Alkalitalea saponilacus gen. nov., sp. nov., an obligately anaerobic, alkaliphilic, xylanolytic bacterium from a meromictic soda lake

Xiashengella succiniciproducens gen. nov., sp. nov., a succinate-producing bacterium isolated from an anaerobic digestion tank in the family Marinilabiliaceae of the order Bacteroidales

A strictly anaerobic, motile bacterium, designated as strain Ai-910T, was isolated from the sludge of an anaerobic digestion tank in China. Cells were Gram-stain-negative rods. Optimal growth was observed at 38 °C (growth range 25-42 °C), pH 8.5 (growth range 5.5-10.5), and under a NaCl concentration of 0.06% (w/v) (range 0-2.0%). Major cellular fatty acids were iso-C15 : 0 and anteiso-C15 : 0. The respiratory quinone was MK-7. Using xylose as the growth substrate, succinate was produced as the fermentation product. Phylogenetic analysis based on the 16 S rRNA gene sequences indicated that strain Ai-910T formed a distinct phylogenetic lineage that reflects a new genus in the family Marinilabiliaceae, sharing high similarities to Alkaliflexus imshenetskii Z-7010T (92.78%), Alkalitalea saponilacus SC/BZ-SP2T (92.51%), and Geofilum rubicundum JAM-BA0501T (92.36%). Genomic similarity (average nucleotide identity and digital DNA-DNA hybridization) values between strain Ai-910T and its phylogenetic neighbors were below 65.27 and 16.90%, respectively, indicating that strain Ai-910T represented a novel species. The average amino acid identity between strain Ai-910T and other related members of the family Marinilabiliaceae were below 69.41%, supporting that strain Ai-910T was a member of a new genus within the family Marinilabiliaceae. Phylogenetic, genomic, and phenotypic analysis revealed that strain Ai-910T was distinguished from other phylogenetic relatives within the family Marinilabiliaceae. The genome size was 3.10 Mbp, and the DNA G + C content of the isolate was 42.8 mol%. Collectively, differences of the phenotypic and phylogenetic features of strain Ai-910T from its close relatives suggest that strain Ai-910T represented a novel species in a new genus of the family Marinilabiliaceae, for which the name Xiashengella succiniciproducens gen. nov., sp. nov. was proposed. The type strain of Xiashengella succiniciproducens is Ai-910T (= CGMCC 1.17893T = KCTC 25,304T).

The effect of low-pH concrete on microbial community development in bentonite suspensions as a model for microbial activity prediction in future nuclear waste repository

Concrete as an important component of an engineered barrier system in deep geological repositories (DGR) for radioactive waste may come into contact with bentonite, or other clays, rich in indigenous microorganisms, with potentially harmful impacts on barrier integrity. Our study aimed to assess the effect of a concrete environment on indigenous bentonite and groundwater microbial communities as these particular conditions will select for the potentially harmful microorganisms to the concrete in the future DGR. The two-month experiment under anoxic conditions consisted of crushed, aged, low-pH concrete, Czech Ca-Mg bentonite, and anoxic groundwater, with control samples without concrete or with sterile groundwater. The microbial diversity and proliferation were estimated by qPCR and 16S rRNA gene amplicon sequencing. The presence of concrete had a strong effect on microbial diversity and reduced the increase in total microbial biomass, though low-pH concrete harbored indigenous bacteria. The growth of sulfate reducers was also limited in concrete samples. Several genera, such as Massilia, Citrifermentans, and Lacunisphaera, dominant in bentonite controls, were suppressed in concrete-containing samples. In contrast, genera such as Bacillus, Dethiobacter and Anaerosolibacter specifically proliferated in the presence of concrete. Genera such as Thermincola or Pseudomonas exhibited high versatility and proliferated well under both conditions. Because several of the detected bacterial genera are known to affect concrete integrity, further long-term studies are needed to estimate the effect of bentonite and groundwater microorganisms on concrete stability in future DGR.

Quantitative assessment of exposure to fecal contamination in urban environment across nine cities in low-income and lower-middle-income countries and a city in the United States

BACKGROUND

During 2014 to 2019, the SaniPath Exposure Assessment Tool, a standardized set of methods to evaluate risk of exposure to fecal contamination in the urban environment through multiple exposure pathways, was deployed in 45 neighborhoods in ten cities, including Accra and Kumasi, Ghana; Vellore, India; Maputo, Mozambique; Siem Reap, Cambodia; Atlanta, United States; Dhaka, Bangladesh; Lusaka, Zambia; Kampala, Uganda; Dakar, Senegal.

