Advances in Research on Synthetic Microbial Communities

The synthetic microbial community is a synthetic microbial system co-cultured with multiple species, which has the characteristics of clear composition and strong controllability. Compared with a single colony, it can achieve more complex functions and adapt to the changing environment more easily, so as to meet a wide range of needs. In this paper, the contents and concepts of microbial community and synthetic microbial community are briefly introduced, the principles that should be followed in the construction of microbial community are expounded, the methods and mathematical models used in the construction of synthetic microbial community are introduced, and the applications of synthetic microbial community in various fields are summarized. Finally, the challenges in the research of synthetic microbial communities are briefly described.

Soil conditioners improve Cd-contaminated farmland soil microbial communities to inhibit Cd accumulation in rice

The addition of silicon(Si)and organic fertilizers to soil conditioners can inhibit the transfer of heavy metal ions from soil to crops.However,it is not clear how Si and organic fertilizers affect soil properties and the micro-ecological environment and thereby reduce cadmium(Cd)accumulation in rice.In this study,the effects of L-type soil conditioners containing Si and organic fertilizers on bacterial and fungal community diversity,soil pH,organic matter,and available Si were analyzed with field experiments at two sites in Liuzhou City and Hezhou City,respectively,in Guangxi,China.With the increase of Si and organic fertilizer content in soil conditioner,rice yield respectively increased by 16.8–25.8 and 6.8–13.1%,and rice Cd content decreased significantly by 8.2–21.1 and 10.8–40.6%,respectively,at the two experimental sites.Soil microbiome analysis showed that the increase in abundance of Firmicutes and Actinobacteriota bacteria associated with Cd adsorption and sequestration,and Basidiomycota fungal populations associated with degradation of macromolecules favored the inhibition of soil Cd activity(soil exchangeable Cd decreased by 14.4–14.8 and 18.1–20.6%).This was associated with an increase in organic matter and Si content caused by applying soil conditioners.In conclusion,L-type soil conditioners,rich in Si and organic fertilizer,can reduce soil Cd bioavailability by regulating the dominant Cd passivating flora in the soil and ultimately reduce Cd accumulation in rice.

Changes in soil microbial communities induced by warming and N deposition accelerate the CO 2 emissions of coarse woody debris

Warming and nitrogen(N)deposition are two important drivers of global climate changes.Coarse woody debris(CWD)contains a large proportion of the carbon(C)in the total global C pool.The composition of soil microbial communities and environmental changes(i.e.,N deposition and warming)are the key drivers of CWD decomposition,but the interactive impact between N deposition and warming on the composition of soil microbial communities and CWD decomposition is still unclear.In a laboratory experiment,we study and simulate respiration during decomposition of the CWD(C 98)of Cryptomeria japonica(CR)and Platycarya strobilacea(PL)in response to warming and N deposition over 98 days.Resuts show that either warming or N addition signifi cantly accelerated the C 98 of the two tree species by altering the soil microbial community(bacterial:fungi and G+:G–).The combined treatment(warming+N)resulted in a decomposition eff ect equal to the sum of the individual eff ects.In addition,the species composition of bacteria and fungi was obviously aff ected by warming.However,N deposition had a remarkable infl uence on G+:G–.Our results indicated that N deposition and warming will observably alter the composition and growth of the microbial community and thus work synergistically to accelerate CWD decomposition in forest ecosystems.We also present evidence that N deposition and warming infl uenced the composition and balance of soil microbial communities and biogeochemical cycling of forest ecosystems.

Residue Return Effects Outweigh Tillage Effects on Soil Microbial Communities and Functional Genes in Black Soil Region of Northeast China

