The fermentation of industrial bacteria encounters a serious problem in continuous culture, i.e. the production traits lose. However, current research on the mechanism of strain degeneration is not clear enough, and there are few methods to effectively control the degeneration. Under growth restriction, the mutation rate of fermentation strains increases. Many cellular processes and poor fermentation conditions can trigger the transposition of transposable elements, SOS response, and RpoS-controlled adaptive mutations, causing genetic instability. Genetic instability which resulted from point mutations and genomic rearrangements can be responsible for strain degeneration. This mini-review summarizes the degeneration phenomena and mechanisms in common industrial bacteria and highlights three mechanisms of strain degeneration, including the transposition of transposable elements, SOS response, and adaptive mutations. According to different mutation mechanisms, many promising strategies have been proposed to increase the stability and the yield of industrial strains, for example, developing platform strains free of insertion sequence to enhance the stability of recombinant plasmid, using SOS inhibitors to block the SOS response, and improving environmental tolerance capacity and fermentation conditions to reduce adaptive mutations.

中文翻译：

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基因不稳定性导致工业细菌退化

工业菌的发酵在连续培养中遇到了严重的问题，即失去了生产性状。然而，目前对应变退化机理的研究还不够明确，有效控制退化的方法很少。在生长限制下，发酵菌株的突变率增加。许多细胞过程和较差的发酵条件会触发转座因子的转座、SOS 反应和 RpoS 控制的适应性突变，从而导致遗传不稳定。由点突变和基因组重排引起的遗传不稳定性可能是菌株退化的原因。这篇小综述总结了常见工业细菌的退化现象和机制，并重点介绍了菌株退化的三种机制，包括转座因子的转座、SOS 反应和适应性突变。根据不同的突变机制，人们提出了许多有前景的策略来提高工业菌株的稳定性和产量，例如，开发无插入序列的平台菌株以增强重组质粒的稳定性，使用 SOS 抑制剂阻断 SOS 反应，提高环境耐受能力和发酵条件，减少适应性突变。