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Anemia of inflammation (AI) is associated with inflammatory diseases, and inflammation-induced iron metabolism disorder is the major pathogenic factor. Earlier studies have reported a tendency of AI in periodontitis patients, but the explicit relationship and possible pathological mechanisms remain unclear. Here, the analyses of both periodontitis patients and a mouse model of ligature-induced experimental periodontitis showed that periodontitis was associated with lower levels of hemoglobin and hematocrit with evidence of systemic inflammation (increased white blood cell levels) and evidence of iron restriction (low serum iron along with a high serum hepcidin and ferritin levels), in accordance with the current diagnosis criteria for AI. Moreover, periodontal therapy improved the anemia status and iron metabolism disorders. Furthermore, the increased level of hepcidin and significant correlation between hepcidin and key indicators of iron metabolism emphasized the pivotal role of hepcidin in the pathogenesis of periodontitis-related AI. Administration of the signal transducer and activator of transcription 3 (STAT3) inhibitors Stattic suggested that the IL-6–STAT3–hepcidin signaling pathway participated in this regulatory process. Together, these findings demonstrated that periodontitis should be considered an inflammatory disease that contributes to the development of AI; furthermore, IL-6–STAT3–hepcidin signaling pathway plays a key regulatory role in the pathogenesis of periodontitis-related AI. Our study will provide new insights into the systemic effects of periodontitis, while meaningfully expanding the spectrum of inflammatory diseases that contribute to AI.

Background MCM3AP-AS1 is a recently characterized lncRNA playing an oncogenic role in several cancers. However, its role in lung cancer remains unknown. Here, we aimed to explore the functions of MCM3AP-AS1 in small cell lung cancer (SCLC) and the possible underlying mechanisms. Methods MCM3AP-AS1 and ROCK1 levels in SCLC patients were analyzed by qPCR. RNA pull-down and luciferase assays were performed to analyze the interaction between MCM3AP-AS1 and miR-148a. ROCK1 mRNA and protein levels were detected by qPCR and Western blot, respectively. Cell invasion and migration were analyzed by Transwell assays. Results MCM3AP-AS1 was upregulated in patients with SCLC, and a high MCM3AP-AS1 level was accompanied by a low survival rate. The binding of MCM3AP-AS1 to miR-148a predicted by bioinformatics analysis was verified by RNA pull-down and luciferase assays. However, MCM3AP-AS1 and miR-148a did not affect each other’s expression. ROCK1 was upregulated in SCLC tissues and positively correlated with MCM3AP-AS1. In SCLC cells, MCM3AP-AS1 overexpression increased ROCK1 and promoted cancer cell invasion and migration, while miR-148a overexpression showed the opposite effects and attenuated the effects of MCM3AP-AS1 overexpression on ROCK1 expression and cell behaviors. Conclusions MCM3AP-AS1 sponges miR-148a, thereby increasing SCLC cell invasion and migration via upregulating ROCK1 expression.

