RNA-Seq of Escherichia coli Nissle 1917 strains modified to produce different amounts of the bacteriocin microcin C

A popular strategy for enhancing the antibacterial properties of probiotic bacteria is to retrofit them with the ability to overproduce heterologous bacteriocins. This is often achieved from strong, non-native promoters. How the dysregulated overproduction of heterologous bacteriocins affects the fitness and antibacterial efficacy of the retrofitted probiotic bacteria is often overlooked. We conferred the prototypical probiotic Escherichia coli strain Nissle (EcN) the ability to produce different amounts of the bacteriocin microcin C (McC). Expression of the bacteriocin synthesis genes was driven from the native promoter (Pmcc-WT), or from promoters manipulated to be stronger (Pmcc-High) and weaker (Pmcc-Low) than the WT, in a plasmid-based system. Pmcc-Low and Pmcc-High retained their native regulation. A strain harbouring a non-functional promoter (Pmcc-Mut) produces no McC and was used as a control. Each strain was grown to early stationary phase, when production of McC starts, in Luria-Bertani broth at 37 degrees. The RNA was isolated and the effects of different levels of production of McC on the transcriptome of EcN was examined by RNA-Seq.