Myka Kamila K, McGlynn Peter, Ferguson Gail P
Present address: Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY 10032, USA.
School of Medicine and Dentistry, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
Microbiology (Reading). 2018 Jun;164(6):920-933. doi: 10.1099/mic.0.000663. Epub 2018 May 14.
How DNA metabolism is adapted to survival of organisms such as the bacterium Photobacterium profundum SS9 at high pressure is unknown. Previously, a high pressure-sensitive P. profundum SS9 transposon mutant (FL31) was identified, with an insertion in a putative rctB gene. The Vibrio cholerae RctB protein is essential for replication initiation at the origin of chromosome II, oriCII. Using a plasmid-based system in E. coli we have identified the replication origin of chromosome II from P. profundum SS9 and have shown that the putative rctB gene, disrupted in FL31, is essential for oriCII function. Moreover, we found that a region corresponding to the V. cholerae oriCII incompatibility region (incII) exerts an inhibitory effect on P. profundum oriCII. The truncated rctB gene in FL31 confers insensitivity to incII inhibition, indicating that the C-terminus of RctB is important for the negative regulation of replication. The RctB proteins of V. cholerae and P. profundum are partially interchangeable, but full functionality is achieved only with the cognate origin. Our findings provide the first characterization of the replication origin of chromosome II in a deep-sea bacterium.
诸如深海发光杆菌SS9这样的生物体的DNA代谢如何适应高压环境下的生存尚不清楚。此前，已鉴定出一种对高压敏感的深海发光杆菌SS9转座子突变体（FL31），其在一个假定的rctB基因中存在插入。霍乱弧菌的RctB蛋白对于在染色体II的复制起点oriCII处启动复制至关重要。利用大肠杆菌中的基于质粒的系统，我们已鉴定出深海发光杆菌SS9染色体II的复制起点，并表明在FL31中被破坏的假定rctB基因对于oriCII功能至关重要。此外，我们发现一个与霍乱弧菌oriCII不相容区域（incII）相对应的区域对深海发光杆菌oriCII具有抑制作用。FL31中截短的rctB基因赋予了对incII抑制的不敏感性，表明RctB的C末端对于复制的负调控很重要。霍乱弧菌和深海发光杆菌的RctB蛋白部分可互换，但只有与同源起点结合时才能实现完全功能。我们的研究结果首次对深海细菌染色体II的复制起点进行了表征。
