Meaning of mesosome

mes•o•some

Pronunciation: (mez'u-sōm", mes'-, mē'zu-, -su-), [key]
— n.
  1. the anterior portion of the abdomen in arachnids.
  2. a whorled structure extending inward from the cell membrane in Gram-positive bacteria and containing enzymes for cellular respiration.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.