Mycoplasma is the smallest and simplest prokaryotes, discovered by Louis Pasteur (1843) from cattle suffering from pleura-pneumonia, hence were called as pleura-pneumonia like organisms (PPLO). These are wall-less, pleomorphic organisms (Monerans), containing fatty substances, proteins, a long coiled DNA extending almost throughout the cell, RNA and ribosomes in their cytoplasm.

These are anaerobic and chemo-organotrophs causing plant diseases like potato witches broom, bunchy top of papaya, little leaf of brinjal, maize stunt, etc. and animal and human diseases like rheumatism, arthritis, respiratory and urinogenital tract infections and human infertility etc.