Shifts of sediment bacterial community and respiration along a successional gradient in a typical karst plateau lake wetland(China)

Bacteria are important regulators of carbon cycling in lakes and are central to sediment ecosystem processes.However,the sediment microbial communities and their respiratory responses to the lake wetland succession are poorly understood.In this study,we collected sediment samples from four different succession points(the Potamogeton lucens zone,the Scirpus tabernaemontani zone,the Scirpus triqueter zone,and the Juncus effusus zone)in the Caohai Wetland of the Guizhou Plateau(China).The bacterial communities at these succession points were studied using a high-throughput sequencing approach.The sediment microbial respiration(SR)was measured using static chambers in the field and basal respiration(BR)was determined in the laboratory.The results show that the dominant bacterial taxa in the sediment was Proteobacteria(34.7%),Chloroflexi(17.8%),Bacteroidetes(7.3%),Acidobacteria(6.6%),and Cyanobacteria(6.1%).Principal coordinate analysis showed that the microbial community structure differs significantly at different sampling points along the successional gradient,indicating that the bacterial community structure is sensitive to the lake wetland succession.Different hydrological regimes and soil characteristics such as NH_(4)^(+)-N,Fe^(2+),Mn^(2+),and sediment organic carbon(SOC)content may be important factors responsible for the differences in the sediment microbial characteristics of the different successional stages in the Caohai wetland.Additionally,it was found that the SR increased significantly from the P.lucens zone to the J.effusus zone,but BR had the opposite response.The shifts in the bacterial community structure along the successional gradient may be the main reason for the observed differences in sediment respiration.

Effects of bacteria on nitrogen and phosphorus release from river sediment

To better understand the mechanisms of eutrophication, we addressed the microbial processes that influence many key aspects of water-sediment systems. In this study, a large column experiment was conducted for 30 d. Along the column, solution samples were collected at different locations at different time. The samples were analyzed for physical, chemical, and biological properties of the sediment and overlying water. The results showed that the amount of nitrogen transforming bacteria was higher than that of phosphorous bacteria. The amount of nitrogen transforming bacteria was in the order： ammonifier 〉 denitrifying bacteria 〉 nitrobacteria and nitrosomonas. Principal component analysis indicated that the three main factors accounted for more than 90% overall contributions for bacterium growth, which represented nutrition, organics and oxygen, and pH and redox potential （Eh） of the environment. Corresponding to the bacteria, the concentrations of nitrogen in the system was in the order： ammonia （NH4＋-N） 〉 nitrate （NO3^--N） 〉 nitrite （NO2^--N）. The fluxes of N and P clearly showed a temporal release and adsorption processes in the water-sediment system. The large magnitude of N fluxes suggested that N might act as an important contamination source for the water quality. However, P exchange between the sediment and overlying water was less intensive during the experiment.

Numerical Modelling Sediment-Bacteria Interaction Processes in the Severn Estuary

Faecal bacteria exist in both free-living and attached forms in estuarine waters. The deposition of sediments can take faecal bacteria out of the water column and to the bed. The sediments can subsequently be re-suspended to the water column, which can then lead to re-suspension of the faecal bacteria of the attached forms back to the water column. Therefore, the fate and transport of faecal bacteria is highly related to the governing sediment transport processes, particularly where these processes are significant, such as the Severn Estuary, UK. However, little attempt has been made to model such processes in terms of predicting the impact of the sediment fluxes on faecal bacteria levels. Details are given of the refinement of a numerical model of faecal bacteria transport, where the sediment transport processes are significant. After testing the sediment-bacteria interaction model favourably against known results in previous study, the model was applied to the Severn Estuary and Bristol Channel, UK, to investigate the impact of suspended sediment fluxes on the corresponding faecal bacteria transport processes. The model predictions have proved to be encouraging, with the results being compared to a traditional faecal bacteria modelling approach, where sediment bacteria interactions were not included. The new model provides improved predictions of faecal bacteria concentrations when sediment transport is included and for the Bristol Channel Severn Estuary it can be seen that the effects of the sediments on the bacterial levels in the water column can be significant.

