Mitigation of biofouling in membrane bioreactors by quorum-quenching bacteria during the treatment of metal-containing wastewater.

Quorum quenching (QQ) is an efficient way to mitigate membrane biofouling in a membrane bioreactor (MBR) during wastewater treatment. A QQ bacterium, Lysinibacillus sp. A4, was isolated and used to mitigate biofouling in an MBR during the treatment of wastewater containing metals. A QQ enzyme (named AilY) was cloned from A4 and identified as a metallo-ß-lactamase-like lactonase. The QQ activity of A4 and that of Escherichia coli BL21 (DE3) overexpressing AilY could be promoted by Fe2+, Mn2+, and Zn2+ while remaining unaffected by other metals tested. The two bacteria effectively mitigated biofouling by reducing the transmembrane pressure from around 30 to 20 kPa without negative influence on the COD, NH4+-N, or total phosphorus of the effluent. The relative abundance of Lysinibacillus sp. A4 increased greatly from 0.04 to 8.29% in the MBR with metal-containing wastewater, suggesting that Lysinibacillus sp. A4 could multiply quickly and adapt to this environment. Taken together, the findings suggested that A4 could tolerate metal to a certain degree, and this property could allow A4 to adapt well to metal-containing wastewater, making it a valuable strain for mitigating biofouling in MBR during the treatment of metal-containing wastewater.

Microbial features with uranium pollution in artificial reservoir sediments at different depths under drought stress.

The uranium (U) containing leachate from uranium tailings dam into the natural settings, may greatly affect the downstream environment. To reveal such relationship between uranium contamination and microbial communities in the most affected downstream environment under drought stress, a 180 cm downstream artificial reservoir depth sediment profile was collected, and the microbial communities and related genes were analyzed by 16S rDNA and metagenomics. Besides, the sequential extraction scheme was employed to shed light on the distinct role of U geochemical speciations in shaping microbial community structures. The results showed that U content ranged from 28.1 to 70.1 mg/kg, with an average content of 44.9 mg/kg, significantly exceeding the value of background sediments. Further, U in all the studied sediments was related to remarkably high portions of mobile fractions, and U was likely deposited layer by layer depending on the discharge/leachate inputs from uranium-involving anthoropogenic facilities/activities upstream. The nexus between U speciation, physico-chemical indicators and microbial composition showed that Fe, S, and N metabolism played a vital role in microbial adaptation to U-enriched environment; meanwhile, the fraction of Ureducible and the Fe and S contents had the most significant effects on microbial community composition in the sediments under drought stress.

Characterization of an N-acylhomoserine lactonase from Serratia sp. and its biofouling mitigation in a membrane bioreactor.

Membrane biofouling is a process that can impede the development of membrane bioreactor (MBR), which constitutes an important system of the wastewater treatment process. Membrane biofouling is governed by quorum sensing (QS), a communication system heavily dependent on the activities of signal molecules. Certain bacteria, known as quorum quenching (QQ) bacteria, can quench the QS process by destroying the signal molecules. These QQ bacteria are considered a sustainable and feasible way of mitigating membrane biofouling in MBR. In this study, a QQ enzyme (designated as AisZ) from a Serratia sp. was first identified and characterized. Escherichia coli BL21 expressing AisZ was able to degrade different QS signal molecules. Furthermore, these cells could also mitigate membrane biofouling in MBR during a 29-day operation by reducing the transmembrane pressure from 31 to 21 kPa. The metal ions Co2+ and Ni2+ were relatively important to AisZ in that they could significantly enhance the activity of AisZ and restore the EDTA-inactivated AisZ. Expression of the aisA gene was not influenced by Co2+, Ni2+ and QS signal molecules. AisZ might, therefore, extend the diversity of potential candidates for the mitigation of biofouling associated with membrane filtration technologies.

Microplastics in the soil: A review of distribution, anthropogenic impact, and interaction with soil microorganisms based on meta-analysis.

