Removal of odors and VOCs in municipal solid waste comprehensive treatment plants using a novel three-stage integrated biofilter: Performance and bioaerosol emissions

• TSIBF was composed of ABRS, FRS and HBRS. • THIBF can effectively remove various odors, VOCs and bioaerosols. • Different reaction segments in TSIBF can remove different types of odors and VOCs. • TSIBF can reduce the emission of bioaerosols through enhanced interception. A novel three-stage integrated biofilter (TSIBF) composed of acidophilic bacteria reaction segment (ABRS), fungal reaction segment (FRS) and heterotrophic bacteria reaction segment (HBRS) was constructed for the treatment of odors and volatile organic compounds (VOCs)from municipal solid waste (MSW) comprehensive treatment plants. The performance, counts of predominant microorganisms, and bioaerosol emissions of a full-scale TSIBF system were studied. High and stable removal efficiencies of hydrogen sulfide, ammonia and VOCs could be achieved with the TSIBF system, and the emissions of culturable heterotrophic bacteria, fungi and acidophilic sulfur bacteria were relatively low. The removal efficiencies of different odors and VOCs, emissions of culturable microorganisms, and types of predominant microorganisms were different in the ABRS, FRS and HBRS due to the differences in reaction conditions and mass transfer in each segment. The emissions of bioaerosols from the TSIBF depended on the capture of microorganisms and their volatilization from the packing. The rational segmentation, filling of high-density packings and the accumulation of the predominant functional microorganisms in each segment enhanced the capture effect of the bioaerosols, thus reducing the emissions of microorganisms from the bioreactor.     

Filtration of the enteric bacteria Escherichia coli by two filter-feeding bivalves,Venus verrucosa and Mytilus galloprovincialis

We investigated the filtration and utilization of the enteric bacteria Escherichia coli by two suspensionfeeding bivalves, Venus verrucosa (Linné), collected, during April 1990, in Port-Vendres harbour (France), and Mytilus galloprovincialis (Lamarck) collected from rearing units in the bay of Banyuls-sur-mer during June 1990. Because of a significant decrease in the concentration of culturable E. coli in filtered seawater, we used ¹⁴C glutamic acid to label the bacteria. Labelling efficiency was low (20%) compared to the 30% reported for the marine bacteria Lactobacillus sp. by Amouroux (1982). However, the labelling by this radioisotope was very stable, enabling its use to monitor filtration. Concentrations of culturable E. coli decreased more rapidly in the presence of M. galloprovincialis than in the presence of V. verrucosa. In both bivalve species, changes of radioactivity within the bivalve, particulate organic matter (POM), dissolved organic matter (DOM) and CO₂ compartments were similar and resulted from the interaction of several processes: filtration, biodeposition, and recycling. This interaction complicates the determination of the actual ingestion and assimilation rates, and necessitates the use of mathematical modelling.     

High recovery of culturable bacteria from the surfaces of marine algae

The culturability of heterotrophic marine bacteria obtained from the surfaces of two species of marine algae (Lobophora variegata andHalimeda copiosa) was assessed by comparing total DAPI-stained cell counts to colony-forming bacterial counts on two agar media. The colony-forming bacterial counts on a low-nutrient medium (LN) consisting of seawater and agar were significantly greater for both algal species than counts obtained on a high-nutrient medium (HN) similar in composition to that typically used for the isolation of heterotrophic marine bacteria. On average, 14 and 58%, respectively, of the total bacteria fromL. variegata andH. copiosa were culturable on LN. These recovery rates far exceed those typically reported for marine bacteria. Of 119 LN strains obtained in pure culture, 55% failed to grow on HN. The yeast extract component of HN (1.5 gl^-1) was responsible for the majority of the observed inhibition, suggesting that this nutrient can be highly toxic to marine bacteria. Eighty-nine percent of the strains inhibited by HN were capable of growth when the nutrients in this medium were diluted by a factor of 100 with seawater. Of 66 epiphytic strains, 30 (45%) initially inhibited by HN showed the ability to adapt to this medium after a period of laboratory handling. The initial inability of low-nutrient-adapted bacteria to grow on high-nutrient media may be due to nutrient shock. The results presented here indicate that the culturability of specific populations of marine bacteria can be dramatically improved by the use of low-nutrient media. Further, the importance of developing new medium formulations that eliminate traditional nutrients, some of which are clearly toxic to bacteria, is demonstrated.     

