Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights Reserved.): Yeast plasmid-host cell interactions. (Top) The yeast 2μm plasmid tagged by green fluorescence shows unequal segregation due to mutations affecting the cohesin complex (left), the nuclear spindle (center), or the SUMO-specific Ulp1 protease (right). The plasmid appears light blue where colocalized with DAPI (4′,6′-diamidino-2-phenylindole)-stained chromosomal DNA (dark blue). (Center) Merged light and fluorescent time-lapse images of a wild-type yeast cell showing normal equal plasmid segregation. (Bottom) Effect on cell and colony morphologies when SUMO conjugation to the plasmid-encoded Flp recombinase is reduced (center), or when the Ulp1 protease is mutated (right), compared to wild-type yeast (left). (See related articles in May 2005, vol. 25: issue 10, p. 4283, 4299, and 4311.)