OBJECTIVE

Assess and compare risk of exposure to fecal contamination via multiple pathways in ten cities.

METHODS

In total, 4053 environmental samples, 4586 household surveys, 128 community surveys, and 124 school surveys were collected. E. coli concentrations were measured in environmental samples as an indicator of fecal contamination magnitude. Bayesian methods were used to estimate the distributions of fecal contamination concentration and contact frequency. Exposure to fecal contamination was estimated by the Monte Carlo method. The contamination levels of ten environmental compartments, frequency of contact with those compartments for adults and children, and estimated exposure to fecal contamination through any of the surveyed environmental pathways were compared across cities and neighborhoods.

RESULTS

Distribution of fecal contamination in the environment and human contact behavior varied by city. Universally, food pathways were the most common dominant route of exposure to fecal contamination across cities in low-income and lower-middle-income countries. Risks of fecal exposure via water pathways, such as open drains, flood water, and municipal drinking water, were site-specific and often limited to smaller geographic areas (i.e., neighborhoods) instead of larger areas (i.e., cities).

CONCLUSIONS

Knowledge of the relative contribution to fecal exposure from multiple pathways, and the environmental contamination level and frequency of contact for those "dominant pathways" could provide guidance for Water, Sanitation, and Hygiene (WASH) programming and investments and enable local governments and municipalities to improve intervention strategies to reduce the risk of exposure to fecal contamination.

Responses of bacterial communities and organic matter degradation in surface sediment to Macrobrachium nipponense bioturbation

The excessive accumulation of organic matter (OM) in sediments in aquaculture ponds is a potential environmental threat due to the risk of endogenous water pollution and eutrophication. From the perspective of inhibiting OM accumulation to prevent endogenous water pollution, the present study investigated the OM degradation states, variations of bacterial communities and basic environmental factors in sediments with/without Macrobrachium nipponense treatment/control groups in triplicate for effects of bioturbation on OM degradation in 90-day incubation. The total organic carbon (TOC) and total nitrogen (TN) in the M. nipponense treatment were higher than in the control at the 30th and 60th days, while no significant differences between treatment and control were found at the end of the experiment. Significantly higher oxidation-reduction potential (ORP) and more extensively degraded OM were observed in the M. nipponense treatment. Eleven significantly differential bacterial taxa were enriched in the sediments of M. nipponense treatment, of which eight (Actinobacteria, Chitinophagales, Chitinophagaceae, Flavihumibacter, Marinilabiliaceae, Cytophaga xylanolytica group, Christensenellaceae, and Christensenellaceae R-7 group) were significantly correlated with at least two OM degradation indicators. The functional groups chemoheterotrophy, aerobic chemoheterotrophy, xylanolysis, ureolysis, and intracellular parasites were enhanced by M. nipponense and were negatively correlated with OM degradation indictors. Overall, the M. nipponense bioturbation effectively increased the ORP to provide better conditions for OM degradation, altered the taxonomic composition and functional groups to enhance the bacterial ability for OM degradation, and finally promoted the OM degradation of the surface sediment in an artificial aquaculture system.

Enrichment of specific microbial communities by optimum applied voltages for enhanced methane production by microbial electrosynthesis in anaerobic digestion

This study investigates the distribution of microbiome in microbial electrosynthesis systems at different applied voltages (0.5, 1.0, and 1.5 V) for methane production. Results revealed that more favorable conditions for methane production were observed with 1.0 V applied voltage. In Venn plots, the bioelectrodes at 1.0 V had higher numbers of unique operational taxonomic units compared to those at 0.5 and 1.5 V. Hierarchical cluster, non-metric multidimensional scaling, and principal component ordinate analyses revealed that the biocathode at 1.0 V clustered separately from the rest of the biofilms mainly because of the quantitative differences in the microbial distribution. Taxonomically, exoelectrogens (Geobacter spp.) dominated the bioanode at 1.0 V, while the syntrophic assemblages of hydrogen-producing bacteria (i.e., Bacteroidetes and Firmicutes) and hydrogen-consuming methanogens (i.e., Methanobacterium sp.) existed in the biocathode. These results suggest that the optimum applied voltage enriched specific microbial communities on the anode and cathode for enhanced methane production.

