An increase in negative supercoiling in bacteria reveals topology-reacting gene clusters and a homeostatic response mediated by the DNA topoisomerase I gene.

We studied the transcriptional response to an increase in DNA supercoiling in Streptococcus pneumoniae by using seconeolitsine, a new topoisomerase I inhibitor. A homeostatic response allowing recovery of supercoiling was observed in cells treated with subinhibitory seconeolitsine concentrations. Supercoiling increases of 40.