三峡库区支流蓝藻水华对浮游细菌群落组成的影响

为探究蓝藻水华生消过程对浮游细菌群落组成的影响, 对三峡库区小江支流进行了采样检测, 结果表明小江采样点的水华优势蓝藻主要为水华鱼腥藻和铜绿微囊藻, 水华中期藻细胞密度分别达6.22109和8.77108个/L, 占总生物量的67%和26%。水华中、末期, 浮游细菌群落变化显著。其中, 水华中期主要以玫瑰单胞菌(Roseomona)等属细菌为主, 水华末期则以芽孢杆菌(Bacillus)等属细菌为优势, 且变形菌门(Proteobacteria)及放线菌门(Actinobacteria)细菌相对丰度明显增加, 暗示了细菌群落组成与库区支流蓝藻水华生消变化可能具有相关性。     

微囊藻毒素生物合成及其检测的分子生物学研究进展

随着世界各地水体富营养化的日益加剧,蓝藻水华的爆发频率越来越高,爆发范围也越来越广,已经成为国内外学者高度关注的重大环境问题。微囊藻水华是淡水水体中危害最严重的一类,特别是在我国巢湖、太湖和滇池等大型湖泊,经常爆发微囊藻水华,给水体生态系统和人类健康带来了巨大的危害。本文简介了微囊藻毒素的化学结构与危害,综述了微囊藻毒素mcy基因簇、Adda生物活性结构以及肽链合成与环化等关键生物合成过程,并重点归纳了聚合酶链式反应(polymerase chain reaction,PCR)、实时定量PCR(real time quantitative PCR detecting system,QPCR)、基因芯片(gene microarray)和变性梯度凝胶电泳(denaturing gradient gel electrophoresis,DGGE)等用于藻毒素检测的分子生物学技术方法,最后对相关研究进行了展望。     

细菌溶藻的初步研究

滇池是我国西南地区的大型浅水湖泊,近十几年来,滇池蓝藻水华发生的频率和数量均明显增加。其中微囊藻(Microcystis spp.)水华是危害最严重的一类,由于这类水华发生普遍,持续时间长,而且多数产毒,危害性很大,因而倍受人们的关注。人们不断致力于微囊藻水华的消除、其毒素的降解、危害防治等方面的研究,期望减少以至消除微囊藻对生态系统和人类健康的影响。对于控制水体中有毒藻类及其负面影响乃至最终消除,人们采取了多种措施,总的说来为两种基本途径:一是控制它们在水体中的生长繁殖而保持其较低的生物量,二是采用各种办法来杀死它们。       

应用环境微生物治理淡水湖泊微囊藻毒素污染的研究进展

近年来,随着水体富营养化程度的加剧,蓝藻水华现象时有发生,蓝藻及其释放的藻毒素对生态环境和人类健康构成严重威胁。在各种藻毒素中,以微囊藻毒素(Microcystins,MCs)毒性最强,对人类危害也最大,微囊藻毒素的化学性质相对稳定且难以通过常规水处理方法消除,因此如何有效去除环境中的MCs是国内外普遍关注的难题。研究发现自然界中的微生物能够有效降解和消除MCs污染,由此产生的环保技术极具应用价值。本文主要概述了微囊藻毒素的产生机理、化学结构以及毒性危害,总结了微囊藻毒素的自然分解过程以及微生物群落对微囊藻毒素的响应机制,重点分析了微生物群落在微囊藻毒素污染控制技术中的潜在应用,并对应用微生物技术治理微囊藻毒素污染的技术瓶颈提出了建议,以期加速微囊藻毒素微生物降解技术的完善和应用。     

NaNO3胁迫对两种微囊藻VOCs释放的影响

为了揭示硝酸盐过量积累对藻类产生胁迫后对藻类挥发性有机化合物(VOCs)释放以及水体气味的影响, 研究以形成蓝藻水华的主要种类铜绿微囊藻和水华微囊藻为材料, 在NaNO3胁迫下, 对其细胞生长和释放的VOCs进行测定分析。结果表明, NaNO3胁迫24h后, 铜绿微囊藻和水华微囊藻细胞生长均受到明显影响, 与对照相比细胞密度分别降低了29.6%和43.0%。在正常条件下, 铜绿微囊藻和水华微囊藻分别释放出26和27种化合物, 其主要类型是硫化物、烃类、萜烯类、苯类、醛类和酯类化合物。在NaNO3胁迫下, VOCs含量均明显增加, 其中铜绿微囊藻释放的此6类VOCs含量分别增加了60.5%、14.3%、136.6%、92.1%、730.0%和120.7%, 水华微囊分别增加了172.7%、162.5%、154.0%、55.9%、51.2%和109.4%。此外, 铜绿微囊藻VOCs中出现4种新成分, 水华微囊藻VOCs中出现1种新成分。由此可见, 硝酸盐过量积累对藻细胞产生胁迫后会诱导其释放出大量VOCs, 从而增加水体气味、破坏水质。       