Enhancing hydrogenotrophic activities by zero-valent iron addition as an effective method to improve sulfadiazine removal during anaerobic digestion of swine manure

In this study, the feasibility of Fe⁰ addition for driving sulfadiazine (SDZ) removal during anaerobic digestion of swine manure (SM) was tested. Compared with the Fe⁰-free digesters spiked with 200 mg/L SDZ (R_SDZ), treatments with 5.0 g/L Fe⁰ (R_SDZ/Fe⁰) significantly accelerated and optimized the acidification process by enriching Clostridia and Bacteroidia (key members responsible for VFAs/H₂ production), providing more readily available substrates for methanogenesis. Furthermore, Fe⁰ increased the overall abundance of hydrogenotrophic methanogens, specifically toxicant resistant Methanoculleus and Methanosphaera spp. were selectively enriched, helping achieve a 36.9% higher CH₄ yield and a 26.4% greater total solids removal efficiency. A positive correlation between the solid content and the SDZ concentration adsorbed in SM was observed. The addition of Fe⁰ increased the distribution of SDZ in liquid and facilitated its removal through the enhanced biodegradation and physicochemical processes. Overall, the total SDZ removal efficiency was improved by 86.8% with Fe⁰.

Current Status and Potential Applications of Underexplored Prokaryotes

Thousands of prokaryotic genera have been published, but methodological bias in the study of prokaryotes is noted. Prokaryotes that are relatively easy to isolate have been well-studied from multiple aspects. Massive quantities of experimental findings and knowledge generated from the well-known prokaryotic strains are inundating scientific publications. However, researchers may neglect or pay little attention to the uncommon prokaryotes and hard-to-cultivate microorganisms. In this review, we provide a systematic update on the discovery of underexplored culturable and unculturable prokaryotes and discuss the insights accumulated from various research efforts. Examining these neglected prokaryotes may elucidate their novelties and functions and pave the way for their industrial applications. In addition, we hope that this review will prompt the scientific community to reconsider these untapped pragmatic resources.

Analysis of 1,000 Type-Strain Genomes Improves Taxonomic Classification of Bacteroidetes

Although considerable progress has been made in recent years regarding the classification of bacteria assigned to the phylum Bacteroidetes, there remains a need to further clarify taxonomic relationships within a diverse assemblage that includes organisms of clinical, piscicultural, and ecological importance. Bacteroidetes classification has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees and a limited number of phenotypic features. Here, draft genome sequences of a greatly enlarged collection of genomes of more than 1,000 Bacteroidetes and outgroup type strains were used to infer phylogenetic trees from genome-scale data using the principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families and genera, including taxa proposed long ago such as Bacteroides, Cytophaga, and Flavobacterium but also quite recent taxa, as well as a few species were shown to be in need of revision. According proposals are made for the recognition of new orders, families and genera, as well as the transfer of a variety of species to other genera. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which can be considered valuable taxonomic markers. We detected many incongruities when comparing the results of the present study with existing classifications, which appear to be caused by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. The few significant incongruities found between 16S rRNA gene and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences and the impediment in using ordinary bootstrapping in phylogenomic studies, particularly when combined with too narrow gene selections. While a significant degree of phylogenetic conservation was detected in all phenotypic characters investigated, the overall fit to the tree varied considerably, which is one of the probable causes of misclassifications in the past, much like the use of plesiomorphic character states as diagnostic features.

Alkaline Active Hemicellulases

Xylan and mannan are the two most abundant hemicelluloses, and enzymes that modify these polysaccharides are prominent hemicellulases with immense biotechnological importance. Among these enzymes, xylanases and mannanases which play the vital role in the hydrolysis of xylan and mannan, respectively, attracted a great deal of interest. These hemicellulases have got applications in food, feed, bioethanol, pulp and paper, chemical, and beverage producing industries as well as in biorefineries and environmental biotechnology. The great majority of the enzymes used in these applications are optimally active in mildly acidic to neutral range. However, in recent years, alkaline active enzymes have also become increasingly important. This is mainly due to some benefits of utilizing alkaline active hemicellulases over that of neutral or acid active enzymes. One of the advantages is that the alkaline active enzymes are most suitable to applications that require high pH such as Kraft pulp delignification, detergent formulation, and cotton bioscouring. The other benefit is related to the better solubility of hemicelluloses at high pH. Since the efficiency of enzymatic hydrolysis is often positively correlated to substrate solubility, the hydrolysis of hemicelluloses can be more efficient if performed at high pH. High pH hydrolysis requires the use of alkaline active enzymes. Moreover, alkaline extraction is the most common hemicellulose extraction method, and direct hydrolysis of the alkali-extracted hemicellulose could be of great interest in the valorization of hemicellulose. Direct hydrolysis avoids the time-consuming extensive washing, and neutralization processes required if non-alkaline active enzymes are opted to be used. Furthermore, most alkaline active enzymes are relatively active in a wide range of pH, and at least some of them are significantly or even optimally active in slightly acidic to neutral pH range. Such enzymes can be eligible for non-alkaline applications such as in feed, food, and beverage industries.This chapter largely focuses on the most important alkaline active hemicellulases, endo-β-1,4-xylanases and β-mannanases. It summarizes the relevant catalytic properties, structural features, as well as the real and potential applications of these remarkable hemicellulases in textile, paper and pulp, detergent, feed, food, and prebiotic producing industries. In addition, the chapter depicts the role of these extremozymes in valorization of hemicelluloses to platform chemicals and alike in biorefineries. It also reviews hemicelluloses and discusses their biotechnological importance.

