【摘要】 【目的】基于紫菜外生细菌抑菌活性的研究,本文对具有广谱抑菌活性的菌株进行了多聚酮合酶(Polyketide synthase I,PKSI)基因的筛选,以期获得PKSI阳性菌株及探讨紫菜藻际微生物区系细菌的拮抗机制与PKSI途径的关系。【方法】利用琼脂柱法筛选出具广谱抑菌活性的菌株31株,以其基因组DNA为模板,设计引物扩增酮基合成酶(Ketosynthase,KS)片段基因并将其克隆到pMD19-T Vector,筛选出PKS I阳性菌,进行16S rDNA测序分析。【结果】紫菜外生细菌表现出广谱抑菌性。从温州病烂紫菜外生菌中筛选出3株具强抑菌活性的PKS I阳性菌,BLAST比对结果显示:菌株WPhG3、WPySw1和WPySw2扩增得到PKSI的KS结构域核苷酸序列所对应的氨基酸序列与Bacillus subtilis subsp.subtilis str.168(NP-389602)、Bacillus subtilis(ABR19776)和Aspergillus carbonarius(AAZ99721)的PKS I的KS结构域的同源性分别达到98%、99%和98%;16S rDNA系统发生学分析显示它们均与Bacillus的同源性最高。【结论】紫菜藻际微生物群落组成复杂,通过多条途径调节藻际微生物区系的平衡。PKS I途径可能是温州病烂紫菜外生菌Bacillus表现抑菌活性的一种方式。更多还原

【Abstract】 [Objective]Based on the antibacterial analysis, we screened Polyketide synthase (PKS I) gene from the epiphytic bacteria of Porphyra spp., in order to obtain the PKS I positive strains and detect the potential connection between the PKS pathway and the antibacterial mechanisms. [Methods] A total of 31 bacteria with broad-spectrum antibacterial activity were screened by agar-screening methods. The 16S rDNA and the Ketosynthase gene were amplified from the genome DNA of these bacteria, which were cloned into pMD19-T vector for sequencing analysis.[Results] Porphyra spp. epiphytic bacteria showed broad-spectrum antibacterial activity. Three PKS I positive epiphytic bacteria were obtained from Wenzhou rotten Porphyra spp. samples which had high antibacterial activity. The BLAST results indicated that the Ketosynthase fragments of PKS I from the strains of WPhG3, WPySw1 and WPySw2 shared highest similarity (98%, 99%, 98%) to the strains of Bacillus subtilis subsp. Subtilis str. 168 (NP_-389602), Bacillus subtilis (ABR19776) and Aspergillus carbonarius (AAZ99721), respectively. Furthermore, the phylogenetic analysis based on 16S rDNA sequences indicated that they belonged to the genus of Bacillus. [Conclusion] The flora of Porphyra spp. epiphytic bacteria was complex, which regulated the phycosphere in many ways. The PKS I pathway might be a performance of antibacterial function of Bacillus from Wenzhou rotten samples.更多还原