Fig 1.

PAPs of S. pneumoniae wild-type and murA1 knockout strains. An experiment representative of three independent experiments is shown. The concentration of fosfomycin used to select subpopulations with higher fosfomycin resistance levels is shown against the frequency of bacteria able to grow at that concentration. Wild-type and murA1 knockout mutant forms of Swiss clinical strain 106.44 (A), international reference strain Taiwan^23F (B), laboratory strain D39 (C), and international reference strain Hungary^19A (D) are shown. A horizontal plateau in the curve, such as that shown for strain 106.44 in panel A, indicates heteroresistance, in contrast to a steep drop in the curve indicating no heteroresistance, as shown for strains Hungary^19A in panel D.