The role of marine aggregates in the ingestion of picoplankton-size particles by suspension-feeding molluscs

Suspension-feeding molluscs are important members of coastal communities and a large body of literature focuses on their feeding processes, including the efficiency of particle capture. Some molluscs, such as bivalves, capture individual picoplankton cells (0.2–2.0 μm) with a retention efficiency of less than 50%, leading to the assumption that such particles are not an important food resource. Picoplankton, however, are often concentrated in particle aggregates of much larger size. This study investigates the ability of suspension feeders to ingest picoplankton-size particles (0.2–2.0 μm) bound in marine aggregates. We fed clams (Mercenaria mercenaria), mussels (Mytilus edulis), oysters (Crassostrea virginica), scallops (Argopecten irradians) and slipper snails (Crepidula fornicata) 1.0- and 0.5-μm fluorescent particles (either polystyrene beads or bacteria) that were (1) dispersed in seawater, or (2) embedded within laboratory-made aggregates. Dispersed 10-μm beads were also delivered so that feeding activity could be determined. Ingested fluorescent particles were recovered in feces or isolated digestive glands and quantified. Results indicate that aggregates significantly enhance the ingestion of 1.0- and 0.5-μm beads by all species of bivalves, and enhance the ingestion of bacteria (greatest cell dimension ca. 0.6 μm) by all suspension feeders examined. Differences among species in their ability to ingest aggregates and picoplankton-size particles, however, were evident. Compared to mussels and clams, scallops and oysters ingested fewer aggregates with 1.0-μm beads or bacteria, and slipper snails ingested the most dispersed beads and bacteria. These differences may be a consequence of variations in gill structure and mechanisms of particle processing. Our data demonstrate that suspension feeders can ingest picoplankton-size particles that are embedded within aggregates, and suggest that such constituent particles may be an important food resource.     

Effects of cotton straw amendment on soil fertility and microbial communities

Maintaining soil fertility, while controlling pollution from excessive chemical fertilizer application is important for keeping soil productivity of sustainable agriculture. Variety of straws have been used and proven to be good soil amendments for increasing soil organic matter (OM) and a range of additional soil nutrients. However, little is known about the utilization of cotton straw for soil amendment. To better understand the mechanism behind cotton straw soil amendments, investigations were performed upon cucumber seedlings, where changes to soil nutrients and microbial communities were investigated. The results revealed that the cotton straw application promoted the cucumber seedling growth by significantly increasing the soil OM, available nitrogen, available phosphorus, and available potassium. The concentration of cotton straw was positively correlated to both the number of the culturable microorganisms and also the total microbial biomass within soil. Furthermore, assessment of cotton straw application using Biolog metabolic profiling and phospholipid fatty acid analysis revealed that such application increased the microbial community metabolic activity, and markedly changed the structure of microbial community. 16S rRNA gene clone library construction and phylogenetic analysis of soil bacteria revealed γ- Proteobacteria sequences dominated the cotton straw amendment soil, comprising 27.8% of the total number of analyzed sequences, while they were less represented in control soil (13.4%). On the contrary, the Sphingobacteria (7.8%) and Verrucomicrobia (2.4%) in the cotton straw amendment soil decreased after application when compared to the control soil 15.2% and 15.2%.     

纳米银与银离子对土壤微生物及酶活性的影响

为研究纳米银和银离子对土壤微生物的影响,采用土壤培养方式,对不同剂量纳米银(10、50、100 mg·kg~(-1))和银离子(1、5、10 mg·kg~(-1))暴露下黄褐土、砖红壤中可培养微生物数量及土壤酶活性(脲酶、荧光素二乙酸酯水解酶、蔗糖酶、过氧化氢酶)进行研究,并采用纯培养方法对纳米银和银离子暴露下的大肠杆菌(Escherichia coli)、金黄色葡萄球菌(Staphylococcus aureus)凋亡情况进行检测,对纳米银释放的银离子毒性进行评估。结果表明,随着纳米银剂量的增加,土壤可培养微生物数量显著减少,脲酶和过氧化氢酶活性降低,蔗糖酶、荧光素二乙酸酯水解酶(FDA酶)活性没有显著变化;银离子处理中微生物数量明显减少,但土壤酶活性被激活。10 mg·L~(-1)纳米银暴露1 h后大肠杆菌、金黄色葡萄球菌凋亡率、死亡率增高;随着培养时间的延长,纳米银缓慢释放银离子,并促进大肠杆菌的凋亡。综上分析,纳米银能够抑制土壤可培养微生物生长和酶活性,其中脲酶、过氧化氢酶对纳米银较为敏感,蔗糖酶、FDA酶受纳米银的影响较小;纳米银的毒性一方面是其本身的特异抗菌性,也有部分来自缓慢释放的银离子。     

