Standard Microbiological Practices

aka the approximately Ten Commandments of Microbiology

  1. Thou shalt always include a media blank
    Otherwise you may contaminate all of your cultures and strains without ever knowing it. Bacterial cells can start growing in a bottle of media stored at room temperature and remain undetectable for a long period of time until they are incubated at 37C.
  2. Do not overfill your culture vessels
    When growing cultures in Erlenmeyer flasks, never exceed 20% of the capacity of the flask (e.g., 10 ml for a 50 ml flask). Doing so prevents adequate agitation and aeration of the culture and will result in incomplete growth, biofilms, or other inconsistencies.
  3. Always precondition your culture in the media in which you will be doing your experiment
    Otherwise your cultures may not consistently be in the same physiological state when you do your experiment. If you are doing an evolution experiment, only test the cells under the conditions in which they evolved!
  4. Always wash auxotrophic cells when transferring from rich media to minimal media
    Or else you may carry over enough of an amino acid or vitamin for the cells to grow.
  5. Thou shalt not shock thy cells by washing them in water
    Bacterial cells will rapidly die due to extreme osmotic shock if resuspended in pure water. It is safest to wash your cells with growth medium. Robust microbes such as E. coli can be washed in sterile saline. If you are using another microbial species, you need to test whether this is safe.
  6. Be skeptical of strains and plasmids that you get from others
    Verify their genetic markers and/or sequence important regions. It might take you weeks to figure out that a mixed up tube or mutated plasmid was causing your experiments to fail.
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Topic revision: r4 - 2018-03-22 - 19:13:27 - Main.JeffreyBarrick
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