Production level of tetrodotoxin in Aeromonas is associated with the copy number of a plasmid
Production level of tetrodotoxin in Aeromonas is associated with the copy number of a plasmid
复制标题
气单胞菌中河豚毒素的产生水平与质粒的拷贝数有关
DOI：
10.1016/j.toxicon.2015.04.009
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发表时间：
2015-07-01
期刊：
影响因子：
2.8
通讯作者：
Bao, Baolong
中科院分区：
文献类型：
--
作者：
Liu, Jing;Wei, Fen;Bao, Baolong
河豚毒素（TTX）已从分类学上不同的生物中鉴定出来。TTX的人工合成已有报道，但TTX的生物合成途径仍不清楚。在本研究中，我们发现气单胞菌Ne-1菌株在发酵过程中产生TTX的能力与质粒pNe-1的拷贝数有关，这表明至少有一个编码TTX合成酶的基因位于该质粒上。与细菌基因组相比，质粒较小，更容易筛选与TTX生物合成相关的基因。对pNe-1的约100 kb基因组进行测序。该质粒含有60个完整的开放阅读框（orfs），其中32个（53.3%）编码假想蛋白。其中7个基因与IV型分泌系统（T4 SS）相关，2个基因与转座子相关，表明产TTX气单胞菌可能具有通过质粒pNe-1的接合和感染转移TTX生物合成基因的能力。此外，我们意外地发现，气单胞菌Ne-1含有未知的TTX降解物质，表明存在一种稳态机制来维持细菌中TTX的稳定量。这些结果将有助于我们更好地了解TTX的生物合成，TTX的细菌来源和TTX的降解。(C)2015爱思唯尔有限公司版权所有。
Tetrodotoxin (TTX) has been identified from taxonomically diverse organisms. Artificial synthesis of TTX has been reported, but the biosynthetic pathway of TTX remains elusive. In this study, we found TTX producing ability was associated with the copy number of plasmid pNe-1 in Aeromonas strain Ne-1 during fermentation, suggesting that at least one gene encoding a TTX-synthesis enzyme is located on this plasmid. Compared with bacterial genomes, plasmids are small and easier to screen for genes associated with TTX biosynthesis. The approximately 100 kb genome of pNe-1 was sequenced. The plasmid contains 60 complete open reading frames (orfs) of which 32 (53.3%) encode hypothetical proteins. Seven genes are related to the type IV secretion system (T4SS) and 2 genes are related to transposons, indicating that the TTX-producing bacterium Aeromonas might have the ability to transfer the TTX biosynthesis gene via the conjugation and contagion of plasmid pNe-1. In addition, we unexpectedly found that Aeromonas Ne-1 contains unknown TTX-degrading materials, indicating there is a homeostatic mechanism to maintain a stable amount of TTX in the bacterium. These results will help us to better understand TTX biosynthesis, the bacterial origin of TTX, and TTX degradation. (C) 2015 Elsevier Ltd. All rights reserved.