胶州湾聚球菌(Synechococcus spp.)蓝细菌的分布及其对初级生产力的贡献

自2002—2004年应用表面荧光显微镜计数法对胶州湾聚球菌(Synechococcusspp.)蓝细菌的季节变化、月变化及其对浮游植物总初级生产力的贡献进行调查研究。结果显示,胶州湾Synechococcusspp.丰度处于0.16×104—21×104cells/ml之间,最大与最小值之间相差约两个数量级,其中夏天Synechococcusspp.丰度最高,春、秋季相当,冬季最低。夏季Synechococcusspp.丰度平均值约是冬季的3—4倍。Synechococcusspp.的季节变化呈现一定周期性。Synechococcusspp.月最高值(21×104cells/ml)出现在8月的B2站表层,最低值(0.15×104cells/ml)出现在12月A1站表层。对18个月的胶州湾Synechococcusspp.水平分布进行分析,结果显示,河口和近岸区域Synechococcusspp.丰度相对较高。以D8站为典型站位对Synechococcusspp.垂直分布进行的分析发现,不同季节Synechococcusspp.最大值出现的水深不同。胶州湾Synechococcusspp.在总浮游植物生物量中所占的比例在0.2%—77%之间,平均为4.7%。此外,对2003—2004年温度与Syne-chococcusspp.丰度的相关性分析中发现,两者呈正线性相关(相关系数达0.6)。

游离和固定化Synechococcus sp.细胞对铬(Ⅵ)生物吸附性能的比较研究

从pH值、温度及吸附动力学等方面比较研究游离和经海藻酸固定化的微藻Synechococcus sp.细胞生物吸附剂对Cr（VI）的吸附性能. 研究结果表明： 游离细胞吸附剂在较宽的pH值（1～12）范围内稳定, 其表面电位等电点为pH=3;在等电点前（pH〈3）细胞对Cr（VI）吸附明显增强;在等电点后（pH＞3）细胞对Cr（VI）也表现出一定的吸附. 这表明Cr（VI）主要通过静电吸附到细胞上, 吸附的作用点为蛋白质表面的质子化氨基. 游离细胞经海藻酸固定化后, 其表面电位等电点移至pH=2, 但两者的吸附行为相似, 且都与在海藻酸钙上的吸附行为显著不同, 说明固定化细胞对Cr（VI）的吸附主要是游离微藻细胞的作用;Cr（VI）在游离和固定化细胞上的吸附是一个快速的过程, 在其质量浓度低于1 g/L的范围内符合Freundlich吸附等温方程, 在10～50 ℃吸附不受温度影响.

南海北部海域Synechococcus和Prochlorococcus生长率和被摄食消亡率——变化范围及其与环境因子的关系

2004年首次在南海北部海域使用选择性代谢抑制剂技术进行了Synechococcus和Prochlorococcus生长率和被摄食消亡率的研究.研究结果表明,ynechococcus高丰度值出现在次表层（15 m或20m）,位于温跃层之上,高生长率往往出现在丰度最大值水层上方;Prochlorococcus丰度在夏季出现次表层最大值,与温跃层深度基本一致,表层生长率高于真光层底部.Synechococcus真光层平均生长率为0.11～1.18 d^-1,被摄食消亡率为0.11～0.76 d^-1,分布格局均为从沿岸向外海方向升高.Prochlorococcus真光层平均生长率为0.23～0.49 d^-1,存在较明显的季节变化,夏季近岸略高于外海,而冬季的趋势正好相反;真光层平均被摄食消亡率为0.12～0.33 d^-1,冬夏两季均是近岸高于外海。温度、营养盐和光是影响Synechococcus生长率变化的重要因子.Synechococcus和Prochlorococcus丰度与群落生长率之间不存在相关关系,而与被摄食消亡率之间则存在显著的指数相关.根据Synechococcus和Prochlorococcus的生长率估算了它们的生产力及其对Pico-生产力的贡献.

