Week 6 Activity: Culturing Microbes!

Last week you collected sediments and stored them in the refrigerator. Let’s first find out why you put them in the refrigerator. Microbes are living organisms adapted to their environment - and the cold temperatures of the refrigerator keeps the microbial environment stable until we are ready to investigate the microbes themselves. We don’t want anything to change. On board the JOIDES Resolution, these sediment cores are immediately put in a large refrigerator for the same reason. The microbiologists insist that the cores be stored this way until they are ready for them.

For this activity, we will learn about the microbes that live in your core sediments. You will probably need to purchase a microbe surface testing kit.  You can buy one online at many science supply houses (or go to Option 2 below if you can’t get one).  Follow the directions and cautions that come with the kit. The only modification that we will make is to change where you will swab for your microbes.

Option 1

  1. Take your sediments out of the refrigerator and take the tube out of the plastic bag.
  2. Carefully push the sediments out of the plastic coring tube onto a clean piece of wax paper, disturbing them as little as possible. You might need to use the eraser end of a pencil or a wooden dowel to do this. Wrap the pencil eraser or dowel in plastic wrap first so that there is little, if any, contamination.
  3. Rub the cotton swab across the top of the sample and use a clean swab to collect microbes near the bottom of the sample. Follow the directions that came with the kit.

Be sure to take photos of your sample and cultures and email them to JR!

Option 2
If you can’t get a surface microbe testing kit, here is another experiment you can try out.

Step 1: You’ll need to round up a few supplies, which might require a trip to the grocery store. What you’ll need: 
  • A package of gelatin dessert powder mix (like Jell-O) 
  • a few waxed paper disposable drinking cups (like Dixie cups) 
  • clear plastic wrap, like what you use for wrapping your leftovers 
  • cotton swabs 
  • tape 
  • a pot and hot water for making the gelatin 
Step 2: Heat and mix the gelatin as directed on the package. When the solution is ready to be poured, place about an inch of the hot gelatin solution into a few of the plastic cups (you might want to use some scissors to make the cup shorter (1.5 inches) beforehand, to make it easier to see inside later). If you have leftover gelatin, you could always use it to make dessert! Allow the gelatin to cool and set.

Step 3: After the gelatin has set, rub the cotton swab on your sample’s top and bottom (as in Option 1 above) to get good samples of the microbes in your core sample. Then rub the cotton swab around on the surface of the gelatin to transfer your microbes to the gelatin surface. If you weren’t able to get a sediment sample, you can still do this! Collect microbes from your teeth with a cotton swab or toothpick.

Step 4: Cover the paper cup with a piece of cling wrap, and then tape the cling wrap around the cup to keep it sealed. Write the date and time on your cup. Then keep your cup somewhere inside, out of direct sunlight, some place safe where it won’t get knocked over or eaten.

Step 5: Over the next 2-3 days, check on your gelatin surface every 12 hours or so. Have any dots appeared on the gel? If yes, these might be colonies of microbes! Or, do you see spots that look like mold?

Step 6: Take a picture of your gelatin cup and send it to us by Thursday, November 29, 2010. In the email, please let us know what you swabbed and what you think about your experiment.

Step 7: Try not to open up the gelatin cup once you have sealed it up – some of the things growing in there may be harmful. When you are done with the experiment, please have an adult carefully place a drop or two of bleach (or some vinegar) into the cup to disinfect the gelatin for a few minutes, and then it can be placed into the trash. If you have any household pets, please make sure they don’t get into the trash! 

A scientist interested in culturing the microbes growing on subsurface rocks might try out very similar experiments to see what would grow. If something grew, that scientist would then conduct a whole bunch of other experiments to try to figure out how the microbes get energy and carbon, and what the identities of the microbe are.

If you have any questions about these experiments, please don't hesitate to ask us!

Liability disclaimer: The experiments outlined above should be safe to perform with adult supervision, but participation in the activity is completely voluntary and done at your own risk. Please read and follow the directions carefully and avoid contact with anything that grows inside your experiment, just to be on the safe side. The Adopt A Microbe project has no liability for events that may occur during the course of the experiment. The Adopt A Microbe project has no affiliation with the makers of the ‘Subsurface Microbes Experimenter Kit’ kit or proprietors of the www.scifair.org website.