Blot M, Hauer B, Monnet G
Department of Microbiology, University of Basel, Switzerland.
Mol Gen Genet. 1994 Mar;242(5):595-601. doi: 10.1007/BF00285283.
The bleomycin resistance gene (ble) of transposon Tn5 is known to decrease the death rate of Escherichia coli during stationary phase. Bleomycin is a DNA-damaging agent and bleomycin resistance is produced by improved DNA repair which also requires the host genes aidC and polA coding, respectively, for an alkylation-inducible gene product and DNA polymerase I. In the absence of the drug, this DNA repair system is believed to cause the slower death rate of bleomycin-resistant bacteria. In this study, the effect of ble and aidC genes on the viability of bacteria and their growth rate in chemostat competitions was studied. The results indicate, that bleomycin-resistant bacteria display greater fitness under these conditions. Another beneficial effect of transposon Tn5 had been previously attributed to the insertion sequence IS 50 R. We were not able to reproduce this result with IS 50 R, however, the complete transposon was beneficial under similar conditions. Moreover, we showed the Tn5 fitness effect to be aidC-dependent. The ble gene was discovered after the fitness effect of IS 50 R had been established; it has not previously been considered to mediate the beneficial effect of Tn5. This possibility is discussed based on the molecular mechanism of bleomycin resistance.
转座子Tn5的博来霉素抗性基因（ble）已知可降低大肠杆菌在稳定期的死亡率。博来霉素是一种DNA损伤剂，博来霉素抗性是通过改善DNA修复产生的，这也分别需要宿主基因aidC和polA编码烷基化诱导基因产物和DNA聚合酶I。在没有药物的情况下，这种DNA修复系统被认为会导致博来霉素抗性细菌的死亡速度较慢。在本研究中，研究了ble和aidC基因对细菌活力及其在恒化器竞争中的生长速率的影响。结果表明，在这些条件下，博来霉素抗性细菌表现出更高的适应性。转座子Tn5的另一个有益作用先前归因于插入序列IS 50R。然而，我们无法用IS 50R重现这一结果，不过，完整的转座子在类似条件下是有益的。此外，我们表明Tn5的适应性效应依赖于aidC。ble基因是在IS 50R的适应性效应确立后发现的；以前从未认为它介导Tn5的有益作用。基于博来霉素抗性的分子机制讨论了这种可能性。
