Fig. 4.

Cell–cell contact is important for Pa to inhibit C. neoformans. An assay in YPD media using a U-tube was performed. A sterile membrane was used to separate the two sides of the U-tube, in which Pa strains and C. neoformans (Cn) were cultured. Separately, Erlenmeyer flasks were used for controls, including co-cultures of Cn with PAO1 or PA14, Cn with E. coli and cultures of Cn alone and PAO1 or PA14 alone. The inhibitory effect of Pa on Cn, in the U-tube and in co-culture, was determined by CFU counting (a, c). When E. coli and Cn were co-cultured, no inhibitory effects of Cn were observed (a, c). The growth of PAO1 and PA14 was not affected by Cn (b, d). P values were calculated by Student’s t test, *P < 0.05; **P < 0.01; ***P < 0.001