Insights into Xylan Degradation and Haloalkaline Adaptation through Whole-Genome Analysis of Alkalitalea saponilacus, an Anaerobic Haloalkaliphilic Bacterium Capable of Secreting Novel Halostable Xylanase

The obligately anaerobic haloalkaliphilic bacterium Alkalitalea saponilacus can use xylan as the sole carbon source and produce propionate as the main fermentation product. Using mixed carbon sources of 0.4% (w/v) sucrose and 0.1% (w/v) birch xylan, xylanase production from A. saponilacus was 3.2-fold greater than that of individual carbon sources of 0.5% (w/v) sucrose or 0.5% (w/v) birch xylan. The xylanse is halostable and exhibits optimal activity over a broad salt concentration (2–6% NaCl). Its activity increased approximately 1.16-fold by adding 0.2% (v/v) Tween 20. To understand the potential genetic mechanisms of xylan degradation and molecular adaptation to saline-alkali extremes, the complete genome sequence of A. saponilacus was performed with the pacBio single-molecule real-time (SMRT) and Illumina Misseq platforms. The genome contained one chromosome with a total size of 4,775,573 bps, and a G+C genomic content of 39.27%. Ten genes relating to the pathway for complete xylan degradation were systematically identified. Furthermore, various genes were predicted to be involved in isosmotic cytoplasm via the “compatible-solutes strategy” and cytoplasmic pH homeostasis though the “influx of hydrogen ions”. The halostable xylanase from A. saponilacus and its genomic sequence information provide some insight for potential applications in industry under double extreme conditions.

Biofilm formation and granule properties in anaerobic digestion at high salinity

For the anaerobic biological treatment of saline wastewater, Anaerobic Digestion (AD) is currently a possibility, even though elevated salt concentrations can be a major obstacle. Anaerobic consortia and especially methanogenic archaea are very sensitive to fluctuations in salinity. When working with Upflow Sludge Blanket Reactor (UASB) technology, in which the microorganisms are aggregated and retained in the system as a granular biofilm, high sodium concentration negatively affects aggregation and consequently process performances. In this research, we analysed the structure of the biofilm and granules formed during the anaerobic treatment of high salinity (at 10 and 20 g/L of sodium) synthetic wastewater at lab scale. The acclimated inoculum was able to accomplish high rates of organics removal at all the salinity levels tested. 16S rRNA gene clonal analysis and Fluorescence In Situ Hybridization (FISH) analyses identified the acetoclastic Methanosaeta harundinacea as the key player involved acetate degradation and microbial attachment/granulation. When additional calcium (1 g/L) was added to overcome the negative effect of sodium on microbial aggregation, during the biofilm formation process microbial attachment and acetate degradation decreased. The same result was observed on granules formation: while calcium had a positive effect on granules strength when added to UASB reactors, Methanosaeta filaments were not present and the degradation of the partially acidified substrate was negatively influenced. This research demonstrated the possibility to get granulation at high salinity, bringing to the forefront the importance of a selection towards Methanosaeta cells growing in filamentous form to obtain strong and healthy granules.

CD44 deletion leading to attenuation of experimental autoimmune encephalomyelitis results from alterations in gut microbiome in mice

Dysbiosis in gut microbiome has been shown to be associated with inflammatory and autoimmune diseases. Previous studies from our laboratory demonstrated the pivotal role played by CD44 in the regulation of EAE, a murine model of multiple sclerosis. In the current study, we determined whether these effects resulted from an alteration in gut microbiota and the short-chain fatty acid (SCFA) production in CD44 knockout (CD44KO) mice. Fecal transfer from naïve CD44KO but not C57BL/6 wild type (CD44WT) mice, into EAE-induced CD44WT mice, led to significant amelioration of EAE. High-throughput bacterial 16S rRNA gene sequencing, followed by clustering sequences into operational taxonomic units (OTUs) and biochemical analysis, revealed that EAE-induced CD44KO mice showed significant diversity, richness, and evenness when compared to EAE-induced CD44WT mice at the phylum level, with dominant Bacteroidetes (68.5%) and low Firmicutes (26.8%). Further, data showed a significant change in the abundance of SCFAs, propionic acid, and i-butyric acid in EAE-CD44KO compared to EAE-CD44WT mice. In conclusion, our results demonstrate that the attenuation of EAE seen following CD44 gene deletion in mice may result from alterations in the gut microbiota and SCFAs. Furthermore, our studies also demonstrate that the phenotype of gene knock-out animals may be shaped by gut microbiota.

