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Department of Plant Pathology and Microbiology
The Robert H. Smith Faculty of Agriculture, Food & Environment
The Hebrew University of Jerusalem

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Bacterial-induced pH shifts link individual cell physiology to macroscale collective behavior


Dharanishanthi, V. ; Orgad, A. ; Rotem, N. ; Hagai, E. ; Kerstnus-Banchik, J. ; Ben-Ari, J. ; Harig, T. ; Ravella, S. R. ; Schulz, S. ; Helman, Y. Bacterial-induced pH shifts link individual cell physiology to macroscale collective behavior. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2021, 118.

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Bacteria have evolved a diverse array of signaling pathways that enable them to quickly respond to environmental changes. Understanding how these pathways reflect environmental conditions and produce an orchestrated response is an ongoing challenge. Herein, we present a role for collective modifications of environmental pH carried out by microbial colonies living on a surface. We show that by collectively adjusting the local pH value, Paenibacillus spp., specifically, regulate their swarming motility. Moreover, we show that such pH-dependent regulation can converge with the carbon repression pathway to down-regulate flagellin expression and inhibit swarming in the presence of glucose. Interestingly, our results demonstrate that the observed glucose-dependent swarming repression is not mediated by the glucose molecule per se, as commonly thought to occur in carbon repression pathways, but rather is governed by a decrease in pH due to glucose metabolism. In fact, modification of the environmental pH by neighboring bacterial species could override this glucose-dependent repression and induce swarming of Paenibacillus spp. away from a glucose-rich area. Our results suggest that bacteria can use local pH modulations to reflect nutrient availability and link individual bacterial physiology to macroscale collective behavior.