Chien Mei-Fang, Ho Ying-Ning, Yang Hui-Erh, Narita Masaru, Miyauchi Keisuke, Endo Ginro, Huang Chieh-Chen
Graduate School of Environmental Studies, Tohoku University, Aramaki, Aoba-ku, 6-6-20 Aoba, Sendai 980-8579, Japan.
Institute of Marine Biology and Center of Excellence for the Oceans, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung 20224, Taiwan.
Microorganisms. 2019 Nov 16;7(11):566. doi: 10.3390/microorganisms7110566.
A novel Tn1-like transposon designated as Tn1 was identified from mercury resistant isolated from Minamata Bay sediment. Two adjacent operon-like gene clusters, and , flanked by a pair of 78-bp inverted repeat sequences, which resulted in a 13.8-kbp transposon-like fragment, were found to be sandwiched between two transposable genes of the Tn1-like transposon of a mercury resistant bacterium, sp. MB24. The presence of a single transcription start site in each cluster determined by 5'-RACE suggested that both are operons. Quantitative real time RT-PCR showed that the transcription of the genes contained in each operon was induced by arsenite, while responded to arsenite more sensitively and strikingly than did. Further, arsenic resistance complementary experiments showed that the operon conferred arsenate and arsenite resistance to an -knocked out host, while the operon only raised arsenite resistance slightly. This transposon nested in Tn1 was designated as Tn1. Multi-gene cluster blast against bacteria and whole genome sequence databases suggested that Tn1 is the first case of a Tn1-like transposon combined with an arsenic resistance transposon. The findings of this study suggested that Tn1-like transposons could recruit other mobile elements into its genetic structure, and subsequently cause horizontal dissemination of both mercury and arsenic resistances among in Minamata Bay.
从水俣湾沉积物中分离出的耐汞菌中鉴定出一种新型的类Tn1转座子，命名为Tn1。在耐汞细菌sp. MB24的类Tn1转座子的两个转座基因之间，发现了两个相邻的操纵子样基因簇，和，两侧是一对78bp的反向重复序列，形成了一个13.8kbp的类转座子片段。5'-RACE确定每个簇中存在单个转录起始位点，表明两者均为操纵子。定量实时RT-PCR表明，每个操纵子中包含的基因的转录由亚砷酸盐诱导，而对亚砷酸盐的反应比更敏感和显著。此外，抗砷互补实验表明，操纵子赋予敲除宿主对砷酸盐和亚砷酸盐的抗性，而操纵子仅略微提高亚砷酸盐抗性。嵌套在Tn1中的这个转座子被命名为Tn1。对细菌和全基因组序列数据库进行的多基因簇比对表明，Tn1是类Tn1转座子与抗砷转座子结合的首例。本研究结果表明，类Tn1转座子可以将其他移动元件招募到其遗传结构中，随后导致水俣湾中汞和砷抗性在之间水平传播。