Labilibacter aurantiacus gen. nov., sp. nov., isolated from sea squirt (Styela clava) and reclassification of Saccharicrinis marinus as Labilibacter marinus comb. nov

A Gram-stain-negative, facultatively anaerobic, orange-pigmented bacterium, designated HQYD1T, was isolated from a sea squirt (Styelaclava) and characterized using a polyphasic approach. Morphologically, strain HQYD1T exhibited rods with gliding motility. This novel isolate grew optimally at 28 °C in the presence of 2-3 % (w/v) NaCl. The 16S rRNA gene sequence was most similar to [Saccharicrinis] marinus Y11T (96.3 %), followed by Saccharicinis fermentans DSM 9555T (93.8 %). The dominant fatty acids of strain HQYD1T were identified as C16 : 0, C18 : 0 and iso-C15 : 0. Major polar lipids included an unidentified lipid and a phospholipid. The major respiratory quinone was found to be MK-7, and the genomic DNA G+C content was determined to be 35.1 mol%. Based on evidence from this taxonomic study, a novel genus, Labilibacter gen. nov., is proposed in the family Marinilabiliaceae with type species Labilibacter aurantiacus sp. nov. The type strain of the type species is HQYD1T (=MCCC 1K02304T=KCTC 42583T). As [Saccharicrinis] marinus Y11T clustered phylogenetically with strain HQYD1T, we also propose [Saccharicrinis] marinus Y11T be reclassified as Labilibacter marinus comb. nov. (type strain Y11T=CICC 10837T=KCTC 42400T).

Carboxylicivirga flava sp. nov., isolated from marine surface sediment

A novel bacterial strain, designated Q15T, was isolated from sediments obtained from the Bohai Sea in China and subjected to a polyphasic taxonomic study. Cells of strain Q15T were Gram-stain-negative, strictly aerobic rods that produced circular, flat, orange colonies. Phylogenetic analysis based on 16S rRNA gene sequences revealed that Q15T was affiliated with the genus Carboxylicivirga in the family Marinilabiliaceae of the phylum Bacteroidetes. Strain Q15T differed genotypically from the type strains of the three recognized species of this genus (Carboxylicivirga taeanensis MEBiC 08903T, Carboxylicivirga mesophila MEBiC 07026T and Carboxylicivirga linearis FB218T) and shared 94.0-95.2 % 16S rRNA gene sequence similarity with them. The DNA G+C content of strain Q15T was 44.7 mol%. The predominant cellular fatty acids were iso-C15 : 0, anteiso-C15 : 0 and iso-C17 : 0 3-OH, and menaquinone MK-7 was the main respiratory quinone. Polar lipids contained phosphatidylethanolamine, an unidentified aminolipid, an unidentified phospholipid and other unknown lipids. Based on the data from the current polyphasic analysis, a novel species, Carboxylicivirga flava sp. nov., is hereby proposed with Q15T (=CICC 23923T=KCTC 42707T) as the type strain.

Description of Ancylomarina subtilis gen. nov., sp. nov., isolated from coastal sediment, proposal of Marinilabiliales ord. nov. and transfer of Marinilabiliaceae, Prolixibacteraceae and Marinifilaceae to the order Marinilabiliales

A Gram-stain-negative, facultatively anaerobic, moderately halophilic, filamentous, non-motile bacterium, designated FA102T, was isolated from marine sediment from the coast of Weihai, PR China. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain FA102T formed a distinct evolutionary lineage within the family Marinifilaceae and its closest relative was Marinifilum fragile JCM 15579T (93.2 % sequence similarity). The DNA G+C content of the novel strain was 36.5 mol%. The predominant cellular fatty acids and respiratory quinone were iso-C15 : 0 and iso-C15 : 0 3-OH, and MK-7, respectively. On the basis of the phylogenetic, phenotypic and physiological data, strain FA102T represents a novel genus and species, for which the name Ancylomarina subtilis gen. nov., sp. nov. is proposed. The type strain of Ancylomarina subtilis is FA102T (=KCTC 42257T=DSM 28825T=CICC 10902T). Furthermore, a new order named Marinilabiliales is proposed to accommodate three families previously classified in the order Bacteroidales. Marinilabiliales ord. nov. encompasses the families Marinilabiliaceae, Prolixibacteraceae and Marinifilaceae.

