The Setup

• You each get a tube with a mixed broth culture. Be sure to record your number.
• Each contains a mixture of 2 bacterial species which are visibly different either in shape, gram stain characteristics, or both.

Your Task (document everything with notes and drawings)

• Isolate each bacterial species by growing them on trypticase soy agar.
• Determine the following for each species:
  • Their colony characteristics.
  • Their shape and arrangement of cells.
  • Their gram stain characteristics.
  • Their motility.
• Document each of these characteristics with digital drawings or pictures.
• Write up your report and hand it in on time.
• You will have until Friday March 20 to work on your unknowns.
• Your report is due at the start of your lab session on Tuesday March 24th.

Day 1

• Isolate:  2 streak plates — one incubated at 37 degrees C, the other at 25 degrees C.
• Characterize from the broth cultures:
  • Motility — hanging drop or wet mount
  • Gram stain — prepare at least two slides for gram stains of you unknown.

Day 2

• Examine plates for isolated colonies (ideally with 2 different appearances).
  • Take a digital picture of your plate.
  • If you failed in your isolation attempt you may do one additional streak plate (that’s all, just one more).
  • If you do an additional plate it is your responsibility to incubate the plate and to remove it from the incubator.  Do not leave plates at 37 degrees C for more than 48 hours — they will dry out.  At least come in and put your plate in the refrigerator.
• Confirm isolation by doing a gram stain from each colony.
  • Don’t forget that a control (mixture of Gram + and Gram -) must be done with each and every gram stain.
• Negative stain if you didn’t do it on Day 1.

Due Dates etc.

• You have two weeks to complete your unknown project:
  • Both labs this week and one hour of the first lab next week.
  • You may come in on your own time to work on it until Friday October 30
• Your final paper (both digital and paper copies) is due before the start of your lab on Monday Nov. 2 or Tuesday Nov. 3rd (depending upon the date of your first lab of the week).
• The instructions for your paper are posted on the Lab Briefing Blog and there are sample papers posted in  lab.
  • NOTE:  do not go through the steps of the different stains and other procedures — just say that you did them and that you used aseptic technique throughout!