Bacterial communities in haloalkaliphilic sulfate-reducing bioreactors under different electron donors revealed by 16S rRNA MiSeq sequencing

In situ enrichment of sulphate-reducing microbial communities with different carbon sources stimulating the acid mine drainage sediments

The applications of sulphate-reducing microorganisms (SRMs) in acid mine drainage (AMD) treatment systems have received extensive attention due to their ability to reduce sulphate and stabilize metal(loid)s. Despite great phylogenetic diversity of SRMs, only a few have been used in AMD treatment bioreactors. In situ enrichment could be an efficient approach to select new effective SRMs for AMD treatment. Here, we performed in situ enrichment of SRMs in highly stratified AMD sediment cores using different kinds of carbon source mixture. The dsrAB (dissimilatory sulfite reductase) genes affiliated with nine phyla (two archaeal and seven bacterial phyla) and 26 genera were enriched. Remarkably, those genes affiliated with Aciduliprofundum and Vulcanisaeta were enriched in situ in AMD-related environments for the first time, and their relative abundances were negatively correlated with pH. Furthermore, 107 dsrAB-containing metagenome-assembled genomes (MAGs) were recovered from metagenomic datasets, with 14 phyla (two archaeal and 12 bacterial phyla) and 15 genera. The relative abundances of MAGs were positively correlated with total carbon and sulphate contents. Our findings expanded the diversity of SRMs that can be enriched in AMD sediment, and revealed the physiochemical properties that might affect the growth of SRMs, which provided guidance for AMD treatment bioreators.

Pollutant impacts on bacteria in surface water and sediment: Conventional versus emerging pollutants in Taihu Lake, China

Bacteria play a critical role in biogeochemical cycling, self-purification, and food web fueling in surface freshwater ecosystems. However, the comparison between the impacts of conventional and emerging pollutants on the bacteria in surface water and sediment remains unclear and requires for an in-depth understanding to assess ecological risk and select associated bioindicators. Taihu Lake, a typical shallow lake in China, was divided into pollutant impacted and less-impacted zones for sampling. Spatial distributions of conventional pollutants, emerging pharmaceuticals, and bacterial communities were investigated in surface water and sediment. The correlations of pollutants with bacterial communities and the variations in bacterial functions were analyzed to help assess the pollutant influences on bacteria. The results showed that the water quality index and trophic level index across the whole lake were at medium to good, and mesotropher to light eutropher grades, respectively, indicating a relatively good control on conventional pollutants in water. Target pharmaceuticals were at much higher concentrations in water of the impacted zone compared to the less-impacted zone, exhibiting close positive relationships with the bacterial phyla in the impacted water. The ratio of Firmicutes to Proteobacteria in surface water is suggested as a plausible bioindicator to evaluate the level of inflow pharmaceutical contamination and the risk of relevant bacterial resistance in the outflow. In sediment, no significant difference was observed for pharmaceuticals between the two zones, whereas total phosphorus and orthophosphate were substantially higher in the impacted zone. Phosphorus pollutants were tightly associated with the bacterial genera in the impacted sediment, likely relating to the increase in iron- or sulfate-reducing bacteria which implies the potential risk of phosphorus releasing from sediment to water.

Nitrogen and boron co-doped lignin biochar for enhancing calcium peroxide activation toward organic micropollutants decontamination in waste activated sludge and related microbial structure dynamics

This study synthesized dual heteroatom nitrogen and boron-co-doped lignin-based biochar (NB-LGBC) for calcium peroxide (CP) activation to enhance the removal of organic micropollutants (OMPs), namely, 4-nonylphenol (4-NP) from waste activated sludge (WAS). NB-LGBC/CP enhanced 4-NP degradation by arriving at 83 % removal in 12 h. The NB-LGBC/CP system degraded 4-NP via a synergistic interaction (HO•, O₂^•- radicals, and singlet oxygen) and electron transfer due to the N-B-C bonding configurations. Results of fluorescence excitation-emission matrix (FEEM) analysis revealed significantly increase in biodegradable organics from treated WAS mixture. NB-LGBC/CP treatment enriched alkaliphilic bacterium associated with the predominance of the genus Desulfonatronum within the phylum Proteobacteria in the WAS, which improved the biological treatment capacity of 4-NP. Thus, NB-LGBC in HR-CAOP will be a novel approach for WAS decontamination.