Conservation tillage as an effective alternative to mitigate soil degradation has attracted worldwide attention,but the influences of conservation tillage on soil microbial community and especially function remain unclear.Shotgun metagenomics sequencing was performed to examine the taxonomic and functional community variations of black soils under three tillage regimes,namely no-tillage with residue(maize straw)return(NTS),moldboard plow with residue return(MPS),and moldboard plow without residue return(MPN)in Northeast China.The results revealed:1)Soil bacterial and archaeal communities differed significantly under different tillage regimes in contrast to soil fungal community.2)The overlay of less tillage and residues return under NTS led to unique soil microbial community composition and functional composition.Specifically,in contrast to other treatments,NTS increased the relative abundances of some taxa such as Bradyrhizobium,Candidatus Solibacter,and Reyranella,along with the relative abundances of some taxa such as Sphingomonas,Unclassified Chloroflexi and Nitrososphaera decreased;NTS had a unique advantage of increasing the relative abundances of genes involved in‘ATP-binding cassette(ABC)transporters’and‘quorum sensing(QS)’pathways,while MPN favored the genes involved in‘flagellar assembly’pathway and some metabolic pathways such as‘carbon’and‘glyoxylate and dicarboxylate’and‘selenocompound’metabolisms.3)Significantly different soil bacterial phyla(Acidobacteria,Gemmatimonadetes,and Chloroflexi)and metabolic pathways existed between MPN and another two treatments(NTS and MPS),while did not exist between NTS and MPS.4)Dissolved organic carbon(DOC)and soil bulk density were significantly affected(P<0.05)by tillage and accounted for the variance both in microbial(bacterial)community structure and functional composition.These results indicated that a change in tillage regime from conventional to conservation tillage results in a shift of microbial community and functional genes,and we inferred that residue return played a more prominent role than less tillage in functional shifts in the microbial community of black soils.

Effects of Bio-organic Fertilizer with Antagonistic Bacteria against Tobacco Bacterial Wilt on Soil Microbial Communities and Disease Resistance of Tobacco

In this study, the effects of bio-organic fertilizer with antagonistic bacteria against tobacco bacterial wilt on soil microbial communities and disease resist- ance of tobacco were investigated by field experiment. The results showed that the incidence of tobacco bacterial wilt in bio-organic fertilizer treatments （T3 and T4） decreased remarkably among four treatments in the field. Compared with the local conventional fertilization group, the incidence of tobacco bacterial wilt was re- duced by 21.9% and 25.0% in T3 and T4, respectively ; the yield of flue-cured tobacco was improved by 5.7% and 5.3%, respectively ; the proportion of mid- high grade tobacco leaves increased by 2.3% and 2.6%, respectively. After application of bio-organie fertilizer with antagonistic bacteria against tobacco bacterial wilt, rhizosphere soil microbial communities exhibited vast amount and abundant species ; the amount of rhizosphere soil bacteria of infected tobacco plants was im- proved by 218.5% with fewer species. It could be concluded that the application of bio-organic fertilizer with antagonistic bacteria against tobacco bacterial wilt could improve the ecological environment of tobacco field, inhibit the growth of pathogenic bacteria, decrease the incidence of tobacco bacterial wilt, and enhance the quality of flue-cured tobacco. This study laid the foundation for further ecological prevention and control of soil-borne diseases of tobacco.

Responses of soil inhabiting nitrogen-cycling microbial communities to wetland degradation on the Zoige Plateau,China

The wetlands on the Zoige Plateau have experienced serious degradation,with most of the original marsh being converted to marsh meadow or meadow.Based on the 3 wetland degradation stages,we determined the effects of wetland degradation on the structure and relative abundance of nitrogencycling(nitrogen-fixing,ammonia-oxidizing,and denitrifying) microbial communities in 3 soil types(intact wetland:marsh soil;early degrading wetland:marsh meadow soil;and degraded wetland:meadow soil) using 454-pyrosequencing.The structure and relative abundance of nitrogen-cycling microbial communities differed in the 3 soil types.Proteobacteria was the predominant phylum in most soil samples but the most abundant soil nitrogenfixing and denitrifying microbial bacteria differed at the class,order,family,and genus levels among the 3soil types.At the genus level,the majority of nitrogenfixing bacterium sequences related to Bradyrhizobium were from marsh and marsh meadow soils;whereas those related to Geobacter originated from meadow soil.The majority of ammonia-oxidizing bacterium sequences related to Nitrosospira were from marsh(except for the 40-60 cm layer),marsh meadow and meadow soils;whereas those related to Candidatus Solibacter originated from 40-60 cm layer of marsh soil.The majority of denitrifying bacterium sequences related to Candidatus Solibacter and Anaeromyxobacter were from marsh and meadow soils;whereas those related to Herbaspirillum originated from meadow soil.The distribution of operational taxonomic units(OTUs)and species were correlated with soil type based upon Venn and Principal Coordinates Analysis(PCoA).Changes in soil type,caused by different water regimes were the most important factors influencing compositional changes in the nitrogen-fixing,ammonia-oxidizing,and denitrifying microbial communities.

