VMC 211: General Veterinary Microbiology (1+1)

PROTOPLAST AND SPHEROPLAST

Protoplast

• Bacterial cell without cell wall can be prepared from Gram positive bacteria by treatment with lysozyme to dissolve the cell wall or by growing the cells in the presence of an antibiotic such as penicillin which inhibits cell wall synthesis. Such cells are termed protoplasts.
• The osmotic pressure of the medium should be high to prevent the protoplasts from bursting. The protoplasts under such circumstances are soft, fragile and spherical.

Spheroplast

• In Gram negative bacteria also the peptidoglycan of the cell wall can be broken down by lysozyme or its synthesis can be inhibited by antibiotics.
• But the flexible outer membrane remains. This generates cells with two membranes, the cytoplasmic membrane and outer membrane. They are called as spheroplasts

L-forms

• They are bacterial variants with defective cell walls and irregular growth and multiplication. They are produced by the degradation of peptidoglycan by bacteriolytic enzymes or affecting its synthesis by inhibitors, or by  mutations in essential genes for cell wall synthesis.