紫菜外生细菌抑菌活性及其多聚酮合酶（PKS I） 基因筛选

Antibacterial Activity of Porphyra spp. Epiphytic Bacteria and Polyketide Synthase I Gene Screening

摘要:

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, PKS I)基因的筛选，以期获得PKS I 阳性菌株及探讨紫菜藻际微生物区系细菌的拮抗机制与PKS I 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PKS I 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。

Abstract:

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.