The main difference between protoplasts and spheroplasts is that protoplasts have one membrane, whereas spheroplasts have two membranes as inner and outer membranes.
The cell wall is a structural component in some cells of living organisms like plants. Certain prokaryotes, such as slime moulds, algae, and fungi, have cell walls. The cell wall is the outermost structure covering the cell. It is a comparatively tough and rigid structure that performs many functions. Some of these include giving shape to the cell, providing protection, helping to develop turgor pressure, withstanding osmotic stress and turgor pressure, and providing mechanical support to the cells. The main function of the cell wall is to provide structural support to leaves, stems, roots, and the overall plant.
Cell walls of different types of cells may have different constituents, such as cellulose and lignin. Animal cells do not have a cell wall, and this is a major difference between animal and plant cells. Protoplasts and spheroplasts are altered forms of bacteria, plant, or fungal cells that have their cell walls partially removed or fully removed. Protoplasts and spheroplasts occur naturally, too. Another name for them is L-forms. Bacillus, clostridium, pseudomonas, and vibrio are some of the microorganisms that produce the L- forms.
Key Areas Covered
Naked Cells, Protoplasts, Spheroplasts
What are Protoplasts
Protoplasts are cells whose cell walls are withdrawn and are covered by plasmalemma. We also call them naked cells. Protoplasts can be cells of bacteria, fungi, etc. The removal of the cell wall to form a protoplast could happen chemically, physically, or with the help of enzymes.
Protoplasts are osmotically sensitive. Their size varies according to the surrounding osmotic pressure. Pectin and cellulose surround the protoplasts. In bacteria, it comprises several layers of peptidoglycan, while in fungi, it comprises chitin.
Additionally, there are different types of enzymes scientists use for protoplast isolation. Generally, enzymes degrade the cell wall material. As most cell walls are formed from polysaccharides, polysaccharide-degrading enzymes are used in the process of degradation. Moreover, the enzymes that help with the degradation are cellulase, pectinase, chitinase, lysozyme, lysostaphin, and xylanase.
What are Spheroplasts
Spheroplasts are the cells from which the entire cell wall has been removed. They can occur naturally or can be created within the laboratory. After the removal of the outer cell wall, the cells remain spherical or round in shape. This spherical nature also helps them survive in harsh environmental conditions. These cells constantly face stresses from the environment, such as osmotic and mechanical stress, due to the loss of protection due to the loss of cell walls. However, the method of formation of spheroplasts depends on the type of cells. Spheroplasts can form from treatments such as pectinases, xylanase, and cellulase treatments of plant cells and chitinase treatment of fungal cells.
Bacterial cells are susceptible to osmotic pressure; hence the formation of spheroplasts occurs in isotonic solutions. This is to prevent their cell membranes from rupturing or shivering. Here, it is necessary to maintain an optimum ionic balance to ensure the successful transformation to the desired form.
Difference Between Protoplasts and Spheroplasts
Protoplasts are plant or microbial cells that are formed by removing the cell wall completely, while spheroplasts are plant or microbial cells that are formed by removing the cell wall partially.
Protoplasts have one membrane, whereas spheroplasts have two membranes as inner and outer membranes.
Presence of the Cell Wall
In protoplasts, the cell walls are fully removed, while in spheroplasts, some of the cell wall structure is retained.
Protoplasts have round or oval shapes, whereas spheroplasts have spherical shapes.
Method of Removal of Cell Wall
In protoplasts, the main methods of removal of the cell wall are enzymatic and mechanical methods. In spheroplasts, the methods used in the removal of the cell walls are mechanical methods such as grinding or osmotic shock.
In brief, protoplasts and spheroplasts are altered forms of bacteria, plant, or fungal cells that have their cell walls partially removed or fully removed. The key difference between protoplasts and spheroplasts is that protoplasts have one membrane, while spheroplasts have two membranes: the inner membrane and the outer membrane.
1. “Protoplast – An Overview.” Science Direct.
1. “Physcomitrella protoplasts” By Lab of Ralf Reski – University of Freiburg, Lab of Ralf Reski (CC BY-SA 3.0) via Commons Wikimedia
2. “Penicillin spheroplast generation horizontal” By Shudde – Own work (CC BY-SA 3.0) via Commons Wikimedia