Role of the substrate on Ni inhibition in biological sulfate reduction

In treating mine-impacted waters using sulfate-reducing bacteria (SRB), metal inhibition and substrate selection are important factors affecting the efficiency of the bioprocess. This work investigated the role of the substrate (i.e. lactate, formate, glycerol and glucose) on Ni inhibition to SRB with sulfate-reducing activity tests at initial pH 5, 7 and 9 and 100 mg/L of Ni. Results indicated that the type of substrate was a significant factor affecting Ni inhibition in SRB, which was the most negligible in the lactate system, followed by glycerol, glucose, and formate. Although less significant, Ni inhibition also varied with the pH, leading for instance, to a reduction of 77% in the sulfate reducing activity for the formate system, but only of 28% for lactate at pH 5. The added substrate also influenced the precipitation kinetics and the characteristics of the precipitates, reaching Ni precipitation extents above 95%, except for glucose (83.2%).

Hydrogen Sulfide Production with a Microbial Consortium Isolated from Marine Sediments Offshore

Hydrogen, electric energy production, and metal toxic bioremediation are some of the biotechnological applications of sulfate-reducing organisms, which potentially depend on the sulfide produced. In this study, offshore of Yucatan, the capacity to produce hydrogen sulfide using microbial consortia from marine sediment (SC469, PD102, SD636) in batch reactors was evaluated. Kinetic tests were characterized by lactate oxidation to acetate, propionate, CO2 and methane. The inoculum SC469, located in open-ocean, differed strongly in microbial diversity and showed better performance in substrate utilization with the highest hydrogen sulfide production (246 mmolg−1 VSS) at a specific hydrogen sulfide rate of 113 mmol g−1 VSS d−1 with a 0.79 molar ratio of sulfate/lactate. Sulfate-reducing microbial consortia enriched in the laboratory from marine sediments collected offshore in Yucatan and with a moderate eutrophication index, differed strongly in microbial diversity with loss of microorganisms with greater capacity for degradation of organic macromolecules. The sulfate-reducing microorganisms were characterized using Illumina MiSeq technology and were mainly Desulfomicrobium, Clostridium and Desulfobacter.

Haloalkaliphilic denitrifiers-dependent sulfate-reducing bacteria thrive in nitrate-enriched environments

As bridge in global cycles of carbon, nitrogen, and sulfur, sulfate-reducing bacteria (SRB) play more and more important role under various environments, especially the saline-alkali environments with significant increase in area caused by human activities. Sulfate reduction can be inhibited by environmental nitrate. However, how SRB cope with environmental nitrate stress in these extreme environments still remain unclear. Here, after a long-term enrichment of sediment from saline-alkali Qinghai Lake of China using anaerobic filter reactors, nitrate was added to evaluate the response of SRB. With the increase in nitrate concentrations, the inhibition on sulfate reduction was gradually observed. Interestingly, extension of hydraulic retention time can relieve the inhibition caused by high nitrate concentration. Mass balance analysis showed that nitrate reduction is prior to sulfate reduction. Further metatranscriptomic analysis shows that, genes of nitrite reductase (periplasmic cytochrome c nitrite reductase gene) and energy metabolisms (lactate dehydrogenase, formate dehydrogenase, pyruvate:ferredoxin-oxidoreductase, and fumarate reductase genes) in SRB was down-regulated, challenging the long-held opinion that up-regulation of these genes can relieve the nitrate inhibition. Most importantly, the nitrate addition activated the denitrification pathway in denitrifying bacteria (DB) via significantly up-regulating the expression of the corresponding genes (nitrite reductase, nitric oxide reductase c subunit, nitric oxide reductase activation protein and nitrous oxide reductase genes), quickly reducing the environmental nitrate and relieving the nitrate inhibition on SRB. Our findings unravel that in response to environmental nitrate stress, haloalkaliphilic SRB show dependency on DB, and expand our knowledge of microbial relationship during sulfur and nitrogen cycles.

Change in microbial profile and environmental conditions in a constructed wetland system treating greywater

The objective of this work was to verify the relationships between environmental conditions and microbial processes along a raw-light greywater flow in an improved constructed wetland (CW) system. Physicochemical analysis and high-throughput DNA sequencing were performed in the different zones to investigate the environmental conditions and microbial communities. The results showed that the system operated predominantly under anaerobic conditions, with redox potential (Eh) increasing from the inlet (-342.9 mV) to the outlet (-316.4 mV). Conversely, the chemical oxygen demand (COD) decreased along the greywater flow, suggesting negative correlation between these characteristics. The zones of the evapotranspiration and treatment tank (CEvaT) were characterized by lower community diversity and richness and by the presence of specific groups: Proteobacteria and Synergistetes related to the first steps of the conversion of organic carbon, in the bottom layer inside the anaerobic chamber (AnC); methanogens (Methanosaeta and Methanobacterium) and sulphate-reducing bacteria (Desulfovibrio, Desulforhabdus and Desulfomonile) in the middle layer; and microorganisms associated with the nitrogen cycle and oxygen release (Acinetobacter, Novosphingobium, Candidatus Nitrososphaera) in the top layer. On the other hand, the increase of the ORP and decrease of organic matter concentrations were associated with higher community diversity and richness in the middle layer of the CW, which showed higher abundance of microorganisms involved in methane (Methylobacterium and Candidatus Koribacter) and sulphur (Rhodoblastus and Thiobacillus) oxidation.

