Cell/bacterial cell lysis is a crucial step in molecular biology experiments to obtain target substances such as intracellular proteins and nucleic acids. Its core principle is to disrupt the integrity of the cell structure while preserving the activity of the target substances to the greatest extent possible. Commonly used lysis methods, based on differences in their mechanisms of action, can be categorized into physical, chemical, and combined methods, adaptable to different experimental scenarios and sample types.
The repeated freeze-thaw method is a simple physical lysis technique that relies on rapid temperature changes to disrupt cell structure. The cell suspension is alternately frozen at -20°C and thawed at room temperature or 37°C. Ice crystal formation and changes in intracellular osmotic pressure induce cell swelling and lysis. This process typically requires at least three repetitions to ensure complete lysis. An optimized approach involves collecting cells by low-temperature centrifugation, resuspending them in buffer, and then cycling through liquid nitrogen quenching and water bath thawing 3-4 times. Shaking after thawing enhances the lysis effect. This method is suitable for samples with minimal impact on enzyme activity.
The ultrasonic treatment method uses ultrasonic energy to disrupt cells. Precise parameter control is required to protect the target substances. The core principle is to set appropriate sonication time and intervals. Generally, the sonication time should not exceed 5 seconds, and the interval time should be longer than the sonication time to avoid localized overheating that could lead to protein denaturation. In practical applications, lysozyme pretreatment can be combined. After the bacterial solution is suspended in buffer, lysozyme is added and the solution is placed on ice for 30 minutes, followed by sonication at an appropriate power. Combining this with freeze-thaw cycles can improve lysis efficiency and is commonly used for processing large quantities of bacterial samples.
The osmosis method uses a hypotonic buffer to disrupt cell membrane permeability and is suitable for samples sensitive to denaturation conditions. Cells are treated with a pre-cooled Tris-Cl and EDTA mixed buffer and placed on ice for 10 minutes. The osmotic pressure difference causes the cells to absorb water and rupture. This method is gentle and preserves the natural conformation of intracellular substances well, and is commonly used in sophisticated molecular biology experiments.
The lysis buffer treatment method is the most widely used chemical method. It involves the synergistic action of detergents, denaturants, and other components to lyse cells. The core components of the lysis buffer include a buffer system to maintain pH stability, detergents to disrupt the lipid bilayer, protease inhibitors to inhibit protein degradation, and denaturants to assist in protein dissolution. Common formulations include Tris-Cl, NaCl, Triton X-100, or NP-40, and the component ratios can be adjusted according to needs.
For protein detection scenarios, the lysis procedure can be simplified: After centrifuging a small amount of bacterial culture, resuspend the precipitate in protein loading buffer, boil for 3-10 minutes, centrifuge again, and use the supernatant for electrophoresis. For obtaining whole protein, it is recommended to use a buffer containing multiple protease inhibitors, incubate on ice for 30-60 minutes, centrifuge, and the supernatant can be used directly for subsequent purification.
When choosing a lysis method, the sample volume, the characteristics of the target substance, and subsequent experimental requirements must be considered. Physical methods are suitable for samples with tough cell walls, chemical methods are suitable for routine cell lysis, and combined methods can balance efficiency and activity retention. Reasonable parameter optimization can significantly improve the success rate of experiments.