Ammonia oxidation is an important process in both the natural nitrogen cycle and nitrogen removal from engineered ecosystems. Recently, a new ammonia oxidation pathway termed Dirammox (direct ammonia oxidation, NH(3)→NH(2)OH→N(2)) has been identified in Alcaligenes ammonioxydans. However, whether Dirammox is present in other microbes, as well as its genetic regulation, remains unknown. In this study, it was found that the metabolically versatile bacterium Alcaligenes faecalis strain JQ135 could efficiently convert ammonia into N(2) via NH(2)OH under aerobic conditions. Genetic deletion and complementation results suggest that dnfABC is responsible for the ammonia oxidation to N(2) in this strain. Strain JQ135 also employs aerobic denitrification, mainly producing N(2)O and trace amounts of N(2), with nitrite as the sole nitrogen source. Deletion of the nirK and nosZ genes, which are essential for denitrification, did not impair the capability of JQ135 to oxidize ammonia to N(2) (i.e., Dirammox is independent of denitrification). Furthermore, it was also demonstrated that pod (which encodes pyruvic oxime dioxygenase) was not involved in Dirammox and that AFA_16745 (which was previously annotated as ammonia monooxygenase and is widespread in heterotrophic bacteria) was not an ammonia monooxygenase. The MocR-family transcriptional regulator DnfR was characterized as an activator of the dnfABC operon with the binding motif 5′-TGGTCTGT-3′ in the promoter region. A bioinformatic survey showed that homologs of dnf genes are widely distributed in heterotrophic bacteria. In conclusion, this work demonstrates that, besides A. ammonioxydans, Dirammox occurs in other bacteria and is regulated by the MocR-family transcriptional regulator DnfR. IMPORTANCE Microbial ammonia oxidation is a key and rate-limiting step of the nitrogen cycle. Three previously known ammonia oxidation pathways (i.e., nitrification, anaerobic ammonia oxidation [Anammox], and complete ammonia oxidation [Comammox]) are mediated by autotrophic microbes. However, the genetic foundations of ammonia oxidation by heterotrophic microorganisms have not been investigated in depth. Recently, a previously unknown pathway, termed direct ammonia oxidation to N(2) (Dirammox), has been identified in the heterotrophic bacterium Alcaligenes ammonioxydans HO-1. This paper shows that, in the metabolically versatile bacterium Alcaligenes faecalis JQ135, the Dirammox pathway is mediated by dnf genes, which are independent of the denitrification pathway. A bioinformatic survey suggests that homologs of dnf genes are widely distributed in bacteria. These findings enhance the understanding of the molecular mechanisms of heterotrophic ammonia oxidation to N(2).

Nitrate accumulation causes long-time threat to aquatic animals in recirculating aquaculture system (RAS); thus, nitrate removal is also required in RASs. However, the lack of carbon sources makes denitrification difficult to function. Nitrate removal performance of an aerobic denitrifying and extracellular polyhydroxyalkanoate depolymerase–producing bacterium, Pseudomonas sp. AOB-7, using polyhydroxyalkanoate (PHA) granules as a solid sustained-release carbon source in RAS was evaluated. With the initial nitrate-N concentration of 140 mg/L, the high denitrification rates of 0.056 g NO3−-N L−1 day−1 and 0.035 g NO3−-N L−1 day−1 were achieved in denitrification medium containing poly-β-hydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), respectively. Significant erosions and pits formed on the surface of the granules made them a good biofilm carrier for AOB-7, and 3-hydroxybutyrate (3-HB) monomer was the major product released to aquatic phase, which was benefit to animals. SEM photos showed that AOB-7 entered and attached on the inside of the PHA particle holes. A 4-week application trial was conducted to reveal the effects of PHB (AOB-7) denitrifying agent and 3-HB produced on growth of zebrafish (Brachydanio rerio) by adding 0.1% (w/v) PHB (AOB-7) denitrifying agent. Result indicated that PHB (AOB-7) denitrifying agent can significantly reduce nitrate-N content in RASs. Compared with the control group, feed coefficient ratio reduced by 18% and weight gain ratio increased by 29% in the PHB (AOB-7) denitrifying agent group. 3-HB monomer produced during the denitrification was speculated to function as a prebiotic and promote zebrafish growth. • AOB-7 showed a good aerobic denitrifying ability on PHA granules as sustained-release C source. • PHB (AOB-7) denitrifying agent can significantly reduce nitrate content in RAS. • R-3-HB monomer was the major product released to aquatic phase and function as a prebiotic.

