Spontaneous settling of 042 and mutants. Overnight L-broth cultures containing 0.2 mM IPTG were permitted to settle undisturbed at room temperature. At 15-minute intervals, a 100-μl sample was withdrawn from the top of each broth culture and the OD₆₀₀ of the withdrawn sample was determined. Rate of clearing of the uppermost portion of the culture correlates with rate of spontaneous settling, a measure of agglutination. Samples were tested in triplicate. Bars represent SEM.