A vacuole is a membrane organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. http://www.springerlink.com/content/b23m0r26770x8206/ Microbiology Monographs Volume 1/2006 Vacuoles Heide N. Schulz-Vogt Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including various enzymes in solution, though in certain cases they may contain solids which have been engulfed. Vacuoles are formed… (More on Vacuole)