Background Phaffia rhodozyma has many desirable properties for astaxanthin production, including rapid heterotrophic metabolism and high cell densities in fermenter culture. The low optimal temperature range (17–21 °C) for cell growth and astaxanthin synthesis in this species presents an obstacle to efficient industrial-scale astaxanthin production. The inhibition mechanism of cell growth at > 21 °C in P. rhodozyma have not been investigated. Results MK19, a mutant P. rhodozyma strain grows well at moderate temperatures, its cell growth was also inhibited at 28 °C, but such inhibition was mitigated, and low biomass 6 g/L was obtained after 100 h culture. Transcriptome analysis indicated that low biomass at 28 °C resulted from strong suppression of DNA and RNA synthesis in MK19. Growth inhibition at 28 °C was due to cell membrane damage with a characteristic of low mRNA content of fatty acid (f.a.) pathway transcripts (acc, fas1, fas2), and consequent low f.a. content. Thinning of cell wall and low mannose content (leading to loss of cell wall integrity) also contributed to reduced cell growth at 28 °C in MK19. Levels of astaxanthin and ergosterol, two end-products of isoprenoid biosynthesis (a shunt pathway of f.a. biosynthesis), reached 2000 µg/g and 7500 µg/g respectively; ~2-fold higher than levels at 21 or 25 °C. Abundance of ergosterol, an important cell membrane component, compensated for lack of f.a., making possible the biomass production of 6 g/L for MK19 at 28 °C. Conclusions Inhibition of growth of P. rhodozyma at 28 °C results from blocking of DNA, RNA, f.a., and cell wall biosynthesis. In MK19, abundant ergosterol made possible biomass production 6 g/L at 28 °C. Significant accumulation of astaxanthin and ergosterol indicated an active MVA pathway in MK19 at 28 °C. Strengthening of the MVA pathway can be a feasible metabolic engineering approach for enhancement of astaxanthin synthesis in P. rhodozyma. The present findings provide useful mechanistic insights regarding adaptation of P. rhodozyma to 28 °C, and improved understanding of feasible metabolic engineering techniques for industrial scale astaxanthin production by this economically important yeast species.

Hydroxylamine is a key intermediate of microbial ammonia oxidation and plays an important role in the biogeochemical cycling of N-compounds. Hydroxylamine is oxidized to NO or N2O by hydroxylamine oxidases or cytochrome P460 from heterotrophic or autotrophic bacteria, but its enzymatic oxidation to N2 has not yet been observed. Here, we report on the discovery of a novel oxidase that converts hydroxylamine to N2 from the newly isolated heterotrophic nitrifier Alcaligenes strain HO-1. Strain HO-1 accumulated hydroxylamine and produced N2 from ammonia oxidation. Using transcriptome analysis and heterologous expression via fosmid library screening, we identified three genes (dnfABC) of strain HO-1 that enabled E. coli cells not only to produce hydroxylamine from 15N-labelled ammonium but also to further convert it to 15N2. The three genes were individually cloned and expressed, and their translational products DnfA, DnfB, and DnfC were purified. In vitro DnfA bound to hydroxylamine and catalyzed the conversion of hydroxylamine to N2 in the presence of FAD, NADH and O2. Thus, DnfA was identified as a novel hydroxylamine oxidase and catalyzed a previously unknown N-N bond forming reaction with a yet-to-be discovered mechanism. DnfA homologs were detected in different bacterial groups, suggesting that hydroxylamine oxidation to nitrogen might occur in additional microbial taxa.

Background: MCM3AP-AS1 is a recently characterized lncRNA in hepatocellular carcinoma (HCC) and (GBM). We found that miR-148a may be able to bind MCM3AP-AS1. We explored the functions of lncRNA MCM3AP-AS1 in small cell lung cancer (SCLC). Methods: Gene expression in SCLC patients was analyzed by qPCR. Transient transfections were performed to analyze gene interactions. Cell invasion and migration were analyzed by Transwell assays.Results: We found that MCM3AP-AS1 was upregulated in SCLC and high expression levels were accompanied by low survival rate. Bioinfromatics analysis showed that MCM3AP-AS1 may bind miR-148a, which can target ROCK1. In SCLC tissues, MCM3AP-AS1 was positively correlated with ROCK1. In SCLC cells, MCM3AP-AS1 overexpression mediated the upregulated ROCK1 expression and increased cell invasion and migration rates. However, MCM3AP-AS1 and miR-148a could not regulate each other. However, miR-148a overexpressed led to downregulated ROCK1 expression, decreased cell invasion and migration rates, and reduced effects of MCM3AP-AS1 overexpression. Conclusions: Therefore, MCM3AP-AS1 may sponge miR-148a to cell invasion and migration in SCLC through the upregulation of ROCK1.

