despite the presence of a large proportion of novel, unclassified sequences, the taxonomic profiles obtained with each strategy showed similarities at higher taxonomic levels. However, some groups, such as Spirochaetes and Aquificae, were identified using only one methodology, and more taxa were detected with the gene array, which also shared more groups with the pyrosequencing data. Overall, the combined use of different approaches provided a broader view of the microbial community in this acidic hot spring.     

Distribution and Diversity of Aerobic Carbon Monoxide-Oxidizing Bacteria in Geothermal Springs of China,the Philippines,and the United States

Accumulating genomic evidence suggests that a variety of thermophilic bacteria contain cox operons and may be capable of aerobic carbon monoxide (CO) oxidation. However, little is known about the distribution and diversity of the cox-encoding (COXE) bacteria in natural geothermal environments. In this study, we examined coxL gene (encoding the large subunit of carbon monoxide dehydrogenase: CoxL) sequences retrieved from the sediments of 25 geothermal sites located in the Qinghai-Tibetan Plateau (QTP) and Yunnan Province (YP) of China, the Bacon-Manito Geothermal Production Field (BGPF) of the Philippines, and the Great Basin of the United States (USGB). Temperature and pH ranges of the studied hot springs were 22.1 to 90.8°C and 2.7 to 9.4, respectively. Phylogenetic analyses showed that most CoxL sequences were closely related to the classes Actinobacteria, Deinococci, Ktedonobacteria, Thermomicrobia, and Clostridia, and hot springs from different regions hosted different COXE communities. In addition, these hot springs harbored some COXE bacteria that were phylogenetically distinct from those inhabiting nongeothermal ecosystems. This study revealed no significant correlation between temperature or pH and the composition or diversity of COXE communities at the global scale. However, within a given region, temperature was correlated with the COXE bacterial community composition.     

Metagenomes from High-Temperature Chemotrophic Systems Reveal Geochemical Controls on Microbial Community Structure and Function

The Yellowstone caldera contains the most numerous and diverse geothermal systems on Earth, yielding an extensive array of unique high-temperature environments that host a variety of deeply-rooted and understudied Archaea, Bacteria and Eukarya. The combination of extreme temperature and chemical conditions encountered in geothermal environments often results in considerably less microbial diversity than other terrestrial habitats and offers a tremendous opportunity for studying the structure and function of indigenous microbial communities and for establishing linkages between putative metabolisms and element cycling. Metagenome sequence (14–15,000 Sanger reads per site) was obtained for five high-temperature (>65°C) chemotrophic microbial communities sampled from geothermal springs (or pools) in Yellowstone National Park (YNP) that exhibit a wide range in geochemistry including pH, dissolved sulfide, dissolved oxygen and ferrous iron. Metagenome data revealed significant differences in the predominant phyla associated with each of these geochemical environments. Novel members of the Sulfolobales are dominant in low pH environments, while other Crenarchaeota including distantly-related Thermoproteales and Desulfurococcales populations dominate in suboxic sulfidic sediments. Several novel archaeal groups are well represented in an acidic (pH 3) Fe-oxyhydroxide mat, where a higher O₂ influx is accompanied with an increase in archaeal diversity. The presence or absence of genes and pathways important in S oxidation-reduction, H₂-oxidation, and aerobic respiration (terminal oxidation) provide insight regarding the metabolic strategies of indigenous organisms present in geothermal systems. Multiple-pathway and protein-specific functional analysis of metagenome sequence data corroborated results from phylogenetic analyses and clearly demonstrate major differences in metabolic potential across sites. The distribution of functional genes involved in electron transport is consistent with the hypothesis that geochemical parameters (e.g., pH, sulfide, Fe, O₂) control microbial community structure and function in YNP geothermal springs.     

Analysis of the diversity of aerobic,thermophilic endospore-forming bacteria in two Algerian hot springs using cultural and non-cultural methods

Terrestrial hot environments are important resources for isolation of thermophilic microorganisms. Few studies have been made on microbial diversity of Algerian geothermal sites. This paper reports the diversity of thermophilic, aerobic endospore-forming bacteria from water and sediment samples taken from Hammam Ouled Ali and Hammam Debagh, two hot springs with a wide range of temperatures and a very rich mineral composition, located in the region of Guelma, north-east of Algeria using culture-dependent and culture-independent approaches Sequences of the V4 region of the 16S rRNA gene from environmental DNA extracted from sediment samples were analyzed and a set of isolates from water and sediment have been characterized by phenotypic and molecular methods. Phylogenetic surveys using environmental DNA sequences indicated that three families dominated the two hot springs: Planococcaceae, Bacillaceae, and Paenibacillaceae. Phenotypic characterization revealed the morphological, biochemical, and physiological properties of these microorganisms, all of which exhibited a range of common extracellular enzymatic activities. Amplified ribosomal DNA restriction analysis (ARDRA) was used to cluster isolates into different phylotypic groups and phylogenetic analysis of 16S rRNA gene sequences of selected isolates showed that all were closely related to four genera of thermophilic Bacilli: Bacillus, Anoxybacillus, Geobacillus, and Brevibacillus. Our results provide important insights into the microbial ecology of Guelma hot springs. They showed that the phylogenetic diversity of bacterial communities within the two studied hot springs was mostly aerobic, with the presence of taxonomic groups of great biotechnological interest. Bioprospection of thermozymes and other biomolecules within these communities will probably provide a data basis for their industrial exploitation.     