Halomonas urumqiensis sp. nov., a moderately halophilic bacterium isolated from a saline-alkaline lake

A moderately halophilic, aerobic bacterium, strain BZ-SZ-XJ27T, belonging to the genus Halomonas, was isolated from a saline-alkaline lake in the Xinjiang Uyghur Autonomous Region of China. Phylogenetic analysis based on 16S rRNA gene sequences and a multilocus sequence analysis using the 16S rRNA, gyrB and rpoD genes demonstrated that strain BZ-SZ-XJ27T represents a member of the genus Halomonas. On the basis of 16S rRNA gene sequence similarity, the closest relatives were Halomonas campaniensis 5AGT, H. fontilapidosi 5CRT, H. korlensis XK1T and H. sinaiensis ALO SharmT, with similarities of 96.2-97.2 %. DNA-DNA hybridization with H. korlensis CGMCC 1.6981T (the nearest phylogenetic neighbour) and H. campaniensis DSM 15293T (the highest 16S rRNA gene sequence similarity) showed relatedness values of 53 and 38 %, respectively, demonstrating the separateness of the three taxa. The bacterium stained Gram-negative and the cells were motile and rod-shaped. The strain formed creamy-white colonies and grew under optimal conditions of 1.42 M Na+ (range 0.22-4.32 M Na+), pH 8.0-8.5 (range pH 6.0-10.0) and 39 °C (range 4-43 °C). The dominant fatty acids were summed feature 8 (C18 : 1ω7c/C18 : 1ω6c; 36.6 %), C16 : 0 (25.9 %) and summed feature 3 (C16 : 1ω7c/C16 : 1ω6c; 21.2 %). The dominant polar lipids were two unknown phospholipids, phosphatidylethanolamine and phosphatidylglycerol, and the main respiratory quinones were ubiquinone 9 (Q-9; 89 %) and ubiquinone 8 (Q-8; 10 %). The genomic DNA G+C content was 61.7 ± 0.8 mol% (Tm). On the basis of phenotypic, chemotaxonomic and phylogenetic features, strain BZ-SZ-XJ27T is proposed to represent a novel species, Halomonas urumqiensis sp. nov., within the genus Halomonas of the family Halomonadaceae. The type strain is BZ-SZ-XJ27T ( = JCM 30202T = CGMCC 1.12917T).

Role of an organic carbon-rich soil and Fe(III) reduction in reducing the toxicity and environmental mobility of chromium(VI) at a COPR disposal site

Cr(VI) is an important contaminant found at sites where chromium ore processing residue (COPR) is deposited. No low cost treatment exists for Cr(VI) leaching from such sites. This study investigated the mechanism of interaction of alkaline Cr(VI)-containing leachate with an Fe(II)-containing organic matter rich soil beneath the waste. The soil currently contains 0.8% Cr, shown to be present as Cr(III)(OH)3 in EXAFS analysis. Lab tests confirmed that the reaction of Cr(VI) in site leachate with Fe(II) present in the soil was stoichiometrically correct for a reductive mechanism of Cr accumulation. However, the amount of Fe(II) present in the soil was insufficient to maintain long term Cr(VI) reduction at historic infiltration rates. The soil contains a population of bacteria dominated by a Mangroviflexus-like species, that is closely related to known fermentative bacteria, and a community capable of sustaining Fe(III) reduction in alkaline culture. It is therefore likely that in situ fermentative metabolism supported by organic matter in the soil produces more labile organic substrates (lactate was detected) that support microbial Fe(III) reduction. It is therefore suggested that addition of solid phase organic matter to soils adjacent to COPR may reduce the long term spread of Cr(VI) in the environment.

