紫外光和日光对噬藻体PP活性的影响

分别研究了实验室条件下紫外灯照射及不同季节中日光照射对噬藻体PP活性的影响.结果表明紫外光(UV-A和UV-B)对噬藻体PP有较强的致失活作用,并且其致失活作用强弱与波长有关.日光的作用下,夏季时噬藻体PP的日失活率为88.60%,冬季时为58.86%.同时发现不同季节中,尽管在某些时段的日光强度相似,但噬藻体PP失活率的差别却较大,这一现象可能是由于光质不同引起的.上述结果有助于解释淡水环境中噬藻体种群大小的季节性波动.     

噬藻体PP对野生宿主——丝状蓝藻的吸附率、裂解周期及释放量的影响

研究在日光光照条件下,以自然水体中存在的丝状蓝藻作为噬藻体PP的野生宿主,用离心法测定了噬藻体PP对野生宿主藻的吸附率,用一步生长曲线法获得了噬藻体PP对野生宿主藻的裂解周期及释放量。结果表明:噬藻体PP对野生宿主藻在60min时能够达到的吸附率为1.79‰,吸附系数为8.09%,噬藻体PP感染野生宿主藻的潜伏期介于45～75min之间,平均释放量为34.32PFU·Cell-1。上述结果一方面说明,噬藻体PP感染野生宿主藻的吸附系数、潜伏期及释放量均远小于以实验室培养的鲍氏织线藻作为宿主所得到的数据;另一方面也说明,噬藻体PP具有较强的吸附和裂解野生宿主的能力,这将有助于解释噬藻体PP在淡水富营养化水体中具有广泛分布的现象。     

营养条件对噬藻体PP感染席藻动力学的影响

本试验设计了从正常的AA培养基(CK组)到N和P含量只有正常AA培养基1/600的6种培养基.在25 ℃、2000 lx条件下将宿主席藻在6种培养基中培养8个月后,用显微直接计数法测定了席藻的生长曲线以及噬藻体PP感染宿主席藻的裂解周期与致死率,用离心法测定了噬藻体PP对宿主席藻的吸附率,用一步生长曲线法测定了噬藻体PP的释放量和裂解周期.结果表明: 提高N和P含量会促进宿主席藻的生长,统计分析也显示,在对数中期(第6天),高营养盐浓度中细胞密度显著高于低营养盐浓度中的密度;提高营养盐浓度噬藻体PP的吸附率会显著增高,主要表现为在AA中噬藻体PP的吸附率极显著高于其他组;同时6种培养基条件下噬藻体PP对席藻的致死率变化不大;随着营养水平的升高,噬藻体PP的潜伏期和裂解周期明显缩短,平均释放量显著增加,但裂解宿主的效率却没有显著变化.上述结果说明噬藻体PP对宿主藻的感染力会随着营养水平的提高而明显增强,并可能在水体富营养化进程中发挥着调控藻类种群更替的作用.     

CO_2浓度和温度升高对噬藻体PP增殖的联合作用

在4个条件下培养了鲍氏织线藻:(1)25℃+400μmol/mol(CK组),(2)29℃+400μmol/mol(温度升高组),(3)25℃+800μmol/mol(CO2升高组),(4)29℃+800μmol/mol(温室效应组),测定了藻的生物量及细胞大小,同时用离心法测定了噬藻体PP对相应条件下宿主藻的吸附率,用一步生长曲线法测定噬藻体PP的裂解周期和释放量。结果表明,不同培养条件对藻细胞的大小均没有影响;CO2升高提高了宿主藻的生物量;温度和CO2浓度的升高不仅使噬藻体PP的裂解周期提前,而且对吸附率和释放量存在交互作用,使其发生了明显改变:其中,温度和CO2升高对噬藻体PP吸附率的影响属于协同作用,而对其释放量的影响则能够互相抵消。上述结果说明温室效应将能够导致噬藻体PP增殖能力大幅度增加。     

不同光、温条件下野生宿主对噬藻体PP的光修复率

研究了1株野生宿主藻对UV-B损伤的噬藻体PP的光修复率,结果显示该野生宿主的光修复率显著高于实验室培养的坑形席藻(Phormidium foveolarumIU427)和鲍氏织线藻(Plectonema boryanum IU594)。不同理化条件(光质、光强、水温)下该野生宿主对经UV-B损伤的噬藻体PP光修复情况,结果表明:野生宿主的光修复率与UV-A强度、可见光强度、水温之间均呈显著正相关(P0.05);可见光所驱动的光修复能力明显高于UV-A所驱动的光修复,且修复率会在可见光强达到160μE.m-.2s-1时接近饱和。说明,自然条件下浅水湖泊中可见光介导的宿主光修复作用占主导地位,由于受水温和透明度的双重影响,野生宿主在秋季的修复能力最强,而在冬季的修复能力最弱。     

