The Collaborative International Dictionary of English v.0.48:

mycoderma \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 zoogloea stage of bacteria by
      not having the intermediary mucous substance.
      [1913 Webster]

   2. (Capitalized) A genus of microorganisms of which the
      acetic ferment (Mycoderma aceti), which converts
      alcoholic fluids into vinegar, is a representative. Cf.
      Mother.
      [1913 Webster] Mycologic