Saccharicrinis marinus sp. nov., isolated from marine sediment

A novel bacterial strain, designated Y11T, was isolated from marine sediment at Weihai in China. Comparative analysis of 16S rRNA gene sequences demonstrated that the novel isolate showed highest similarity to Saccharicrinis fermentans DSM 9555T (94.0 %) and Saccharicrinis carchari SS12T (92.7 %). Strain Y11T was a Gram-stain-negative, rod-shaped, non-endospore-forming, yellow-pigmented bacterium and was able to hydrolyse agar weakly. It was catalase-negative, oxidase-positive, facultatively anaerobic and motile by gliding. Optimal growth occurred at 28–30 °C, at pH 7.0–7.5 and in the presence of 2–3 % (w/v) NaCl. The DNA G+C content was 34.4 mol%. The strain contained MK-7 as the prevalent menaquinone. The major cellular fatty acids were iso-C15 : 0, anteiso-C15 : 0 and C15 : 1ω6c. The predominant polar lipids were phosphatidylethanolamine and two unknown lipids. Data from the present polyphasic taxonomic study clearly place the strain as representing a novel species within the genus Saccharicrinis, for which the name Saccharicrinis marinus sp. nov. is proposed. The type strain is Y11T ( = CICC10837T = KCTC42400T).

Ecology and application of haloalkaliphilic anaerobic microbial communities

Haloalkaliphilic microorganisms that grow optimally at high-pH and high-salinity conditions can be found in natural environments such as soda lakes. These globally spread lakes harbour interesting anaerobic microorganisms that have the potential of being applied in existing technologies or create new opportunities. In this review, we discuss the potential application of haloalkaliphilic anaerobic microbial communities in the fermentation of lignocellulosic feedstocks material subjected to an alkaline pre-treatment, methane production and sulfur removal technology. Also, the general advantages of operation at haloalkaline conditions, such as low volatile fatty acid and sulfide toxicity, are addressed. Finally, an outlook into the main challenges like ammonia toxicity and lack of aggregation is provided.

Going from microbial ecology to genome data and back: studies on a haloalkaliphilic bacterium isolated from Soap Lake, Washington State

Soap Lake is a meromictic, alkaline (∼pH 9.8) and saline (∼14–140 g liter^-1) lake located in the semiarid area of eastern Washington State. Of note is the length of time it has been meromictic (at least 2000 years) and the extremely high sulfide level (∼140 mM) in its monimolimnion. As expected, the microbial ecology of this lake is greatly influenced by these conditions. A bacterium, Halanaerobium hydrogeniformans, was isolated from the mixolimnion region of this lake. Halanaerobium hydrogeniformans is a haloalkaliphilic bacterium capable of forming hydrogen from 5- and 6-carbon sugars derived from hemicellulose and cellulose. Due to its ability to produce hydrogen under saline and alkaline conditions, in amounts that rival genetically modified organisms, its genome was sequenced. This sequence data provides an opportunity to explore the unique metabolic capabilities of this organism, including the mechanisms for tolerating the extreme conditions of both high salinity and alkalinity of its environment.

High phylogenetic diversity of glycosyl hydrolase family 10 and 11 xylanases in the sediment of Lake Dabusu in China

Soda lakes are one of the most stable naturally occurring alkaline and saline environments, which harbor abundant microorganisms with diverse functions. In this study, culture-independent molecular methods were used to explore the genetic diversity of glycoside hydrolase (GH) family 10 and GH11 xylanases in Lake Dabusu, a soda lake with a pH value of 10.2 and salinity of 10.1%. A total of 671 xylanase gene fragments were obtained, representing 78 distinct GH10 and 28 GH11 gene fragments respectively, with most of them having low homology with known sequences. Phylogenetic analysis revealed that the GH10 xylanase sequences mainly belonged to Bacteroidetes, Proteobacteria, Actinobacteria, Firmicutes and Verrucomicrobia, while the GH11 sequences mainly consisted of Actinobacteria, Firmicutes and Fungi. A full-length GH10 xylanase gene (xynAS10-66) was directly cloned and expressed in Escherichia coli, and the recombinant enzymes showed high activity at alkaline pH. These results suggest that xylanase gene diversity within Lake Dabusu is high and that most of the identified genes might be novel, indicating great potential for applications in industry and agriculture.

How could haloalkaliphilic microorganisms contribute to biotechnology?

Haloalkaliphiles are microorganisms requiring Na+concentrations of at least 0.5 mol·L–1and an alkaline pH of 9 for optimal growth. Their unique features enable them to make significant contributions to a wide array of biotechnological applications. Organic compatible solutes produced by haloalkaliphiles, such as ectoine and glycine betaine, are correlated with osmoadaptation and may serve as stabilizers of intracellular proteins, salt antagonists, osmoprotectants, and dermatological moisturizers. Haloalkaliphiles are an important source of secondary metabolites like rhodopsin, polyhydroxyalkanoates, and exopolysaccharides that play essential roles in biogeocycling organic compounds. These microorganisms also can secrete unique exoenzymes, including proteases, amylases, and cellulases, that are highly active and stable in extreme haloalkaline conditions and can be used for the production of laundry detergent. Furthermore, the unique metabolic pathways of haloalkaliphiles can be applied in the biodegradation and (or) biotransformation of a broad range of toxic industrial pollutants and heavy metals, in wastewater treatment, and in the biofuel industry.

