Journal: bioRxiv

Article Title: Species and strain diversity in Staphylococcus drive divergent host responses in human skin

doi: 10.64898/2026.04.30.720712

Figure Lengend Snippet: (A) Biofilm formation ability of commensal vs. inflammatory S. epidermidis strains. Biofilm positive strains were defined relative to a canonical biofilm-forming strain (Sep_1457). Numbers indicate strain counts per category and P-value and odds ratio calculated using Fisher’s exact test. (B-E) Survival ability in blood as measured by CFUs at 0, 2, and 24h of S. epidermidis strains (D) with respect to a bloodstream infection S. aureus strain (USA300LAC, (B)) with or without complement (+/-Comp) depletion (C, E). Points represent individual strains (or replicates for S. aureus) and boxes indicate IQR with median. Lines connect matched conditions. Significance was assessed by paired t-test with Bonferroni correction. (F-G) PCA plot of Staphylococcus cellular (F) or extracellular (G) metabolomes. Staphylococcus metabolomes were inferred by metabolic feature intensity within untargeted metabolomes. (H) Diagram of arginine metabolism pathway highlighting reactions catalyzed by arcA , argF , and argG . (I-K) Violin plots showing the metabolite abundance of arginine (I), carbamoyl-P (J), and argininosuccinate (K) in strains with or without arcA , argF , or argG. Points indicate normalized metabolite intensity; violins show distributions with embedded boxplots (median and IQR). Gene labels are black if acting on or downstream of the metabolite, grey otherwise. (L-N) Growth dynamics of inflammatory vs. commensal S. epidermidis strains in skin-like media with (+Arg) or without (-Arg) arginine. Maximum growth rate (L), maximum density (M), and area under the curve (AUC) (N) are derived from OD600 measurements every 0.5h over 10 hours at 37C. Points represent strains with paired conditions connected with lines. Statistical significance was determined by paired t -test followed by Bonferroni correction. (O-Q) Protein expression of cytokines IL-8 (O), CCL20 (P) and IL-36γ (Q) in the basal media of Staphylococcus -colonized RHE was measured by ELISA (n=3-4 replicates per strain in an independent experiment colonizing 3 inflammatory and 4 commensal S. epidermidis strains and S. aureus as a reference). Points represent individual replicates colored by cluster and boxes show IQR with median. (R) Model summarizing species- and strain-level effects of Staphylococcus on RHE. Species-level differences distinguish commensal and pathogenic effects, while strain-level variation within S. epidermidis identifies inflammatory strains that activate a proinflammatory transcriptional program including upstream regulators (e.g. NFKB), chemokines (e.g., CCL20), cytokines (e.g., IL36γ) and downstream antimicrobial effectors (e.g. LCN2). Inflammatory S. epidermidis also enhances skin barrier defensive genes, particularly members of the LCE and SPRR gene families, which contribute to both barrier integrity and antimicrobial defense, and are regulated by transcription factors such as MAFB. These effects are linked to differences in gene content (e.g., cell surface genes), transcriptional programs, metabolism (e.g., arginine pathway), and pathogen-like growth phenotypes. P-values: **** p ≤ 0.0001, *** 0.0001 < p ≤ 0.001, ** 0.001 < p ≤ 0.01, * 0.01 < p ≤ 0.05., ns p > 0.05.

Article Snippet: Rabbit red blood cells with complement (Innovative Research Inc.; #IRBRBC10ML) was aliquoted into 96-well plates (150 μL per well).

Techniques: Infection, Derivative Assay, Expressing, Enzyme-linked Immunosorbent Assay