Characteristics of the microbial communities in the integrated vertical-flow constructed wetlands

Microorganisms play an important role in removing pollutants from constructed wetlands. We investigated the microbial characteristics in a novel integrated vertical-flow constructed wetland （IVCW）, which has been in operation in Wuhan, China since 1998. We used phospholipid fatty acid （PLFA） and amoA gene to analyze the structure and diversity of the microbial community within the IVCW. PLFA results suggested that the amount of bacterial PLFA was significantly higher than that of fungal PLFA, but the total microbial biomass represented by PLFA index was low in the system. Microbial spatial distribution showed significantly higher bacterial （both G^＋ and G^-） and fungal biomass in the surface than in the subsurface layers. The ratios of monounsaturated to branched PLFA demonstrated that an anaerobic layer sandwiched by two aerobic layers existed in the IVCW, consistent with the redox potential results. Analysis of the amoA revealed the presence of Nitrosomonas-like sequences in the surface substrate of the downflow chamber and apparent diversities of ammonia-oxidizing bacteria in the system. These results suggest that microorganisms, despite their relatively low biomass, have inhabited the IVCW, and the results will offer some valuable information on microbe to system designers and managers.

Changes in enzymes activity, substrate utilization pattern and diversity of soil microbial communities under cadmium pollution

Heavy metal pollution has received increasing attention in recent years mainly because of the public awareness of environmental issues. In this study we have evaluated the effect of cadmium （Cd） on enzymes activity, substrate utilization pattern and diversity of microbial communities in soil spiked with 0, 20, 40, 60, 80, and 100 mg/kg Cd, during 60 d of incubation at 25℃. Enzyme activities determined at 0, 15, 30, 45, and 60 d after heavy metal application（DAA） showed marked declines for various Cd treatments, and up to 60 DAA, 100 mg/kg Cd resulted in 50.1%, 47.4%, and 39.8% decreases in soil urease, acid phosphatase and dehydrogenase activities, respectively to control. At 60 DAA, substrate utilization pattern of soil microbial communities determined by inoculating Biolog ECO plates indicated that Cd addition had markedly inhibited the functional activity of soil microbial communities and multivariate analysis of sole carbon source utilization showed significantly different utilization patterns for 80 and 100 mg/kg Cd treatments. The structural diversity of soil microbial communities assessed by PCR-DGGE method at 60 DAA, illustrated that DGGE patterns in soil simplified with increasing Cd concentration, and clustering of DGGE profiles for various Cd treatments revealed that they had more than 50% difference with that of control.

Intrauterine growth restriction alters growth performance, plasma hormones,and small intestinal microbial communities in growing-finishing pigs

