ClbR Is the Key Transcriptional Activator of Colibactin Gene Expression in Escherichia coli

Abstract

The nonribosomal peptide/polyketide hybrid colibactin can be considered a bacterial virulence factor involved in extraintestinal infection and also a procarcinogen. Nevertheless, and despite its genotoxic effect, colibactin expression can also inhibit bacterial or tumor growth and correlates with probiotic anti-inflammatory and analgesic properties. Although the biological function of this natural compound has been studied extensively, our understanding of the regulation of colibactin expression is still far from complete. We investigated in detail the role of regulatory elements involved in colibactin expression and in the growth conditions that promote colibactin expression. In this way, our data shed light on the regulatory mechanisms involved in colibactin expression and may support the expression and purification of this interesting nonribosomal peptide/polyketide hybrid for further molecular characterization.

Inulin and Galacto-oligosaccharides Increase the Genotoxic Effect of Colibactin Produced by pks+ Escherichia Coli Strains

“…2A), whereas clbA transcript levels were reduced in a concentration-dependent-manner (Fig. 2B), as expected (22,23). Addition of inulin increased the growth of EcN as con rmed by our previous experiments ( Fig.…”

“…Most importantly, clbA has been shown to contribute to the production of siderophores, which are small iron chelating compounds produced by bacteria (21). Addition of ferric chloride to the medium inhibited the expression of colibactin relatedgenes (23,34). We further showed that addition of iron abolished the increased transcription of clbA induced by inulin and GOS, counteracting the effect of these fermentable bers.…”

The Polyphosphate Kinase of Escherichia coli Is Required for Full Production of the Genotoxin Colibactin

“…2a and b ). Additionally, we deleted ppk in the previously described reporter strain Nissle 1917 (EcN) carrying a transcriptional fusion of P clbB and the lux operon on the chromosome (EcN clbB :: lux ) ( 17 , 26 ), resulting in strain EcN clbB :: lux Δ ppk ( Fig. S1b ).…”

“…This work highlights the role of PPK in P clbB activity, which is correlated with the production of colibactin. A recent study has shown that ClbR is the transcriptional activator of clbB ( 17 ). In this work, we discovered the first regulator of clbB transcriptional activity outside of the pks island.…”

“…Given the role of colibactin in bacterial virulence and tumorigenesis, it is important to understand the regulation of its production, to provide clues for the development of anticolibactin strategies. It was recently reported that ClbR is an (auto)transcriptional activator of the clbB gene ( 17 ). In addition, the two master regulators of bacterial iron homeostasis Fur (ferric uptake regulator) and the small regulatory noncoding RNA RyhB regulate the transcription of clbA ( 18 , 19 ).…”