The bacterium Aeromonas salmonicida is the causative agent of furunculosis, a systemic, ubiquitous disease of fish in the salmon family, characterized by high mortality and morbidity. Probiotics are a promising approach for prevention of furunculosis in aquaculture. A bacterial strain with anti-A. salmonicida properties, Bacillus velezensis V4, was isolated and the mechanisms underlying these properties were investigated. Anti-A. salmonicida compounds present in cell-free supernatant of V4 were purified and structurally identified as members of the iturin, macrolactin, and difficidin groups. The compounds contributed jointly to inhibition of A. salmonicida, and the diversity of the compounds was related to the versatility of their mode of action. Addition of the compounds to A. salmonicida cell suspensions reduced cell density. Analyses by confocal microscopy and scanning electron microscopy revealed cell membrane disruption, deletion of cellular content, and cell lysis of A. salmonicida. The V4 genome was sequenced, and gene clusters involved in synthesis of anti-Aeromonas compounds were detected and identified. A possible probiotic effect on growth performance of Oncorhynchus mykiss (rainbow trout) was investigated by addition of 0, 1, and 3 % (v/w) V4. Relative to control, mortality was reduced 27.25 % in the 1 % addition group and 81.86 % in the 3 % addition group. Feed coefficient ratio was reduced 19.49 % and weight gain ratio was increased 71.22 % in the 1 % addition group. Our findings demonstrate that V4 is an effective probiotic strain in O. mykiss and has clear potential for both control of furunculosis and growth promotion of aquaculture animals.

Two novel coordination compounds, [Sr(atzp)2(H2O)2]·CH3OH (1) and [Sr(dtzpha)(H2O)3]·4H2O (2) [Hatzp=5-aminotetrazole-1-propionic acid, H2dtzpha=1,3-di(tetrazol-5-yl)benzene-N2,N2′-diacetic acid)], have been generated by using 5-aminotetrazole-1-propionic acid and 1,3-di(tetrazol-5-yl)benzene-N2,N2′-diacetic acid to react with strontium salts, respectively. X-ray diffraction analysis reveals that carboxylic groups of two ligands show the same coordination mode (the μ 1,1,3-COO coordination mode), compound 1 displays a 1D structure while compound 2 shows a 2D structure, which implies the influence of the number of the carboxylic acid groups. Luminescence properties of 1 and 2 were investigated at room temperature in the solid state.

Psychrophilic enzymes play crucial roles in cold adaptation of microbes and provide useful models for studies of protein evolution, folding, and dynamic properties. We examined the crystal structure (2.2-Å resolution) of the psychrophilic β-glucosidase BglU, a member of the glycosyl hydrolase 1 (GH1) enzyme family found in the cold-adapted bacterium Micrococcus antarcticus . Structural comparison and sequence alignment between BglU and its mesophilic and thermophilic counterpart enzymes (BglB and GlyTn, respectively) revealed two notable features distinct to BglU: (i) a unique long-loop L3 (35 versus 7 amino acids in others) involved in substrate binding and (ii) a unique amino acid, His299 (Tyr in others), involved in the stabilization of an ordered water molecule chain. Shortening of loop L3 to 25 amino acids reduced low-temperature catalytic activity, substrate-binding ability, the optimal temperature, and the melting temperature ( T m ). Mutation of His299 to Tyr increased the optimal temperature, the T m , and the catalytic activity. Conversely, mutation of Tyr301 to His in BglB caused a reduction in catalytic activity, thermostability, and the optimal temperature (45 to 35°C). Loop L3 shortening and H299Y substitution jointly restored enzyme activity to the level of BglU, but at moderate temperatures. Our findings indicate that loop L3 controls the level of catalytic activity at low temperatures, residue His299 is responsible for thermolability (particularly heat lability of the active center), and long-loop L3 and His299 are jointly responsible for the psychrophilic properties. The described structural basis for the cold adaptedness of BglU will be helpful for structure-based engineering of new cold-adapted enzymes and for the production of mutants useful in a variety of industrial processes at different temperatures.

