Bacillus subtilis extracellular protease production incurs a context‐dependent cost

• Published in: Molecular microbiology Vol. 120; no. 2; pp. 105 - 121
• Main Authors: Rosazza, Thibault, Eigentler, Lukas, Earl, Chris, Davidson, Fordyce A., Stanley‐Wall, Nicola R.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.08.2023; John Wiley and Sons Inc
• Subjects: Bacillus subtilis; Bacillus subtilis - genetics; Bacteria; Carbon sources; Editor's Choice; Endopeptidases; extracellular proteases; Food sources; nutrient accessibility; Nutrient sources; Pathogenesis; Peptide Hydrolases; Public good; public good dilemma; Rhizosphere; Soil; Soil environment; Soils; extracellular proteases; public good dilemma; nutrient accessibility
• ISSN: 0950-382X; 1365-2958; 1365-2958
• DOI: 10.1111/mmi.15110

Microbes encounter a wide range of polymeric nutrient sources in various environmental settings, which require processing to facilitate growth. Bacillus subtilis, a bacterium found in the rhizosphere and broader soil environment, is highly adaptable and resilient due to its ability to utilise diverse sources of carbon and nitrogen. Here, we explore the role of extracellular proteases in supporting growth and assess the cost associated with their production. We provide evidence of the essentiality of extracellular proteases when B. subtilis is provided with an abundant, but polymeric nutrient source and demonstrate the extracellular proteases as a shared public good that can operate over a distance. We show that B. subtilis is subjected to a public good dilemma, specifically in the context of growth sustained by the digestion of a polymeric food source. Furthermore, using mathematical simulations, we uncover that this selectively enforced dilemma is driven by the relative cost of producing the public good. Collectively, our findings reveal how bacteria can survive in environments that vary in terms of immediate nutrient accessibility and the consequent impact on the population composition. These findings enhance our fundamental understanding of how bacteria respond to diverse environments, which has importance to contexts ranging from survival in the soil to infection and pathogenesis scenarios. Bacillus subtilis uses extracellular proteases to access nutrients contained in polymeric sources. The extracellular proteases are a public good and support the growth of non‐producers. The cells producing the proteases are subject to a context‐dependent cost that triggers the public good dilemma.