Characterization of uncultivated magnetotactic bacteria from the sediments of Yuehu Lake, China

Marine magnetotactic bacteria were collected from the intertidal sediments of Yuehu Lake（China）, where their abundance reached 103–104 ind./cm3. Diverse morphotypes of magnetotactic bacteria were observed, including cocci and oval, vibrio-, spirillum-, rod-, elliptical-, handle- and bar-shaped forms. The magnetococci were the most abundant, and had flagella arranged in parallel within a bundle. The majority of magnetosomes were arranged in one, two or multiple chains, although irregular arrangements were also evident. All the results of high-resolution transmission electron microscopy（HRTEM） analysis show that magnetosome crystals were composed of Fe3O4, and their morphology was specific to particular cell morphotypes. By the 16 S r RNA gene sequence analysis, we found fourteen operational taxonomic units（OTUs） which were related to magnetotactic bacteria. Among these, thirteen belonged to the Alphaproteobacteria and one to the Gammaproteobacteria.Compared with known axenic and uncultured marine magnetotactic bacteria, the 16 S r RNA gene sequences of most magnetotactic bacteria collected from the Yuehu Lake exhibited sequence identities ranging from 90.1% to96.2%（〈97%）. The results indicate that microbial communities containing previously unidentified magnetotactic bacteria occur in the Yuehu Lake.

Bacterial diversity in the sediments collected from the Shikoku Basin

Diversity of bacteria was studied in deep-sea sediments from the Shikoku Basin in the Northwest Pacific Ocean by PCR, RFLP and sequence analysis of 16S rDNA and comparing with Genbank database. Based on the RFLP profile generated, 77 clones from the 16S rDNA library were divided into 27 types. Phylogenetic analysis showed that the 27 independent clones fell into four groups: Proteobac-teria (62.96%), Chloroflexi (14.81%), Planctomycetes (14.81%) and Acidobacteria (7.41%). Among all sequenced clones, 6 were related to the sulfur or sulfate metabolism bacteria and the results also demonstrated that some bacteria in deep-sea sediments had relation to matter-energy circulation.

A Depth Wise Diversity of Free Living N₂Fixing and Nitrifying Bacteria and Its Seasonal Variation with Nitrogen Containing Nutrients in the Mangrove Sediments of Sundarban, WB, India

Mangrove provides a unique ecological niche to different microbes which play various roles in nutrient recycling as well as various environmental activities. The highly productive and diverse microbial community living in mangrove ecosystems continuously transforms dead vegetation and recycle nitrogen, phosphorus, sulphur and other nutrients that can later be used by the plants. Mangrove ecosystems are rich in organic matter, and however, in general, they are nutrient-deficient ecosystems, especially of nitrogen and phosphorus. The present study investigated depth wise variation of Nitrifying bacteria, Nitrogen fixing bacteria, total bacterial population along with nitrate-nitrogen, nitrite-nitrogen and other physicochemical parameters of soil during pre-monsoon, monsoon and post-monsoon periods at three different sampling stations of mangrove sediments viz. deep forest region, rooted region and unrooted region. The microbial population was also found maximum in the deep forest sediment relative to the other two sites. Populations of cultureable microbes were found maximum in surface soil and decreased with increase in depth in Sundarban mangrove environment. A decreasing trend of total microbial load, nitrifying and nitrogen fixing bacteria with increase in depth were recorded throughout the year. Present study revealed the relationship among depth integrated variations of physicochemical components (viz. soil temperature, pH, salinity, nitrite nitrogen and nitrate nitrogen concentration) and total microbial load, nitrifying and nitrogen fixing bacteria microbial populations.

Simulation of the Fate of Faecal Bacteria in Estuarine and Coastal Waters Based on A Fractionated Sediment Transport Model

A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sediment mixture is divided into several fractions according to the grain size. A bed evolution model is adopted to simulate the processes of the bed elevation change and sediment grain size sorting. The faecal bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or re-suspension. A novel partition ratio and dynamic decay rates of faecal bacteria are adopted in the numerical model. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK. The predictions by the present model are compared with field data and those by non-fractionated model.

Abundance of total bacteria, ATP and manganese-oxidating bacteria in the sediments and manganese nodules of the Northwestern Pacific Ocean

In the seawater and sediments of the ocean, there exist huge quantities of bacteria whose living activities cause various chemical reaction processes. It is demonstrated that microorganisms play a fundamental role on chemical changes of the sediments and diageneses. Over the last twenty years, great interest has been increased about the role of deep-sea bacteria in the ferromanganese sedimentary process. Much work has been done on this aspect in the Atlantic Ocean, the Baltic Sea and the Pacific O-

Annual change of the number of anaerobic sulf ite reducing bacteria in sediment of the Daya Bay

<Abstrat>The surface sediment samples were collected month by month at nine stations in the Daya Bay from January to December 1987, and the number of anaerobic sulfite reducing bacteria and their spores and the regularity of seasonal change were determined. The effect of environmental factors, water temperature and the resoluble oxygen concentration in the bottom of seawater on the number of them were discussed. The results show that the number of anaerobic su|fite reducing bacteria were low in sediment of the Daya Bay, indicating that the hay was less contaminated.