Selection and Ultrastructural Observation of a High-CO_2-requiring Mutant of Cyanobacterium Synechococcus sp. PCC7942

A high_CO 2_requiring mutant of Synechococcus sp. PCC7942 has been isolated after chemical mutagenesis of ethyl methane sulphonate (EMS). It was able to grow at 4% CO 2, but not under ambient CO 2. The initial screening of the mutant showed that the genetic reversion rate was about 10 -7 and death occurred 2-3 days after being transferred from 4% CO 2 to the ambient air. Its photosynthetic dependence on external dissolved inorganic carbon was higher than that of the wild type cells, but its carbonic anhydrase activity was comparatively low. In the ultrastructural level, various types of aberrant carboxysomes appeared in the mutant cells: rod_shaped carboxysomes, irregular carboxysomes and the “empty_inclusion carboxysomes" with increasing number of glycogen granules surrounding the thylakoids. All these alterations indicated that the mutant was defective in utilizing the external CO 2. The induction of carboxysomes by lower levels of CO 2 and the biogenesis of carboxysomes are herein discussed.

外源基因的导入对Synechococcus sp.PCC7942SOD活性和同工酶谱的影响

外源DNA导入Synechococcussp.PCC7942后,通过NBT光化还原和PAGE电泳检测发现转基因藻Syne chococcussp.PCC7942的SOD活性和同工酶谱发生了改变.若外源基因整合在受体细胞染色体DNA上,根据整合位点的不同则能提高或减弱Synechococcussp.PCC7942的SOD活性,同时增加同工酶谱带.若外源基因不是整合在染色体上而是以质粒的形式存在,则只改变Synechococcussp.PCC7942SOD活性而不影响其同工酶谱.

Estimating Synechococcus spp. growth rates and grazingpressure by heterotrophic nanoplankton in theEnglish Channel and the Celtic Sea

-Marine chroococcoid phycoerythrin - containing Synechococcus spp. recently have been implicated as a substantial component of the photosynthetic picoplankton in the ocean. Although the importance of Synechococcus as food sources for heterotrophic nanoplankton are now recognized, the information about its cycling of biomass and diel patterns is limited and the methodology used varies according to different authors. A selective metabolic inhibitor method was used to allow simultanous estimation of both growth rates and grazing disappearance rates of Synechococcus. Results obtained in the English Channel show growth rates ranging from 0. 25 to 0. 72 d-1 with an average value of 0. 51 d -1and grazing disappearance rates ranged from 0. 21 to 0. 64 d-1 (mean = 0. 44 d-1). Offshore in the Celtic Sea of the Northeast Atlantic Ocean, both rates were lower than in the channel. The similarity between average growth and grazing rates suggests a rapid recycling of Synechococcus biomass. In diel pattern, Synechococcus grazing mortality rates were higher during the day (mean = 0. 61 d-1) than during the night (mean = 0. 21d-1) in all the experiments. A positive correlation was observed between growth rates and in situ temperature ranged from 9 to 20 ℃. Sire-fractionated experiments demonstrate that up to about 7 0 % of Synechococcus disappearance could be attributed to the grazer smaller than 2 μm in diameter. The variations of Synechococcus cell characteristics such as size and phycoerythin contents in the growth and grazing experiments were determined with a flow cytometer. The methodology recently used on estimating dynamics of Synechococcus population is reviewed.

Production of γ-linolenic acid and stearidonic acid by Synechococcus sp.PCC7002 containing cyanobacterial fatty acid desaturase genes

Genetic modifi cation is useful for improving the nutritional qualities of cyanobacteria. To increase the total unsaturated fatty acid content, along with the ratio of ω-3/ω-6 fatty acids, genetic engineering can be used to modify fatty acid metabolism. S ynechococcus sp. PCC7002, a fast-growing cyanobacterium, does not contain a Δ6 desaturase gene and is therefore unable to synthesize γ-linolenic acid(GLA) and stearidonic acid(SDA), which are important in human health. In this work, we constructed recombinant vectors Syd6 D, Syd15 D and Syd6Dd15 D to express the Δ15 desaturase and Δ6 desaturase genes from Synechocystis PCC6803 in Synechococcus sp. PCC7002, with the aim of expressing polyunsaturated fatty acids. Overexpression of the Δ15 desaturase gene in S ynechococcus resulted in 5.4 times greater accumulation of α-linolenic acid compared with the wild-type while Δ6 desaturase gene expression produced both GLA and SDA. Co-expression of the two genes resulted in low-level accumulation of GLA but much larger amounts of SDA, accounting for as much to 11.64% of the total fatty acid content.

