Contemporaneity of the past in stochastic intergenerational homeostasis

Abstract

What recurring patterns of behaviors are hidden in the stochastic intergenerational dynamics of individual bacterial cells in different environments? Embracing the inherently stochastic nature of the homeostasis process, first we reconceptualize homeostasis as representing a "standing pattern of variation in trajectory space" of a naturally occurring adaptive complex system (rather than the simple "set-point" of a self-regulating apparatus), then delineate two mechanistically distinct potential routes to achieving homeostasis (either elastic, reflexive, memory-free adaptation or plastic, reflective, memoryful adaptation) and show that both schemes are simultaneously utilized during multigenerational stochastic growth and division of an individual cell. From experimental data we identify an intergenerational scaling law which directly yields the exact stochastic map governing stochastic intergenerational cell size homeostasis of individual bacterial cells. Its broad applicability across bacterial species, growth conditions, and microenvironments suggests that the organizational motif representing the nature of coupling of growth to division is effectively the same in all of these scenarios, despite apparent differences in actualization through molecular circuitry. The precise parameters characterizing the intergenerational scaling law vary from condition to condition and provide early hints of two tradeoffs: precision-speed and precision-energy.