Molecular phylogenetic analysis of sulfate-reducing bacteria from deep sediment layers of the tropical West Pacific warm pool

The diversity of sulfate-reducing bacteria （SRB） from deep layers of deep-sea sediments [ more than 2 m bsf （below seafloor） ] of two sites （WO1 -3 and WPO1 -4） in a tropical West Pacific warm pool region was characterized by using molecular phylogenetic analysis. The results of culture-independent samples demonstrated that the dominant clones from both sites were related to Grampositive spore forming genus, Desulfotomaculum, which accounted for 36.8% of all the sequencing clones from Site WP01 - 3 and 62.8% from Site WP01 -4. However, the other SRB group which was generally reported to be predominant in the deep-sea sediments of other regions, δ- subclass of the proteobacteria was found to be in very low percentages. Therefore, it could be speculated that there existed a unique chemical environment in the deep-sea sediment of this warm pool region. When comparing the Desulfotomaculum sp. related sequences from both sites, it was revealed that though the Desulfotomaculum-like sequences from Site WP01 -3 were more diverse than those from Site WP01 -4, all these sequences from both sites showed high similarity and formed a new phylogenetically homogeneous cluster in the Desulfotomaculum genus which had never been reported before. Successful enrichment of SRB was only achieved from samples of Site WP01 -4 and the sequence analysis of culture-dependent samples further confirmed the dominance of Desulfotomaculum genus. But Desulfotomaculum-related sequences from culture-dependent and culture-independent samples belonged to two different clusters respectively. This difference showed the choice of cultivation to the microorganisms.

Coliform Bacteria: The Effect of Sediments on Decay Rates and on Required Detention Times in Stormwater BMPs

Fecal indicator bacteria, such as total coliforms and E. coli, are a challenge to control in urban and rural stormwater runoff. To assess the challenges of improving bacterial water quality standards in surface waters, microcosm experiments were conducted to assess how decay rates of total coliforms and E. coli are affected by sediments and associated organic matter. Samples were collected at a lake embayment to create laboratory microcosms consisting of different combinations of unsterilized and sterilized water and sediment. Calculated first-order decay rate constants ranged from 0.021 to 0.047 h-1 for total coliforms and 0.017 and 0.037 h-1 for E. coli, depending on how each microcosm was prepared. It is evident that sediment in contact with the water column decreases bacteria decay rate, showing that care should be taken when designing stormwater treatment measures. In addition, high organic carbon content in the sediment temporarily increased bacteria concentrations in the water column. The results demonstrate that stormwater treatment measures, such as extended detention basins and constructed wetlands, must hold water for several days to allow for reduction of bacterial concentrations to acceptable levels. In addition, to troubleshoot detention basins and constructed wetlands for causes of high effluent bacterial concentrations, analyses of sediment, organic carbon, and water column depth should be conducted.

Particle Association of Enterococcus and Total Bacteria in the Lower Hudson River Estuary, USA

Bacterial particle association has important consequences for water-quality monitoring and modeling. Particle association can change vertical and horizontal transport of bacterial cells, as well as patterns of persistence and production. In this study, the abundance and particle association of total bacteria and the fecal-indicator, Enterococcus, were quantified between June and October 2008 in the lower Hudson River Estuary (HRE). Twelve sites were sampled, including mid-channel, near shore, and tributary habitats, plus a sewage outfall. Total bacterial cell counts averaged 9.2 × 109 ± 6.4 × 109 cell l–1 (1 standard deviation), comparable to previous sampling in the HRE. Unlike earlier studies, bacterial abundance did not change consistently along the north/south estuarine salinity gradient. Enterococcus concentrations were highly variable, but mid-channel stations had significantly lower values than other habitat categories. Counts of total bacteria and Enterococcus were both correlated with turbidity, which was also significantly lower at mid-channel stations. A larger fraction of Enterococci were associated with particles (52.9 ± 20.9%, 1 standard deviation) than in the pool of total bacteria (23.8 ± 15.0%). This high frequency of particle association, relative to total bacteria, could cause Enterococcus to be preferentially retained near input sources because of enhanced deposition to bottom sediments, where they would be available for later resuspension. In turn, retention and resuspension in nearshore environments may explain the observed cross-channel variability of turbidity and Enterococcus. Assessments and predictive models of estuarine water quality may be improved by incorporating cross-channel variability and the effects of particle association on key indicators.