Spatial and temporal variations of Synechococcus and picoeukaryotes in the Taiwan Strait,China

The size-fractionated phytoplankton biomass, and the spatial and temporal variations in abundance of Synechococcus (SYN) and picoeukaryotes (PEUK) were measured in the Taiwan Strait during three cruises (August 1997, February-March 1998, and August 1998). The results show that picophytoplankton and nanophytoplankton dominate the phytoplankton biomass, in average of 38% and 40%, respectively. SYN and PEUK varied over time in abundance and carbon biomass, greater in summer than in winter, in range of (7.70–209.2)×106 and (0.75–15.4)×106 cells/cm2 in the abundance, and 1.93–52.3 and 1.57–32.4 μgC/cm2 in the carbon biomass, for SYN and PEUK, respectively. The horizontal distributions of both groups were diurnal but heterogeneous in abundance, depending on the groups and layer of depths. Temperature is the key controlling factor for picophytoplankton distribution (especially in winter) in the Strait.

SIMULTANEOUS ESTIMATES OF SYNECHOCOCCUS SPP. GROWTH AND GRAZING MORTALITY RATES IN THE ENGLISH CHANNEL

The marine chroococcoid phycoerythrin-containing Synechococcus spp.cyanobacterium has been impli-cated as a subsetantial component of the photosynthetic picoplankton in the ocean. Although its imppr-tance as food source for heterotrophic nanoplankton is now recognized, information about the cycling ofSynechococcus biomass and its diel pattern is limited and study methodology varies among authors. Theselective metabolic inhibitor method was used to simultaneously estimate growth and grazing disappearancerates of Synechococcus in the English Channel where growth rates ranged from 0.25 to 0.72/d (mean±SD=0.51±0.17/d) and grazing mortality rates ranged from 0.19 to 0.64/d (mean ±SD=0.48±0.17/d).Size-fractionated experiments demonstrated that up to 70% of Synechosoccus disappearance could be attri-buted to grazers going through a 2 μm Nuclepore filter. Synechococcus grazing mortality rates (mean=0.74±0.25/d) during the day were alwnys higher than that (mean=0.21±0.20d) during the night, while

Genetic transformation of marine cyanobacterium Synechococcus sp.CC9311(Cyanophyceae) by electroporation

Synechococcus sp.CC9311 is a marine cyanobacterium characterized by type IV chromatic acclimation(CA).A genetic transformation system was developed as a first step to elucidate the molecular mechanism of CA.The results show that Synechococcus sp.CC9311 cells were sensitive to four commonly used antibiotics:ampicillin,kanamycin,spectinomycin,and chloramphenicol.An integrative plasmid to disrupt the putative phycoerythrin lyase gene mpeV,using a kanamycin resistance gene as selectable marker,was constructed by recombinant polymerase chain reaction.The plasmid was then transformed into Synechococcus sp.CC9311 via electroporation.High transformation efficiency was achieved at a field strength of 2 kV/cm.DNA analysis showed that mpeV was fully disrupted following challenge of the transformants with a high concentration of kanamycin.In addition,the transformants that displayed poor growth on agar SN medium could be successfully plated on agarose SN medium.

The First Isolation of a Cyanophage-Synechococcus System from the East China Sea

A cyanophage strain and its host Synechococcus were isolated from the East China Sea. The host Synechococcus sp. S J01 was characterized by its 16S rRNA, ITS, andpsbA gene sequences as well as by its morphological appearance and pigmentation. The cyanophage, strain S-SJ2, was able to cause a lytic infection of the coastal Synechococcus. TEM of negative-stained specimens showed that the phage isolate has an isometric head with a diameter of 68 nm and a long tail with a length of 280 nm. The cyanophage-Synechococcus system from the East China Sea shares many properties with other marine cyanophage-Synechocoecus systems worldwide.

Isolation and Physiological Characterization of Synechococcus cedrorum 1191 Strain Tolerant to Heavy Metals and Pesticides

The toxicity of heavy metals (Hg2 + , Zn2 + ) and pesticides has been investigated by comparing the physiological properties in wild and tolerant strains of Synechococcus cedrorum 1191. The differential pattern of growth, absorption spectra of pigments and nutrient uptake was observed in tolerant strain.

