Cold shock results in upregulation of UspA2 and increases the binding of vitronectin on the surface of M. catarrhalis. Representative flow-cytometric profiles of M. catarrhalis strains O35E, O35E.uspA1 and O35E.uspA2 after exposure at 26°C (gray) or at 37°C (black) show cold shock-dependent UspA1/A2 upregulation (A) and UspA2-dependent binding to vitronectin (C). The dotted line represents the negative control (bacteria incubated with secondary antibodies only). The mean fluorescence intensity ± 1 standard deviation for 2 experiments performed is shown (B and D). *, p < 0.05 for 26°C versus 37°C (one-way analysis of variance).