Background: The interaction of the gut microbiota with key metabolic and physiological processes may be associated with poor growth outcomes in animals born with intrauterine growth restriction(IUGR).Results: Growth performance, plasma hormone concentrations, and intestinal microbiota composition were analyzed in IUGR pigs and in normal birth weight(NBW) pigs when the NBW pigs reached 25, 50, and 100 kg of body weight(BW). Compared to NBW pigs, IUGR pigs had lower initial, weaned, and final BW, and lower average daily gain and average daily feed intake in all the considered time points. In the 25 kg BW group, IUGR pigs had higher concentrations of plasma ghrelin and pancreatic polypeptide(PP), but lower insulin concentration than NBW pigs, while the situation was reversed in the 50 kg BW group. As compared to NBW pigs, IUGR pigs had higher microbial alpha diversity in the jejunum and ileum;in the 50 and 100 kg BW groups, IUGR pigs had higher Firmicutes abundance but lower Proteobacteria abundance in the jejunum, and lower Lactobacillus abundance in the jejunum and ileum;in the 25 kg BW group, IUGR pigs showed higher unclassified Ruminococcaceae abundance in the ileum;and in 25 and 50 kg BW groups, IUGR pigs showed lower Ochrobactrum abundance in the jejunum.Spearman's correlation revealed that Lactobacillus was negatively correlated with growth performance, while unclassified Ruminococcaceae was positively correlated. Predictive metagenomic analysis detected significantly different expression of genes in the intestinal microbiota between IUGR and NBW pigs, suggesting different metabolic capabilities between the two groups.Conclusions: Growing-finishing IUGR pigs showed lower growth performance, higher microbial alpha diversity, and differences in plasma hormone concentrations compared to NBW pigs. Alterations in the abundance of Firmicutes,Proteobacteria, Ruminococcaceae, Lactobacillus, and Ochrobactrum in the small intestine may be associated with IUGR, and may therefore serve as a future target for gut microbiota intervention in growing-finishing IUGR pigs.

Functional diversity of soil microbial communities in response to supplementing 50% of the mineral N fertilizer with organic fertilizer in an oat field

The effects of supplementing 50%of the mineral N fertilizer with organic fertilizer on the metabolism and diversity of soil microbial communities in an oat field were investigated using Biolog-Eco plates.The experiment consisted of five treatments:no fertilizer(CK),mineral N fertilizer applied at 90 and 45 kg ha^(-1) N in the form of urea(U1 and U2,respectively),and U2 supplemented with organic fertilizer in the form of sheep manure at 90 and 45 kg ha^(-1) N(U2OM1 and U2OM2,respectively).Each treatment had three replications.The experiment was conducted in 2018 and 2019 in Pinglu District,Shanxi Province,China.The carbon source utilization by soil microbial communities,such as amino acids,amines,carbohydrates,carboxylic acids,and polymers,increased when 50%of the mineral N fertilizer was replaced with organic fertilizer in both years.This result was accompanied by increased richness,dominance,and evenness of the microbial communities.The utilization of amino acid,amine,and carboxylic acid carbon sources and community evenness were further improved when the organic fertilizer amount was doubled in both years.Biplot analysis indicated that amines and amino acids were the most representative of the total carbon source utilization by the soil microbial communities in both years.The highest oat yield was achieved at a total N application rate of 135 kg ha^(-1) in the treatment involving 45 kg ha^(-1) N in the form of urea and 90 kg ha^(-1) N in the form of sheep manure in both years.It was concluded that the application of 50%of the conventional rate of mineral N fertilizer supplemented with an appropriate rate of organic fertilizer enhanced both the functional diversity of soil microbial communities and oat yield.Amine and amino acid carbon sources may be used as a substitute for total carbon sources for assessing total carbon source utilization by soil microbial communities in oat fields in future studies.

Comparison of microbial communities in three different mine drainages and their bioleaching efficiencies to low grade of chalcopyrite

Microbial community diversities in the drainage from three mines(Dexing Copper Mine,Qibaoshan Copper Mine and Yaogangxian Tungsten Mine,China)were analyzed using 16S rDNA PCR-RFLP approach.The efficiencies of chalcopyrite bioleaching were compared using enrichment of the three cultures.Phylogenetic analysis indicates that the dominant microorganisms are clustered with the Proteobacteria,the remaining is affiliated with Nitrospira,Acidobacteria and Actinobacteria.At the genus level,Acidithiobacillus is the dominant group in both YTW and QBS samples,while Spingomonas is dominant in YGX sample.Moreover,the principal component analysis(PCA)reveals that QBS and YTW have similar geochemical character and microbial communities.The results also show that pH value and tungsten concentration play a key role in microbial community distribution and relative abundance.The bioleaching efficiency of the enrichment cultures from YTW and QBS is similar.After 15 d,the bioleaching rates of low grade chalcopyrite(0.99%)are both up to 99.5% when using 10 g/L pulp density due to the similar microbial composition of YTW and QBS.Moreover,the leaching efficiencies of enrichment cultures containing multiple bioleaching microorganisms are higher than that of pure culture Acidithiobacillus ferrooxidans.

