However, these improvements may also introduce unexpectednegative effects into the bacterium.6−9For example, classicalrandom mutagenesis may cause low productivity resulting fromundesired mutations.5

After successful screening ofan efficient lysine-ON riboswitch, we integrated it into theC.glutamicumchromosome to upregulate the expression of alysine secretion-related gene,lysE,inresponsetolysineconcentration (Figure 1).

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