one of the forms in which bacteria group themselves; a more or less thick layer of motionless but living bacteria, formed by the bacteria uniting on the surface of the fluid in which they are developed. this production differs from the zooloea stage of bacteria by not having the intermediary mucous substance.-a genus of microorganisms of which the acetic ferment (mycoderma aceti), which converts alcoholic fluids into vinegar, is a representative.  cf. mother.