Benthic community response to petroleum-associated components in Arctic versus temperate marine sediments

We assessed the effects of crude oil and drill cuttings on sediment oxygen demand (SOD) of marine benthic communities from Arctic (Barents Sea) and temperate (Oslofjord) areas of the Norwegian continental shelf. Field-collected cores in both areas were subjected to three different treatments: two concentrations of hydrocarbon-contaminated sediments, and drill cuttings (DC). Cores were incubated for 21 days at 5°C (Barents Sea) and at 10°C (Oslofjord) during which SOD was measured five times. We observed significantly higher SOD in the high oil concentration (HOC) and DC treatments compared to control cores from the Arctic, but not in the temperate Oslofjord. No difference was observed between the low oil concentration (LOC) and control at either location. The clear differences in the response of Arctic benthic communities to petroleum compounds compared to temperate benthic communities is likely related to differences in community structure, sensitivity of individual taxa to petroleum-related compounds and different contamination history of the two study areas.     

Photosynthetic sulfur bacteria from Zimapan Reservoir (Mexico): Seasonal variations and toxic effects of zinc in a microcosm system

Photosynthetic sulfur bacteria oxidize the sulfide produced by dissimilatory sulfate-reducing bacteria, thus preventing the occurrence of pollution by these compounds in the oxygenic zone of aquatic systems. Zinc is one of the most abundant heavy metals. Its toxic effects have been documented in various organisms that can photosynthesize, but a lack of information prevails in this respect, about photosynthetic sulfur bacteria. The aim of the present study was to evaluate the toxic effects of zinc on green sulfur bacteria (Chlorobiaceae) and purple sulfur bacteria (Chromatiaceae) in a microcosm as well to explore the possible relationships between the bacterial population growths with the physicochemical properties of the metalimnion of Zimapan Reservoir (Mexico) during a 1-year period. Hydrosoluble organic carbon (HOC) and light availability in the metalimnion were the limiting factors for growth in these bacteria. Higher HOC levels occurred in Spring, at the end of the wet season and in Winter. Current zinc levels in the reservoir seem to elicit toxic effects. At lethal zinc concentrations, the best concentration-response relationship was shown. The biomarker for purple sulfur bacteria was the bacteriochlorophyll content, while total reducing sugar was the best biomarker for green sulfur bacteria. At sublethal concentrations, zinc alters adenosine triphosphate levels, total reducing sugar, total protein content, and bacteriochlorophyll content. The observed responses indicate that green sulfur bacteria are more sensitive than purple sulfur bacteria and are suitable target organisms for use in establishing the accepted threshold concentration of zinc (NOEC 0.056–0.097 mg L^?1 of Zn) in anoxic deep water.     

城市社区农贸市场空气微生物及抗生素抗性基因研究

社区农贸市场活禽交易区是城市重要的人畜交叉感染区域,区内高存量的微生物和抗生素抗性基因(antibiotic resistance genes,ARGs)可通过粪便、冲洗水、空气等介质传播扩散。而空气介质中通过微生物气溶胶形式的传播途径,因其隐秘性、持久性的特点而对社区居民健康构成严重威胁。本文研究了深圳市某典型社区农贸市场内空气微生物及抗生素抗性基因。结果表明,活禽交易区可培养细菌浓度高达105CFU·m-3,远高于一般室内区域(103CFU·m-3),其中PM2.5精细颗粒物(0.65~3.3μm)中所含菌量占总菌量42%以上;活禽交易区空气介质中,抗生素抗性基因tet G、tet W、sul1和sul2检出率达70%以上,其绝对浓度在10~4~10~9copies·m-3之间;周边环境空气样品中,随着与活禽交易区距离的增加,空气微生物及抗生素抗性基因含量呈显著下降趋势。结果表明,农贸市场活禽交易区是微生物和抗生素抗性基因的一个重要储存库,活禽交易区空气会严重影响农贸市场及其外周边空气质量。     

