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I am trying to determine how quickly detergents act on bacterial cells (cell lysis). I would like to compare some detergents at difference concentrations for bacteriolytic activity. I don’t care about all metabolites inside the cells (proteins, DNA, etc…). Many publications suggest that often more complicated solutions are used. My first thought was to use a simple prepared detergent in PBS or saline for lysing the cells. Do I need a complex solution to lyse the cells? Could someone please give me a suggestion? Thanks in advance.

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What exactly is the purpose of lysing the cells? The "complicated" solutions, as you say, include a bunch of ingredients. The detergent is largely present to dissolve cell membranes (which are lipid-based) and allow for extraction of proteins or other biochemicals from within the cell (and organelles in eukaryotes). There are also two types of detergents: ionic and anionic. Both detergent types will dissolve membranes, but ionic detergents tend to be harsher of the two by strongly disrupting protein structures.

If protein biochemistry is important, then the next most important ingredients will be specific inhibitors of proteases: enzymes which degrade proteins. There are many of these, but some examples include PMSF, EDTA, aprotinin, etc.

Sometimes it is necessary to buffer the pH of lysis solution to monitor protein complexes, or keep a protein natured, or keep DNA in an optimal pH range. General solutions for lysis buffers include Tris-EDTA (TE), PBS, etc. This choice comes down to whether you want a buffer, and in which pH range you wish to keep your lysis solution. Common buffers like TE and PBS are made up for a pH range of between 7-8. There are other buffers that are used for low pH ranges (pH 4-6), but are usually less common.

Lastly, there are ways to lyse cells without using any kind of lysis buffer. One method is to use sonication, which uses directed pulses of high-frequency sound to lyse cells by mechanically shearing them. Another method is to repeatedly freeze-thaw cells from -80°C to 4°C (usually 3 times is sufficient). Lysis in this manner is accomplished by repeated formation of ice crystals which cut open cells, releasing their contents.

If you have a more specific question, one of us can guide you further, but this provides a general overview of what is involved with cell lysis buffers.

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I wonder how you plan to measure lysis? You will find that many lysis methods for E. coli incorporate a treatment with lysozyme and EDTA. This is so that lipopolysaccharide (outer membrane) and peptidoglycan layers of the cell envelope can be breached before detergent (usually SDS or Triton X-100) is added to dissolve the inner or cytoplasmic membrane. I suspect that if you added detergent to intact cells it wouldn't be particularly effective, and any cells that were affected would remain as denatured cells which would, for example, still contribute to optical density.

Since they are usually able to withstand bile salts in the small intestine, Gram-negative bacteria can be quite resistant to detergents. For example many Enterobacteriaciae can grow in 5% SDS - see:

Rajagopal, S et al. (2003) Eight Gram-negative bacteria are 10 000 times more sensitive to cationic detergents than to anionic detergents. Canad. J. Mic. 49:775-779

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