Appreciate this contribution from an expert in this field :) I’m aware of other free radical species like the RNS and I do not know if I am totally correct but the ROS should be more implicated in inducing oxidative stress and maybe that’s where the authors are coming from but thinking about the fact that they tried to discredit a probable role of free radicals in causing aging in anaerobic bacteria, it raises eyebrows as we have other free radicals that are not products of oxygen. Hopefully, we fully understand aging someday :). Interesting paper you cited btw.