EXTRACELLULAR RELEASE OF β-LACTAMASE BY OSMOTIC SHOCK IN SYNECHOCOCCUS TRANSFORMANT

A unicellular cyanobacterium Synechococcus sp. strain PCC 7002 was transformedwith plasmid pQL1, on which β-lactamase gene (bla) and β-galactosidase gene (lacZ) were encoded.The transformant cells released β-lactamase into medium by an abrupt drop of osmotic pressure. This re-sult indicates that this cyanobacterium recognizes and processes the signal sequence of β-lactamase, andaccumulates the enzyme in periplasm. Repeated release of β-lactamase was possible by repeated osmoticshocks without impairing cell viability. On the other hand, most of the β-galactosidase remained in cyto-plasm under the osmotic shock.

Insertal Orientation Has No Influence on the Expression of gfp Gene and the Growth of the Host Synechococcus sp.PCC7942

In transgenic process, a foreign gene can be integrated in the host genome in two directions, which may influence its expression. In order to study the effects of insertal orientation, the gfp reporter gene was inserted in the isiAB locus of Synechococcus sp. PCC7942 in different directions, and the GFP expression levels and the growth of the transgenic algae were compared. It was showed that the gfp gene could express in each direction, and no significant difference was detected on algal growth and GFP expression levels between the two recombinant algae.

Distribution and phenogenetic diversity of Synechococcus in the Bohai Sea, China

Synechococcus is one of the most abundant picocyanobacteria in marine ecosystem,and the absence of Prochlorococcus would make it indispensable as a primary producer in the Bohai Sea,North China.However,the abundance distribution and genetic diversity of Synechococcus in this region have rarely been reported.In this study,the distribution pattern of Synechococcus abundance was investigated during four cruises in April,June,August,and November from 2018 to 2019,moreover,its phenogenetic diversity was studied based on high-throughput sequencing of the cpe BA operon.The results demonstrate that phycoerythrin-containing Synechococcus was most abundant in August when temperature was high and oxygen saturation was low.During this period,Synechococcus pigment type(PT)2 was abundant in the Bohai Bay and Laizhou Bay under conditions of high nutrient concentration,temperature,and turbidity.In comparison,PT3,especially those clusters characterized with high or variable ratio of phycourobilin and phycoerythrobilin,was predominant in the Bohai Strait and Liaodong Bay under conditions of high salinity,pH,and oxygen saturation.Furthermore,co-occurrence correlations using network analysis revealed that Synechococcus PTs were related to 15.37%-43.48%of the prokaryotic genera.Synechococcus PT3c/PT3d and PT2 were the most important PTs in the network.The hierarchical clustering revealed that taxa co-occurred with Synechococcus PTs diff ered among samples.It could be attributed to the substance exchange and the environmental impact,which calls for more studies in the future.

Distribution Patterns of Synechococcus Indicated Their Environmental Constraints and Related Geochemical Processes in the Yellow Sea

Synechococcus is a widely distributed photosynthetic pico-phytoplankton,which contributes mainly to carbon fixation and maintains the stability of the marine ecosystem.To investigate its distribution patterns in the Yellow Sea,seawater samples were collected during September 2018.Results of flow cytometry analysis showed that the Synechococcus abundance ranged from 6.36×10^(2) to 4.51×10^(4) cells mL^(−1),which correlated with salinity(P<0.01)and temperature(P<0.05).At deeper off-shore sites,Synecho-coccus showed high abundance at the subsurface thermo-halocline,which was in accordance with chlorophyll a(Chl a)content along the vertical column.Based on the high-throughput sequencing data of rpoC1(partial gene encoding RNA polymerase),two Synechococcus subclusters,S5.1 and S5.2,were found to coexist in the studied area.Several clades of S5.1,including Clades I,II,and III,were the dominant components,accounting for 6.63%,26.11%,and 45.5%of the total genus,respectively.Redundancy analysis(RDA)showed that nitrite was the main environmental factor that explained the genus composition among samples.Fur-thermore,co-occurrence network revealed that the main phyla that coexisted with Synechococcus were Proteobacteria,Bacteroidetes,Actinobacteria,Planctomycetes,and Verrucomicrobia,which were involved in the carbon(C),nitrogen(N),sulfur(S),and manga-nese(Mn)cycles.Overall,Synechococcus exhibited biogeographic distribution correlated with temperature-salinity and nitrite in the Yellow Sea,and their geochemical function showed diverse but should be further verified in the future.