Microplastics (MPs) are widespread anthropogenic pollutants that contaminate the terrestrial environment and serve as vectors of other contaminants. They trigger toxic effects during their migration and transmission, affecting the soil ecosystem and eventually presenting a serious threat to human health via the food chain. However, comprehensive studies on the distribution of MPs in soil and their correlation with human activities and terrestrial ecosystems are still lacking. In this study, we detected a significant difference in the MP size (both for the size <1 mm (P < 0.01) and the size 1-2 mm (P < 0.05)) in China and other countries based on bibliometric and meta-analysis. Principal component analysis revealed regional variations in MP distribution. The correlation analysis between MP characteristics and anthropogenic activities in China further revealed that industrial production was linked to polypropylene microplastics (PP-MPs) abundance (P < 0.01). We also discussed the interaction between soil MPs and ecosystems, such as soil microbial community, since the transportation of MPs was associated with its distribution and environmental factors in the soil. Linear regression analysis further showed that environmental variables, such as culture temperature, were negatively related to MPs' degradation efficiency by the fungi (P < 0.05). This study aims to evaluate the distribution, transfer, and impact of MPs, and their interaction with the soil ecosystem and provides information on the prevention and management of MP pollution in the terrestrial environment.

Biotreatment of Cr(VI) and pyrene combined water pollution by loofa-immobilized bacteria.

Hexavalent chromium (Cr(VI)) and pyrene are toxic pollutants that are difficult to remediate from soils and wastewater. Serratia sp. strains have been previously demonstrated to remove either Cr(VI) or pyrene and here a new isolate, called the Z6 strain, was demonstrated to remove both simultaneously. The removal occurs primarily by Cr(VI) reduction and pyrene biodegradation, and genome analysis suggests the removal mechanisms are the putative chromate reductase and two assumable pathways of pyrene degradation. The Z6 strain effectively removed most Cr(VI) (up to approximately 86%) and pyrene (up to approximately 57%) in seven different types of wastewater after 7 days of biotreatment. Additionally, the carrier loofa used for bacteria immobilization did not change the kinetics of Cr(VI) reduction or pyrene degradation. The carrier loofa was also effective for multiple uses, with removal capacity not being significantly affected over the first seven cycles with the same carrier loofa. These results provide data for developing practical biotreatment applications of Cr(VI) and pyrene contaminated sites.

Biotreatment of pyrene and Cr(VI) combined water pollution by mixed bacteria.

Pyrene and chromium (Cr(VI)) are persistent pollutants and cause serious environmental problems because they are toxic to organisms and difficult to remediate. The toxicity of pyrene and Cr(VI) to three crops (cotton, soybean and maize) was confirmed by the significant decrease in root and shoot biomass during growth in pyrene/Cr(VI) contaminated hydroponic solution. Two bacterial strains capable of simultaneous pyrene biodegradation and Cr(VI) reduction were isolated and identified as Serratia sp. and Arthrobacter sp. A mixture of the isolated strains at a ratio of 1:1 was more efficient for biotreatment of pyrene and Cr(VI) than either strain alone; the mixture effectively carried out bioremediation of contaminated water in a hydroponic system mainly through pyrene biodegradation and Cr(VI) reduction. Application of these isolates shows potential for practical microbial remediation of pyrene and Cr(VI) combined water pollution.

Microbial insights into the biogeochemical features of thallium occurrence: A case study from polluted river sediments.

Thallium (Tl) is a trace element with extreme toxicity. Widespread Tl pollution in riverine systems, mainly due to escalating mining and smelting activities of Tl-bearing sulfide minerals, has attracted increasing attention. Insights into the function of the microbial communities with advanced characterization tools are critical for understanding the biogeochemical cycle of Tl. Herein, microbial communities and their adaptive evolution strategies in river sediments from a representative Tl-bearing pyrite mine area in southern China were profiled via 16S rRNA gene sequence analysis and shotgun metagenomic analysis. In total, 64 phyla and 778 genera of microorganisms were observed in the studied sediments. The results showed that pH, Tl, Pb, Zn and total organic carbon (TOC) had a significant influence on microbial community structure. Some important reductive microorganisms (such as Erysipelothrix, Geobacter, desulfatiferula, desulfatihabadium and fusibacter) were involved in the biogeochemical cycle of Tl. The ruv, rec, ars and other resistance genes enhanced the tolerance of microorganisms to Tl. The study suggested that relevant C, N and S cycle genes were the main metabolic paths of microorganisms surviving in the high Tl-polluted environment. The findings were critical for establishment, operation and regulation in the microbial treatment of Tl containing or related wastewater.

Response of microbial communities and interactions to thallium in contaminated sediments near a pyrite mining area.