Background A major obstacle to industrial-scale astaxanthin production by the yeast Phaffia rhodozyma is the strong inhibitory effect of high glucose concentration on astaxanthin synthesis. We investigated, for the first time, the mechanism of the regulatory effect of high glucose (> 100 g/L) at the metabolite and transcription levels. Results Total carotenoid, β-carotene, and astaxanthin contents were greatly reduced in wild-type JCM9042 at high (110 g/L) glucose; in particular, β-carotene content at 24–72 h was only 14–17% of that at low (40 g/L) glucose. The inhibitory effect of high glucose on astaxanthin synthesis appeared to be due mainly to repression of lycopene-to-β-carotene and β-carotene-to-astaxanthin steps in the pathway. Expression of carotenogenic genes crtE, pbs, and ast was also strongly inhibited by high glucose; such inhibition was mediated by creA, a global negative regulator of carotenogenic genes which is strongly induced by glucose. In contrast, astaxanthin-overproducing, glucose metabolic derepression mutant strain MK19 displayed de-inhibition of astaxanthin synthesis at 110 g/L glucose; this de-inhibition was due mainly to deregulation of pbs and ast expression, which in turn resulted from low creA expression. Failure of glucose to induce the genes reg1 and hxk2, which maintain CreA activity, also accounts for the fact that astaxanthin synthesis in MK19 was not repressed at high glucose. Conclusion We conclude that astaxanthin synthesis in MK19 at high glucose is enhanced primarily through derepression of carotenogenic genes (particularly pbs), and that this process is mediated by CreA, Reg1, and Hxk2 in the glucose signaling pathway.

Bacterial community dynamics of the ANAMMOX reactor of an integrated “UASB + SHARON + ANAMMOX” system for treating piggery wastewater were investigated using the Illumina MiSeq method with samples obtained at ~ 2-week intervals during a 314-day period. With aerobic activated sludge as seeds and low content artificial wastewater (NH4+–N 50 mg/L; NO2−–N 55 mg/L) as influent for the ANAMMOX reactor, nitrogen removal was initially observed on day 38 with a removal rate 1.3 mg N L−1 day−1, and increased to 90.4 mg N L−1 day−1 on day 55 with almost complete removal of ammonia and nitrite, indicating a successful startup of the reactor. Increasing influent load stepwise to NH4+–N 272.7 mg/L/NO2−–N 300 mg/L, nitrogen removal rate increased gradually to 470 mg N L−1 day−1 on day 228, and maintained a stable level (~ 420 mg N L−1 day−1) following introduction of SHARON effluent since day 229. Correlation between microbial community dynamics and nitrogen removal capability was significant (r = 0.489, p 300 mg/L), suggesting their different niches and application for different loads. These findings improve the understanding of relationships among microbial community/functional taxa, running parameters and reactor performance, and will be useful in optimizing running parameters for rapid startup and high, stable efficiency. Electronic supplementary material The online version of this article (10.1186/s13568-018-0686-0) contains supplementary material, which is available to authorized users.

An efficient heterotrophic nitrifying/aerobic denitrifying strain, Photobacterium sp. NNA4 was isolated from a recirculating aquaculture system (RAS). NNA4 was capable of utilizing ammonia, nitrate or nitrite as sole N-source with maximal removal rates of 12.5 mg/L/h for NH4+ N, 16.4 mg/L/h for NO3--N, and 4.5 mg/L/h for NO2--N, respectively. Optimal nitrification conditions were: sodium succinate as C-source, 30–37°C, NaCl 1–4%, pH 7.0–8.0, dissolved oxygen 5.89 mg/L, C/N > 10. Gas chromatography/mass spectrometry and gas chromatography/isotope ratio mass spectrometry analyses showed that N2 and N2O were aerobic denitrification products of nitrite and nitrate. NNA4 could tolerate high concentration of hydroxylamine and displayed efficient hydroxylamine-transforming capability. Hydroxylamine oxidoreductase activity using potassium ferricyanide as electron acceptor was 0.042 U. Results revealed that strain NNA4 could oxidize NH2OH directly to N2O at aerobic conditions. In view of its high removal ability of inorganic nitrogen pollutants and broad salinity tolerance range, NNA4 has great potential in denitrification treatment of types of wastewater with either low salinity (e.g., municipal facilities) or high salinity (e.g., aquaculture, seafood processing).