Effects of different dissolved organic matter on microbial communities and arsenic mobilization in aquifers

Dissolved organic matter (DOM) play key roles in the biotransformation of arsenic in groundwater systems. However, the effects of different types of DOM on arsenic biogeochemistry remain poorly understood. In this study, four typical DOM compounds (acetate, lactate, AQS and humic acid) were amended to high As aquifer sediments to investigate their effects on arsenic/iron biotransformation and microbial community response. Results demonstrated that different DOM drove different microbial community shifts and then enhanced microbially-mediated arsenic release and iron reduction. With labile DOM (acetate and lactate) amendment, the abundance of putative dissimilatory iron and sulfate reducers Desulfomicrobium and Clostridium sensu stricto increased within the first week, and subsequently the anaerobic fermentative bacterial genus Acetobacterium and arsenate/sulfate-reducing bacterial genus Fusibacter became predominant. In contrast, recalcitrant DOM (AQS and humic acid) mainly stimulated the abundances of sulfur compounds respiratory genus Desulfomicrobium and fermentative bacterial genus Alkalibacter in the whole incubation. Accompanied with the microbial community structure and function shifts, dissolved organic carbon concentration and oxidation-reduction potential changed and the arsenic/iron reduction increased, which resulted in the enhanced arsenic mobilization. Collectively, the present study linked DOM type to microbial community structure and explored the potential roles of different DOM on arsenic biotransformation in aquifers.

Improved High-Throughput Sequencing of the Human Oral Microbiome: From Illumina to PacBio

Background

A comprehensive understanding of the commensal microflora and its relation to health is essential for preventing and combating diseases. The aim of this study was to examine the structure of the oral microbiome by using different sequencing technologies. Material and Methods. Five preschool children with no symptoms of oral and systemic diseases were recruited. Samples of saliva were collected. A 468 bp insert size library was constructed on the MiSeq platform and then subjected to 300 bp paired-end sequencing. Libraries with longer insert sizes, including a full-length 16S rDNA gene, were sequenced on the PacBio RS II platform.

Results

A total of 122.6 Mb of raw data, including 244,967 high-quality sequences, were generated by the MiSeq platform, while 134.6 Mb of raw data, including 70,030 high-quality reads, were generated by the PacBio RS II platform. Clustering of the unique sequences into OTUs at 3% dissimilarity resulted in an average of 225 OTUs on the MiSeq platform; however, the number of OTUs generated on the PacBio RS II platform was 449, far greater than the number of OTUs generated on the MiSeq platform. A total of 437 species belonging to 10 phyla and 60 genera were detected by the PacBio RS II platform, while 163 species belonging to 12 phyla and 72 genera were detected by the MiSeq platform.

Conclusions

The oral microflora of healthy Chinese children were analyzed. Compared with traditional 16S rRNA sequencing technology, the PacBio system, despite providing a lower amount of clean data, surpassed the resolution of the MiSeq platform by improving the read length and annotating the nucleotide sequences at the species or strain level. This trial is registered with NCT02341352.

Immobilization of sulfate and thiosulfate-reducing biomass on sand under haloalkaline conditions

Biological sulfate and thiosulfate reduction under haloalkaline conditions can be applied to treat waste streams from biodesulfurization systems. However, the lack of microbial aggregation under haloalkaline conditions limits the volumetric rates of sulfate and thiosulfate reducing bioreactors. As biomass retention in haloalkaline bioreactors has not been studied before, sand was chosen as a biomass carrier material to increase cell retention and consequently raise the volumetric rates. The results showed that ~10 fold higher biomass concentrations could be achieved with sand, compared to previous studies without carrier addition. The volumetric rates of sulfate/thiosulfate reduction increased approximately 4.5 times. Biomass attachment to the sand was restricted to cavities within the sand particles. Acetate produced by acetogenic bacteria from H₂ and CO₂ was used as carbon source for biomass growth, while formate that was also produced from H₂ and CO₂ enhanced sulfate reduction. The microbial community composition was analyzed by 16S rRNA gene amplicon sequencing, and Tindallia related bacteria were probably responsible for formate formation from hydrogen. The community attached to the sand particles was similar to the suspended fraction, but the relative abundance of sequences most closely related to Desulfohalobiaceae was much higher in the attached fraction compared to the suspended fraction (30% and 13%, respectively). The results indicated that even though the biomass attachment to sand was poor, it still increased the biomass concentration and consequently the sulfate and thiosulfate reduction volumetric rates.