云南不同高原湖泊噬藻体psbA基因多样性

【目的】噬藻体(cyanophage)广泛存在于自然水体生态系统中,通过侵染蓝藻进而调控蓝藻种群及群落结构,具有重要生态功能和生态地位,在控制蓝藻水华方面有巨大开发潜力。本研究旨在探究云南高原湖泊噬藻体psbA基因多样性,分析其系统进化地位,为深入了解高原湖泊生态功能、开发利用噬藻体资源奠定理论基础。【方法】以云南高原主要湖泊滇池、抚仙湖和星云湖等为研究对象,以psbA基因作为分子靶标,对湖泊水体中噬藻体遗传多样性进行研究。【结果】从不同湖泊中共获得100条环境噬藻体psbA基因序列,系统发育分析表明,湖泊的噬藻体psbA基因序列与中国东湖、中国东北稻田、日本稻田等淡水中的环境噬藻体psbA基因亲缘关系较近,与海洋环境噬藻体psbA基因亲缘关系较远;抚仙湖中的噬藻体psbA基因多样性高于滇池、星云湖和异龙湖中的噬藻体psbA基因多样性;云南高原湖泊中存在新的噬藻体类群;各湖泊秋冬季节噬藻体psbA基因遗传多样性差异不明显。【结论】云南主要高原湖泊噬藻体psbA基因遗传多样性高,与淡水环境噬藻体psbA基因亲缘关系较近,且存在独特的噬藻体类群。     

噬藻体感染相关基因的研究进展

噬藻体是感染蓝细菌(蓝藻)的病毒,能调控蓝细菌种群的丰度和多样性,在许多水生生态系统的食物网动态变化和生物地球化学循环中起关键作用。噬藻体与宿主细胞发生各种相互作用,包括吸附、入侵和复制,参与感染过程,从而完成噬藻体的生命周期。本文在综述噬藻体生命周期与基因组结构相互关联的基础上,重点介绍噬藻体与宿主蓝细菌相互作用的蛋白,如噬藻体吸附蛋白、内肽酶、穿孔素、DNA聚合酶、藻胆体降解蛋白A(NblA)、毒力因子、抗CRISPR蛋白(Acr)和小分子热休克蛋白等,分析它们的分子特性,阐述它们在噬藻体感染蓝细菌以及噬藻体-蓝细菌相互作用的分子机制。为了更好地认识驱动不同噬藻体与宿主及水生环境相互作用的策略、感染效率及生态学影响,本文不仅对这些与噬藻体感染相关的重要基因研究动态进行综述与讨论,还在了解噬藻体丰富的多样性和复杂性的基础上,提出应用新技术对噬藻体感染相关基因的功能进行广泛研究,以期扩展全球水生病毒数据库,进一步认识噬藻体与宿主的相互作用机理。     

东北稻田水体噬藻体psbA基因多样性

【目的】揭示东北稻田噬藻体psbA基因多样性,分析其系统进化地位,为噬藻体生态学研究提供数据支持。【方法】采用滤膜分离并浓缩噬体、PCR-克隆测序技术对我国东北稻田水体中噬藻体psbA基因进行调查。【结果】在东北稻田水体中共得到17条来自于噬藻体的psbA基因,经系统进化分析表明,我国东北稻田具有新的噬藻体的类群,与日本稻田生态系统中psbA基因类群相比,两地间噬藻体类群存在显著的差异,稻田水体中噬藻体psbA基因类群有别于海洋、湖泊类群。【结论】采用PCR-克隆测序技术以psbA基因为分子标记首次对我国东北稻田水体噬藻体类群进行调查,发现有新的噬藻体类群。     

失活蓝藻的趋光性

将固氮鱼腥藻置于０．５ｍｏｌＫ３ＰＯ４,７％甲醛或３６－３８％甲醛,７０％或９５％乙醇,冰醋酸,或将藻丝悬浮液煮沸或经１５磅１５分高温高压处理之后,藻丝立即变色失活,但仍能向光照方向移动和聚集,此种能力保持１－２周。在１ｍｏｌＮａＯＨ或ＨＣｌ溶液中,此种能力丧失。失活的东湖项圈藻,钝顶螺旋藻和组囊藻也有趋光性。     

