Isolation Of Interspore Bridges From The Budding Yeast Saccharomycodes Ludwigii

In the budding yeast Saccharomycodes ludwigii, four spores in an ascus are in pairs of two spores, and the two spores of opposite mating type are tightly tethered by an interspore bridge, a so-called ledge. A pair of spores germinates and immediately conjugates to form zygotes in rich medium. We found that the interspore bridges are detached from spore walls during germination of spores and zygote formation. We successfully isolated the interspore bridges morphologically intact from the spores by a combination of treatment of zygotes with Zymolyase, sonication, and sucrose density gradient centrifugation. The interspore bridges are disc structures with a diameter of approximately 2 mu m and a thickness of approximately 0.5 mu m. The interspore bridges are composed of three layers, with the outer two being stained by Calcoflour. Detailed observations of the sporulation process suggested that the interspore bridges are formed concomitant with spore wall formation. This is the first report of the isolation of interspore bridges from yeast.