Nitric oxide–inducing Genistein elicits apoptosis-like death via an intense SOS response in Escherichia coli

Increasing prevalence of multidrug-resistant untreatable infections has prompted researchers to trial alternative treatments such as a substitute for traditional antibiotics. This study endeavored to elucidate the antibacterial mechanism(s) of this isoflavone, via analysis of relationship between genistein and Escherichia coli. Furthermore, this investigation analyzed whether genistein generates nitric oxide (NO) in E. coli as NO contributes to cell death. RecA, an essential protein for the bacterial SOS response, was detected through western blot, and the activated caspases decreased without RecA. The results showed that the NO induced by genistein affected the bacterial DNA. Under conditions of acute DNA damage, an SOS response called apoptosis-like death occurred, affecting DNA repair. These results suggested that RecA was bacterial caspase-like protein. In addition, NO was toxic to the bacterial cells and induced dysfunction of the plasma membrane. Thus, membrane depolarization and phosphatidylserine exposure were observed similarly to eukaryotic apoptosis. In conclusion, the combined results demonstrated that the antibacterial mode of action(s) of genistein was a NO-induced apoptosis-like death, and the role of RecA suggested that it contributed to the SOS response of NO defense. KEY POINTS: • Genistein generates nitric oxide in E. coli. • Genistein exhibits intense SOS response in E. coli. • Genistein-induced NO causes apoptosis-like death in E. coli.