(174bk) Toxic Metabolites Generate Phenotypic Bifurcations and Cheating in Escherichia coli without Transcription Elongation Factors

Transcription elongation factors, which in Escherichia coli are encoded by greA and greB, help back-tracked RNA polymerases (RNAP) resume transcription after stalling events. We discovered that loss of transcription elongation factors compromised the ability of E. coli to detoxify ·NO. That deficiency was produced by a nitric oxide (·NO)-induced bifurcation in ΔgreAΔgreB cultures, where half of the population responded normally and the other half were unresponsive. Diversification was absent in unstressed conditions and in wild-type with or without ·NO. Notably, a similar bifurcation occurred in the presence of hydrogen peroxide, which showed that the phenomenon translated to an unrelated toxic metabolite. Further analyses revealed that the bifurcation was phenotypic, it solely arose at the level of transcription, and it produced cheating between neighbors, where unresponsive cells benefited from the ·NO detoxification activities of their responsive counterparts. Altogether, this study highlights a new role for transcription elongation factors as systems-level mediators of transcription under toxic metabolite stress that serve to reduce cheating and enhance collective behavior.