[Antibacterial activity of Porphyra spp. epiphytic bacteria and polyketide synthase I gene screening].
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, WPySwl 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.


CONCLUSIONS
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.
Fang
Wenya
W
Key Laboratory of Applied Marine Biotechnology, Ningbo University, Ningbo 315211, China. fangwenya1984@163.com
Yang
Rui
R
Zhu
Peng
P
Shan
Yuanyuan
Y
Yan
Xiaojun
X
D000595:Amino Acid Sequence; D000898:Antibiosis; D001407:Bacillus / Q000145:classification / Q000201:enzymology* / Q000302:isolation & purification / Q000502:physiology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D048630:Polyketide Synthases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D044664:Porphyra / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D016415:Sequence Alignment
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D048630:Polyketide Synthases