Interaction of soil microbial communities and phosphorus fractions under long-term fertilization in paddy soil

Understanding the impact of biological activities on the soil phosphorus(P)distribution under long-term fertilizer application can facilitate better soil P fertility management.Therefore,the primary objectives of this study were to investigate the effect of long-term(since 1981)fertilizer application on the soil P fractions and microbial community and to evaluate correlations between the microbial community structure and P distribution.The following treatments were implemented in a long-term field trial:no fertilization(CK),inorganic N and K(NK),inorganic P and K(PK),inorganic N,P and K(NPK)and manure+NPK(MNPK)fertilization.The study showed that the soil pH,soil organic carbon and total and available N and P concentrations were considerably higher in the MNPK treatment than in the CK treatment.The soil microbial biomass C,N and P concentrations were also significantly higher in the MNPK treatment than in the CK treatment.Among fertilization treatments,theβ-1,4-glucosidase,α-1,4-glucosidase,urease,acid phosphatase and phosphodiesterase activities were the highest in the MNPK treatment.Compared to inorganic fertilization,the MNPK treatment increased the labile soil P fractions and decreased the residual soil P concentration.Continuous fertilization significantly affected the soil microbial composition.The total phospholipid fatty acid(PLFA)concentrations in the NK,PK,NPK and MNPK treatments were 23.3,43.1,48.7 and 87.7%higher,respectively,than in the CK treatment.A significant correlation was observed between the microbial community and soil P fractions.Moreover,the aggregated boosted tree(ABT)model showed that among the various soil biochemical properties,the total PLFA concentration was the factor that most influenced the active P pool,accounting for 35.4%of the relative influence of all soil biochemical properties examined.These findings reveal that combined manure and inorganic fertilizer application is a better approach than applying inorganic fertilizer alone for sustaining long-term P fertility by mediating soil biological activity.

Characterization of microbial communities in sediments of the South Yellow Sea

Illumina sequencing and quantitative PCR(qPCR)based on the 16 S ribosomal RNA(rRNA)gene were conducted to characterize the vertical distribution of bacterial and archaeal communities in the sediments of two sites from the South Yellow Sea.Both bacterial and archaeal communities showed a clear stratified distribution with sediment depth.The microbial communities in the upper layers were distinct from those in the deeper layers;the relative abundances of sequences of Thaumarchaeota,Gammaproteobacteria,and Actinobacteria were higher in the upper than in the deeper sediments,whereas the sequences of Bathyarchaeia,Lokiarchaeota,Euryarchaeota,Chloroflexi,and Deltaproteobacteria were relatively more abundant in the deeper sediments.Sediment depth and total organic carbon(TOC)can significantly influence both the bacterial and archaeal communities.Furthermore,bacterial and archaeal groups potentially involved in nitrogen,sulfur,and methane metabolism were detected in both sites.In our study,both ammonia-oxidizing bacteria(Nitrospira)and ammonia-oxidizing archaea(Candidatus Nitrosopumilus)were responsible for ammonia oxidization.Additionally,sulfur-reducing bacteria SEEP-SRB1 forming consortia with anaerobic methane-oxidizing archaea ANME-2 a-2 b were capable of anaerobic methane oxidation(AOM)in the 3400-02 sediment samples.

Prevalence of Opportunistic Pathogens and Diversity of Microbial Communities in the Water System of a Pulmonary Hospital