微囊藻群体形成影响因子及机理

富营养化导致的湖泊、水库蓝藻水华带来了一系列环境和生态问题。微囊藻群体形成,在水体表面的聚集是形成水华的重要策略之一。微囊藻群体形成有效抵御了草食性动物摄食、病毒、细菌的侵害,耐受不良环境因子(紫外辐射、高光强、重金属等)能力显著增强。文章探讨了野外微囊藻群体占优势的机制并综述了影响微囊藻群体形成的外源因子及作用机理,包括非生物因子(营养、温度、光照、重金属、微囊藻毒素、乙醛酸)、生物因子(草食性动物、细菌、鱼类、藻类)。基于现有研究,本综述还对未来研究进行展望:(1)非生物因子与生物因子协同效应对藻类形态影响研究; (2)人类活动对浮游藻类形态及动态的影响研究;(3)藻类形态对沉水植物的响应在未来淡水生态系统修复中的应用; (4)促进藻类群体形成的胞外多糖分泌在未来工业生产中的作用。     

微囊藻毒素降解方法的研究进展

当前,由于水体富营养化情况的不断加重,导致蓝藻等一些淡水藻类的过度生长,给生态环境及人类健康带来了一系列严重的问题.藻类水华对环境及对人类的危害已经越来越受到人们重视,其中微囊藻毒素会引发各种致命的疾病,包括肝癌、肠癌等,对人类的健康已经构成较大的威胁.如何对微囊藻毒素进行有效地降解,已经成为了国内外相关科研人员的研究重点.本文就当前对于微囊藻毒素的传统处理方法包括混凝法、活性炭吸附法、反渗透及膜滤处理法、氯化法、臭氧氧化法、光催化氧化、高锰酸盐降解以及较新的生物处理方法包括纯种菌的降解和混合菌的降解进行一个全面的综述,对各种方法的特点、适用范围以及应用前景做一个归纳和展望.     

淡水湖泊中微囊藻水华的成因分析

我国藻型富营养化湖泊中一个重要的生物类群是微囊藻,结合国内近几年来对微囊藻形成水华的机制的研究,从微囊藻的结构和生理特点以及环境中温度、光照、pH和营养盐等生态因子综合作用上分析了微囊藻水华的成因。     

环境水体微囊藻毒素微生物降解技术研究进展

湖库水体富营养化及其产生的藻毒素污染已对生态环境和人类健康构成极大威胁,而目前常规水污染控制技术存在一定的局限性,因此水环境中藻毒素处理新工艺亟待研发.鉴于环境水体中的微囊藻毒素可被微生物降解为无毒或低毒的中间产物,本文综述了微囊藻毒素的降解菌株、生物降解过程影响因素与机理、降解产物及其结构特性等,总结了目前微囊藻毒素降解菌株在水环境修复中的应用,并对今后微生物降解微囊藻毒素的研究方向进行了展望,以期为解决我国日益严峻的湖库水体藻毒素污染和饮用水安全问题提供技术思路.     

应用高通量实时荧光定量PCR方法筛选FL细胞对低剂量微囊藻毒素LR暴露的应答基因

微囊藻毒素是蓝藻的一些属产生的单环七肽,在发生水华的水体中普遍存在[1]。含有微囊藻毒素的水华能引起野生动物、鱼类、家畜、家禽等中毒和死亡,也对人类健康构成严重威胁[2,3]。流行病学调查发现,人群原发性肝癌、大肠癌发病率与饮水源中的微囊藻毒素有关[4]。其中微囊藻毒素LR是微囊藻毒素中最常见的一种,因其高急性毒性,强促癌活性而受到广泛的关注。有研究结果表明微囊藻毒素LR可引起多种细胞发生凋亡[5],本实验室先前的研究也发现微囊藻毒素LR能激活在凋亡过程中起重要作用的酶Caspase-3[6],及引起P53、Bax、Bcl-2等凋亡相关蛋白…     

Host-Specificity and Dynamics in Bacterial Communities Associated with Bloom-Forming Freshwater Phytoplankton

