Fig. 4
a LC–MS analysis of ethyl acetate extracts derived from 50 ml R5A cultures inoculated with wild-type and S. albus mutant strains. Cultures were grown for 6 days at 30°C. The major peaks that are present in Δwbla and [+ermE*crpSC] backgrounds but absent in wild-type and Δpfk strains are identified as paulomycin/paulomenol molecules. Corresponding masses (M + Na+) and maximum UV absorption spectra are shown. b Biomass accumulation over 6-day fermentation in R5A liquid media. 25 ml media were inoculated with inoculum directly from glycerol stocks to OD450 0.03. Following incubation, 1 ml culture sample was removed and spun for 3 min at 14,000 rpm. Supernatants were discarded and the pellet was dried at 80 °C overnight and weighed. Values are means of three replicates. Error bars represent standard deviation. DCW dried cell weight. Deletion of pfk SA gene and crpSC overexpression has no effect on growth rate relative to wild-type whereas Δwbla mutant accumulates ~ 5 times more biomass than the wild type (p < 0.0001). Statistical significance was calculated with Student’s t-test. c Chemical structures of paulomenols/paulomycins compounds. Paulomenol B, calculated m/z of 661.26; paulomenol A, calculated m/z of 675.27; paulomycin B, calculated m/z of 786.25; paulomycin A, calculated m/z of 800.27. Paulic acid moiety conferring the antimicrobial activity of paulomycins is indicated with blue shade