\My`co*der"ma\, n. [NL., from Gr. my`khs a fungus +
de`rma skin.]
1. (Biol.) 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 zo["o]l[oe]a stage of bacteria
   by not having the intermediary mucous substance.
2. A genus of micro["o]rganisms of which the acetic ferment
   ({Mycoderma aceti}), which converts alcoholic fluids into
   vinegar, is a representative. Cf. {Mother}.