Staphylococcus epidermidis is largely dependent on iron availability to form biofilms

Abstract

Staphylococcus epidermidis has long been known as a major bacterial coloniser of the human skin, yet it is also a prominent nosocomial pathogen. Its remarkable ability to assemble structured biofilms has been its major known pathogenic feature to date. Notwithstanding important discoveries that have been accomplished, several questions about S. epidermidis biofilm formation still remain to be elucidated. This study aimed to assess whether iron availability modulates S. epidermidis biofilm formation and, if so, to explore how such modulation occurs. Biofilms of three S. epidermidis strains were grown under iron-enriched/-deficient conditions and several physiologic and transcriptomic changes were assessed. Our data revealed that while physiologic iron levels do not compromise biofilm formation, iron excess or deficiency is detrimental for this process. Conversely, biofilm cells were not affected in the same way when grown planktonically. By studying biofilm cells in detail we found that their viability and cultivability were seriously compromised by iron deficiency. Also, a temporal analysis of biofilm formation revealed that iron excess/deficiency: i) impaired biomass accumulation from 6h onwards, and ii) induced changes in the biofilm structure, indicating that iron availability plays a pivotal role from an early biofilm development stage. The expression of several putative iron-related genes, namely encoding siderophore biosynthesis/transport-related proteins, was found to be modulated by iron availability, providing a biological validation of their function on S. epidermidis iron metabolism. This study therefore provides evidence that iron plays a pivotal role on S. epidermidis biofilm formation.

Elizabethkingia anophelisresponse to iron stress: physiologic, genomic, and transcriptomic analyses

“…Iron availability impacted biofilm formation early in its development (67). In this study, the siderophore-deficient mutant formed less biofilm than the WT under iron-depleted conditions.…”

“…Iron-responsive genes such as siderophore synthesis and iron uptake genes were strongly induced by biofilm formation rather than by planktonic growth in Mycobacterium smegmatis (68). Further, deficiency in the exochelin biosynthesis or uptake systems led to poor biofilm formation, the viability and cultivability of biofilm cells under iron-limiting conditions (67, 68). Biofilm formation in vitro often led to weaker ability to attach to animal cells in Elizabethkingia .…”

Comparative transcriptomic analysis of Lactiplantibacillus plantarum RS66CD biofilm in high-salt conditions and planktonic cells

“…The formation of the initial biofilm of Pseudomonas fluorescens can be promoted by Mg 2+ , yet higher concentrations lead to blockage of mass transfer channels, affecting the intake of nutrients and inhibiting the further development of biofilm ( Song & Leff, 2003 ; Hoyle, Wong & Costerton, 1992 ). Fe 3+ promoted the secretion of EPS and increased the expression level of genes to improve the stability of biofilms in Staphylococcus epidermidis ( Oliveira, France & Ccerca, 2017 ). Salt stress by NaCl or KCl promoted biofilm formation in L. plantarum and compensated for biofilm phenotypic instability, possibly by regulating the expression of biofilm formation related genes ( Valle et al, 2007 ; Rachid et al, 2000 ).…”

The Antibacterial Effect of Silver Nanoparticles on Staphylococcus Epidermidis Strains with Different Biofilm-Forming Ability

“…Their most significant virulence factor is the ability to form biofilm [2,3]. They deposit polymer substances (exopolysacharide slime, adhesines, collagen-binding protein) on the surface of catheters or other biomaterials, which are the basis for biofilm formation [4,5]. Biofilm is a population of bacteria, growing on a specific surface (biotic, e.g., tissues, or abiotic, e.g., a catheter), which constitutes a mere 10% to 15% of its total volume, and is surrounded by extracellular matrix, composed of sugars, proteins, and extracellular DNA (eDNA), which make up the remaining 85%-90% of the whole biofilm structure.…”