Degradation of glycolic acid by acidophilic Firmicutes. Symbols: ▴, S. thermosulfidooxidans strain TH1; ▪, S. acidophilus strain YTF1; ▾, S. benefaciens type strain; •, isolate SLC1; ○, noninoculated control. The symbols indicate the mean glycolic acid concentrations for duplicate cultures, and the error bars (where visible) indicate the ranges.