Biogeochemical probing of microbial communities in a basalt‐hosted hot spring at Kverkfjöll volcano,Iceland

We investigated bacterial and archaeal communities along an ice‐fed surficial hot spring at Kverkfjöll volcano—a partially ice‐covered basaltic volcano at Vatnajökull glacier, Iceland, using biomolecular (16S rRNA, apsA, mcrA, amoA, nifH genes) and stable isotope techniques. The hot spring environment is characterized by high temperatures and low dissolved oxygen concentrations at the source (68°C and <1 mg/L (±0.1%)) changing to lower temperatures and higher dissolved oxygen downstream (34.7°C and 5.9 mg/L), with sulfate the dominant anion (225 mg/L at the source). Sediments are comprised of detrital basalt, low‐temperature alteration phases and pyrite, with <0.4 wt. % total organic carbon (TOC). 16S rRNA gene profiles reveal that organisms affiliated with Hydrogenobaculum (54%–87% bacterial population) and Thermoproteales (35%–63% archaeal population) dominate the micro‐oxic hot spring source, while sulfur‐oxidizing archaea (Sulfolobales, 57%–82%), and putative sulfur‐oxidizing and heterotrophic bacterial groups dominate oxic downstream environments. The δ¹³C_org (‰ V‐PDB) values for sediment TOC and microbial biomass range from ?9.4‰ at the spring's source decreasing to ?12.6‰ downstream. A reverse effect isotope fractionation of ~3‰ between sediment sulfide (δ³⁴S ~0‰) and dissolved water sulfate (δ³⁴S +3.2‰), and δ¹⁸O values of ~ ?5.3‰ suggest pyrite forms abiogenically from volcanic sulfide, followed by abiogenic and microbial oxidation. These environments represent an unexplored surficial geothermal environment analogous to transient volcanogenic habitats during putative “snowball Earth” scenarios and volcano–ice geothermal environments on Mars.     

Metagenomic Investigation of Bacterial and Archaeal Diversity of Hammam Essalihine Hot Spring from Khenchela,Algeria

Abstract

Hot springs are natural environments where hot groundwater comes out from the earth. Exploring the microbial diversity present in hot springs is important first to determine the microorganisms able to proliferate there and to understand their role in biogeochemical cycles. In Algeria, research concerning microbial populations in those ecosystems is limited. This study describes bacterial and archaeal diversity of the ‘Hammam Essalihine’ hot spring in Khenchela province in north-east Algeria using a culture-independent approach. This is the first microbial diversity investigation in the ‘Hammam Essalihine’ hot spring using next-generation sequencing techniques to assess the species classification of thermophilic microorganisms. Genomic DNA was extracted from water samples and the V4–V5 region of 16S rRNA gene were amplified, sequenced, and analyzed. The average temperature of water varies from 68 to 70?°C. High-throughput sequencing analysis revealed the presence of 21 bacterial phyla, including an unknown phylum and distributed across 42 families and 39 genera. The majority of the sequences were observed to belong to the kingdom Bacteria. The bacterial community from this hot spring is dominated by Proteobacteria (41.52%), Chloroflexi (7.62%), and Bacteroidetes (7.62%), whereas the community of Archaea is scarcely present in the study site and the two identified operational taxonomic units (OTUs) are far from what is known in the GenBank database. The study shows several uncharacterized sequences, indicating that the water of ‘Hammam Essalihine’ hot spring contains undescribed microorganisms. This study is thought to add to the understanding of thermophile diversity and ecology of ‘Hammam Essalihine’ hot spring.     

Archaeal and bacterial diversity in two hot spring microbial mats from a geothermal region in Romania

The diversity of archaea and bacteria was investigated in two slightly alkaline, mesophilic hot springs from the Western Plain of Romania. Phylogenetic analysis showed a low diversity of Archaea, only three Euryarchaeota taxa being detected: Methanomethylovorans thermophila, Methanomassiliicoccus luminyensis and Methanococcus aeolicus. Twelve major bacterial groups were identified, both springs being dominated by Cyanobacteria, Chloroflexi and Proteobacteria. While at the phylum/class-level the microbial mats share a similar biodiversity; at the species level the geothermal springs investigated seem to be colonized by specific consortia. The dominant taxa were filamentous heterocyst-containing Fischerella, at 45 °C and non-heterocyst Leptolyngbya and Geitlerinema, at 55 °C. Other bacterial taxa (Thauera sp., Methyloversatilis universalis, Pannonibacter phragmitetus, Polymorphum gilvum, Metallibacterium sp. and Spartobacteria) were observed for the first time in association with a geothermal habitat. Based on their bacterial diversity the two mats were clustered together with other similar habitats from Europe and part of Asia, most likely the water temperature playing a major role in the formation of specific microbial communities that colonize the investigated thermal springs.