Mechanism and Modes of Microbial Minerogenesis of Polymetallic Nodules on the Ocean Floor

: This paper presents a quantitative analysis of the relations of the occurrence of polymetallic nodules with the geochemical actions of microbes in the seawater, pore water and sediments at the bottom of the eastern Pacific Ocean basin. Emphasis is laid on the relations of the activity intensity and biochemical transformation rate of aerobic bacteria (iron bacteria, Thiobacillus thioparus, halobacteria and manganese—oxidizing bacteria) and anaerobic bacteria (sulphate—reducing bacteria, denitrifying bacteria, Thiobacillus denitrificans) with mineralization. The experimental research on the migration and accumulation of ore-forming elements caused by microbial and chemical actions shows that the microbes have changed the conditions of oxidation and reduction in the system, and their effect on the element precipitation is much stronger than the chemical actions and accelerates the enrichment of Fe and Ma It demonstrates that the microbes can change the environment to promote the accumulation of ore-forming elements, thus leading to indirect mineralization.

Co-incorporation of Chinese milk vetch(Astragalus sinicus L.)and chemical fertilizers alters microbial functional genes supporting short-time scale positive nitrogen priming effects in paddy soils

Nitrogen(N)priming is a microbially mediated biochemical process as affected by different incorporation practices.However,little information is known about the microbial mechanisms driving the response of N priming to co-operation of Chinese milk vetch(CMV,Astragalus sinicus L.)and different rates of chemical fertilizers in paddy soils in South China.Here,an anaerobic incubation experiment was conducted to study N priming effects(PE)and their relationships with soil microbial functional genes after CMV incorporation alone(M),co-incorporation of CMV with 100%(normal dosage)chemical fertilizers(MC100),and co-incorporation of CMV with 80% chemical fertilizers(MC80).Co-incorporation of CMV and chemical fertilizers enhanced the short-time scale(the first 20 d of incubation)positive PE of N,while no significant differences existed among the three treatments on day 60 or 90 of incubation(P>0.05).Compared with the M treatment,gross priming effect(GPE)in the MC100 and MC80 treatments significantly increased by 34.0% and 31.3%,respectively,and net priming effect(NPE)increased by 47.7% and 47.8%,respectively,during the first 20 d of incubation(P<0.05).This was likely attributed to soil nutrient availability and added substrate quality.The MC100 and MC80 treatments increased the gdhA gene abundance by 5.0% and 9.8%,increased the gdh2 gene abundance by 12.7% and 45.7%,and increased the nasB gene abundance by 9.5% and 41.4%,respectively,in comparison with the M treatment on day 20 of incubation.Correlation analyses indicated that soil microbial functional genes involved in N mineralization(gdhA and gdh2),assimilatory nitrate reduction(nasB),and nitrification(amoB)were significantly correlated with N priming under different incorporation practices during the incubation period(P<0.05).Thus,co-incorporation of CMV and chemical fertilizers can regulate soil microbial community functional gene structure,which may accelerate mineralization and assimilatory nitrate reduction and inhibit nitrification,thereby increasing the short-term positive PE of N in the present study.

Degradation properties of fulvic acid and its microbially driven mechanism from a partial nitritation bioreactor through multi-spectral and bioinformatic analysis

This study employed multispectral techniques to evaluate fulvic acid(FA)compositional characteristic and elucidate its biodegradation mechanisms during partial nitritation(PN)process.Results showed that FA removal efficiency(FRE)decreased from 90.22 to 23.11%when FA concentrations in the reactor were increased from 0 to 162.30 mg/L,and that molecular size,degree of aromatization and humification of the effluent FA macromolecules all increased after treatment.Microbial population analysis indicated that the proliferation of the Comamonas,OLB12 and Thauera exhibit high FA utilization capacity in lower concentrations(<50.59 mg/L),promoting the degradation and removal of macromolecular FA.In addition,the sustained increase in external FA may decrease the abundance of above functional microorganisms,resulting in a rapid drop in FRE.Furthermore,from the genetic perspective,the elevated FA levels restricted carbohydrate(ko00620,ko00010 and ko00020)and nitrogen(HAO,AMO,NIR and NOR)metabolism-related pathways,thereby impeding FA removal and total nitrogen loss associated with N_(2)O emissions.

