Science Buddies: "Ask an Expert"

collecting bacterial samples. I purchased a kit for collecting bacteria and i'm not quite sure what I am suppose to do with the halobacterium broth. Do i place my swab in it and then swab the area being tested . Thenstreak my petri dish with the swab? Or do i swab the area firs, then dip into the halobacterium broth and then streak my petri dish?

Hi Scimon1,

I’m not familiar with the kit that you purchased. What is the name of your kit? Halobacteria are bacteria that require high concentrations of salt to grow. They are found in salt ponds and other extremely salty bodies of water like the Great Salt Lake or Mono Lake. They grow slowly in either halobacterium broth or agar. You may have both types of media in your kit. Do you have a suitable place to collect a sample for this experiment? I would probably recommend enriching the sample in the broth medium first and then plating onto the agar, but I’m not certain what you are trying to accomplish with your experiment. Please let us know more about the kit.

Donna Hardy

My science fair project is on where would I find the worst bacteria in my school.I am testing different locations ( door knobs water fountains, key boards, hand rails, bathroom stall) My aunt sent me a kit form a company called Carolina. The set included petri dishes , bottles of agar and testubes with halobacterium broth. I made the agar and coated the petri dish with the agar. After it hardened, I went to school and took samples. I dipped a sterile loop in the broth and then on the area i was testing. Then i took the loop and swirled the petri dish with the loop. I labeled the dish and dated it. I sealed the dish with tape and placed in a plastic bag. i placed the dishes of samples in a dark place away from light and nothing is happening. Did I use the broth correctly? I was hoping by now that I would have something to look at but not sure I used the broth correctly. Is there a better place to put my dishes to see the bacteria grow. What should I do? I need to correct this if there is a better way before its too late. Any suggestions?

Hi,

Carolina company produces a line of kits that contain medium for growing Halobacterium, an bacterium that grows only in the presence of high concentrations of salt. The Halobacterium medium contains greater than 4 moles per liter sodium chloride and will inhibit the growth of most other organisms and that’s why you are not seeing any growth. You would need to obtain the Halobacterium from Carolina company or visit the Great Salt Lake (or similar environment) to collect a sample that would grow on this medium. If you are culturing bacteria from door knobs, water fountains, and key boards, etc. you will need a general all-purpose medium like nutrient agar, also supplied by Carolina Biologicals.

If it is too late for you to repeat the experiment, you can report your results (no growth in any sample) and explain why you obtained no growth. You actually obtained the expected results with the samples and culture medium you were using.

I hope this helps.


Donna Hardy