Deep and high-efficiency removal of sulfate through a coupling system with sulfate-reducing and sulfur-oxidizing capacity under haloalkaliphilic condition

Sulfide from anaerobic treatment of high-sulfate wastewater would always have some adverse effects on downstream processes. In this study, a coupling anaerobic/aerobic system was developed and operated under haloalkaliphilic condition to realize deep and high-efficiency removal of sulfate without production of sulfide. A haloalkaliphilic sulfur-oxidizing strain, Thioalkalivibrio versutus SOB306, was responsible for oxidation of sulfide. The anaerobic part was first operated at optimum condition based on a previous study. Then, its effluent with an average sulfide concentration of 674 ± 33 mg·l^-1 was further directly treated by a set of 1 l biofilter with SOB306 strain under aerobic condition. Finally, 100% removal rate of sulfide was achieved at aeration rate of 0.75 l·l^-1·min^-1, ORP of - 392 mV and HRT of 4 h. The average yield of elemental sulfur reached 79.1 ± 1.3% in the filter, and the CROS achieved a conversion rate of sulfate to sulfur beyond 54%. This study for the first time revealed the characteristics and performance of the haloalkaliphilic CROS in deep treatment of high-sulfate wastewater, which paved the way for the development and application of this method in the real world.

Individual and combined effects of ammonia-N and sulfide on the immune function and intestinal microbiota of Pacific white shrimp Litopenaeus vannamei

In this study, we explored the individual and combined effects of ammonia-N and sulfide stress (1 mg/L sulfide and 15 mg/L ammonia-N) on the oxidation resistance, immune response and intestinal health of Litopenaeus vannamei during 72 h exposure. The total antioxidant capacity (T-AOC), malonaldehyde (MDA) and nitric oxide (NO) content, superoxide dismutase (SOD) and catalase activity (CAT), the immune-relative gene (caspase-3, hsp70 and IMD) expression in hepatopancreas and intestine of L.vannamei and the intestinal microbiota were measured. The result showed that MDA and NO contents in hepatopancreas of L. vannamei in all treatment groups increased and remain were at high levels at the end of the stress exposure. The L. vannamei employ antioxidant defense system by increasing the activities of T-AOC, SOD and CAT enzymes in hepatopancereas and intestine to reduce oxidant damage. More severe damages with combined ammonia-N and sulfide stress to antioxidant systems were observed. The gene expression results also demonstrated that antioxidant capacity of L. vannamei was severely impaired and the apoptosis cell was initiated under the ammonia-N and sulfide stress. In addition, the environmental stress also reshaped the intestinal microbial community structure of L. vannamei that a number of original genera decreased, such as Cellvibrio, Vibrio and Rheinheimera; some new genera increased or appeared, such as Photobacterium in all treatment groups, Arcobacter and Fusibacter in sulfide stress group. Therefore, the health of L. vannamei was severely impacted when exposed to the stress of ammonia nitrogen and sulfide and these two factors can have weak synergic effects.

Simultaneous debromination and mineralization of bromophenol in an up-flow electricity-stimulated anaerobic system

Due to highly recalcitrant and toxicological nature of halogenated organic compounds, conventional anaerobic dehalogenation is often limited by low removal rate and poor process stability. Besides, the reduction intermediates or products formed during dehalogenation process, which are still toxic, required further energy-intensive aerobic post-treatment. In this study, an up-flow electricity-stimulated anaerobic system (ESAS) was developed by installing cathode underneath and anode above to realize simultaneous anaerobic debromination and mineralization of 4-bromophenol (4-BP). When cathode potential was -600 mV, high TOC removal efficiency (98.78 ± 0.96%), complete removal of 4-BP and phenol could be achieved at 4-BP loading rate of 0.58 mol m^-3 d^-1, suggesting debrominated product of 4-BP from cathode (i.e., phenol) would be utilized as the fuel by the bioanode of ESAS. Under high 4-BP loading rate (2.32 mol m^-3 d^-1) and low electron donor dosage (4.88 mM), 4-BP could be completely removed at acetate usage ratio as low as 4.21 ± 1.42 mol acetate mol^-1 4-BP removal in ESAS, whereas only 13.45 ± 1.38% of 4-BP could be removed at acetate usage ratio as high as 31.28 ± 3.38 mol acetate mol^-1 4-BP removal in control reactor. Besides, electrical stimulation distinctly facilitated the growth of various autotrophic dehalogenation species, phenol degradation related species, fermentative species, homoacetogens and electrochemically active species in ESAS. Moreover, based on the identified intermediates and the bacterial taxonomic analysis, possible metabolism mechanism involved in enhanced anaerobic debromination and mineralization of 4-BP in ESAS was proposed.

