Matsuoka Satoshi, Asai Kei, Sadaie Yoshito
Department of Biochemistry and Molecular Biology, Faculty of Science, Saitama University, Saitama 338-8570, Japan.
FEMS Microbiol Lett. 2005 Mar 15;244(2):335-9. doi: 10.1016/j.femsle.2005.02.006.
Bacillus subtilis Marburg has only one intrinsic restriction and modification system BsuM that recognizes the CTCGAG (XhoI site) sequence. It consists of two operons, BsuMM operon for two cytosine DNA methyltransferases, and BsuMR operon for a restriction nuclease and two associated proteins of unknown function. In this communication, we analyzed the BsuM system by utilizing phage SP10 that possesses more than twenty BsuM target sequences on the phage genome. SP10 phages grown in the restriction and modification-deficient strain could not make plaques on the restriction-proficient BsuMR(+) indicator strain. An enforced expression of the wild type BsuMM operon in the BsuMR(+) indicator strain, however, allowed more than thousand times more plaques. DNA extracted from SP10 phages, thus, propagated became more but not completely refractory to XhoI digestion in vitro. Thus, the SP10 phage genome DNA is able to be nearly full-methylated but some BsuM sites are considered to be unmethylated.
枯草芽孢杆菌马尔堡菌株仅有一个识别CTCGAG（XhoI位点）序列的内在限制与修饰系统BsuM。它由两个操纵子组成，用于两个胞嘧啶DNA甲基转移酶的BsuMM操纵子，以及用于一个限制性核酸酶和两个功能未知的相关蛋白的BsuMR操纵子。在本通讯中，我们利用噬菌体SP10分析了BsuM系统，该噬菌体在其基因组上拥有二十多个BsuM靶序列。在限制与修饰缺陷型菌株中生长的SP10噬菌体无法在限制功能正常的BsuMR(+)指示菌株上形成噬菌斑。然而，在BsuMR(+)指示菌株中强制表达野生型BsuMM操纵子，使得噬菌斑数量增加了一千多倍。因此，从这样繁殖得到的SP10噬菌体中提取的DNA在体外对XhoI消化变得更具抗性，但并非完全如此。因此，SP10噬菌体基因组DNA能够几乎完全甲基化，但仍有一些BsuM位点被认为未甲基化。