A review on microbial metabolism to increase coalbed methane generation and coal pretreatment to improve its bioavailability

Abundant unminable coal in deep strata and abandoned mines are also precious sources of clean gas energy,under which biotransformation is a potential path.In recent years,substantial progress has been made in laboratory research on coal degradation to produce methane by microbial metabolism.This paper systematically reviews the research progress of microbial enhancement and microbial stimulation of coal,physicochemical pretreatments of coal,and environmental factors affecting coal biotransformation.The research idea of coal biotransformation should aim at field production increase and gradually clarify the microbial mechanism of coal degradation and the regional distribution and functional composition of microbial communities on the block scale.The research on coal biotransformation helps improve the development level of coalbed methane and the sustainable development of unconventional natural gas resources.

Biochar reduces colloidal phosphorus in leachate by regulating phoD- and phoC-harboring microbial communities during drying/rewetting cycles

Drying and rewetting(DRW)events cause the release of colloidal phosphorus(P_(coll),1-1000 nm)in leachate,and biochar is considered an effective inhibitor;however,the microbial mechanism remains elusive.In this study,three successive DRW cycles were performed on the soil columns to assess the effect of biochar addition on P_(coll) content and its possible associates,including phosphatase-producing microbial populations(phoD- and phoC-harboring microbial communities)and alkaline/acid phosphatase(ALP/ACP)activities.Results showed that the biochar addition significantly decreased the P_(coll) by 15.5-32.1%during three DRW cycles.The structural equation model(SEM)confirmed that biochar addition increased phoD- and phoC-harboring microbial communities and ALP/ACP activities,which reduces the release of P_(coll) into leachate.In addition,the manure biochar was more effective than the straw biochar in promoting competition and cooperation in the co-occurrence network(2-5%nodes increased on average),and the key taxa Proteobacteria and Cyanobacteria were identified as the dominant species of potential ALP/ACP activities and P_(coll) content.Our findings provide a novel understanding of biochar reducing P_(coll) loss from the phosphatase perspective by regulating the phoD-and phoC-harboring communities during DRW events.

Robustness of anammox granular sludge treating low-strength sewage under various shock loadings:Microbial mechanism and little N2O emission

With the increasing application of anammox for the treatment of high-strength industrial wastewater,application of anammox in municipal sewage has been gaining more attention.Sludge granulation in particular enhances the enrichment and retention of anammox bacteria in municipal sewage treatment systems.However,the performance of granular sludge under continuous and varying hydraulic loading shock remains little understood.In this study,the robustness of anammox granular sludge in treating lowstrength municipal sewage under various shock loadings was investigated.Results showed that an upflow anaerobic sludge blanket(UASB)reactor with anammox granules performed well,with anammox specific activity up to 0.28 kg N/kg VSS/day and anti-loading shock capability up to 187.2 L/day during the 8-month testing period.The accumulation rate of N2O(<0.01 kg N/kg VSS/day)in the liquid phase was seven times higher than that of the gas phase,which could be mainly attributed to the incomplete denitrification and insufficient carbon source.However,only a small part of the produced N2O escaped into the atmosphere.High-throughput sequencing and molecular ecological network analyses also identified the bacterial diversity and community structure,indicating the potential resistance against loading shock.The composition and structural analyses showed that polysaccharides were an important functional component in the tightly bound extracellular polymeric substances(TB-EPS),which was the major EPS layer of anammox granules.Scanning electron microscopy(SEM)also showed that the gaps in between the anammoxclusters in the granules inhibit the flotation of the sludge and ensure efficient settling and retention of anammox granules.

Resistance mechanisms and reprogramming of microorganisms for efficient biorefinery under multiple environmental stresses

In the fermentation process of biorefinery,industrial strains are normally subjected to adverse environmental stresses,which leads to their slow growth,yield decline,a substantial increase in energy consumption,and other negative consequences,which ultimately seriously hamper the development of biorefinery.How to minimize the impact of stress on microorganisms is of great significance.This review not only reveals the damaging effects of different environmental stresses on microbial strains but also introduces commonly used strategies to improve microbial tolerance,including adaptive evolution,reprogramming of the industrial host based on genetic circuits,global transcription machinery engineering(gTME)and bioprocess integration.Furthermore,by integrating the advantages of these strategies and reducing the cost of system operation,the tolerance of industrial strains,combined with production efficiency and process stability,will be greatly improved,and the development prospects of biorefinery will be more widespread.