纳帕海高原湿地噬藻体g20基因系统发育多样性分析

【背景】噬藻体是感染蓝藻的病毒,是水生系统的重要组成部分。它们对宿主种群死亡率有重要影响,是控制蓝藻水华生消的潜在因子,对蓝藻群落结构的调控具有重要意义。大量研究揭示了海洋和淡水环境中噬藻体的高度多样性,但目前对高原湿地中噬藻体的多样性知之甚少。【目的】阐明我国纳帕海高原湿地噬藻体g20基因的遗传多样性,为进一步开展高原湿地微生物资源及其生态功能研究提供理论基础。【方法】采集雨季的水体样品,以衣壳蛋白基因g20为标记基因,利用特异性引物Cps1和Cps8对其进行PCR扩增,得到26条不同的g20基因有效序列,并将其与其他生境中g20基因序列进行主坐标分析和系统发育分析。【结果】与其他海洋和淡水的噬藻体序列相比,纳帕海高原湿地中噬藻体的序列与其他稻田序列更为相近;但也存在部分序列单独聚簇,这可能为纳帕海高原湿地中独有的噬藻体类型。【结论】表明该地区的噬藻体较丰富,并具有一定的独特性。     

Spatial and temporal changes of cyanophage communities in paddy field soils as revealed by the capsid assembly protein gene g20

Bacteriophages are ubiquitous in various environments. Our previous study revealed the diversity of the cyanophage community in paddy floodwater. In this study, the phylogeny and genetic diversity of cyanophage communities in paddy field soils were reported. The viral capsid assembly protein gene (g20) of cyanophage was amplified with the primers CPS1 and CPS8 from soil DNA extracted during two different sampling times at three sampling sites in Japan. The sequencing results indicated that about 93% of the clones were g20 genes. In total, 70 clones of g20 genes were obtained in this study, of which 69 clones were of cyanophage origin. As evaluated by g20 sequence assemblages in paddy field soils, the unifrac analyses results indicated that cyanophage communities changed among the sampling sites and times and differed from those communities detected in paddy floodwater. The phylogenetic analysis showed that the g20 sequences in paddy field soils were very diverse and distributed into Clusters α, β and ?, as well as four newly formed clusters. Within Clusters β and ?, four unique subclusters were formed from the g20 clones that were only observed in this study. These findings suggested that the cyanophage communities in paddy field soils are different from those found in freshwater, marine water and paddy floodwater.     

Cyanophage diversity, inferred from g20 gene analyses, in the largest natural lake in France, Lake Bourget

The genetic diversity of the natural freshwater community of cyanophages and its variations over time have been investigated for the first time in the surface waters of the largest natural lake in France. This was done by random screening of clone libraries for the g20 gene and by denaturing gradient gel electrophoresis (DGGE). Nucleotide sequence analysis revealed 35 distinct cyanomyovirus g20 genotypes among the 47 sequences analyzed. Phylogenetic analyses showed that these sequences fell into seven genetically distinct operational taxonomic units (OTUs). The distances between these OTUs were comparable to those reported between marine clusters. Moreover, some of these freshwater cyanophage sequences were genetically more closely related to marine cyanophage sequences than to other freshwater sequences. Both approaches for the g20 gene (sequencing and DGGE analysis) showed that there was a clear seasonal pattern of variation in the composition of the cyanophage community that could reflect changes in its biological, chemical, and/or physical environment.     

Cyanophage Diversity, Inferred from g20 Gene Analyses, in the Largest Natural Lake in France, Lake Bourget

The genetic diversity of the natural freshwater community of cyanophages and its variations over time have been investigated for the first time in the surface waters of the largest natural lake in France. This was done by random screening of clone libraries for the g20 gene and by denaturing gradient gel electrophoresis (DGGE). Nucleotide sequence analysis revealed 35 distinct cyanomyovirus g20 genotypes among the 47 sequences analyzed. Phylogenetic analyses showed that these sequences fell into seven genetically distinct operational taxonomic units (OTUs). The distances between these OTUs were comparable to those reported between marine clusters. Moreover, some of these freshwater cyanophage sequences were genetically more closely related to marine cyanophage sequences than to other freshwater sequences. Both approaches for the g20 gene (sequencing and DGGE analysis) showed that there was a clear seasonal pattern of variation in the composition of the cyanophage community that could reflect changes in its biological, chemical, and/or physical environment.     

Identification of a diagnostic marker to detect freshwater cyanophages of filamentous cyanobacteria

Cyanophages are viruses that infect the cyanobacteria, globally important photosynthetic microorganisms. Cyanophages are considered significant components of microbial communities, playing major roles in influencing host community diversity and primary productivity, terminating cyanobacterial water blooms, and influencing biogeochemical cycles. Cyanophages are ubiquitous in both marine and freshwater systems; however, the majority of molecular research has been biased toward the study of marine cyanophages. In this study, a diagnostic probe was developed to detect freshwater cyanophages in natural waters. Oligonucleotide PCR-based primers were designed to specifically amplify the major capsid protein gene from previously characterized freshwater cyanomyoviruses that are infectious to the filamentous, nitrogen-fixing cyanobacterial genera Anabaena and Nostoc. The primers were also successful in yielding PCR products from mixed virus communities concentrated from water samples collected from freshwater lakes in the United Kingdom. The probes are thought to provide a useful tool for the investigation of cyanophage diversity in freshwater environments.     