Thallium (Tl) is a well-recognized hazardous heavy metal with very high toxicity. It is usually concentrated in sulfide minerals, such as pyrite (FeS2), sphalerite (ZnS), chalcopyrite (CuS) and galena (PbS). Here, this study was carried out to investigate the indigenous microbial communities via 16S rRNA gene sequence analysis in typical surface sediments with various levels of Tl pollution (1.8-16.1 mg/kg) due to acid mine drainage from an active Tl-containing pyrite mining site in South China. It was found with more than 50 phyla from the domain Bacteria and 1 phyla from the domain Archaea. Sequences assigned to the genera Ferroplasma, Leptospirillum, Ferrovum, Metallibacterium, Acidithiobacillus, and Sulfuriferula manifested high relative abundances in all sequencing libraries from the relatively high Tl contamination. Canonical correspondence analysis further uncovered that the overall microbial community in this area was dominantly structured by the geochemical fractionation of Tl and geochemical parameters such as pH and Eh. Spearman's rank correlation analysis indicated a strong positive correlation between acidophilic Fe-metabolizing species and Tltotal, Tloxi, and Tlres. The findings clarify potential roles of such phylotypes in the biogeochemical cycling of Tl, which may facilitate the development of in-situ bioremediation technology for Tl-contaminated sediments.

Mechanism of uranium release from uranium mill tailings under long-term exposure to simulated acid rain: Geochemical evidence and environmental implication.

To date, there is not sufficient knowledge to fully understand the occurrence, transport and fate of residual uranium (U) from uranium mill tailings (UMT). Herein this study investigated different U release behaviors from natural UMT (without grinding) under four simulated acid rain (pH = 2.0-5.0) compared with controlled scenario (pH = 6.0) for 25 weeks. The results showed that the most notable U release was observed from UMTpH2.0, followed by UMTpH3.0 whereas a nonlinear relationship between pH and U release was observed from UMTpH4.0-6.0. The divergence of U release behaviors was attributed to the presence of minerals such as calcite and clinochlore. Autunite, a secondary mineral formed after leaching, might regulate U release in UMTpH3.0-6.0. Fick theory model revealed the shift of U release mechanism from surface dissolution to diffusion transport for UMTpH2.0, UMTpH3.0 and UMTpH5.0 at varied stage, whereas UMTpH4.0 and UMTpH6.0 displayed univocal dissolution and diffusion mechanism, respectively. This study highlights the necessity of performing long-term leaching tests to detect the "shift event" of leaching kinetics and to better understand the mechanism of U release influenced by mineralogy of the natural UMT under simulated acid rain conditions, which is conducive to developing UMT management strategies to minimize the risk of U release and exposure.

High-Quality Draft Genome Sequence of Leucobacter sp. Strain G161, a Distinct and Effective Chromium Reducer.

Here, we report the genome sequence for Leucobacter sp. strain G161 due to its distinct and effective hexavalent chromium reduction under aerobic growth conditions, followed by facultative anaerobic incubation. The draft genome sequence of Leucobacter sp. G161 comprises 3,554,188 bp, with an average G+C content of 65.3%, exhibiting 3,341 protein-coding genes and 55 predicted RNA genes.

Bioremediation of hexavalent chromate using permeabilized Brevibacterium sp. and Stenotrophomonas sp. cells.

Bioremediation has been found to be a useful method for removing hexavalent chromium (Cr(VI)), which is very toxic, from wastewater. Two strains of bacteria that were able to reduce Cr(VI) effectively were isolated from Cr(VI) contaminated soil samples and identified as Brevibacterium sp. K1 and Stenotrophomonas sp. D6, respectively, based on 16S rRNA gene sequence analyses. Brevibacterium sp. K1 and Stenotrophomonas sp. D6 could grow in Luria-Broth medium containing K2Cr2O7 at 1000 and 1600 mg/L, respectively, and they completely reduced the Cr(VI) in LB medium containing K2Cr2O7 at 200 mg/L within 72 h. Further analyses revealed that permeabilized K1 and D6 cells reduced Cr(VI) more effectively than did the resting cells. Triton X-100 was the best permeabilizing agent that was tested. The permeabilized cells of both strains could completely reduce Cr(VI) in industrial wastewater twice before needing to be replenished. The results suggested that these chromate-reducing bacteria are potential candidates for practical use biotreating industrial effluents containing Cr(VI) with Stenotrophomonas sp. D6 being the more effective bacterium.

