Isolation of an Unknown


As with most of the experiments in this course, you will be handling a variety of undomesticated organisms of unknown identity or pathogenicity. Handle all cultures with respect and using standard microbiological procedure.


Rather than identify some boring standard teaching lab bacterium from a pure culture or simple mixture, in this
experiment you will isolate something, who knows what, from an environmental sample you bring in, and then identify
it phylogenetically from the sequence of the small subunit ribosomal RNA.


  • whatever media is at hand
  • whatever source of innoculum is at hand


  1. Decide which of the environmental samples you brought in you want to use for innoculum - any of them should do. Alternatively, you can take a swab or sample of anything else - use your imagination!
  2. Streak this innoculum onto whatever media is available and interesting to you. Incubate at 30C (or whatever temp is available or desired)
  3. Examine the resulting colonies and pick a few interesting ones for microscopic examination. The key here is to find something different - colored, odd shape, funny edges, whatever. Go for the oddballs! Decide on two to go with and make extensive notes on both colony and microscopic morphology.
  4. Restreak these organisms and incubate as before
  5. If needed, restreak and incubate once again to get a pure culture. Examine microscopically to make sure nothing has changed.


Make notes on both the colonial and cellular (in wet mounts) morphology. Plan to use this isolate for molecular phylogenetic anaylsis.