CELL LYSIS: PROCESS, CAUSES AND TYPES - BIOLOGY - 2025

The cell lysis is the process by which a cell disintegrates or is destroyed by the breaking of their plasma membrane and / or cell wall. Etymologically speaking, the word "lysis" comes from the Greek λύσις (read "Lúsis") which means "loosening", "weakening", "interruption" or "decrease" (from English loosening).

The result of the lysis of one or more cells is known as the "lysate", a term widely used in experimental biology to refer to the mixture of the "broken" plasma membrane and all the cytosolic components that are released after said rupture.

Life cycle of a bacteriophage virus (Source: Phage2.JPG: Suly12derivative work: DZadventiste via Wikimedia Commons)

Cell lysis is a normal process that can occur in different contexts and has been extensively studied in relation to bacterial invasions and enzymatic "attack" by proteins such as lysozyme, for example.

Experimentally it is one of the first steps to study any intracellular or membrane element, for which there are many different techniques, the basis of which varies according to the purpose of the study.

Process

The lysis process depends mainly on the type of cell considered. For plant, fungal, and bacterial cells, for example, this begins with the disintegration of the cell wall.

For animal cells and / or protoplasts of plant or bacterial cells (cell without a cell wall, only plasma membrane and cytosol), the lytic process generally occurs when the integrity of the plasma membrane is affected, thereby releasing cellular contents to the extracellular environment.

The rupture of the cell membrane can be caused by enzymes, detergents, toxins, by high-frequency ultrasound waves or by mechanical or physical processes, among others.

Causes

Cell lysis can occur in response to different environmental conditions, as well as endogenous factors or specific signals.

In many bacteria, for example, cell lysis can occur after infection with some species of viruses known as "phages" or "bacteriophages", in whose life cycle they can use the bacterial replication machinery to multiply and produce lytic enzymes that promote the "destruction" of the cell.

Other cells can undergo lysis due to the presence of toxins secreted by some pathogen and, in an animal or plant tissue, for example, some cells can be lysed thanks to various signaling processes that end with the release of cell content to the surroundings (necrosis).

Types of lysis

In the literature, reference is made to different types of lysis. Some authors classify them according to the “stimulus” or the triggering factor, while others classify them according to the type of cell that is smooth.

According to the mechanism that operates to achieve the disintegration of a cell, osmotic lysis, chemical lysis, mechanical lysis and enzymatic lysis have been defined. However, these types have been specially defined from the experimental point of view, so that their description obeys different techniques, rather than naturally occurring processes.

Regarding the type of cell that is lysed, however, many authors have coined terms such as "oncolysis", "plasmolysis", "cytolysis", "hemolysis", etc.

Oncolysis refers to the lysis of tumor or cancer cells, either by chemical or physical methods (medical treatments) or by infection with some strain of virus that can break down cells. Plasmolysis, on the other hand, refers to a phenomenon that takes place in plant cells when they are subjected to hypertonic solutions, with which the water inside them leaves the cell.

Plasmolysis of plant cells (Source: CNX OpenStax via Wikimedia Commons)

Finally, hemolysis is the process by which cells or red blood cells are lysed, either by specific enzymes (hemolysins), by the presence of toxins produced by pathogens or by high intensity physical exercise, among others.

Osmotic lysis

Osmotic lysis or "cytolysis" is the rupture of the plasma membrane due to an exaggerated flow of water from the extracellular medium to the cytosol.

This type of lysis is quite common in animal cells. The reason is that they lack a cell wall like those of plant cells, fungi or bacteria, which helps them control cell volume after the entry of fluid due to osmotic differences between the cytosol and the surrounding environment.

When an animal cell is faced with a hypotonic solution (either due to environmental fluctuations or under experimental conditions), they swell, which can end with their lysis. A hypotonic solution is one that has, with respect to the interior of the cell, a lower concentration of solutes, so that water tends to "enter" into the cell, seeking its water balance.

In experimental biology osmotic lysis or "shock" is regularly employed to break cells in order to analyze their internal components, especially cytosolic proteins, nucleic acids, etc.

Chemical lysis

Chemical lysis is one by which the cell membrane is broken or disintegrated by the action of some specific chemical substance. It can occur in a natural environment, if we consider the cells of a tissue or some unicellular organism that is accidentally exposed to some chemical compound capable of affecting the integrity of the plasma membrane.

It is also typically used in the experimental context, where detergents with different properties are used to affect the fundamental structure of the membrane, causing lysis. It is applied directly or indirectly, depending on the type of cell in question and for what purpose it is subjected to said process.

Mechanical or physical lysis

The plasma membrane of a cell can be ruptured experimentally by mechanical or physical methods. This type of lysis can also occur, under certain conditions, in natural environments, but experimentally it is achieved through the use of:

- Blade homogenizers for tissue or cell culture processing

- Sonicators, which break cells by means of high frequency ultrasound waves

- Presses, which cause cell lysis thanks to a progressive increase in the pressure to which a tissue or a group of cells is subjected

- Abrasive materials that cause friction, among others

Enzymatic lysis

Enzymatic lysis is a biological "method" of lysis that can be artificial or natural. In the natural context, this can occur due to different factors, but it has been specially reviewed with respect to some proteins with enzymatic activity secreted by bacteria, fungi and other organisms or their cells to fight infections, for example.

In this sense, lysozyme has been one of the most studied enzymes. It is found in some plant tissues, in the white of eggs, and also in the liver, cartilage, saliva, mucus, tears, and many cells of the hematopoietic lineage of humans and other animals.

The lytic capacity of this enzyme lies in its hydrolytic activity on the glycosidic bonds of peptidoglycan, which is one of the most abundant polysaccharides in the cell wall of bacteria.

Other common enzymes in nature and in industry or in the experimental setting are mannanases, chitinases, ananasses, glucanases, and the like, which function in the disintegration of the cell wall of fungi and yeasts, to name a few.

The lysis caused by viral enzymes is also a type of enzymatic lysis, since the bacteriophages that infect bacteria produce "lysines" that break the membrane and the bacterial cell wall.

Experimentally, some authors consider that internal proteases and other hydrolytic enzymes typical of the cytosol can be used for the enzymatic lysis of other cells, which also occurs when, in a tissue, a set of cells dies from necrosis and releases their internal content to the surrounding medium, causing lysis of adjacent cells.

References

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2. Brown, RB, & Audet, J. (2008). Current techniques for single-cell lysis. Journal of the Royal Society Interface, 5 (suppl_2), S131-S138.
3. Fleet, GH (2011). Yeast spoilage of foods and beverages. In The yeasts (pp. 53-63). Elsevier.
4. Luckey, M. (2014). Membrane structural biology: with biochemical and biophysical foundations. Cambridge University Press.
5. Solomon, EP, Berg, LR, & Martin, DW (2011). Biology (9th edn). Brooks / Cole, Cengage Learning: USA.