Many freshwater phytoplankton species have the potential to form transient nuisance blooms that affect water quality and other aquatic biota. Heterotrophic bacteria can influence such blooms via nutrient regeneration but also via antagonism and other biotic interactions. We studied the composition of bacterial communities associated with three bloom-forming freshwater phytoplankton species, the diatom Aulacoseira granulata and the cyanobacteria Microcystis aeruginosa and Cylindrospermopsis raciborskii. Experimental cultures incubated with and without lake bacteria were sampled in three different growth phases and bacterial community composition was assessed by 454-Pyrosequencing of 16S rRNA gene amplicons. Betaproteobacteria were dominant in all cultures inoculated with lake bacteria, but decreased during the experiment. In contrast, Alphaproteobacteria, which made up the second most abundant class of bacteria, increased overall during the course of the experiment. Other bacterial classes responded in contrasting ways to the experimental incubations causing significantly different bacterial communities to develop in response to host phytoplankton species, growth phase and between attached and free-living fractions. Differences in bacterial community composition between cyanobacteria and diatom cultures were greater than between the two cyanobacteria. Despite the significance, major differences between phytoplankton cultures were in the proportion of the OTUs rather than in the absence or presence of specific taxa. Different phytoplankton species favoring different bacterial communities may have important consequences for the fate of organic matter in systems where these bloom forming species occur. The dynamics and development of transient blooms may also be affected as bacterial communities seem to influence phytoplankton species growth in contrasting ways.     

Temperature and biotic factors influence bacterial communities associated with the cyanobacterium Microcystis sp

Cyanobacterial blooms represent a nutritious niche for associated bacteria including potential pathogens for humans as well as livestock. We investigated bacterial community composition associated with Microcystis sp. using different approaches: batch experiments on Microcystis sp. or its enriched exudates, field enclosures (dialysis bags) and field sampling during natural blooms in freshwaters. Bacterial community composition associated with Microcystis sp. differed significantly with temperature, bacterial source community and number of incubated cyanobacterial strains. Interestingly, Actinobacteria of the AcI cluster were only present in the 20°C treatments and disappeared at higher incubation temperatures. Moreover, Archaea were present in all field samples but did not show any regional patterns, which is consistent with bacteria. Absence of Archaea in the experimental treatments indicates reduced growth under experimental conditions. In contrast, members of the genus Sphingomonas (Alphaproteobacteria), which includes species known as human pathogens, occurred in almost all samples. Thus Sphingomonadales seem to be an integral element of Microcystis sp. blooms - even affecting concentrations of microcystins as a result of their breakdown of the toxins. Depending on environmental conditions such as temperature, light, currents and nutrients, the role of heterotrophic Bacteria associated with Cyanobacteria can greatly vary by either increasing (pathogens) or decreasing (breakdown of toxins) health risks caused by mass developments of potentially toxic Cyanobacteria.     

Molecular detection of potentially toxic cyanobacteria and their associated bacteria in lake water column and sediment

We investigated the molecular diversity of cyanobacteria and bacteria during a water bloom in a lake with a long history of toxic cyanobacterial blooms (Lake Kastoria, Greece). We also tested the hypothesis whether bloom-forming cyanobacteria are preserved in the lake’s sediment 2 years after the bloom. The dominant cyanobacteria during the bloom included the potentially toxin-producing Microcystis aeruginosa and several other Chroococcales forms closely related to the genus Microcystis. This suggests that the use of cyanobacterial-specific primers seems to be very informative in describing the cyanobacteria during the water blooms. The bacterial community showed high diversity, consisting mostly of singleton and doubleton phylotypes. The majority of the phylotypes were typical lake bacteria including some potential pathogens and toxin metabolising bacteria, suggesting that the dominant toxic cyanobacteria did not have any significant effect on the bacterial community structure. In the sediment, 2 years after the water bloom, no bloom-forming cyanobacteria were retrieved, suggesting that they cannot be preserved in the sediment. Similar to the water column, sediment bacterial diversity was also high, consisting mostly of yet-uncultured bacteria that are related to environments where organic matter degradation takes place.     

Composition of freshwater bacterial communities associated with cyanobacterial blooms in four Swedish lakes

The diversity of freshwater bacterioplankton communities has not been extensively studied despite their key role in foodwebs and the cycling of carbon and associated major elements. In order to explore and characterize the composition of bacterioplankton associated with cyanobacterial blooms, large 16S rRNA clone libraries from four lakes experiencing such blooms were analysed. The four libraries contained 1461 clones, of which 559 were prokaryotic sequences of non-cyanobacterial origin. These clones were classified into 158 operational taxonomic units affiliated mainly with bacterial divisions commonly found in freshwater systems, e.g. Proteobacteria, Bacteriodetes, Actinobacteria, Verrucomicrobia and Planctomycetes. Richness and evenness of non-cyanobacterial clones were similar to other clone libraries obtained for freshwater bacterioplankton, suggesting that bacterial communities accompanying cyanobacterial blooms are as diverse as non-bloom communities. Many of the identified operational taxonomic units grouped with known freshwater clusters but the libraries also contained novel clusters of bacterial sequences that may be characteristic for cyanobacterial blooms. About 25% of the operational taxonomic units were detected in more than one lake. Even so, 16S rRNA heterogeneity analysis demonstrated large differences in community composition between lakes regardless of their similar characteristics and close proximity. Hence even the similar environmental conditions created by different cyanobacterial blooms may foster very dissimilar bacterial communities, which could indicate that the genetic diversity in lake bacteria have been underestimated in the past.     

