FAQs: MolecuLab 110/115/120

Q: Why isn’t my bioluminescent E. coli glowing?

Bioluminescent strains need to be treated differently from other more common bacterial strains.  Here are some tips to help make sure you see bioluminescence.

  • Bioluminescent strains are not viable in stabs for long periods of time. They should be grown out and stored in the appropriate media in an ultra cold freezer or transferred every 1-2 months.
  • Once plated, all bioluminescent strains should be grown at room temperature not at 37ºC.
  • If a plate containing colonies is refrigerated, it should be incubated at room temperature for 2-3 hours before visualization to allow bacterial colonies containing the lux operon to express bioluminescence.
  • Be aware that dark mutants are fairly common especially after repeated culturing.


Q: Why must I pour my own agar plates?

Melting and pouring your own agar plates is an extra step to help ensure that the plates remain sterile until the time of their use.  Be sure to follow the provided directions and be as sterile as possible.  Some good practices include:

  • washing your hands before working with the plates or wearing gloves
  • sterilizing your work surface with 10% bleach or 70% ethanol
  • keeping the cover on the agar plates at all times and only opening it slightly while pouring the melted agar
  • refraining from touching the mouth of the bottle containing the melted agar

Q: How can I help prevent contamination of my agar plates?

Be sure that your agar plates are stored in the refrigerator after they are poured and as soon as the plates have cooled.  Their covers should remain in place until they are ready to have bacteria streaked or spread on their agar surface.

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