Stratification of microbial communities throughout a biological sulphate reducing up-flow anaerobic packed bed reactor, revealed through 16S metagenomics

Biological sulphate reduction (BSR) is a promising low-cost treatment of acid rock drainage effluents. In this paper, the system performance and microbial ecology of a lactate supplemented BSR up-flow anaerobic packed bed reactor (UAPBR) are evaluated across reactor height and compared to a continuous stirred tank reactor (CSTR). The biomass concentrations of planktonic and biofilm communities were quantified and subsequently characterised by 16S rRNA gene amplicon sequencing. The defined microbial communities were shown to correlate with differing availability of lactate, volatile fatty acids produced from lactate degradation and sulphate concentration. The UAPBR was able to achieve near complete sulphate conversion at a 4-day hydraulic residence time (HRT) at a sulphate feed concentration of 10.41 mM (1 g/L). The high volumetric sulphate reduction rate of 0.184 mM/L.h achieved in the first third of the reactor was attributed to OTUs present in the planktonic and biofilm communities. While the scavenging of sulphate within the final third of the UAPBR was attributed to an acetate oxidising genus of SRB which was not detected in the lactate-fed CSTR. The detailed analyses of the microbial communities throughout the UAPBR and CSTR contribute to the growing understanding of the impact of the microbial communities of BSR reactors on system performance.

Airborne microbial communities in the atmospheric environment of urban hospitals in China

Clinically relevant antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in bioaerosols have become a greater threat to public health. However, few reports have shown that ARB and ARGs were found in the atmosphere. High-throughput sequencing applied to environmental sciences has enhanced the exploration of microbial populations in atmospheric samples. Thus, five nosocomial bioaerosols were collected, and the dominant microbial and pathogenic microorganisms were identified by high-throughput sequencing in this study. The results suggested that the dominant microorganisms at the genus level were Massilia, Sphingomonas, Methylobacterium, Methylophilus, Micrococcineae, and Corynebacterineae. The most abundant pathogenic microorganisms were Staphylococcus saprophyticus, Corynebacterium minutissimum, Streptococcus pneumoniae, Escherichia coli, Arcobacter butzleri, Aeromonas veronii, Pseudomonas aeruginosa, and Bacillus cereus. The relationship between microbial communities and environmental factors was evaluated with canonical correspondence analysis (CCA). Meanwhile, differences in the pathogenic bacteria between bioaerosols and dust in a typical hospital was investigated. Furthermore, cultivable Staphylococcus isolates with multi-drug resistance phenotype (>3 antibiotics) in the inpatient departments were much higher than those in the transfusion area and out-patient departments, possibly attributed to the dense usage of antibiotics in inpatient departments. The results of this study might be helpful for scientifically air quality control in hospitals.

Highly diverse endophytes in roots of Cycas bifida (Cycadaceae), an ancient but endangered gymnosperm

As an ancient seed plant, cycads are one of the few gymnosperms that develop a root symbiosis with cyanobacteria, which has allowed cycads to cope with harsh geologic and climatic conditions during the evolutionary process. However, the endophytic microbes in cycad roots remain poorly identified. In this study, using next-generation sequencing techniques, we investigated the microbial diversity and composition of both the coralloid and regular roots of Cycas bifida (Dyer) K.D. Hill. Highly diverse endophytic communities were observed in both the coralloid and regular roots. Of the associated bacteria, the top five families were the Nostocaceae, Sinobacteraceae, Bradyrhizobiaceae, Bacillaceae, and Hyphomicrobiaceae. The Nectriaceae, Trichocomaceae, and Incertae sedis were the predominant fungal families in all root samples. A significant difference in the endophytic bacterial community was detected between coralloid roots and regular roots, but no difference was observed between the fungal communities in the two root types. Cyanobacteria were more dominant in coralloid roots than in regular roots. The divergence of cycad root structures and the modified physiological processes may have contributed to the abundance of cyanobionts in coralloid roots. Consequently, the colonization of cyanobacteria inhibits the assemblage of other endophytes. Our results contribute to an understanding of the species diversity and composition of the cycad-endophyte microbiome and provide an abbreviated list of potential ecological roles of the core microbes present.

