Monumental Microbes Part 2

This past week a few lab members and summer interns headed down to the national mall to test out kit S-30 in a unique place. Under the sweltering heat, interns collected bacterial swabs and water samples of various fountains and statues.  The trip started with a visit to the Lincoln Memorial and it’s iconic stairs.

Following the stairs, a sample of water was taken from the reflecting pool.  After collecting these samples, the group stopped by to see Albert Einstein and Martin Luther King Jr.’s statues. Both of the sculptures produced plates full of bacteria!  Directly below is a picture of  bacteria from the Lincoln Memorial.

Additional water samples were taken from the WWII memorial fountain and the Tidal Basin. Surprisingly the WWII fountain plate did not grow much bacteria. Below is a picture of the Martin Luther King Jr. plate.

The above plate is a picture of the WWII fountain water which proved to be almost bacteria free.

After growing our monumental bacteria on agar plates we selected individual colonies to gram stain. Below is a gram stain from the Lincoln Memorial which looks to be very gram positive and a gram stain from the tidal basin which is gram negative. Gram staining also revealed microbes in the WWII fountains that were not apparent on our agar plate.

And lastly the key to the match up game from Monday is 1-E, 2-B, 3-D, 4-A, 5-C.

Happy microbial searching, hot weather vacationing, and summer scienceing!

Monumental Microbes

We chose one of the hottest weeks on record to tour some of DC’s most iconic sites and to investigate some of its most diverse and under-the-radar inhabitants. We used Edvotek’s Kit S-30 (How Clean is the Water We Drink and the Air We Breathe) and gram staining to explored the microbial ecology of our nation’s capital. See if you can guess which community matches which monument.

*Our next post will include the answer key.

Microbial ecology without the microbes.

Today at daycare there was the dreaded sign warning parents that Streptococcus pyogenes (the bacteria that causes strep throat) had been found on the premises. This got me thinking about bacteria cultures…and jello.

Bacteria can be grown in petri dishes that have been prepared with a layer of agar and growth medium. Such cultures are used to determine the type of organism and its abundance in a sample. Consequently, this method is frequently used to help doctors determine the cause of many infectious diseases.

It’s also a key step in many synthetic biology and bitech experiments.

If your looking for a noncontagious – and maybe even delicious – way to introduce students to microbial cultures check out the easy activity below. This activity also works as a great precursor to a transformation experiment such as our Rainbow Transformation Kit as it allows students to practice essential microbial biology techniques beforehand.

For this activity you will need a pack of Jell-O®, a small tube of icing or similarly viscous liquid, water, a beaker and ten additional petri plates (or the lids from any wide mouth jar or container). You will also need ten toothpicks or inoculating loops and ten small test tubes.

  1. Make 10 Jell-O® practice petri plates.
  • In a large breaker mix Jell-O® powder and water according to the package directions.
  • Quickly pour the Jell-O® into petri plates, filling about half way.
  • Allow plates to solidify in the fridge for 30-60 minutes.
  • Add 10 dots using whatever liquid you choose. Dots may be larger than true bacterial colonies.
  1. Give each student group a plate, a toothpick or loop, and a microcentrifuge tube containing water.
  2. Challenge students to transfer all the “bacteria” colonies into the tube without breaking the Jell-O®.Screen Shot 2019-07-16 at 8.42.22 AM

Students can also practice preparing a plate by mixing the frosting and water and then spreading the mixture back onto the plate with their loop. They can even practice streaking of plate. However, for this activity we recommend switching the solutions to something like balsamic salad dressing. While this doesn’t exactly compliment the taste of jello, it does let the students see the decline in density from streak to streak because of its color and viscosity.

Happy plating.




Tips on Making Bacterial Slides

Thanks to Jordan M. one of our summer interns from Mckinley Technology High School for writing this guest post. 

Making bacteria slides is messy but can be fun! Imagine seeing all the tiny bacteria that grows that nobody gets to see. The end product is amazing and useful. Gram staining is used to help identify infections in your body and to indicate the type of bacteria. Here are some great tips that will help you make beautiful gram stained bacteria slides:

  • Make sure your slides are completely dried so you will not see water droplets under the microscope.
  • Wear protection on your hands and body to avoid getting any bacteria or dye on them and to avoid contaminating the slides. (Lab coat, goggles, closed toed shoes and gloves.)
  • Make sure to not burn your hands when holding a slide over the burner! Hold the slide by its tip and hold in the fire for about 10 seconds.
  • Use as little Gram’s crystal as possible to cover the slides.
  • If the slide is over stained, use more alcohol.
  • Make sure to pat not rub when removing water on a slide.
  • When picking up bacteria on a toothpick do not take too little (hard to see under a microscope) or too much (bacteria looks bunched up).


Here are some examples of the slides that I made during my internship at Edvotek.


This is a picture of Citrobacter frundii that I made using Gram staining.


This is a picture of Escherichia coli also with Gram stain.

Your first slides may not come out as perfect. (I had to try several times before I discovered how to make the slides just right.) However, in the end, your slides will come out looking like a real scientist. Also, the bacteria are beautiful under a microscope. You will be amazed how they look!