Uptake of dissolved organics by marine bacteria as a function of fluid motion

A mass transfer analysis predicts that fluid motion can increase the assimilation of dissolved organics by attached compared to free-living microorganisms under certain conditions. To test this we examined the effect of advective flow and fluid shear on the uptake of model compounds (leucine and glucose) by natural assemblages of heterotrophic bacteria, collected from Roosevelt Inlet, Delaware Bay (USA), in 1989. We found that [³H]leucine uptake by cells held in fluid moving at 20 to 70 m d^–1 was eight times larger than uptake by cells at a velocity of 3 m d^–1. This effect was only observed at low leucine concentrations (ca. 1 nM), when uptake was likely not saturated. When we added leucine at concentrations expected to saturate leucine uptake (ca. 11 nM), fluid motion past cells did not affect uptake. Fluid flow past bacteria did not increase [³H]glucose uptake, and laminar shear rates of 0.5 to 2.1 s^–1 did not increase either glucose or leucine uptake by suspended bacteria. These results indicate that fluid motion increases bacterial uptake of certain lowmolecular-weight dissolved organics only when the microorganism exists in an advective flow field. As predicted from a mass transfer model, fluid shear rates in natural systems are too low to affect bacterial uptake of such compounds.     

Effect of rhizosphere on soil microbial community and in-situ pyrene biodegradation

To access the influence of a vegetation on soil microorganisms toward organic pollutant biogegration, this study examined the rhizospheric effects of four plant species (sudan grass, white clover, alfalfa, and fescue) on the soil microbial community and in-situ pyrene (PYR) biodegradation. The results indicated that the spiked PYR levels in soils decreased substantially compared to the control soil without planting. With equal planted densities, the efficiencies of PYR degradation in rhizosphere with sudan grass, white clover, alfalfa and fescue were 34.0%, 28.4%, 27.7%, and 9.9%, respectively. However, on the basis of equal root biomass the efficiencies were in order of white clover >> alfalfa > sudan > fescue. The increased PYR biodegradation was attributed to the enhanced bacterial population and activity induced by plant roots in the rhizosphere. Soil microbial species and biomasses were elucidated in terms of microbial phospholipid ester-linked fatty acid (PLFA) biomarkers. The principal component analysis (PCA) revealed significant changes in PLFA pattern in planted and non-planted soils spiked with PYR. Total PLFAs in planted soils were all higher than those in non-planted soils. PLFA assemblages indicated that bacteria were the primary PYR degrading microorganisms, and that Gram-positive bacteria exhibited higher tolerance to PYR than Gram-negative bacteria did.     

Determination of living and active bacterioplankton: a comparison of methods

The purpose of this study was the quantification, through the comparison of different methods, of viable and metabolically active bacteria in marine environments. To quantify the living and active bacterioplankton fractions, we compared the total cell count (TC using DAPI staining), plate count on marine agar (CFU), and three viability-staining methods: nucleoid-containing cell count (NuCC), Live/Dead staining procedure (L/D) and direct viable count (DVC). With respect to TC (mean value 3.0 ± 2.3 × 10⁵ cell ml^-1) CFU represented less than 0.1% and DVC cells 1%, both showing significant differences. NuCC and L/D cells were 18.0% and 15.9% of TC, respectively, showing no significant differences and higher percentages in the Ionian Sea than the Adriatic Sea. Moreover, NuCC and L/D were two orders of magnitude greater than the culturable fraction, while active cells (DVC) exceeded CFU by one order of magnitude. The comparison of different staining methods allowed us to confirm the simultaneous presence of different physiological states within the bacterial population in natural marine environments. The NuCC and L/D methods gave comparable values to those of other authors, while the DVC procedure gave lower values than previously reported. This research provides information on the fraction of living and/or metabolically active bacteria in aquatic ecosystems. Since each method has its own detection limits, the study highlights the need to simultaneously compare the different methods to validate their results.     

