Striking photo shows all the bacteria on an 8-year-old’s hand after playing outside

By Efrosini Costa

Striking photo shows all the bacteria on an 8-year-old’s hand after playing outside

Warning, if you are a self-confessed ‘germaphobe’ you may not want to read on!

A lab technician at Cabrillo College in California, has created an extraordinary set of images that illustrate the diverse world of microbes that lives on our skin.

This colourful petri dish is full of bacteria, yeast and fungi that were found on her 8-year-old son’s hand after he finished playing outside.

Tasha Sturm, explained the process on Microbe World, where she posted the images originally, before sending the online world into a obsessive-compulsive cleaning frenzy.

Sturm used tryptic soy agar, which forms a nutritious jelly perfect for growing microbial cultures. After her son pressed his hand gently into the gel, she incubated it and let the bacteria flourish for a few days.

Before you rush out in horror to wash your hands thoroughly, it’s worth mentioning that, though the resulting petri dish should be treated as a biohazard, having bacteria on your hands and skin is perfectly normal.

In fact, exposure to safe amounts and types of bacteria ensures a healthy ‘microbiome,’ immune system and digestive tract.

This isn’t the first time the mother-of-two has used her child’s hands to create a petri-dish of bacteria, as Sturm explained to reporters, she has printed both of her kids’ hands for years now and saves the results for microbiology classes at the college.

“I used to do my daughter’s hand until her hand became too big for the large plates and then started doing my son. I save the plates and give it to the instructors to use as a demo for the class. My kids think it is “cool” and the students like it as well.”

The varying visible structures of these bacterial colonies reflect their microscopic characteristics. Microbes with and without protective membranes or flagella (which allow them to swim) will all create colonies of different colours, shapes, textures and sizes.

Achieving the various coloured bacteria is no easy feat either. The plate needs to be cultured and incubated to get the best results — apparently some of the colonies of yeast and fungi only take on colour when they are grown at room temperature.

Determining the exact species of each of the bacteria would require further testing, but Sturm added some tentative IDs in the comment section of the original post.

White colonies are probably a form of Staphylococcus, which lives in people’s noses and skin. Most strains are harmless or even beneficial but some can cause disease when they grow where they shouldn’t, especially when they develop antibiotic resistance.

Sturm also posted two close ups of colonies that are either species of Bacillus — a common soil bacterium, though one species is responsible for making feet stinky — or a yeast.


A colony from outside the handprint, pictured below, may be contamination by Tasha Sturm herself.


Researchers are still working to explain exactly what this abundance of microbes on the body and its stunning diversity means for human health and disease. But one thing that is increasingly evident is that a germ-laden hand is perfectly normal and can even be beautiful.

Perhaps then, the photos should be appreciated rather than reviled. What do you think? Share your thoughts with us in the comments section below?


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