Nitrogen pollution is an increasingly severe worldwide problem because of drainage of nitrogen-containing wastewater and intensive application of nitrogen-containing fertilizers. Denitrification, a key process in nitrogen cycles, is commonly employed for nitrogen removal in engineered wastewater treatment systems. Biological denitrification is performed by denitrifying microbes (bacteria) that use nitrate as terminal electron acceptor. Better understanding the functions of diverse microbial populations in denitrification-based wastewater treatment systems, and the interactions of these populations with operating environments, is essential for improving both treatment performance and system stability. Recent advances in "meta-omics" (e. g., genomics, transcriptomics, proteomics, metabolomics), other molecular biology tools, and microbiome analysis have greatly enhanced such understanding. This minireview summarizes recent findings regarding microbial community structure and composition, key functional microbes and their physiology, functional genes involved in nitrogen cycle, and responses of microbes and their genes to changes of environmental factors or operating parameters, in denitrification processes in wastewater treatment systems. Of particular interest are heterotrophic denitrification systems (which require alternative organic carbon sources) and the autotrophic denitrification systems (which do not require an external carbon source). Integrated microbiome and -omics approaches have great future potential for determination of optimal environmental and biotechnological parameters, novel process development, and improvement of nitrogen removal efficiency and system stability.

Optimization of running parameters in a bioreactor requires detailed understanding of microbial community dynamics during the startup and running periods. Using a novel piggery wastewater treatment system termed “UASB + SHARON + ANAMMOX” constructed in our laboratory, we investigated microbial community dynamics using the Illumina MiSeq method, taking activated sludge samples at ~2-week intervals during a ~300-day period. Ammonia-oxidizing bacteria (AOB) were further investigated by quantification of AOB amoA genes and construction of gene clone libraries. Major changes in bacterial community composition and dynamics occurred when running manner was changed from continuous flow manner (CFM) to sequencing batch manner (SBM), and when effluent from an upflow anaerobic sludge blanket (UASB) reactor for practical treatment of real piggery wastewater was used as influent; differences among these three experimental groups were significant (R2 = 0.94, p

Psychrophilic enzymes display efficient activity at moderate or low temperatures (4–25 °C) and are therefore of great interest in biotechnological industries. We previously examined the crystal structure of BglU, a psychrophilic β-glucosidase from the bacterium Micrococcus antarcticus, at 2.2 A resolution. In structural comparison and sequence alignment with mesophilic (BglB) and thermophilic (GlyTn) counterpart enzymes, BglU showed much lower contents of Pro residue and of charged amino acids (particularly positively charged) on the accessible surface area. In the present study, we investigated the roles of specific amino acid residues in the cold adaptedness of BglU. Mutagenesis assays showed that the mutations G261R and Q448P increased optimal temperature (from 25 to 40–45 °C) at the expense of low-temperature activity, but had no notable effects on maximal activity or heat lability. Mutations A368P, T383P, and A389E significantly increased optimal temperature (from 25 to 35–40 °C) and maximal activity (~1.5-fold relative to BglU). Thermostability of A368P and A389E increased slightly at 30 °C. Mutations K163P, N228P, and H301A greatly reduced enzymatic activity—almost completely in the case of H301A. Low contents of Pro, Arg, and Glu are important factors contributing to BglU’s psychrophilic properties. Our findings will be useful in structure-based engineering of psychrophilic enzymes and in production of mutants suitable for a variety of industrial processes (e.g., food production, sewage treatment) at cold or moderate temperatures.

The bacterial strain F6 was isolated from a biological aerated filter that is used for purifying recirculating water in a marine aquaculture system and was identified as Marinobacter sp. based on the analysis of its 16S rRNA gene sequence. Strain F6 showed efficient aerobic denitrifying ability. One hundred percent of nitrates and 73.10% of nitrites were removed, and the total nitrogen (TN) removal rates reached 50.08% and 33.03% under a high nitrate and nitrite concentration in the medium, respectively. N2O and 15N2, as revealed by GC–MS and GC–IRMS, were the products of aerobic denitrification. Factors affecting the growth and aerobic denitrifying performance of strain F6 were investigated. The results showed that the optimum aerobic denitrification conditions for strain F6 were the presence of sodium succinate as a carbon source, a C/N ratio of 15, salinity ranging from 32–35 g/L of NaCl, incubation temperature of 30°C, an initial pH of 7.5, and rotation speed of 150 rpm [dissolved oxygen (DO) 6.75 mg/L]. In addition, strain F6 was confirmed to be a heterotrophic nitrifier through its NO 2 − generation and 25.96% TN removal when NH4+ was used as the sole N source. Therefore, strain F6, the first reported member of genus Marinobacter with aerobic heterotrophic nitrifying–denitrifying ability, is an excellent candidate for facilitating simultaneous nitrification and denitrification (SND) in industry and aquaculture wastewater.

