【作者】 程凯；

【导师】 赵以军；

【作者基本信息】 华中师范大学 ， 微生物， 2002， 硕士

【摘要】 我们在国内首次分离和报道了淡水噬藻体（蓝藻病毒），其宿主为织线藻和席藻。电镜照片显示该噬藻体为噬菌体形态，头部直径为52nm，尾部很短，几乎不可见。我们研究了确定该噬藻体裂解周期和释放量的多种方法，认为细胞计数法是测量裂解周期既方便又准确的方法，而采用1PFU的感染可获得噬藻体的准确释放量。在上述研究的基础上，我们还系统开展了噬藻体生理与生态特性的研究。 对噬藻体的生理特性的研究结果显示：噬藻体在28℃下裂解织线藻的周期为4h，其中潜伏期为3h，裂解期为1h，病毒释放量约200PFU·细胞^-1；噬藻体的感染对光照有依赖性，且在光照条件下的吸附率显著高于遮光条件下的吸附率；噬藻体的吸附率还受宿主生长状态的影响：随着培养时间的延长，噬藻体的吸附率不断上升，稳定期宿主的吸附速率最快；感染过程中，织线藻的光合放氧速率急剧下降；温度会影响噬藻体的活性：40℃下处理10min，活性保持100％；50℃下处理1min，失活率小于25％；50℃下处理10min，失活率为40％；60℃下处理1min，失活率为85％；60℃下处理10min，失活率大于99％。此外，固体培养条件下，织线藻的生长速率与噬藻斑的扩大之间有明显的同步性，即生长速度越大，噬藻斑的扩大就越明显。 对淡水噬藻体的生态学进行了初步研究，包括淡水中噬藻体分布及感染力的调查与人工混合培养条件下噬藻体裂解宿主引起微生物和藻类种群变化的研究。调查结果显示，19个采集的水样中有6个含有裂解织线藻的噬藻体，而且水样未经浓缩即能裂解宿主，说明噬藻体在淡水中分布较广泛，裂解性也较强；混合培养条件下的研究结果表明，噬藻体裂解宿主后，细菌数量快速增加，而当培养系统中有非宿主藻类存在时，细菌的增殖则受到非宿主藻的抑制，说明噬藻体可以显著改变系统中微生物的种群结构。更多还原

【Abstract】 Investigation in details on a freshwater cyanophage isolated in China infecting Plectonema and Phormidium is presented in this thesis. Under Trasmission Electronic Microscope (TEM), the cyanophage showed a bacteria-phage shape with head diameter at 52nm and short tail (almost invisible). Several methods for measuring the lysing cycle and burst size of the cyanophage were tested. It was established that cell counting method was more convenient and exact for confirming the lysing cycle. Burst size obtained by 1 PFU infecting was reliable. More studies were conducted on both the physiology and ecology of the cyanophage.Results involved in the physiological characters are as below: the cycle of lysing Plectonema at 28 癈 was 4hrs, including 3hrs of patent period and Ihr of lysing period. The burst size of the cyanophage was ca. 200 PFU ?Cell"1. The rate of adsorption to host was markedly higher under light condition than that under dark condition (P=0.02), and light was necessary for infection. Moreover, the adsorption rate was affected by the growth of host: it became greater along with the host growth and reached the maxium at stable stage. During infection, the photosynthetic oxygen releasing rate decreased drastically. The activity of cyanophage changed under different temperatures: 100% activity remained at 40癈 for lOmin, more than 75% at 50癈 for Imin, 60% at 50癈for lOmin, 15% at 60癈 for Imin and less than 1% at 60癈 for lOmin. It was also indicated that the enlargement of plaque related to the growth of host, i.e, the more rapid the growth, the more notable the enlargement of the plaque.Preliminary studies on the ecological characters of freshwater cyanophage were carried out under both field condition and culturing system. The field investigation result showed that 6 in 19 water samples contained cyanophages lysing plectonema and the lysis phenomenon were readily observed without concentrating the water. Thus it could be presumed that there was a widespread distribution and a high infectivity of cyanophage in nature. Under mixed culturing conditions, it was observed that bacterial number rapidly incre;ised soon after the lysing of hostcells. On the contrary, while the non-host cyanobacterium( i.e. Anabaena flos-aquae) was incubated in the mix culturing system, the breeding of the bacteria could be inhibited. It may be suggested from the result above that cyanophage could bring about the changes in microorganism populations.更多还原