Identification of a Diagnostic Marker To Detect Freshwater Cyanophages of Filamentous Cyanobacteria

Cyanophages are viruses that infect the cyanobacteria, globally important photosynthetic microorganisms. Cyanophages are considered significant components of microbial communities, playing major roles in influencing host community diversity and primary productivity, terminating cyanobacterial water blooms, and influencing biogeochemical cycles. Cyanophages are ubiquitous in both marine and freshwater systems; however, the majority of molecular research has been biased toward the study of marine cyanophages. In this study, a diagnostic probe was developed to detect freshwater cyanophages in natural waters. Oligonucleotide PCR-based primers were designed to specifically amplify the major capsid protein gene from previously characterized freshwater cyanomyoviruses that are infectious to the filamentous, nitrogen-fixing cyanobacterial genera Anabaena and Nostoc. The primers were also successful in yielding PCR products from mixed virus communities concentrated from water samples collected from freshwater lakes in the United Kingdom. The probes are thought to provide a useful tool for the investigation of cyanophage diversity in freshwater environments.     

Characterisation of Host Growth after Infection with a Broad-Range Freshwater Cyanopodophage

Freshwater cyanophages are poorly characterised in comparison to their marine counterparts, however, the level of genetic diversity that exists in freshwater cyanophage communities is likely to exceed that found in marine environments, due to the habitat heterogeneity within freshwater systems. Many cyanophages are specialists, infecting a single host species or strain; however, some are less fastidious and infect a number of different host genotypes within the same species or even hosts from different genera. Few instances of host growth characterisation after infection by broad host-range phages have been described. Here we provide an initial characterisation of interactions between a cyanophage isolated from a freshwater fishing lake in the south of England and its hosts. Designated ΦMHI42, the phage is able to infect isolates from two genera of freshwater cyanobacteria, Planktothrix and Microcystis. Transmission Electron Microscopy and Atomic Force Microscopy indicate that ΦMHI42 is a member of the Podoviridae, albeit with a larger than expected capsid. The kinetics of host growth after infection with ΦMHI42 differed across host genera, species and strains in a way that was not related to the growth rate of the uninfected host. To our knowledge, this is the first characterisation of the growth of cyanobacteria in the presence of a broad host-range freshwater cyanophage.     

噬藻体辅助代谢基因(AMGs)研究进展

噬藻体是一类广泛存在于海洋及淡水环境中以蓝藻为感染宿主的病毒,对蓝藻种群结构与多样性以及水生态环境具有重要的影响。噬藻体携带一系列与宿主新陈代谢相关的同源基因被称为辅助代谢基因。它们编码的蛋白在噬藻体感染蓝藻过程中,可参与宿主的光合作用、戊糖磷酸循环、营养物质摄取以及核苷酸生物合成等代谢活动。近年来,一些辅助代谢基因被作为噬藻体分子检测的靶标基因,并用于噬藻体遗传多样性及其与蓝藻间相互关系的研究。本文综述了国内外有关噬藻体辅助代谢基因的来源、生物学功能及其多样性等方面的研究进展。     

新型聚球藻噬藻体Yong-L2-223的分离及基因组分析

【目的】噬藻体(cyanophages)是特异性侵染蓝藻(cyanobacteria)的病毒，广泛分布于各类水体中，在调节蓝藻种群动态和密度、推动生物地球水生生态系统循环中起着重要作用。本研究的目的在于分离、鉴定噬藻体。【方法】本研究以海洋聚球藻(Synechococcus sp.) PCC 7002为指示宿主，从淡水水样中分离培养一株新型噬藻体Yong-L2-223，对其进行了宿主范围实验、全基因组测序、基因功能注释和系统进化分析。【结果】针对31株供试蓝藻的宿主范围实验，结果除指示藻PCC 7002 [属于聚球藻目(Synechococcales)]外，Yong-L2-223能够感染2株淡水蓝藻，分别是来源于滇池的绿色微囊藻(Microcystis viridis) FACHB-1342 [属于色球藻目(Chroococcales)]和水华束丝藻(Aphanizomenon flos-aquae)FACHB-1209[属于念珠藻目(Nostocales)]。既可在高盐条件下感染海洋蓝藻，又可在低盐条件下感染淡水蓝藻，Yong-L2-223具有广盐性。透射电镜观察表明，Yong-L2...