FIG 3.

Adaptation of C. difficile to growth on glucose in the absence of proline and leucine. To adapt cells to grow without proline and leucine, cells harvested from a BHIS day culture were used to inoculate adaptation medium (ADM) which contained 5 mM glucose, 10 mM glycine, and low concentrations of leucine, isoleucine, valine, proline, methionine, and tryptophan in a basal salt mixture supplemented with trace elements and vitamins, as described in Materials and Methods. Growths were monitored in triplicate by OD₆₀₀ (*, □, and ×), aliquots were removed over time and centrifuged, and the supernatants were assayed for amino acids and glucose. (A) Concentrations are given for glucose (Glc), glycine (Gly), alanine (Ala), and ammonia (NH₃). (B) The same cultures as in panel A, assayed for leucine (Leu), isoleucine (Ile), valine (Val), proline (Pro), and 5-aminovalerate (5-AV).