The influence of introducing soft-shelled turtle on soil nitrogen-fixing microorganisms in paddy field北大核心CSCD

Soil microorganisms are an important part of the soil ecosystem, but studies on the structure of the soil bacterial community, especially the related genes, is lacking. This study aimed to investigate the structure of soil microorganisms and the connection between the soil microorganisms and different farming systems. We used the Illumina Genome Analyzer IIx to compare root soil bacteria (nifH gene) diversity characteristics between the rice-turtle co-culture system (R-T) and rice monoculture system (R-M), aiming to reveal the structural characteristics of soil microorganisms, and the connection between the soil microorganisms and different farming systems. The results of High Throughput Sequencing of nitrogen-fixing bacteria showed that the main nitrogen-fixing bacteria were classified as Bradyrhizobium, Geobacter, Anaeromyxobacter, Desulfovibrio, Sideroxydans, Desulfuromonas, Halorhodospira, Azotobacter, Desulfobulbus, Methylomonas, Pseudacidovorax, and Azospirillum. The diversity index of nitrogen-fixing bacteria in the root soil of R-T was higher than that of R-M, which was 6.85-0.07. The difference of soil nitrogen-fixation bacteria in the root soil of rice paddy was 23.86% among the different farming systems, and the difference in the different rice growth period was 16.97%. In summary, the rice growth period and different farming systems both have an influence on the nitrogen-fixation bacteria in paddy soil; the influence of the growth period on the nitrogen-fixation bacteria in the paddy soil was greater. © 2018 Science Press. All rights reserved.     

Presence of hydrocarbon-degrading bacteria in the gills of mussel Mytilus galloprovincialis in a contaminated environment: a mesoscale simulation study

A number of previous studies have shown that the relationships of symbiosis existing between mussels and microorganisms are directly dependent on the environmental conditions. However, little is known about existing relationships between mussels and bacteria in hydrocarbon-impacted marine environments. The aim of this preliminary study is to investigate the presence of oil-degrading bacteria in the mussel Mytilus galloprovincialis during growth in polluted ecosystems. All the experiments were carried out in a mesocosm system designed to simulate chronic pollution and to enable direct exposure of mussels to chemicals. Quantitative (4′,6-diamidino-2-phenylindole, colony-forming units, Most Probable Number) analyses and screening (presence/absence) of metabolic functional genes were performed to analyse bacterial populations inside the gills of mussels exposed and not exposed to hydrocarbons. The data obtained show that the presence of hydrocarbons affected the abundance of bacteria inside the gills of specimens and determines selection for specific (hydrocarbon-degrading) bacteria (i.e. Alcanivorax sp. and Marinobacter sp.). However, is not yet clear whether the presence of such genera of bacteria inside the mussel is due to symbiosis or as a result of filtration.     

In-vitro antimicrobial activity and synergistic/antagonistic effect of interactions between antibiotics and some spice essential oils

Spices and herbs have been used for many years by different cultures. The aim of the present study is (1) to investigate in-vitro antimicrobial effects of different spices and herbs (5 species: Rosmarinus officinalis (Rosemary), Coriandrum sativum (coriander), Micromeria fruticosa (L.) Druce subsp. Brachycalyx P.H. Davis (White micromeria), Cumium cyminum (cumin), Mentha piperita (Peppermint) against different bacteria and fungi species, and (2) to discuss the in-vitro possible effects between the plants and antibiotics. The microorganisms used were Micrococcus luteus LA 2971, Bacillus megaterium NRS, Bacillus brevis FMC 3, Enterococcus faecalis ATCC 15753, Pseudomonas pyocyaneus DC 127, Mycobacterium smegmatis CCM 2067, Escherichia coil DM, Aeromonas hydrophila ATCC 7966, Yersinia enterocolitica AU 19, Staphylococcus aureus Cowan 1, Streptococcus faecalis DC 74 bacteria, and Saccharomyces cerevisiae WET 136, Kluvyeromyces fragilis DC 98 fungi in this study. The results indicated that essential oils of Rosmarinus officinalis, Coriandrum sativum L., Micromeria fruticosa (L.) Druce subsp. brachycalyx P.H. Davis, Cumium cyminum L., Mentha piperita L. were shown antimicrobial activity in the range of 7-60 mm 2 microl(-1) inhibition zone to the microorganisms tested, using disc diffusion method. Standard antibiotic such as Gentamicin (10 microg), Cephalothin (30 microg), Ceftriaxone (10 microg), Nystatin (10 U) discs were used for comparison with the antimicrobial activities of essential oils of these plants. In addition, antibacterial activity of essential oils of these plants was researched by effects when it was used together with these standard antibiotics in vitro. However, antibacterial activity changed also by in vitro interactions between these standard antibiotics and essential oils of these plants. Synergic, additive or antagonist effects were observed in antibacterial activity.     