Comparative evaluations on bio-treatment of hexavalent chromate by resting cells of Pseudochrobactrum sp. and Proteus sp. in wastewater.

Two marine bacterial strains, B5 and H24, were isolated from long-term Cr(VI) contaminated seawater and identified as Pseudochrobactrum and Proteus, respectively, based on 16S rRNA gene sequence analyses. Both strains were examined for their tolerance to Cr(VI) and other metal salts and their abilities to reduce Cr(VI) to trivalent chromium [Cr(III)]. Growing cells of Pseudochrobactrum sp. B5 and Proteus sp. H24 could tolerate Cr(VI) at a concentration of 2000 and 1500 mg/l and completely reduce 1000 mg/l Cr(VI) in LB medium within 96 and 144 h, respectively. Resting cells of the two strains were able to reduce 200mg/l Cr(VI) in Tris-HCl buffer within 16 and 24h, respectively. Furthermore, resting cells of both strains were able to reduce Cr(VI) in industrial wastewaters three times consecutively. Overall, this study provides evidence of the potential for application of chromate-reducing bacteria to direct Cr(VI) decontamination of industrial effluents.

Distinct and effective biotransformation of hexavalent chromium by a novel isolate under aerobic growth followed by facultative anaerobic incubation.

A bacterial isolate (G161) with high Cr(VI)-reducing capacity was isolated from Cr(VI)-contaminated soil and identified as Leucobacter sp. on the basis of 16S rRNA gene sequence analysis. The isolate was a Gram-positive, aerobic rod. The hexavalent chromate-reducing capability of the isolate was investigated under three conditions of oxygen stress. The isolate was found to reduce Cr(VI) under all conditions but performed most effectively during aerobic growth followed by facultative anaerobic incubation. Under these conditions, the isolate tolerated K(2)Cr(2)O(7) concentrations up to 1,000 mg/l and completely reduced 400 mg/l K(2)Cr(2)O(7) within 96 h. The strain reduced Cr(VI) over a wide range of pH (6.0-11.0) and temperatures (15-45 °C) with optimum performance at pH 8.0 and 35 °C. The presence of other metals, such as Ca(2+), Co(2+), Cu(2+), Mn(2+), Ni(2+), and Zn(2+), induced no effect or else played a stimulatory role on Cr(VI)-reduction activity of the strain. The strain was tested for Cr(VI) removal in wastewaters and proved capable of completely reducing the contained Cr(VI). This is the novel report of a bacterial growth and Cr(VI)-reduction process under sequential aerobic growth and facultative anaerobic conditions. The study suggested that the isolate possesses a distinct capability for Cr(VI) reduction which could be harnessed for the detoxification of chromate-contaminated wastewaters.

Molecular mechanism for cadmium-induced anthocyanin accumulation in Azolla imbricata.

Anthocyanins inducibly synthesized by Cd treatment showed high antioxidant activity and might be involved in internal detoxification mechanisms of Azolla imbricata against Cd toxicity. In order to understand anthocyanin biosynthesis mechanism during Cd stress, the cDNAs encoding chalcone synthase (CHS) and dihydroflavonol reductase (DFR), two key enzymes in the anthocyanin synthesis pathway, were isolated from A. imbricata. Deduced amino acid sequences of the cDNAs showed high homology to the sequences from other plants. Expression of AiDFR, and to a lesser extent AiCHS, was significantly induced in Cd treatment plant in comparison with the control. CHS and DFR enzymatic activities showed similar pattern changes with these genes expression during Cd stress. These results strongly indicate that Cd induced anthocyanin accumulation is probably mediated by up-regulation of structural genes including CHS and DFR, which might further increase the activities of enzymes encoded by these structural genes that control the anthocyanin biosynthetic steps.

Molluscicidal activity of cardiac glycosides from Nerium indicum against Pomacea canaliculata and its implications for the mechanisms of toxicity.

