Fig. 1.

Strain A1153 invades more efficiently than strain 972. (A) Strains 972 and A1153 were plated on LNB medium at high density, and after 4 days, the surface cells were removed by washing. (B) Strain A1153 forms invasive filaments that extend beyond the immediate area of the surface colony. Bar, 50 μm. (C) Mating of strain A1153 with strain 972. Strains 972 (*), A1153 (#), and 14 progeny of a cross between the two (remaining segments) were incubated for 2 days. Strain A1153 had invaded more strongly than strain 972, while the progeny from the cross showed various levels of invasion intermediate between the two parental strains.