Oxidative stress induces E. coli aryl polyene expression, sensitizing the bacterial stress response and modulating the redox environment of innate immune cells.

Abstract

UNLABELLED: Aryl polyenes (APEs) are specialized polyunsaturated outer membrane lipids that protect their producers from oxidative stress and contribute to biofilm formation. APEs are produced by an abundant biosynthetic gene cluster (BGC) family conserved across Gram-negative bacterial clades. The APE biosynthesis pathway involves 11 different enzymes and culminates in the attachment of APEs to an anchor molecule in the Gram-negative outer membrane. Unlike most other small molecule BGCs, the APE BGC does not contain a dedicated regulatory gene that controls the production of its metabolically costly compounds. Building from our prior observations of APEs' role in acute oxidative stress protection, we use a uropathogenic Escherichia coli (UPEC) strain to show that APE expression conveys a potential competitive advantage characterized by increased early-stage growth, sensitization of the bacterial oxidative stress response, and dampening of the redox stress of innate immune cells after in vitro infection. Our data indicate that APEs could act as a UPEC fitness factor, and in future work, we aim to study their contribution to overall bacterial pathogenicity and survival, as well as how APEs could facilitate the transition from an oxygen-poor environment, such as the gut, to the oxygen-rich environment of the urinary tract. IMPORTANCE: Bacterial pathogens use various mechanisms to achieve a competitive advantage under harsh conditions, such as during interactions with their host. We studied the function of aryl polyenes (APEs), specialized polyunsaturated fatty acids in the outer membrane, in the context of a uropathogenic E. coli strain. APE expression is induced by an oxidative environment and contributes to early-stage growth and sensitization of the oxidative stress response. Furthermore, APE-expressing E. coli dampen the intracellular oxidative milieu of target host phagocytes. These findings suggest a role for APEs as a fitness factor and create opportunities to study their in vivo function and explore them as a potential drug target.