Discovery of a novel MarR-type transcriptional regulator that controls cell death inBacillus subtilisbiofilms

AbstractPulcherriminic acid (PA) is a cyclic-L-leu-L-leu di-peptide produced byBacillus subtilisduring biofilm formation. When secreted, PA strongly chelates extracellular iron and forms a reddish- brown pigment, pulcherrimin. Production of pulcherriminic acid and formation of pulcherrimin modulate iron homeostasis inB. subtilis. Pulcherriminic acid also functions as an antioxidant to protect cells from increasing oxidative stress during biofilm formation. We previously showed that PA is involved in gene regulation, differentially regulating hundreds of genes inB. subtilis. One of the strongly upregulated genes by PA isyhjH, encoding a putative MarR-type transcription repressor. In this study, we characterized the regulation of theyhjHgene by PA, by PchR, a known transcription repressor for PA biosynthesis, and by YhjH itself. We also found that high expression ofyhjHtriggers rapid cell lysis inB. subtilis. Results from RNA-seq suggest that YhjH differentially regulates about 180 genes, among which there is a significant number of prophage genes. Lastly, we propose that YhjH be re-named as PcdR, for “pulcherriminic acidcelldeathregulator”.