中文摘要：

三亚珊瑚礁自然保护区部分珊瑚礁退化后逐渐演替为以泰来藻（Thalassia hemprichii）为优势种的海草床群落，采用选择性无氮培养基从泰来藻植株的根际，分离得到一株固氮菌，编号为G33-1，经形态学、生理生化鉴定和16SrDNA及固氮基因nifH的序列分析，初步鉴定为成团泛菌（Pantoea agglomerans）。该菌为革兰氏阴性菌，以周生鞭毛运动，呈直杆状，菌落圆形，半透明乳白色，比较湿润，有光泽，直径约1mm，低凸，光滑，边缘比较整齐。最适培养条件为：氯化钠浓度25‰，生长温度为37℃，起始pH值为8。与成团泛菌标准菌株（ATCC27155^TM）相比较，在碳源利用、精氨酸双水解、苯丙氨酸脱胺酶、乌氨酸脱胺酶、以及生长温度和盐度等方面都具有较高的相似性，以16SrDNA为基础构建的系统进化树分析结果，表明其与成团泛菌属Pantoea agglomerans WAB1870进化距离最近，相似性大于99％。此外，利用乙炔还原法对固氮活性进行测定，其具有较高的固氮活性，达299．16nmol C2H2／（mL·h）。

英文摘要：

A strain capable of growth at high rates under nitrogen fixation conditions was isolated from the root of the seagrass （Thalassia hemprichii）, which appeared after the degradation of coral reefs in Sanya natural reserves. The bacterium was identified as Pantoea agglomerans, which was also called Enterobacter agglomerans, on the basis of its morphology, physiological and biochemical characteristics, and the sequence analysis of 16S rDNA and the nitrogenase structural gene nifH. It was identified as a gram-negative, smooth, low raised, straight-rodded bacterium, which formed translucent colony with diameter of about 1 mm on the solid agar medium. Compared with the standard strain of the species Pantoea agglomerans （ATCC27155TM）, there were high similarity in the carbon sources utility, hydrolysis and the optimal growth temperature and salinity, It could use a series of hydrocarbons as carbon sources, such as D-glucose, L-arabinose, sucrose, raffinose, maltose, rhamnose, D-xylose, D-mannitol, cellobiose, micronesia disaccharide. The results of the arginine dihydrolase, phenylalanine deaminase, lysine decarboxylation, ornithine deaminase were negative. The optimal growth temperature, pH and salinity were 37℃, 8 and 25‰, respectively. It could also grow at 40℃ and pH was 10 but could not grow at zero salinity. Phylogenetic analysis of the 16S rDNA gene sequences （EU841417） showed more than 99% similarities to that from other recognized Pantoea agglomerans. The nitrogen fixation rate of G33-1 was 299.16 nmol C2H2/（mL·h）.