Microbial communities in the native habitats of Agaricus sinodeliciosus from Xinjiang Province revealed by amplicon sequencing

Agaricus sinodeliciosus is an edible species described from China and has been successfully cultivated. However, no studies have yet reported the influence factors implicated in the process of fructification. To better know abiotic and biotic factors, physiochemical characteristics and microbial communities were investigated in five different soil samples collected in the native habitats of specimens from northern Xinjiang, southern Xinjiang, and Zhejiang Province, respectively. There are major differences in texture and morphology among different specimens of A. sinodeliciosus from Xinjiang Province. A. sinodeliciosus from southern Xinjiang was the largest. Concentrations of DOC and TN and C/N ratio are not the main reason for the differences. Microbial communities were analyzed to find out mushroom growth promoting microbes (MGPM), which may lead to the differences. Functional microbes were picked out and can be divided into two categories. Microbes in the first category may belong to MGPM. There may be symbiotic relationships between microbes in the second category and A. sinodeliciosus. Certain analyses of microbial communities support the hypothesis that interactions between microbes and mushrooms would be implicated in morphological variation of the collected mushrooms. Redundancy analysis results indicate that high DOC/NH₄⁺-N ratio and NH₄⁺-N concentration can improve the yield of A. sinodeliciosus.

Anolyte recycling enhanced bioelectricity generation of the buffer-free single-chamber air-cathode microbial fuel cell

Anolyte acidification is an inevitable restriction for the bioelectricity generation of buffer-free microbial fuel cells (MFCs). In this work, acidification of the buffer-free KCl anolyte has been thoroughly eliminated through anolyte recycling. The accumulated HCO₃^- concentration in the recycled KCl anolyte was above 50mM, which played as natural buffer and elevated the anolyte pH to above 8. The maximum power density (P_max) increased from 322.9mWm^-2 to 527.2mWm^-2, which is comparable with the phosphate buffered MFC. Besides Geobacter genus, the gradually increased anolyte pH and conductivity induced the growing of electrochemically active Geoalkalibacter genus, in the anode biofilm. Anolyte recycling is a feasible strategy to strengthen the self-buffering capacity of buffer-free MFCs, thoroughly eliminate the anolyte acidification and prominently enhance the electric power.

Biogeochemical oxidation of calcium sulfite hemihydrate to gypsum in flue gas desulfurization byproduct using sulfur-oxidizing bacteria

Flue gas desulfurization (FGD) is a well-established air treatment technology for coal and oil combustion gases that commonly uses lime or pulverized limestone aqueous slurries to precipitate sulfur dioxide (SO₂) as crystalline calcium salts. Under forced oxidation (excess oxygen) conditions, FGD byproduct contains almost entirely (>92%) gypsum (CaSO₄·2H₂O), a useful and marketable commodity. In contrast, FGD byproduct formed in oxygen deficient oxidation systems contains a high percentage of hannebachite (CaSO₃·0.5H₂O) to yield a material with no commercial value, poor dewatering characteristics, and that is typically disposed in landfills. Hannebachite in FGD byproduct can be chemically converted to gypsum; however, the conditions that support rapid formation of gypsum require large quantities of acids or oxidizers. This work describes a novel, patent pending application of microbial physiology where a natural consortium of sulfur-oxidizing bacteria (SOB) was used to convert hannebachite-enriched FGD byproduct into a commercially valuable, gypsum-enriched product (US Patent Assignment 503373611). To optimize the conversion of hannebachite into gypsum, physiological studies on the SOB were performed to define their growth characteristics. The SOB were found to be aerobic, mesophilic, neutrophilic, and dependent on a ready supply of ammonia. They were capable of converting hannebachite to gypsum at a rate of approximately five percent per day when the culture was applied to a 20 percent FGD byproduct slurry and SOB growth medium. 16S rDNA sequencing revealed that the SOB consortium contained a variety of different bacterial genera including both SOB and sulfate-reducing bacteria. Halothiobacillus, Thiovirga and Thiomonas were the dominant sulfur-oxidizing genera.

