FIG. 2.

a-Pheromone induces a dramatic increase (>100-fold) in adhesion in white cells of all tested α/α strains of C. albicans. A modified version of the methods of Daniels et al. (5) was employed. In brief, majority white cells (99%) of each strain were mixed with minority opaque cells (1%), the latter composed of a 50:50 mixture of opaque a/a (P37005) and opaque α/α (WO-1) cells. Presumably, the α/α opaque cells in the mixture produced α-pheromone, which upregulated a-pheromone production in the opaque a/a cells (5). White cells of each test strain, alone or mixed with the minority opaque cell mixture, were then assayed for adhesion as described in the legend to Fig. 1 for the α-pheromone response of a/a cells. (A) Histogram of the average number of cells adhering to the well bottom for each of 14 α/α strains. The three α/α strains P48076, P75010, and P75006 were obtained by growing the natural a/α strains with sorbose (6), screening for opaque sectors (MTL-homozygous offspring), and genotyping for α/α strains by PCR (9, 15). The four α/α strains P80001, P34048, P37039, and P75063 were spontaneous α/α derivatives of natural a/α strains. The mean of results from three well bottoms plus the standard deviation are presented for each strain. 1% Op, 1% opaque cell mixture. (B) The well bottoms for strain WO-1 in the absence (−) or presence (+) of the mixture of minority opaque cells were representative of all α/α strains tested.