Peters Kostman, M. | bioRxiv Science

bioRxiv2026

Bacteria hyperpolarize in response to oxygen drop

Aerobic microbes use oxygen as a terminal electron acceptor to establish an electrochemical gradient across their cell membranes. While this membrane potential ({triangleup}{Psi}) is essential for multiple cellular processes, it is unknown if and how it is maintained in bacteria during shifts in oxygen availability. We find that bacteria hyperpolarize in response to drops in oxygen. Focusing on Bacillus subtilis and guided by modeling, we report that hyperpolarization magnitude scales with the degree of electron acceptor deprivation. We find that potassium efflux contributes to the response. Surveying mutants, we uncover genes involved in potassium homeostasis and oxygen stress that contribute to hyperpolarization. We show that hyperpolarization scales with faster growth rates resulting from nutrient type and colony spatial heterogeneity. Finally, we demonstrate that oxygen shift increases susceptibility to antibiotics. Our results demonstrate a conserved link between {triangleup}{Psi} and oxygen stress, suggesting a common mechanism for responding to shifting oxygen availability.

microbiology↗

bioRxiv2024

An Agent-Based Model of Metabolic Signaling Oscillations in Bacillus subtilis Biofilms

Microbes of nearly every species can form biofilms, communities of cells bound together by a self-produced matrix. It is not understood how variation at the cellular level impacts putatively beneficial, colony-level behaviors, such as cell-to-cell signaling. Here we investigate this problem with an agent-based computational model of metabolically driven electrochemical signaling in Bacillus subtilis biofilms. In this process, glutamate-starved interior cells release potassium, triggering a depolarizing wave that spreads to exterior cells and limits their glutamate uptake. More nutrients diffuse to the interior, temporarily reducing glutamate stress and leading to oscillations. In our model, each cell has a membrane potential coupled to metabolism. As a simulated biofilm grows, collective membrane potential oscillations arise spontaneously as cells deplete nutrients and trigger potassium release, reproducing experimental observations. We further validate our model by comparing spatial signaling patterns and cellular signaling rates with those observed experimentally. By oscillating external glutamate and potassium, we find that biofilms synchronize to external potassium more strongly than to glutamate, providing a potential mechanism for previously observed biofilm synchronization. By tracking cellular glutamate concentrations, we find that oscillations evenly distribute nutrients in space: non-oscillating biofilms have an external layer of well-fed cells surrounding a starved core, whereas oscillating biofilms exhibit a relatively uniform distribution of glutamate. Our work shows the potential of agent-based models to connect cellular properties to collective phenomena and facilitates studies of how inheritance of cellular traits can affect the evolution of group behaviors.

microbiology↗