Fig. 1: Pneumococcal growth in the presence and absence of peptides.

a Growth curves of pneumococcal strain D39 in the presence and absence of 11 amino acid peptide V11A (VNATDEDRWNA) and its longer versions (13- and 15-amino acid length) in chemically defined medium (CDM). b Growth curves of pneumococcal strain D39 in the presence and absence of peptide V11A and peptides with naturally occurring amino acid differences compared to V11A in CDM. Difference at position 3 occurs in strains of K. pneumoniae and Salmonella enterica, at position 4 in strains of E. coli, at positions 3 and 4 in strains of Arsenophonus, E. coli, Moritella, Pasteurellales, and Psychromonas, at position 7 in strains of K. pneumoniae and S. enterica, at position 10 in some strains of Cedecea, Psychromonas and S. enterica. Amino acid differences from V11A are underlined. All peptides at a concentration of 0.5 mg/ml. c Growth curves of trimethoprim-sulfamethoxazole resistant clinical pneumococal isolate 1154.75 (serotype 23F) in the presence and absence of peptide V11A and K. pneumoniae ribosomal peptides AmiA (AKTIKITQTR) or AliA (FNEMQPIVDRQ) ligand in CDM. d Growth curves of pneumococcal strain 1154.75 in the presence and absence of peptide V11A in human cerebrospinal fluid (hCSF) of donor 1 (see Supplementary Fig. 2 for equivalent results in hCSF from four other donors). Bacterial inoculum was twice that used in CDM due to anticipated slower growth in hCSF. e Time-kill assay of S. pneumoniae strain D39. Bacteria were untreated (negative control) or exposed to 0.5 mg/ml peptide V11A or 0.5 mg/ml penicillin G (positive control for bacteriolytic effect). Increasing cfu/ml represents bacterial growth over time, steady cfu/ml represents bacteriostatic effect, and decreasing cfu/ml represents bacteriolytic effect. Growth was measured by optical density OD (450 nm) measurement in peptide-free CDM for (a–c), undiluted human cerebrospinal fluid for (d) or by plating dilutions of bacterial sample onto agar plates at the timepoints indicated and counting colony forming units (cfu) for (e). Results represent three independent experiments, error bars indicate SEM. Peptide concentration = 0.5 mg/ml unless otherwise indicated.