Cardiac glycosides from fresh leaves of Nerium indicum were evaluated for its molluscicidal activity against Pomacea canaliculata (golden apple snail: GAS) under laboratory conditions. The results showed that LC(50) value of cardiac glycosides against GAS was time dependent and the LC(50) value at 96 h was as low as 3.71 mg/L, which was comparable with that of metaldehyde at 72 h (3.88 mg/L). These results indicate that cardiac glycosides could be an effective molluscicide against GAS. The toxicological mechanism of cardiac glucosides on GAS was also evaluated through changes of selected biochemical parameters, including cholinesterase (ChE) and esterase (EST) activities, glycogen and protein contents in hepatopancreas tissues of GAS. Exposure to sublethal concentrations of cardiac glycosides, GAS showed lower activities of EST isozyme in the later stages of the exposure period as well as drastically decreased glycogen content, although total protein content was not affected at the end of 24 and 48 h followed by a significant depletion at the end of 72 and 96 h. The initial increase followed by a decline of ChE activity was also observed during the experiment. These results suggest that cardiac glycosides seriously impair normal physiological metabolism, resulting in fatal alterations in major biochemical constituents of hepatopancreas tissues of P. canaliculata.

Gene expression profiling in porcine mammary gland during lactation and identification of breed- and developmental-stage-specific genes.

A total of 28941 ESTs were sequenced from five 5'-directed non-normalized cDNA libraries, which were assembled into 2212 contigs and 5642 singlets using CAP3. These sequences were annotated and clustered into 6857 unique genes, 2072 of which having no functional annotations were considered as novel genes. These genes were further classified into Gene Ontology categories. By comparing the expression profiles, we identified some breed- and developmental-stage-specific gene groups. These genes may be relative to reproductive performance or play important roles in milk synthesis, secretion and mammary involution. The unknown EST sequences and expression profiles at different developmental stages and breeds are very important resources for further research.

Decolorization of anthraquinone dye with immobilized Penicillium jensenii.

Cells of Penicillium jensenii were immobilized by entrapment in natural and synthetic polymeric matrices. The decolorization of Reactive Brilliant Blue KN-R by immobilized cells has been studied. It was found that CA-immobilized cells could effectively decolorize reactive brilliant blue KN-R. Many factors affecting the decolorization process were studied, including: pH, temperature, dye concentration, shaker speed and culture time. The reusability of the immobilized cells was evaluated with repeated-batch decolorization experiments. The optimum pH, temperature, shaker speed and culture time of decolorization with CA-, CGN-, and PAA- immobilized cells are 4.0 and 30 degrees C and 150r/min and 48hr respectively, dye concentration could have some effects on decolorization. After four repeated experiments, the decolorization rate of CA-, CGN-, and PAA- immobilized cells could still remain 73.6%, 60.8%, 50.5%, respectively.

A comparative study of Cu (II) biosorption on Ca-alginate and immobilized live and inactivated Cladosporium sp.

Spores of Cladosporium sp. were immobilized into Ca-alginate beads via entrapment. The alginate beads and both entrapped live and inactivated spores of Cladosporium sp. were used for comparison of biosorptive capacity from aqueous solutions. The factors affecting the adsorption ability on Cu (II), such as the contact time, initial pH, temperature were investigated. The results showed that the Ca-alginate beads containing live spores of Cladosporium sp. had the maximum biosorptive capacity. The biosorption equilibrium was established in about 3 h. The maximum biosorption of Cu (II) on Ca-alginate entrapping spores and no spores were obtained between pH 4.0 and 3.5. Temperature over the range of 15-45 degrees C had no significant effect on the biosorption capacity. The biosorptive capacity increased with initial concentrations in the concentration range of 30-800mg/l. The equilibrium was well described by Langmuir biosorption isotherms. The Ca-alginate beads could be regenerated using 0.1M HCl, The biosorbents were reused in three biosorption-desorption cycles with negligible decrease in biosorptive capacity.

Decolourization of reactive brilliant blue KN-R by immobilized cells of Aspergillus ficuum.

Aspergillus ficuum was immobilized with sodium alginate, and decolourization of Reactive Brilliant Blue KN-R was studied on immobilized and free Aspergillus ficuum. The optimal preparation condition of the strain immobilization was obtained by the orthogonal test, it is sodium alginate 3%, CaCl2 5%, wet mycelia 30 g/L, calcific time 8 h. It was found that the immobilized cells could effectively decolourize Reactive Brilliant Blue KN-R, the optimum temperature and pH were 33 degrees C and 5.0, respectively. The kinetics study of decolourization of immobilized cells showed that the decolourization of Aspergillus ficuum immobilized conformed to zero-order reaction model. The decolourization efficiency of immobilized cell compared with that of free cell in different physical conditions. Results showed that the decolourization of immobilized cells with mycelia had the best efficiency. The immobilized cells could be reused after the first decolourization.