中文摘要：

为研究藻际微生物多样性与紫菜健康养殖的关系，从江苏南通（养殖）、山东青岛（野生）、浙江温州（养殖）三地的条斑紫菜叶状体和江苏东台条斑紫菜贝壳丝状体及其周围的海水样品中分离了条斑紫菜外生细菌。根据菌落特征和菌体形态将、获得的63株细菌分为21种表型。16S rDNA—V3片段DGGE分析结合序列测序比对结果表明：这些菌株与假交替单孢菌（Pseudoalteromonas）、嗜冷单胞菌（Psychrobacter）和芽孢杆菌（Bacillus）等10属相应菌株具有较高的同源性。通过对条斑紫菜外生细菌区系多样性分析得出：条斑紫菜藻体外生细菌组成与生活环境相关，但不同于周围海水细菌群落；不同来源（地点）、不同生理状况（健康与病烂）和不同生长阶段（叶状体和丝状体）的条斑紫菜外生菌种群组成差异较大。许多外生细菌对常见测试菌、海水养殖动物致病菌和人致病菌具有抑菌活性，其抑菌特点与紫菜生理性状相关。从健康条斑紫菜样品分离的外生菌中假交替单孢菌占优势，病烂紫菜未分离到假交替单孢菌，提示假交替单孢菌可能与紫菜健康生长有密切关系。

英文摘要：

Epiphytic bacteria were isolated from Porphyra yezoensis cultivated in the fields or wildly distributed in natural coasts from Nantong （Jiangsu）; Qingdao （Shandong） and Wenzhou （Zhejiang） in China, and the conchocelis cultured in Dongtai （Jiangsu） in order to investigate their diversity and the relationship with healthy culture of Porphyra. On the basis of morphological observation, DGGE of 16S rDNA-V3 fragments and 16S rDNA sequence, 63 isolated strains were grouped into 21 morphotypes, which had high similarities with strains of 10 genus such as Pseudoalterornonas, Psychrobacter, Bacillus and so on. The analysis showed that the epiphytic bacteria flora in P. yezoensis were relevant with its growth habitats but different from its surroundings. The flora of epiphytic bacteria from different origins, different physiological status （health and disease） and different development stages （thallus and conchocelis） were quite various. The bioactivities of the epiphytic bacteria were measured by the normal tested bacteria and pathogenic bacteria of animal aquaculture or human beings, which showed correlation with the physiological status of their hosts. Dominating bacteria from healthy Porphyra belonged to the genus Pseudoalterornonas, which were not found in rotted samples. The significant difference of epiphytic bacterial flora might have some relationships with the healthy growth of P. yezoensis.