Conjugative transfer is a primary means of spread of mobile genetic elements (plasmids and transposons) between bacteria.It leads to the dissemination and evolution of the genes (such as those conferring resistance to antibiotics) which are carried by the plasmid. Expression of the plasmid genes needed for conjugative transfer is tightly regulated so as to minimise the burden on the host. For plasmids such as those belonging to the IncP group this results in downregulation of the transfer genes once all bacteria have a functional conjugative apparatus. For F-like plasmids (apart from F itself which is a derepressed mutant) tight control results in very few bacteria having a conjugative apparatus. Chance encounters between the rare transfer-proficient bacteria and a potential recipient initiate a cascade of transfer which can continue until all potential recipients have acquired the plasmid. Other systems express their transfer genes in response to specific stimuli. For the pheromone-responsive plasmids of Enterococcus it is small peptide signals from potential recipients which trigger the conjugative transfer genes. For the Ti plasmids of Agrobacterium it is the presence of wounded plants which are susceptible to infection which stimulates T-DNA transfer to plants. Transfer and integration of T-DNA induces production of opines which the plasmid-positive bacteria can utilise. They multiply and when they reach an appropriate density their plasmid transfer system is switched on to allow transfer of the Ti plasmid to other bacteria. Finally some conjugative transfer systems are induced by the antibiotics to which the elements confer resistance. Understanding these control circuits may help to modify management of microbial communities where plasmid transfer is either desirable or undesirable. z 1998 Published by Elsevier Science B.V.

中文翻译：

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质粒和其他移动元件结合转移的基因控制。

结合转移是细菌之间可移动遗传元件（质粒和转座子）传播的主要手段，它导致质粒携带的基因（例如赋予抗生素抗性的基因）的传播和进化。紧密调节共轭转移所需的质粒基因的表达，以最小化宿主的负担。对于所有属于IncP组的质粒，一旦所有细菌都具有功能性的结合装置，这将导致转移基因的下调。对于F样质粒（除F本身外，F本身是被抑制的突变体），严格的控制导致很少的细菌具有结合装置。稀有转移能力强的细菌与潜在受体之间的机会相遇会引发一连串的转移，这种转移可以持续到所有潜在受体都已获得质粒为止。其他系统响应特定刺激而表达其转移基因。对于肠球菌的信息素应答质粒，它是来自潜在受体的小肽信号，这些信号触发了结合转移基因。对于农杆菌属的Ti质粒，存在易受感染的受伤植物，其刺激T-DNA转移至植物。T-DNA的转移和整合诱导产生了阿片质，而质粒阳性细菌可以利用这些阿片质。它们繁殖并且当它们达到合适的密度时，它们的质粒转移系统被打开以允许Ti质粒转移到其他细菌。最终，一些抗生素产生了一些共轭转移系统，这些元素赋予了抗药性。了解这些控制电路可能有助于在需要或不希望进行质粒转移的地方修改微生物群落的管理方法。z 1998由Elsevier Science BV发布