Abstract
Communities of bacteria called biofilms are characterized by reduced diffusion, steep oxygen, and redox gradients and specific properties compared to individualized planktonic bacteria. In this study, we investigated whether signaling via nitrosylation of protein cysteine thiols (S-nitrosylation), regulating a wide range of functions in eukaryotes, could also specifically occur in biofilms and contribute to bacterial adaptation to this widespread lifestyle. We used a redox proteomic approach to compare cysteine S-nitrosylation in aerobic and anaerobic biofilm and planktonic Escherichia coli cultures and we identified proteins with biofilm-specific S-nitrosylation status. Using bacterial genetics and various phenotypic screens, we showed that impairing S-nitrosylation in proteins involved in redox homeostasis and amino acid synthesis such as OxyR, KatG, and GltD altered important biofilm properties, including motility, biofilm maturation, or resistance to oxidative stress. Our study therefore revealed that S-nitrosylation constitutes a physiological basis underlying functions critical for E. coli adaptation to the biofilm environment.
Highlights
The formation of surface-attached communities of bacteria embedded in a matrix called biofilms provides a microenvironment preserved from external variations, which allows biofilms to colonize most surfaces, with both positive or negative ecological, medical and industrial consequences[1,2]
We showed that proteins extracted from planktonic bacteria possess more
S-nitric oxide (NO) and S-OX cysteines compared to protein extracted from poorly oxygenated biofilm environment
Summary
The formation of surface-attached communities of bacteria embedded in a matrix called biofilms provides a microenvironment preserved from external variations, which allows biofilms to colonize most surfaces, with both positive or negative ecological, medical and industrial consequences[1,2]. Metabolic redox processes often generate reactive oxygen and nitrogen intermediates such as hydroxyl radical (OH·) leading to hydrogen peroxide (H2O2), or nitric oxide (NO) produced during anaerobic respiration on nitrate[20,21] These highly reactive intermediates can, in turn, activate various signaling pathways via covalent binding to protein sensors including cysteine thiols, heme and nonheme metal centers, or iron–sulfur clusters[22,23,24]. We validated the initial steps of the biotin-switch protocol amino acid synthesis affects E. coli biofilm formation and oxidative using planktonic E. coli cultures grown in anaerobic conditions, stress resistance, identifying S-nitrosylation as a mechanism regulating functions critical for E. coli adaptation to the biofilm lifestyle.
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