Siderophore-Dependent Growth of Staphylococcal Strains

Growth of S. lugdunensis and S. aureus strains was assessed in C-TMS with serum. Single, isolated colonies were resuspended in 2 ml C-TMS and grown for over 4 h until OD₆₀₀ was above 1. Each culture was normalized to an OD₆₀₀ of 1 and subcultured 1:200 in C-TMS:HS. WT S. lugdunensis as well as S. aureus strains bearing Δsbn and Δsfa mutations are impaired for growth in this media compared to siderophore-producing strains (35 (link), 38 (link)). Human stress hormones were added to the media for a final concentration of 50 μM to assess for catecholamine–iron acquisition for growth enhancement. Dopamine hydrochloride, L-DOPA, DL-NE hydrochloride, (-)-epinephrine, 2,3-dihydroxybenzoic acid (DHBA), and 2,5-DHBA were purchased from Sigma. Chloramphenicol was also included for strains harboring pRMC2 or derivatives. Cultures were grown in a Bioscreen C plate reader (Growth Curves USA) at 37 °C with constant shaking at medium amplitude. OD₆₀₀ was assessed at 15-min intervals; however, for graphical clarity, 4 h intervals are shown.