【作者】 张燕；

【导师】 赵以军；

【作者基本信息】 华中师范大学 ， 水生生物学， 2013， 硕士

【摘要】 从我国东海沿岸2011年8月采集的样品中分离出了2株聚球藻及其噬藻体和4株原绿球藻。所有纯化培养的海洋聚球藻和原绿球藻均能利用NH4+和NO3-,只是生长速率有所差异。2株聚球藻的吸收光谱显示其能有效吸收蓝光,并且具有较高的PUB/PEB比值,而4株原绿球藻的叶绿素b/a比值普遍高于0.95,与已知大多数原绿球藻情况相似。基于16S rDNA、ITS和psbA基因序列的分析比对显示,2株聚球藻为近岸种且与marine cluster A(MC-A)类群中的clade III成员极其相似,而4株原绿球藻与High-B/A类群中的clade IV(LLIV)成员极其相似。从16S rDNA.ITS、 psbA基因构建的进化树来看,这2株聚球藻总是聚类在一起；而16S rDNA序列构建的进化树显示从相同氮源生长培养基中分离出来的原绿球藻之间亲缘关系更加密切。从与宿主相同的采样点处分离出了2株感染上述海洋MC-A型聚球藻的噬藻体,并且建立了稳定的聚球藻-噬藻体系统。通过蔗糖密度梯度离心法和最大可能数法分离纯化了这2株聚球藻噬藻体。对噬藻体负染样品进行透射电子显微观察发现,聚球藻噬藻体SS-2具有一个等二十面体的头部,直径为65nm,和一条灵活的长尾约210nm；聚球藻噬藻体SJ-2具有一个等二十面体的头部,直径为68nm,和一条灵活的长尾约280nm。这2株聚球藻噬藻体都具有严格的宿主特异性,其中聚球藻噬藻体SS-2能够感染亲缘关系密切的海洋聚球藻SS01和SJ01；聚球藻噬藻体SJ-2仅能感染海洋聚球藻SJ01。这2株聚球藻噬藻体的基因组均小于23kb,且SJ-2的基因组比SS-2更小。此外,这2株噬藻体的基因组对内切酶HindⅢ、 BamHI、EcoRI不敏感,且均无法扩增出g20、psbA、DNApol基因序列,这些特征与已报道的聚球藻长尾噬藻体一致,并且与已知的聚球藻肌尾噬藻体和短尾噬藻体区别明显。更多还原

【Abstract】 Two marine Synechococcus sp. strains and their cyanophages, four marine Prochlorococcus sp. strains were isolated from the coastal sample waters of East China Sea during August 2011. All the cultures isolates of marine Synechococcus and Prochlorococcus could utilize both NH4+and NO3-, occasionally at different growth rates. The in vivo absorption spectra indicate that these Synechococcus spp. absorbs light efficiently in the blue region, with high PUB/PEB ratios and the Ch1 b/a ratios of these Prochlorococcus were higher than 0.95, which was similar to most known Prochlorococcus strains. Based on their 16S rDNA、ITS and psbA gene sequences, the two Synechococcus strains were very similar to those members of clade III of the marine cluster A(MC-A) group, and the four Prochlorococcus strains were very similar to those members of High-B/A Prochlrococcus clade Ⅳ. The phylogenetic trees of 16S rDNA、 ITS、psbA sequences showed that the two coastal Synechococcus strains always clustered together; and the phylogenetic tree of 16S rDNA sequences showed that the Prochlrococcus strains selected from same N sources during isolation were closely related.Two new cyanophages infecting the above mentioned MC-A Synechococcus strains had been isolated from the same sampling locations, and the stable systems of Synechococcus-Cyanophage were established. The two Synechococcus caynophages SS-2 and SJ-2 were isolated and purified via the methods of the sucrose density gradient centrifugation and Most Probable Number. Transmission electron micrography of negative-stained specimens revealed that the cyanophage isolate SS-2 has an isometric head with a diameter of 65 nm and a long flexible tail 210 nm in length, and the cyanophage isolate SJ-2 has an isometric head with a diameter of 68 nm and a long flexible tail 280 nm in length. Both of the two Synechococcus cyanophages are specific to their hosts, the cyanophage SS-2 could infect marine Synechococcus strains SS01 and SJ01, which are closely related; the cyanophage SJ-2 could only infect marine Synechococcus strain SJ01. The genomes of the two Synehcococcus cyanophages were smaller than 23kb, and the genomes of SJ-2 were smaller than SS-2. Moreover, the two cyanophages DNA could not be digested with the restriction enzymes HindⅢ、 BamHI、 EcoRI, and the genomic DNA could not be amplified with the specific primers of g20、 psbA、DNApol genes. This is consistent with the characteristics of reported Synechococcus siphoviruses, but differentiated from any known Synechococcus myoviruses and podoviruses.更多还原