Experimental study of Microcystis-associated and free-living cyanobacteria

In the experiment with water from the hypereutrophic Lake Frederiksborg Slotso (Denmark) sampled during the autumn peak of Microcystis growth, the quantity and production of free-living and cyanobacteria-associated heterotrophic bacteria were determined, as well as the extracellular enzymatic (aminopeptidase) activity. The functional diversities of associated and free-living bacterial communities were additionally compared using BIOLOG GN microplates to reveal the possible export of Microcystis-attached bacteria into ambient water. It has been shown that the cell size, production values, and growth rates of associated bacteria were less than those of free-living bacteria. At the same time, the potential aminopeptidase activity of associated bacteria was always higher than that of free-living bacteria. The experimental results have shown significant compositional differences in the structure of bacterial communities from different habitats.     

A multiomics approach to study the microbiome response to phytoplankton blooms

Phytoplankton blooms are predictable features of marine and freshwater habitats. Despite a good knowledge base of the environmental factors controlling blooms, complex interactions between the bacterial and archaeal communities and phytoplankton bloom taxa are only now emerging. Here, the current research on bacterial community’s structural and functional response to phytoplankton blooms is reviewed and discussed and further research is proposed. More attention should be paid on structure and function of autotrophic bacteria and archaea during phytoplankton blooms. A multiomics integration approach is needed to investigate bacterial and archaeal communities’ diversity, metabolic diversity, and biogeochemical functions of microbial interactions during phytoplankton blooms.     

Comparative metagenomics of toxic freshwater cyanobacteria bloom communities on two continents

Toxic cyanobacterial blooms have persisted in freshwater systems around the world for centuries and appear to be globally increasing in frequency and severity. Toxins produced by bloom-associated cyanobacteria can have drastic impacts on the ecosystem and surrounding communities, and bloom biomass can disrupt aquatic food webs and act as a driver for hypoxia. Little is currently known regarding the genomic content of the Microcystis strains that form blooms or the companion heterotrophic community associated with bloom events. To address these issues, we examined the bloom-associated microbial communities in single samples from Lake Erie (North America), Lake Tai (Taihu, China), and Grand Lakes St. Marys (OH, USA) using comparative metagenomics. Together the Cyanobacteria and Proteobacteria comprised >90% of each bloom bacterial community sample, although the dominant phylum varied between systems. Relative to the existing Microcystis aeruginosa NIES 843 genome, sequences from Lake Erie and Taihu revealed a number of metagenomic islands that were absent in the environmental samples. Moreover, despite variation in the phylogenetic assignments of bloom-associated organisms, the functional potential of bloom members remained relatively constant between systems. This pattern was particularly noticeable in the genomic contribution of nitrogen assimilation genes. In Taihu, the genetic elements associated with the assimilation and metabolism of nitrogen were predominantly associated with Proteobacteria, while these functions in the North American lakes were primarily contributed to by the Cyanobacteria. Our observations build on an emerging body of metagenomic surveys describing the functional potential of microbial communities as more highly conserved than that of their phylogenetic makeup within natural systems.     

Biodegradation of Microcystins during Gravity-Driven Membrane (GDM) Ultrafiltration

Gravity-driven membrane (GDM) ultrafiltration systems require little maintenance: they operate without electricity at ultra-low pressure in dead-end mode and without control of the biofilm formation. These systems are already in use for water purification in some regions of the world where adequate treatment and distribution of drinking water is not readily available. However, many water bodies worldwide exhibit harmful blooms of cyanobacteria that severely lower the water quality due to the production of toxic microcystins (MCs). We studied the performance of a GDM system during an artificial Microcystis aeruginosa bloom in lake water and its simulated collapse (i.e., the massive release of microcystins) over a period of 21 days. Presence of live or destroyed cyanobacterial cells in the feed water decreased the permeate flux in the Microcystis treatments considerably. At the same time, the microbial biofilms on the filter membranes could successfully reduce the amount of microcystins in the filtrate below the critical threshold concentration of 1 µg L⁻¹ MC for human consumption in three out of four replicates after 15 days. We found pronounced differences in the composition of bacterial communities of the biofilms on the filter membranes. Bacterial genera that could be related to microcystin degradation substantially enriched in the biofilms amended with microcystin-containing cyanobacteria. In addition to bacteria previously characterized as microcystin degraders, members of other bacterial clades potentially involved in MC degradation could be identified.     

The existence of cyanobactericidal bacteria and growth-inhibiting bacteria on water plants in Lake Ohnuma,Japan

Limnology - Microorganisms such as bacteria are considered to be control agents against toxic cyanobacterial blooms such as Microcystis aeruginosa. We investigated cyanobactericidal bacteria and...