Potential shift of bacterial community structure and corrosion-related bacteria in drinking water distribution pipeline driven by water source switching

• Bacterial release from aged pipe sections under extreme conditions was quantified. • Released bacterial community structure exhibited large variation after transition. • Risks from transition reduced significantly with cleaner source. As a result of pollution in the present water sources, cities have been forced to utilize cleaner water sources. There are few reports regarding the potential shift of bacterial community structure driven by water source switching, especially that of corrosion-related bacteria. Three types of finished water were used for simulation, the polluted source water from the Qiantang and Dongtiaoxi Rivers (China) was replaced by cleaner water from Qiandao Lake (China). Here, we discussed the transition effects through three simulated reactors. The bacterial characteristics were identified using the high-throughput sequencing and heterotrophic plate count method. It was observed that the level of culturable bacteria declined by 2–3 orders of magnitude after water source switching. The bacterial community released from the pipeline reactor was significantly different under different finished water, and it exhibited large variation at the genus level. Porphyrobacter (58.2%) and Phreatobacter (14.5%) clearly replaced Novosphingobium, Aquabacterium, and Cupriavidus as new dominant genera in system A, which could be attributed to the lower carbon and nitrogen content of the new water source. Although corrosion-inhibiting bacteria decreased after switching, they still maintained dominant in three reactors (6.6%, 15.9%, and 19.7%). Furthermore, potential opportunistic pathogens such as Sphingomonas were detected. Our study shows that after transition to a high quality water source, the total culturable bacteria released was in a downtrend, which leads to a great reduction in the risk of bacterial leakage in the produced drinking water.     

Effects of feeding history on mobilisation and deposition of body constituents and on growth in juvenile Ambassis vachelli (Pisces: Chandidae)

Young Ambassis vachelli (Richardson) 40 to 50 d old, were used in a laboratory experiment to test the effects of starvation and subsequent re-feeding on body constituents and growth. Fish in three laboratory treatments (fed continuously; fed for 9 d and then starved for 15 d; starved for 9 d and fed for 15 d), were compared to fish from a local field population. Different body stores were mobilised at different times and rates during starvation. Carbohydrates were mobilised from the onset of starvation and were depleted after 3 d. Lipid and protein were mobilised at an increasing rate from the onset of starvation. The mortality in starved fish was relatively high (up to 70%) until re-feeding. Upon feeding, all body stores were restored rapidly in fish that were starved, with carbohydrate levels displaying an overshoot (carbohydrate level exceeding normal levels) in comparison to the levels in continuously fed fish. After 15 d of feeding, the starved fish had levels of constituents similar to those in continuously fed fish. Fish that were fed and subsequently starved were able to maintain themselves for at least 15 d prior to death, indicating a better degree of starvation resistance than fish without a history of feeding. This implies that feeding history in the early life of a fish is important in growth and survival but that young fish may have growth regimes flexible enough to survive relatively long periods of starvation.     

