FIG. 7.

Silver-stained preparations following SDS-PAGE of whole cultures of Yersinia pestis strain KIM cultured in Ca²⁺-deficient chemically defined medium lacking both Na⁺ and l-glutamate (A), containing only 100 mM Na⁺ (B), containing only 25 mM l-glutamate (C), and containing both Na⁺ and l-glutamate (D) at an initial pH of 5.0 (lane 2), 5.5 (lane 3), 6.0 (lane 4), 6.5 (lane 5), 7.0 (lane 6), 7.5 (lane 7), 8.0 (lane 8), 8.5 (lane 9), and 9.0 (lane 10); comparable negative (Lcr⁻ cells) and positive (Lcr⁺ cells) controls of Ca²⁺-deficient cultures containing both Na⁺ and l-glutamate are shown in lanes 1 and 11, respectively.