Loss of the type VII secretion ATPase EssC promotes biofilm formation of <i>Staphylococcus</i> <i>aureus</i> under acidic stress.
Loss of the EssC protein enhances biofilm formation in Staphylococcus aureus under acidic conditions, but this may come at the cost of reduced bacterial viability.
Where it sits
this study against the rest of the thymulin (facteur thymique serique) corpusSummary and findings
This study investigated the role of the type VII secretion ATPase EssC in regulating biofilm formation of Staphylococcus aureus under acidic stress. The research utilized an essC deletion mutant and observed that loss of EssC increased biofilm biomass and thickness at pH 5.0. Despite this, bacterial viability within mature biofilms was reduced.
Abstract
<i>Staphylococcus aureus</i> adapts to hostile host-associated niches by dynamically switching between planktonic growth and biofilm lifestyles. Acidic environments, such as the skin surface and intracellular compartments, impose substantial stress on bacterial survival; however, the contribution of the type VII secretion system (T7SS) to biofilm adaptation under acidic conditions remains poorly understood. Here, we investigated the role of the T7SS ATPase EssC in regulating <i>S. aureus</i> biofilm formation under acidic stress. Using an <i>essC</i> deletion mutant in the USA300 background, we demonstrate that loss of EssC markedly enhances biofilm biomass and thickness at pH 5.0, despite reducing bacterial viability within mature biofilms. Mechanistically, <i>essC</i> deletion reprograms multiple stages of biofilm development, including enhanced initial adhesion mediated by upregulated fibronectin-binding proteins (FnBPA and FnBPB), increased intercellular aggregation driven by elevated polysaccharide intercellular adhesin (PIA) production, and biofilm stabilization through augmented autolysis-dependent extracellular DNA release. These phenotypic changes are accompanied by coordinated transcriptional remodeling, characterized by downregulation of the biofilm repressor <i>agr</i> and activation of the <i>arlS-icaA</i> and <i>sigB-icaA</i> regulatory axis. Collectively, our findings uncover an unrecognized link between the T7SS core component EssC and biofilm regulation under acidic stress, highlighting EssC as a potential modulator of <i>S. aureus</i> survival strategies in hostile host microenvironments.
Background
This paper addresses the adaptation mechanisms of Staphylococcus aureus in hostile acidic environments, particularly the role of the type VII secretion system (T7SS) in biofilm formation. Prior research has established that biofilms are critical for bacterial survival in adverse conditions, but the specific contributions of T7SS components like EssC under acidic stress were not well understood. Understanding these mechanisms is essential for developing strategies to combat bacterial infections.
Methods
The study utilized an essC deletion mutant in the USA300 background to investigate biofilm formation under acidic stress. The primary outcomes measured included biofilm biomass, thickness, and bacterial viability at pH 5.0. The study also assessed transcriptional changes and mechanisms of adhesion and aggregation.
Results
Loss of EssC resulted in enhanced biofilm biomass and thickness at pH 5.0. The study observed reduced bacterial viability within mature biofilms, alongside increased initial adhesion and intercellular aggregation. Specific transcriptional changes were noted, including downregulation of the biofilm repressor agr and activation of regulatory axes related to biofilm formation.
Interpretation
These findings suggest that EssC plays a significant role in regulating biofilm formation under acidic stress, which could have implications for understanding bacterial survival strategies. However, the effect sizes and clinical relevance of these findings remain unclear, particularly given the focus on a single mutant strain. Potential confounds include the specific conditions tested and the lack of broader strain analysis.
Key findings
- Loss of EssC markedly enhances biofilm biomass and thickness at pH 5.0.
- Bacterial viability within mature biofilms was reduced.
- Enhanced initial adhesion mediated by upregulated fibronectin-binding proteins (FnBPA and FnBPB).
- Increased intercellular aggregation driven by elevated polysaccharide intercellular adhesin (PIA) production.
- Biofilm stabilization through augmented autolysis-dependent extracellular DNA release.
Limitations
- Focus on a specific essC deletion mutant.
- No broader implications for other strains reported.
- Lack of quantitative data on biofilm biomass and thickness.
- Not reported in abstract.