Microbial Assay of Otamiri River and Its Sediments in Parts of Owerri

The aim of the study was to analyse and identify microbial constituents in the water and sediment samples with comparison of the River to World Health Organisation (WHO, 2011) standard for drinking water and Federal Ministry of Environment (FME, 2006) and their public health implications with respect to water quality. The microbial assay of Otamiri River was investigated using Standard plate count. The result indicates that microbial constituents of Otamiri river obtained at five strategic gauge stations designated SSWS1 (Egbu), SSWS2 (Timber Market), SSWS3 (FUTO), DOWNSTREAM (Mbirichi) and CONTROL POINT with mean Total coliform Count of 3.0 × 102, 3.0 × 103, 4.1 × 103 and 1.0 × 103 cfu/100ml with control point value of 0.5 × 103 respectively. The mean Total Bacteria Count was 3.0 × 104, 2.1 × 103, 1.1 × 103 and 0.8 × 103 cfu/100ml respectively with control point value of 0.2 × 103 while the mean values for Total E. coli Count were 1.1 × 102, 3.0 × 102, 4 × 103 and 2.0 × 103 cfu/100ml with control point value of 0.2 × 103. The biochemical identification of some organisms in water was Escherichia coli, Vibro spp., Klebsiella spp., and Entrobacteria spp. The result of stream sediment samples indicates that the mean Total Bacterial Count was 3.5 × 104, 5.0 × 104, 6.5 × 104 and 2.0 × 104 cfu/g respectively with 1.5 × 102 as control point value and that of Total Coliform Count was 6.5 × 103, 2.0 × 103, 2.5 × 103 and 0.8 × 103 cfu/g respectively with control point value of 0.5 × 102. While for the Total E. coli Count, the values were 2.5 × 103, 1.0 × 103, 2.5 × 103 and 0.5 × 105 cfu/g respective with control as 0.5 × 102. Biochemical identification of some organisms in sediments includes: Escherichia coli, Vibro spp., Klebsiella spp., Entrobacteria spp. and Bacillus spp. The mean total bacterial count, total coli form count and total E. coli, were not in conformity with both World Health Organisation (WHO, 2011) Standard for drinking water and Federal Ministry of Environment (FME) 2006 standard for soil and thus constitute a threat to the River;these are attributed to waste dumps and anthropogenic activities around the five stations. The presence of bacteria in water can cause cholera, hepatitis, dysentery and typhoid. The microbial constituents can be reduced by chlorination.

Fungal Leaching of Heavy Metals from Sediments Dredged from the Deûle Canal, France

Filamentous fungi were used to leach heavy metals from dredged sediments in semi-pilot scale air-lift bioreactors. Prior to the bioleaching experiments, a physico-chemical characterization of the sediments comprising a sequential extraction study was conducted. The sediments turned out to highly contaminated with heavy metals. Most of the studied metals were found to be strongly linked to the matrix because of their association with the sulphides and with the organic matter. The conditions that favored the solubilization of heavy metals by the filamentous fungi turned out to be favorable for the activity of the sediments organotrophic bacterial microflora as well. The latter played a key role in the biosolubilization process by producing organic acids under temporary anoxic conditions. Better solubilization results (Mn: 77%, Zn: 44%, Cu: 12%, Cd and Pb: <2%) were thus obtained in the uninoculated sugar treatment in comparison to the fungal treatment. In general, organotrophic leaching was found to be limited by the poor nature of the organic acids and by their microbial consumption under sugar limited conditions. It was therefore restrained to the relatively mobile metals, namely those linked to the acid-soluble and reducible fractions of the sediments.

污水厂尾水对河流水质和底泥细菌群落的影响

污水厂的出水即尾水,其排放关系到受纳水体的水质和生态状况。分析了武汉市某污水厂尾水排放指标,采用水槽试验探究了污水厂尾水对河流水质指标和底泥细菌群落的影响。结果表明:尾水排放促进了河水中硝酸盐氮的降解,总磷去除更加稳定;尾水使河水pH值提高了0.3、电导率上升幅度55%、溶解氧降低了0.6 mg/L。尾水排放之后,底泥细菌群落的丰富度升高、多样性降低,抑制厌氧菌Anaerolineaceae和SBR1031,促进好氧菌Pseudomonas;反硝化菌Azospira、Dechloromonas、Pseudomonas、Sphingomonas增多,促进了NO_(3)^(-)-N的降解。底泥中致病菌奈瑟菌属、军团菌属、消毒残生细菌相对丰度上升。