Objective Our objective was to investigate the occurrence of opportunistic pathogens and characterize the bacterial community structures in the water system of a pulmonary hospital.Methods The water samples were collected from automatic and manual faucets in the consulting room,treatment room,dressing room,respiratory ward,and other non-medical rooms in three buildings of the hospital.Quantitative polymerase chain reaction was used to quantify the load of several waterborne opportunistic pathogens and related microorganisms,including Legionella spp.,Mycobacterium spp.,and M.avium.Illumina sequencing targeting 16 S r RNA genes was performed to profile bacterial communities.Results The occurrence rates of Legionella spp.,Mycobacterium spp.,and M.avium were 100%,100%,and 76%,respectively in all samples.Higher occurrence rates of M.avium were observed in the outpatient service building(building 1,91.7%)and respiration department and wards(building 2,80%)than in the office building(building 3),where no M.avium was found.M.avium were more abundant in automatic faucets(average 2.21×10~4 gene copies/L)than in manual faucets(average 1.03×10~4 gene copies/m L)(P<0.01).Proteobacteria,Actinobacteria,Bacteroidetes,Cyanobacteria,Firmicutes,and Acidobacteria were the dominant bacterial phyla.Disinfectant residuals,nitrate,and temperature were found to be the key environmental factors driving microbial community structure shifts in water systems.Conclusion This study revealed a high level of colonization of water faucets by opportunistic pathogens and provided insight into the characteristics of microbial communities in a hospital water system and approaches to reduce risks of microbial contamination.

Decomposition of different crop straws and variation in straw-associated microbial communities in a peach orchard,China

Crop residue is a major source of soil organic matter;therefore,application of crop straw to soil contributes to the sustainable development of organic agriculture.To better understand the transformation of crop straw in orchard soils,we investigated the relationship between the characteristics of straw decomposition and functional diversity of associated microbial communities in a long-term peach orchard,China.Mesh bags,each containing 30 g of corn or bean straw,were buried at a soil depth of 20 cm in a 12-year-old peach orchard for 360 d(October 2011–October 2012).Three treatments were applied,i.e.,fresh corn straw,fresh corn straw with nitrogen fertilizer(urea,10.34 g/kg),and fresh bean straw.Changes in straw residual rate,straw water content and soil conditions were monitored after treatment.The functional diversity of straw-associated microbial communities was analyzed by the Biolog-Eco microplate assay.During the decomposition process,straw residual rates did not vary considerably from 10 d(30.4%–45.4%)to 360 d(19.0%–30.3%).Irrespective of nitrogen addition,corn straw decomposed faster than bean straw.Corn straw with nitrogen fertilizer yielded the highest average well color development(AWCD)values(1.11–1.67),followed by corn straw(1.14–1.68)and bean straw(1.18–1.62).Although the AWCD values did not differ significantly among the three treatments,substantial differences occurred across various time periods of the decomposition process(P<0.01).In terms of carbon source utilization,the dominant microbial groups fed mainly on saccharides.Hard-to-decompose substances gradually accumulated in the middle and late stages of straw decomposition.Of the six categories of carbon sources tested,the utilization rate of aromatics was the lowest with corn straw,whereas that of polymers was the lowest with bean straw.Among different treatments,straw residual rate was negatively correlated to soil available phosphorous,soil available potassium and soil temperature(P<0.05),but not to soil water content.In some cases(corn straw with or without nitrogen fertilizer),straw residual rate was negatively correlated to straw water content,amino acid utilization and carboxylic acid utilization,and positively correlated with microbial species richness and evenness(P<0.05).Microbial community associated with corn and bean straw decomposition in soil was respectively dominated by aromatic-and polymer-metabolizing groups during the middle and late stages of this process,which could reduce the stability of microbial community structure and decrease the rate of straw decomposition in the fruit tree orchard.

Analysis of spatiotemporal variations in the characteristics of soil microbial communities in Castanopsis fargesii forests

Castanopsis fargesii is a good afforestation plants and various microorganisms play important roles in mediating the growth and ecological functions of this species.In this study,we evaluated changes in microbial communities in soil samples from C.fargesii forests.The phospholipid fatty acid(PLFA)biomarker method was used to obtain bacteria,fungi,actinomycetes,gram-positive bacteria(G?),gram-negative bacteria(G-),aerobic bacteria,and anaerobic bacteria to investigate spatiotemporal changes in microbial communities during the growing season.The results show that soil microorganisms were mainly concentrated in the upper 20-cm layer,demonstrating an obvious surface aggregation(P<0.05).Large amounts of litter and heavy rainfall during the early growing season resulted in the highest PLFA contents for various microorganisms,whereas relatively low and stable levels were observed during other times.The dominant species during each period were bacteria.G+ or aerobic bacteria were the main bacterial populations,providing insights into the overall trends of soil bacterial PLFA contents.Due to the relative accumulation of refractory substances during the later stages of litter decomposition,the effects of fungi increased significantly.Overall,our findings demonstrate that the main factors influencing microbial communities were litter,rainfall,and soil field capacity.