Microbial community structure and diversity in a municipal solid waste landfill

Municipal solid waste (MSW) landfills are the most prevalent waste disposal method and constitute one of the largest sources of anthropogenic methane emissions in the world. Microbial activities in disposed waste play a crucial role in greenhouse gas emissions; however, only a few studies have examined metagenomic microbial profiles in landfills. Here, the MiSeq high-throughput sequencing method was applied for the first time to examine microbial diversity of the cover soil and stored waste located at different depths (0-150cm) in a typical MSW landfill in Yangzhou City, East China. The abundance of microorganisms in the cover soil (0-30cm) was the lowest among all samples, whereas that in stored waste decreased from the top to the middle layer (30-90cm) and then increased from the middle to the bottom layer (90-150cm). In total, 14 phyla and 18 genera were found in the landfill. A microbial diversity analysis showed that Firmicutes, Proteobacteria, and Bacteroidetes were the dominant phyla, whereas Halanaerobium, Methylohalobius, Syntrophomonas, Fastidiosipila, and Spirochaeta were the dominant genera. Methylohalobius (methanotrophs) was more abundant in the cover layers of soil than in stored waste, whereas Syntrophomonas and Fastidiosipila, which affect methane production, were more abundant in the middle to bottom layers (90-150cm) in stored waste. A canonical correlation analysis showed that microbial diversity in the landfill was most strongly correlated with the conductivity, organic matter, and moisture content of the stored waste.

Long-term effects of increasing acidity on low-pH sulfate-reducing bioprocess and bacterial community

An ethanol-fed, sulfate-reducing anaerobic baffled reactor was operated over a period of 260 days to assess the effects of sequentially more acidic conditions (pH 4.5-2.5) on sulfate reduction and bacterial community. Results showed that the reactor could reduce sulfate and generate alkalinity at progressively lower pH values of 4.5, 3.5, and 2.5 in a synthetic wastewater containing 2500 mg/L sulfate. About 93.9% of the influent sulfate was removed at a rate of 4691 mg/L/day, and the effluent pH was increased to 6.8 even when challenged with influent pH as low as 2.5. Illumina MiSeq sequencing revealed that a step decrease in influent pH from 4.5 to 2.5 resulted in noticeable decrease in the biodiversity inside the sulfidogenic reactor. Additionally, complete and incomplete organic oxidizers Desulfobacter and Desulfovibrio were observed to be the most dominant sulfate reducers at pH 2.5, sustaining the low-pH, high-rate sulfate removal and alkalinity generation.

Thiosulfate Conversion to Sulfide by a Haloalkaliphilic Microbial Community in a Bioreactor Fed with H2 Gas

In industrial gas biodesulfurization systems, where haloalkaline conditions prevail, a thiosulfate containing bleed stream is produced. This bleed stream can be treated in a separate bioreactor by reducing thiosulfate to sulfide and recycling it. By performing treatment and recycling of the bleed stream, its disposal decreases and less caustics are required to maintain the high pH. In this study, anaerobic microbial thiosulfate conversion to sulfide in a H₂/CO₂ fed bioreactor operated at haloalkaline conditions was investigated. Thiosulfate was converted by reduction to sulfide as well as disproportionation to sulfide and sulfate. Formate production from H₂/CO₂ was observed as an important reaction in the bioreactor. Formate, rather than H₂, might have been used as the main electron donor by thiosulfate/sulfate-reducing bacteria. The microbial community was dominated by bacteria belonging to the family Clostridiaceae most closely related to Tindallia texcoconensis. Bacteria phylogenetically related to known haloalkaline sulfate and thiosulfate reducers, thiosulfate-disproportionating bacteria, and remarkably sulfur-oxidizing bacteria were also detected. On the basis of the results, two approaches to treat the biodesulfurization waste stream are proposed: (i) addition of electron donor to reduce thiosulfate to sulfide and (ii) thiosulfate disproportionation without the need for an electron donor. The concept of application of solely thiosulfate disproportionation is discussed.

Microbial Succession and Nitrogen Cycling in Cultured Biofilms as Affected by the Inorganic Nitrogen Availability

Biofilms play important roles in nutrients and energy cycling in aquatic ecosystems. We hypothesized that as eutrophication could change phytoplankton community and decrease phytoplankton diversity, ambient inorganic nitrogen level will affect the microbial community and diversity of biofilms and the roles of biofilms in nutrient cycling. Biofilms were cultured using a flow incubator either with replete inorganic nitrogen (N-rep) or without exogenous inorganic nitrogen supply (N-def). The results showed that the biomass and nitrogen and phosphorous accumulation of biofilms were limited by N deficiency; however, as expected, the N-def biofilms had significantly higher microbial diversity than that of N-rep biofilms. The microbial community of biofilms shifted in composition and abundance in response to ambient inorganic nitrogen level. For example, as compared between the N-def and the N-rep biofilms, the former consisted of more diazotrophs, while the latter consisted of more denitrifying bacteria. As a result of the shift of the functional microbial community, the N concentration of N-rep medium kept decreasing, while that of N-def medium showed an increasing trend in the late stage. This indicates that biofilms can serve as the source or the sink of nitrogen in aquatic ecosystems, and it depends on the inorganic nitrogen availability.