The gene bglU encoding a cold-adapted β-glucosidase (BglU) was cloned from Micrococcus antarcticus . Sequence analysis revealed that the bglU contained an open reading frame of 1419 bp and encoded a protein of 472 amino acid residues. Based on its putative catalytic domains, BglU was classified as a member of the glycosyl hydrolase family 1 (GH1). BglU possessed lower arginine content and Arg/(Arg + Lys) ratio than mesophilic GH1 β-glucosidases. Recombinant BglU was purified with Ni2+ affinity chromatography and subjected to enzymatic characterization. SDS-PAGE and native staining showed that it was a monomeric protein with an apparent molecular mass of 48 kDa. BglU was particularly thermolabile since its half-life time was only 30 min at 30 °C and it exhibited maximal activity at 25 °C and pH 6.5. Recombinant BglU could hydrolyze a wide range of aryl-β-glucosides and β-linked oligosaccharides with highest activity towards cellobiose and then p -nitrophenyl-β- d -glucopyranoside (pNPG). Under the optimal conditions with pNPG as substrate, the K m and k cat were 7 mmol/L and 7.85 × 103/s, respectively. This is the first report of cloning and characterization of a cold-adapted β-glucosidase belonging to GH1 from a psychrotolerant bacterium.

The prokaryotic community composition and diversity and the distribution patterns at various taxonomic levels across gradients of salinity and physiochemical properties in the surface waters of seven plateau lakes in the Qaidam Basin, Tibetan Plateau, were evaluated using Illumina MiSeq sequencing. These lakes included Lakes Keluke (salinity, Bacteria in lakes with salinities of Archaea in Lake Gasikule. The clades At12OctB3 and Salinibacter , previously reported only in hypersaline environments, were found in a hyposaline lake (salinity, 5.5 to 6.6 g/liter) at an abundance of ∼1.0%, indicating their ecological plasticity. Salinity and the concentrations of the chemical ions whose concentrations covary with salinity (Mg 2+ , K + , Cl − , Na + , SO 4 2− , and Ca 2+ ) were found to be the primary environmental factors that directly or indirectly determined the composition and diversity at the level of individual clades as well as entire prokaryotic communities. The distribution patterns of two phyla, five classes, five orders, five families, and three genera were well predicted by salinity. The variation of the prokaryotic community structure also significantly correlated with the dissolved oxygen concentration, pH, the total nitrogen concentration, and the PO 4 3− concentration. Such correlations varied depending on the taxonomic level, demonstrating the importance of comprehensive correlation analyses at various taxonomic levels in evaluating the effects of environmental variable factors on prokaryotic community structures. Our findings clarify the distribution patterns of the prokaryotic community composition in plateau lakes at the levels of individual clades as well as whole communities along gradients of salinity and ionic concentrations.

Vibriosis is a major epizootic disease that impacts free-living and farmed fish species worldwide. Use of probiotics is a promising approach for prevention of Vibrio infections in aquaculture. A probiotic anti-Vibrio strain, Bacillus pumilus H2, was characterized, and the mechanism of its effect was investigated. All 29 Vibrio strains tested were growth-inhibited by H2. The anti-Vibrio substance present in cell-free supernatant of H2 was purified and characterized by reversed-phase HPLC. Minimum inhibitory concentrations of the purified substance, determined in liquid media for various Vibrio strains, ranged from 0.5 to 64 µg/ml. Addition of the purified substance to Vibrio vulnificus culture inhibited cell growth (estimated by OD600). Confocal microscopy and scanning electron microscopy analyses showed that surface structure of V. vulnificus cells was damaged by the purified substance, as reflected by presence of membrane holes, disappearance of cellular contents, and formation of cell cavities. The major mechanism of this anti-Vibrio activity appeared to involve disruption of cell membranes, and consequent cell lysis. The purified anti-Vibrio substance was shown to be structurally identical to amicoumacin A by MS and NMR analysis. Our findings indicate that B. pumilus H2 has strong potential for prevention or treatment of fish vibriosis in the aquaculture industry. Electronic supplementary material The online version of this article (doi:10.1186/s13568-017-0323-3) contains supplementary material, which is available to authorized users.