Description of Mariniphaga anaerophila gen. nov., sp. nov., a facultatively aerobic marine bacterium isolated from tidal flat sediment, reclassification of the Draconibacteriaceae as a later heterotypic synonym of the Prolixibacteraceae and description of the family Marinifilaceae fam. nov

A mesophilic, chemoheterotrophic bacterium, strain Fu11-5(T), was isolated from tidal-flat sediment from Tokyo Bay, Chiba, Japan. Cells of strain Fu11-5(T) were facultatively aerobic, Gram-negative, non-sporulating, non-motile and rod-shaped (1.9-6.9 µm long). Strain Fu11-5(T) grew optimally at 35-37 °C and pH 6.5-7.0 and with 1-2% (w/v) NaCl. Oxygen and l-cysteine were used as an alternative electron acceptor and donor, respectively. Strain Fu11-5(T) also grew fermentatively on some pentoses, hexoses and disaccharides and soluble starch. Succinic acid was the major end product from d-glucose. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain Fu11-5(T) was affiliated with the order Bacteroidales, and its nearest neighbours were members of the genera Meniscus, Prolixibacter, Sunxiuqinia, Mangrovibacterium and Draconibacterium, with 87-91% sequence similarity. Cell morphology, optimum growth temperature and utilization of sugars of strain Fu11-5(T) distinguished the strain from phylogenetically related bacteria. On the basis of its phenotypic features and phylogenetic position, a novel genus and species are proposed to accommodate strain Fu11-5(T), with the name Mariniphaga anaerophila gen. nov., sp. nov. The type strain of Mariniphaga anaerophila is strain Fu11-5(T) ( =JCM 18693(T) =NBRC 109408(T) =DSM 26910(T)). We also propose to combine the family Draconibacteriaceae into the family Prolixibacteraceae as a later heterotypic synonym and to place the distinct sublineage of the genus Marinifilum in the family Marinifilaceae fam. nov.

Carboxylicivirga gen. nov. in the family Marinilabiliaceae with two novel species, Carboxylicivirga mesophila sp. nov. and Carboxylicivirga taeanensis sp. nov., and reclassification of Cytophaga fermentans as Saccharicrinis fermentans gen. nov., comb. nov

Two facultatively anaerobic mesophilic bacteria, strains MEBiC 07026T and MEBiC 08903T, were isolated from two different tidal flat sediments and both strains showed approximately 92.2 % 16S rRNA gene sequence similarity with [Cytophaga] fermentans DSM 9555T. 16S rRNA gene sequence similarity between the two new isolates was 97.5 % but levels of DNA–DNA relatedness between the two were 31.3–31.8 %. Phylogenetic analysis revealed that the two isolates and [Cytophaga] fermentans DSM 9555T were affiliated with the family Marinilabiliaceae in the class Bacteroidia . The dominant fatty acids of strains MEBiC 07026T, MEBiC 08903T and [Cytophaga] fermentans DSM 9555T were branched-type or hydroxylated C15 : 0, but [Cytophaga] fermentans DSM 9555T contained a higher proportion of anteiso-branched fatty acids. The two new isolates contained a markedly higher proportion of monounsaturated fatty acids than other members of the family Marinilabiliaceae . The major respiratory quinone of the strains was MK-7. Strains MEBiC07026T and MEBiC08903T utilized a wide range of carboxylic acids whereas [Cytophaga] fermentans DSM 9555T utilized carbohydrates rather than carboxylic acids. The DNA G+C content of the novel strains was about 44 mol% but that of [Cytophaga] fermentans DSM 9555T revealed from the genome sequence was 37.6 mol%. Based on evidence from this polyphasic taxonomic study, a novel genus, Carboxylicivirga gen. nov., is proposed in the family Marinilabiliaceae with two novel species, Carboxylicivirga mesophila sp. nov. with type strain MEBiC 07026T ( = KCCM 42978T = JCM 18290T) and Carboxylicivirga taeanensis sp. nov. with type strain MEBiC 08903T ( = KCCM 43024T = JCM 19490T). Additionally, [Cytophaga] fermentans DSM 9555T ( = ATCC 19072T) is reclassified as Saccharicrinis fermentans gen. nov., comb. nov.