Monitoring bioaccumulation and toxic effects of hexachlorobenzene using the polyurethane foam unit method in the microbial communities of the Fuhe River,Wuhan

Hexachlorobenzene （HCB） is a chlorinated aromatic hydrocarbon that was widely used for seed dressing in prevention of fungal growth on crops, and also as a component of fireworks, ammunition, and synthetic rubbers. Because of its resistance to degradation and mobility, HCB is widely distributed throughout the environment and is accumulated through food chains in different ecosystems. In this study, a preliminary investigation was carried out on the bioaccumulation and the toxic effects of HCB in the microbial （protozoan in particular） communities in the Fuhe River, Wuhan, a water body receiving industrial wastewaters containing HCB and other pollutants, using the standardized polyurethane foam units （PFU） method. Field samples were taken from eight stations established along the Fuhe River in January and August 2006. The concentration ratios of HCB in microbial communities and in water were 9.66-18.64, and the microbial communities accumulated 13.29-56.88 μg/L of HCB in January and 0.82-10.25 μg/L HCB in August. Correlation analysis showed a negative correlation between the HCB contents in the microbial assemblage, and the number of species and the diversity index of the protozoan communities. This study demonstrated the applicability of the PFU method in monitoring the effects of HCB on the level of microbial communities.

Succession of aquatic microbial communities as a result of the water quality variations in continuous water

The changes of structural and functional parameters of aquatic microbial communities in continuous water on campus of Tsinghua University, China are investigated by polyurethane foam unit(PFU) method. The measured compositions of the communities include alga, protozoa, and some metazoa(such as rotifers). The measured indicators of water quality include water temperature, pH value, dissolved oxygen(DO), potassium permanganate index(COD Mn ), total nitrogen(TN), total phosphorus(TP) and chlorophyll-a(Chla). The trophic level, expressed by the trophic level indices(TLIc), is assessed with analytic hierarchy process and principal component analysis(AHP-PCA) method. The changing trends of the structural and functional parameters of aquatic microbial communities, such as Margalef index of diversity(D), Shannon-weaver index of diversity (H), Heterotropy index(HI), number of species when the colonization gets equilibrium(S eq ), colonizing speed constant(G) and time spent when 90 percent of S eq colonized in PFU(T 90% ), are also analyzed. The experimental results showed the succession of aquatic microbial communities along the water flow is consistent with the water quality changes, so the parameters of microbial community can reflect the changes of water quality from the ecological view.

Microbial communities present on mooring chain steels with different copper contents and corrosion rates

Copper has long been utilized as a disinfectant for bacteria,but its impact on microbial communities attached to the steel surface in seawater remains unknown.In the present study,3 mooring chain steels of different copper contents are subjected to a 3-month marine field exposure,and the corrosion rate increases in the order of BR5 steel(without copper)<BR5 CuH steel(0.8%copper)<BR5 CuL steel(0.4%copper).The microbial community results show that copper introduction does not result in an obvious change in microbial quantity,but it alters the diversity,richness,and structure of microbial communities due to the variation in copper-resistance of different species.BR5 CuH steel holds microbial communities with the highest percentage of some well-known corrosive microbes including sulfate-reducing bacteria,sulfuroxidizing bacteria,and iron-oxidizing bacteria,but possesses the lowest community diversity/richness owing to the toxicity of copper.The microbial community diversity/richness is stimulated by the low-copper content of BR5 CuL steel,and this steel also carries an intermediate proportion of such corrosive bacteria.Both well-known corrosive bacteria and microbial community diversity/richness seem to be involved in the corrosion acceleration of copper-bearing mooring chain steels.

Onshore Contribution to the Microbial Communities in the Lakes on the Qing-Tibetan Plateau

The inland lakes on the Tibetan Plateau are inhabited by diverse microbial communities,which play a significant role in biogeochemical cycles of biogenic elements(e.g.carbon,nitrogen).Onshore inputs provide essential