Anergiobiosis: a testable framework for microbial life under extreme energy flux limitation

Paul Carini, Roland Hatzenpichler, Jennifer F. Biddle

"Aeonophily" was recently suggested as a new category of extremophily for ultra-slow-growing subsurface microorganisms. This terminology misdescribes the physiological state of slow growth as potential extremophilic specialization. Unlike temperature or salinity, time cannot be manipulated to demonstrate a growth optimum, making aeonophily untestable as currently framed. We propose "anergiobiosis" to describe life where energy flux is sufficient to prevent death, but insufficient for cell division, separating the state from questions about specialization. Within this framework, microbes may exhibit distinct energy flux optima, with low-energy-flux specialists representing the potential biological basis for aeonophily. We outline testable hypotheses for establishing whether specific taxa possess such adaptations.