Sorry about the correction, but that number isn't right on two levels.

1: bacteria didn't have sexes. Sometimes they will exchange plasmids via a direct pilus or will pick up strays in the environment.

2: that number is often cited from a book describing certain slime molds (which aren't molds) as having that few, when almost every species we found have something in the 100's. But what I think is cool is that some species of actual fungi have something like 72,000 compatible sexes.