Probiotic bacteria generate ROS in intestinal epithelial cells

The mammalian host maintains a mutually beneficial coexistence with a diverse intestinal microbiota, which can affect many aspects of gut homeostasis. How this bacterial community can modulate host processes is largely unknown. Recently, we reported that commensal bacteria can induce reactive oxygen species (ROS) in gut epithelial cells and influence signaling by transient oxidative inactivation of key pathways such as NF‐kappaB. Here we evaluated the relative capacity of gut bacteria to induce ROS generation in cultured intestinal epithelial cells. Commensal bacteria of the Lactobacillus species were potent ROS inducers, but not other commensals or pathogens. Bacterial ROS stimulating activity was fully recapitulated in cell wall homogenates but not culture supernatant, cytoplasmic extracts, or heat‐treated cell wall preparations, suggesting ROS activation is mediated by an integral membrane protein. ROS generation was inhibited with NAPDH inhibitors and BAPTA (a selective Ca 2+ chelator) suggesting the calcium sensitive NADPH isoform Duox was involved. Bacterial populations (and cell wall preparations) isolated from the ceca of mice fed Lactobacilli for nine days showed increased ROS inducing activity in cultured model epithelia. These data indicate that certain members of the microbiota (and commonly used probiotics) have a selective ability to induce ROS mediated epithelial signaling.