This study investigates the transcriptional response of Escherichia coli to hydrogen peroxide using DNA microarray technology. The researchers examined the expression of 4,169 E. coli open reading frames (ORFs) in wild-type and oxyR deletion strains. They confirmed that the peroxide response regulator OxyR activates most of the highly hydrogen peroxide-inducible genes. The microarray analysis identified several new OxyR-activated genes, including hemH, the six-gene suf operon, and four genes of unknown function. Additionally, some genes were found to be induced in an OxyR-independent manner, suggesting the presence of other peroxide sensors and regulators in E. coli. For example, the isc operon, which is involved in Fe-S cluster formation and repair, was induced by hydrogen peroxide in strains lacking OxyR or the superoxide response regulators SoxRS. These findings expand our understanding of the oxidative stress response in E. coli and raise questions about the nature of other regulators that modulate gene expression in response to hydrogen peroxide. The study also highlights the importance of DNA microarray technology in identifying genes involved in the response to oxidative stress and other environmental conditions. The results suggest that OxyR plays a central role in the peroxide response, but other regulatory pathways also contribute to the cellular response. The study also identifies several genes that are induced by hydrogen peroxide in an OxyR-independent manner, indicating complex regulation of the cellular response to oxidative stress. The findings provide new insights into the molecular mechanisms underlying the response to oxidative stress in E. coli and highlight the importance of OxyR in this process. The study also suggests that other regulatory pathways may be involved in the response to oxidative stress, and further research is needed to fully understand the complex network of regulatory interactions that govern the response to hydrogen peroxide in E. coli.This study investigates the transcriptional response of Escherichia coli to hydrogen peroxide using DNA microarray technology. The researchers examined the expression of 4,169 E. coli open reading frames (ORFs) in wild-type and oxyR deletion strains. They confirmed that the peroxide response regulator OxyR activates most of the highly hydrogen peroxide-inducible genes. The microarray analysis identified several new OxyR-activated genes, including hemH, the six-gene suf operon, and four genes of unknown function. Additionally, some genes were found to be induced in an OxyR-independent manner, suggesting the presence of other peroxide sensors and regulators in E. coli. For example, the isc operon, which is involved in Fe-S cluster formation and repair, was induced by hydrogen peroxide in strains lacking OxyR or the superoxide response regulators SoxRS. These findings expand our understanding of the oxidative stress response in E. coli and raise questions about the nature of other regulators that modulate gene expression in response to hydrogen peroxide. The study also highlights the importance of DNA microarray technology in identifying genes involved in the response to oxidative stress and other environmental conditions. The results suggest that OxyR plays a central role in the peroxide response, but other regulatory pathways also contribute to the cellular response. The study also identifies several genes that are induced by hydrogen peroxide in an OxyR-independent manner, indicating complex regulation of the cellular response to oxidative stress. The findings provide new insights into the molecular mechanisms underlying the response to oxidative stress in E. coli and highlight the importance of OxyR in this process. The study also suggests that other regulatory pathways may be involved in the response to oxidative stress, and further research is needed to fully understand the complex network of regulatory interactions that govern the response to hydrogen peroxide in E. coli.