Elhai J, Vepritskiy A, Muro-Pastor A M, Flores E, Wolk C P
MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing 48824-1312, USA.
J Bacteriol. 1997 Mar;179(6):1998-2005. doi: 10.1128/jb.179.6.1998-2005.1997.
The efficiency of conjugal transfer of plasmids from Escherichia coli to the cyanobacterium Anabaena sp. strain PCC 7120 was quantitated as a function of the number of restriction sites for the restriction enzymes carried by the recipient. In addition to the previously recognized isoschizomers of AvaI and AvaII, PCC 7120 was found to possess an isoschizomer of AvaIII. Plasmids modified in E. coli with methylases that protect in vitro against restriction by the three enzymes were transferred with high efficiency, nearly independent of the number of restriction sites on the plasmid. Plasmids left unprotected against one of the three restriction enzymes were transferred with lower efficiencies. For low numbers of sites, the efficiency of conjugal transfer decreased as an exponential function of the number of unprotected sites. The methods presented may be used to increase the efficiency of conjugal transfer into restriction-competent bacteria.
测定了质粒从大肠杆菌接合转移至蓝藻鱼腥藻属PCC 7120菌株的效率，该效率是受体携带的限制酶的限制位点数量的函数。除了先前已识别的AvaI和AvaII同裂酶外，还发现PCC 7120拥有AvaIII的同裂酶。在大肠杆菌中用甲基化酶修饰的质粒在体外可免受这三种酶的限制，这些质粒能高效转移，几乎与质粒上限制位点的数量无关。未对三种限制酶之一进行保护的质粒转移效率较低。对于少量位点，接合转移效率随着未保护位点数量的指数函数而降低。所提出的方法可用于提高向具有限制能力的细菌中进行接合转移的效率。
