Parsons L M, Jankowski C S, Derbyshire K M
Wadsworth Center, New York State Department of Health and School of Public Health, State University of New York at Albany, David Axelrod Institute, 12201-2002, USA.
Mol Microbiol. 1998 May;28(3):571-82. doi: 10.1046/j.1365-2958.1998.00818.x.
The genus Mycobacterium includes the major human pathogens Mycobacterium tuberculosis and Mycobacterium leprae. The development of rational drug treatments for the diseases caused by these and other mycobacteria requires the establishment of basic molecular techniques to determine the genetic basis of pathogenesis and drug resistance. To date, the ability to manipulate and move DNA between mycobacterial strains has relied on the processes of transformation and transduction. Here, we describe a naturally occurring conjugation system present in Mycobacterium smegmatis, which we anticipate will further facilitate the ability to manipulate the mycobacterial genome. Our data rule out transduction and transformation as possible mechanisms of gene transfer in this system and are most consistent with conjugal transfer. We show that recombinants are not the result of cell fusion and that transfer occurs from a distinct donor to a recipient. One of the donor strains is mc(2)155, a highly transformable derivative that is considered the prototype laboratory strain for mycobacterial genetics; the demonstration that it is conjugative should increase its genetic manipulability dramatically. During conjugation, extensive regions of chromosomal DNA are transferred into the recipient and then integrated into the recipient chromosome by multiple recombination events. We propose that DNA transfer is occurring by a mechanism similar to Hfr conjugation in Escherichia coli.
分枝杆菌属包括主要的人类病原体结核分枝杆菌和麻风分枝杆菌。针对由这些分枝杆菌及其他分枝杆菌引起的疾病开发合理的药物治疗方法，需要建立基本的分子技术来确定发病机制和耐药性的遗传基础。迄今为止，在分枝杆菌菌株之间操纵和转移DNA的能力依赖于转化和转导过程。在此，我们描述了耻垢分枝杆菌中存在的一种天然存在的接合系统，我们预计这将进一步促进对分枝杆菌基因组的操纵能力。我们的数据排除了转导和转化作为该系统中基因转移的可能机制，并且与接合转移最为一致。我们表明重组体不是细胞融合的结果，并且转移是从一个独特的供体到受体发生的。供体菌株之一是mc(2)155，它是一种高度可转化的衍生物，被认为是分枝杆菌遗传学的原型实验室菌株；证明它具有接合性应该会大大提高其遗传可操作性。在接合过程中，大量的染色体DNA区域被转移到受体中，然后通过多次重组事件整合到受体染色体中。我们提出DNA转移是通过一种类似于大肠杆菌中Hfr接合的机制发生的。