Glutathione S-Transferase(GST)Identified from Giant Kelp Macrocystis pyrifera Increases the Copper Tolerance of Synechococcus elongatus PCC 7942

The glutathione S-transferases gene family plays an important regulatory role in growth and development,and responses to environmental change.In this study,six complete GST genes(Mp GST1,Mp GST2,Mp GST3,MpGST4,Mp GST5,and Mp GST6)were cloned from the gametophytes of brown alga Macrocystis pyrifera.Subsequent bioinformatics analysis showed that these six genes encoded proteins with 202,216,288,201,205,and 201 aa,respectively.Moreover,Mp GST3 differs from the other GST genes.Phylogenetic analysis suggested that MpGST3 belongs to the Ure2p type GST.Domain analysis suggested that the other GSTs from M.pyrifera belong to the soluble GST family and form an independent branch with the GSTs found in the other macroalgae,suggesting that a new GST type was formed during macroalgal evolution.GST genes were upregulated in M.pyrifera when 2.5 mg L^(-1)Cu ions were added to the medium.Six GST genes were integrated into the genome of Synechococcus elongatus PCC 7942,and their functions were verified by measuring light absorbance,photosynthetic pigment content,and photosynthetic parameters of the transformed strains under 0.3 mg L^(-1)Cu ion stress.The results showed much higher levels of various parameters in the transformed strains than in the wild strain.The transformed strains(with the MpGST genes)showed significantly enhanced resistance to Cu ion stress,while the wild strain almost died.The results of this study lay a theoretical foundation for further research on the Cu ion stress resistance function of GSTs in M.pyrifera.

Biosorption mechanism of Cr (Ⅵ) onto cells of Synechococcus sp.

The biosorption mechanism of Cr （Ⅳ） ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetics study shows that the adsorption process of Cr （Ⅳ） consists of a very fast stage in the first several minutes, in which more than half of the saturation adsorption is attained, and a slower stage that approximately follows the first order kinetic model, basically Freundlich isotherm models were observed. Comparative studies of FT-LR spectra of K2Cr2O7, free cells of Synechococcus sp., and Cr-bound cells of Synechococcus sp show that the speciation of chromium that binds to the cells ofSynechococcus sp. is Cr （Ⅲ）, instead of Cr （Ⅳ）, and the carboxylic, alcoholic, amido and amino groups may be involved in the binding of Cr （Ⅲ）. Integrative analyses of the surface electric potential, the effect of pH value on adsorption behavior of Cr （Ⅵ）, and the results of FT-IR show that the biosorption of Cr （Ⅵ） follows two subsequent steps, biosorption of Cr2O7 ^2- by electrostatical force at the protonated active sites and reduction of Cr2O7^2- to Cr^3＋ by the reductive groups on the surface of the biosorbents.

Isolation, Purification and Characterization of Nucleoids from <i>Synechococcus elongatus</i>PCC 7942

The genomic DNA of bacteria is highly compacted in one or a few bodies known as nucleoids. In order to understand the overall configuration and physiological activities of the cyanobacterial nucleoid under various growth conditions and the role(s) of each nucleoid protein in clock function, thylakoid membrane-associated nucleoids from the Synechococcus elongatus (se) PCC 7942 strain were isolated and purified in presence of spermidine at low salt concentrations by sucrose density gradient centrifugation. The sedimentation rates, protein/DNA composition and microscopic appearances as well as variation in structural components of clock proteins from the isolated nucleoids were compared under identical conditions. Microscopic appearances of the nucleoids were consistent with the sedimentation profiles. The nucleoid structure in the wild type was more tightly compacted than that in the KaiABC mutant strain. Western immunoblot analyses revealed that the KaiC was associated with the nucleoid fraction whereas maximum KaiA was localized in the cytosolic fraction, supposedly in association with the translation machinery.

Analysis of a Synechococcus sp. Bloom in the East China Sea and Its Causes

In the spring of 2007,a Synechococcus sp. bloom was monitored in station A1( 30° N,123° E) in the East China Sea. The abundance of Synechococcus sp. was nearly 2×10~6 cells/ml,and the contribution of Synechococcus sp. to chlorophyll a was nearly 90%. According to the abundance of Synechococcus sp. in the East China Sea and adjacent Changjiang River estuary in the past tow decades,the main reasons why Synechococcus sp. could form a bloom are listed below: the rising level of nutrients and the further eutrophication of the water body provided sufficient nutrients for Synechococcus sp.;with the global warming,the sea water temperature in the East China Sea rose continuously;the number of major predator heterotrophic flagellates was at a low level,reducing predation pressure.