Comprehensive comparison of bacterial communities in a membrane-free bioelectrochemical system for removing different mononitrophenols from wastewater

Membrane-free bioelectrochemical systems (MFBESs) have been developed for the degradation of nitro-aromatic contaminants, but the microbial communities that are involved have not been comprehensively investigated. In this study, the microbial communities were evaluated and compared for treating different structures of nitrophenols (NPs), i.e., o-nitrophenol (ONP), m-nitrophenol (MNP) and p-nitrophenol (PNP), in the MFBES. The results demonstrated that NPs reduction in the MFBES decreased in efficiency in the following order: ONP>MNP>PNP. Illumina MiSeq sequencing results showed that richness and diversity of bacterial species in the anodic and cathodic communities decreased when fed different NPs. Though remarkable differences in community composition were found between anodic and cathodic biofilms in the MFBES, three core genera-Treponema, Desulfovibrio and Geobacter-were dominant in the anodic or cathodic biofilm, regardless of various NPs. Other functional genera in the anodic or cathodic biofilm were selectively enriched in the MFBES treating the three NPs with different structures.

Performance of a new suspended filler biofilter for removal of nitrogen oxides under thermophilic conditions and microbial community analysis

A suspended biofilter, as a new bioreactor, was constructed for the removal of nitrogen oxides (NOX) from simulated flue gas under thermophilic conditions. The suspended biofilter could be quickly started up by inoculating the thermophilic denitrifying bacterium Chelatococcus daeguensis TAD1. The NO concentration in the inlet stream ranged from 200mg/m(3) to 2000mg/m(3) during the operation, and inlet loading ranged from 8.2-164g/(m(3)·h). The whole operation period was divided into four phases according to the EBRT. The EBRT of phases I, II, III and IV were 88s (9-43d), 44s (44-61d), 66s (62-79d) and 132s (80-97d), respectively. An average NO removal efficiency of 90% was achieved during the whole operation period, and the elimination capacity increased linearly with the increase in NO inlet loading and the maximum elimination capacity reached 146.9g/(m(3)·h). No clogging was observed, although there was a high biomass concentration in the biofilter bed. The remarkable performance in terms of NO removal could be attributed to the rich bacterial communities. The microbial community structure in the biofilm was investigated by high throughput sequencing analysis (16S rRNA MiSeq sequencing). The experimental results showed that the microbial community structure of the biofilm was very rich in diversity, with the most abundant bacterial class of the Alphaproteobacteria, which accounted for 36.5% of the total bacteria, followed by Gammaproteobacteria (30.7%) and Clostridia (27.5%). It was worthwhile to mention that the dominant species in the suspended biofilter biofilm were all common denitrifying bacteria including Rhizobiales (inoculated microbe), Rhodospirillales, Enterobacteriales and Pseudomonadales, which accounted for 19.4%, 17%, 21.6% and 7%, respectively. The inoculated strain TAD1 belonged to Alphaproteobacteria class. Because high-throughput 16S rRNA gene paired-end sequencing has improved resolution of bacterial community analysis, 16S rRNA gene sequencing of these bacteria could provide more functional and phylogenetic information about the bacterial communities.

Metagenomic insights into the effects of volatile fatty acids on microbial community structures and functional genes in organotrophic anammox process

To explore the metabolic versatility of "Candidatus Brocadia sinica" in the presence of VFAs, the impacts of VFAs on anammox activity and nitrogen removal were investigated in this study. Results found that low VFAs concentrations has no affect on anammox activity and the removal efficiencies of NH4(+)-N and NO2(-)-N. However, "Ca. Brocadia sinica" showed higher adaptability to some VFAs stresses. Furthermore, Illumina MiSeq pyrosequencing results indicated that the microbial community structures varied significantly and the phyla Chloroflexi, Proteobacteria, Bacteroidetes and Chlorobi were dominated. Finally, qPCR was performed to validate the growth of anammox bacteria and gain the quantitative insights into the correlation between nitrogen transformation rates and the key functional genes in the organotrophic anammox system. Combined analysis clearly demonstrated that the coupling of the anammox, denitrification and DNRA were the noteworthy pathway for the simultaneous removal of nitrogen and organic carbon.