无机氮和重金属对渤海不同区域沉积物中厌氧氨氧化菌的影响差异

厌氧氨氧化菌(anaerobic ammonium oxidation,Anammox)是驱动厌氧氨氧化过程、去除海洋沉积物中氮元素的重要引擎。为分析无机氮和重金属对厌氧氨氧化菌的影响,以渤海沉积物中厌氧氨氧化菌为研究对象,采用Illumina高通量测序技术和实时荧光定量PCR技术对渤海13个站位表层沉积物中AMX16S rDNA基因进行检测,分析其群落结构以及重金属含量对群落结构和多样性的影响。结果表明,渤海沉积物中厌氧氨氧化菌类群可归为14门、8纲、9目、5科、8属、26种,其中浮霉菌门(Planctomycetota)在渤海沉积物中占主导地位,且在中部区域丰度最高;相对丰度最高的属为Candidatus Scalindua。沉积物中重金属Hg在南部区域浓度最高。随机森林分析结果显示,南部区域厌氧氨氧化菌群落结构变化可能与沉积物中的NH4+、Hg和Cr含量密切关联,在北部区域可能与Pb含量密切相关,而在中部区域可能与NO2-含量密切相关。AMX16S rDNA丰度与重金属Cr和Cu、总氮以及沉积物粒度显著正相关(P<0.05)。研究表明,渤海具有丰富的微生物资源和厌氧氨氧化菌,具有代谢多种污染物的潜力。研究结果为认识近海污染对微生物的地理分布格局、群落生态位分化提供了依据。

红树林沉积物聚乙烯降解菌的筛选和降解特性

【目的】探究湛江市麻章区红树林沉积物中微生物对聚乙烯(PE)塑料的降解特性,丰富红树林塑料降解菌种类。【方法】在湛江市麻章区红树林的高、中、低潮带随机选取9个样点,并采用五点采样法从红树林表层2~5 cm的沉积物中取样。将采集到的沉积物样本在以聚乙烯为唯一碳源的无机盐培养基中进行富集、分离、纯化,以筛选出能够降解PE的菌株,并通过显微形态分析、分子鉴定等方法确定其种属;通过测定生长曲线、失重率、以及分析官能团变化来验证菌株对PE塑料的降解性能。【结果与结论】从沉积物中共筛选出K1-1、K1-2和K1-3三株PE降解能力较强的菌,分别为威尼斯不动杆菌(Acinetobacter venetianus)、Pseudomonas juntendi和维德曼芽孢杆菌(Bacillus wiedmannii)。在120 d的培养周期中,这些菌株的生长曲线均呈抛物线形态。经三株菌作用后,PE表面生成羟基,并形成氨基和羟基化合物,羟基取代羰基,导致PE表观和内部结构明显改变。经120 d处理后,PE膜的失重率分别为6.42%、5.38%和5.73%,其中K1-1菌株处理后PE塑料的失重率相较于目前报道的红树林沉积物中最高降解效率菌株Bacillus gottheilii处理后塑料的失重率提升3.55%。威尼斯不动杆菌(A.venetianus)在PE塑料降解上具有一定潜力,这丰富了湛江红树林沉积物中PE降解菌的种类,为PE塑料的生物降解提供理论支持。

SRB对AMD湿地处理系统沉积物中重金属的钝化作用研究

湿地沉积物既是重金属污染的汇,也是重金属污染的源,沉积物修复技术中的微生物钝化技术是实现重金属原位修复的一种重要手段。以酸性矿山废水(Acid Mine Drainage,AMD)湿地沉积物为对象,研究了硫酸盐还原菌(Sulphate Reducing Bacteria,SRB)对湿地沉积物中铁(Fe)、锰(Mn)、铜(Cu)和锌(Zn)释放及形态的影响,探究了SRB对沉积物中重金属的钝化效果。结果表明:在沉积物中接种SRB可不同程度地提高浸出液p H、电导率(EC)值,降低氧化还原电位(Eh)和硫酸盐(SO_(4)^(2-))浓度,当SRB的接种体积大于100 mL时,浸出液中Fe、Mn、Cu的浓度显著降低,当接种体积为200 mL时,浸出液Zn的浓度显著降低;接种SRB可使沉积物中Fe由弱酸提取态和可还原态转为可氧化态,使可还原态Mn向弱酸提取态及可氧化态转化,而沉积物中Cu、Zn则由弱酸提取态向可氧化态转化;接种14 d后,SRB接种体积为200 mL的处理组中沉积物中Fe、Mn的钝化效率最高,接种体积为100 mL的处理组中SRB对Cu和Zn的钝化效果最为明显。