Inhibitive effects of three compositae plants on Microcystis aeruginosa

Based on common phenomena of biochemical interaction between plants and microorganisms, the inhibitive effects of three common terrestrial compositae plants, namely Artemisia lavandulaefolia DC., Conyza canadensis (L.) Cronq., and Kalimeris indica (L.) Sch.-Bip. on the blue algae Microcystis aeruginosa was studied. Live compositae plants are co-cultivated with algae in two different inoculation doses for 10 days in 5-pools incubators, in order to exclude the influence of bacteria and nutrients. The results show that Artemisia lavandulaefolia DC has the most inhibitive potential among the three plants as evidenced by the most drastic decrease in optical density (OD₆₈₀) of the algae. The inhibition rate is 93.3% (with initial inoculation dose of 2.0 × 10⁶ Cells/mL) and 89.3% (with initial inoculation dose of 4.0 × 10⁶ Cells/mL) respectively on the 10^th day of cultivation. The average inhibition rate during the later half of the experiment is 0.76 (with initial inoculation dose of 2.0 × 10⁶ Cells/mL) and 0.71 (with initial inoculation dose of 4.06106 Cells/mL), respectively. Logistic model analysis shows that compositae plants such as A. lavandulaefolia DC. causes the reduction of the habitat’s carrying capacity of algae. ANOVA analysis is used to determine the similarity and differences between every experimental group and an average inhibitive rate model is used to evaluate the inhibition effects. The results show that A. lavandulaefolia DC., which grow well in the aquatic environment, may have a great potential in controlling algae bloom in eutrophic water.     

不同纤维素降解菌对玉米秸秆的降解效果

该研究旨在探索不同纤维素降解菌对玉米秸秆降解效果的差异性,为秸秆资源化利用提供参考。利用筛选自宁夏秸秆堆、畜粪和土壤中的四株纤维素降解菌,分别为黄曲霉(Aspergillusflavus)Z5-3菌株,非洲哈茨木霉(Trichoderma afroharzianum)Z6-4菌株,藤黄单胞菌(Luteimonas sp.)X11-1菌株,施氏假单胞菌(Pseudomonas stutzeri)X3-5-1菌株,通过室内控温秸秆堆肥发酵试验,研究添加不同纤维素降解菌后堆肥温度、pH值、碳损失、氮损失、有效养分含量的变化规律。试验结果表明,与对照(不加菌处理)比较,加菌处理提前1-2 d进入高温期,最高温度提高了0.3-1.3℃,且细菌处理较真菌处理提前1 d进入高温期,最高温度提高了0.5-0.7℃。pH值总体呈先增加后降低的趋势,且在高温期达到最大值。与对照相比,加菌处理NH3和CO2累积释放量具有降低趋势。以全氮含量变化计,细菌X11-1、X3-5-1处理的氮损失分别为26.14%和26.57%,真菌Z5-3、Z6-4处理分别为36.49%和34.19%,表明添加不同纤维素降解菌可不同程度地降低堆肥物料中的碳损失和氮损失,其中细菌处理保氮效果显著优于真菌处理。与对照相比,细菌X11-1、X3-5-1处理、真菌Z5-3、Z6-4处理分别提前腐熟5、2、2、2d,表明添加纤维素降解菌可减少堆肥物腐熟时间,促进物料养分浓缩。综合判断,玉米秸秆堆肥中加入纤维素降解菌,有利于降低物料的碳、氮损失,且细菌的保氮效果优于真菌,其藤黄单胞菌X11-1处理最先达到腐熟,为最佳处理。     

Effect of rhizosphere on soil microbial community and pyrene biodegradation

To access the influence of a vegetation on soil microorganisms toward organic pollutant biogegration, this study examined the rhizospheric effects of four plant species (sudan grass, white clover, alfalfa, and fescue) on the soil microbial community and in-situ pyrene (PYR) biodegradation. The results indicated that the spiked PYR levels in soils decreased substantially compared to the control soil without planting. With equal planted densities, the efficiencies of PYR degradation in rhizosphere with sudan grass, white clover, alfalfa and fescue were 34.0%, 28.4%, 27.7%, and 9.9%, respectively. However, on the basis of equal root biomass the efficiencies were in order of white clover >> alfalfa > sudan > fescue. The increased PYR biodegradation was attributed to the enhanced bacterial population and activity induced by plant roots in the rhizosphere. Soil microbial species and biomasses were elucidated in terms of microbial phospholipid ester-linked fatty acid (PLFA) biomarkers. The principal component analysis (PCA) revealed significant changes in PLFA pattern in planted and non-planted soils spiked with PYR. Total PLFAs in planted soils were all higher than those in non-planted soils. PLFA assemblages indicated that bacteria were the primary PYR degrading microorganisms, and that Gram-positive bacteria exhibited higher tolerance to PYR than Gram-negative bacteria did.