I’m excited to showcase two agar art pieces in the spirit of Halloween!

Staphyl-o-lantern aureus:

Picture taken by Kevin Hunter

This agar art was made on the orange coloured Vogel-Johnson Agar using Staphylococcus aureus. I had to carefully time this piece, as S. aureus ferments the sugar mannitol into an acidic byproduct. The acidity causes the pH indicator in the agar to turn yellow- meaning that shortly after i took this photo, the agar turned yellow. The agar also contains tellurite which is reduced by S. aureus into metallic tellurium, which causes the bacteria to turn black!

Now the scary part about this piece isn’t the mischievous grin or the spooky eyes, but the organism I used. In medicine, a strain of Staphylococcus aureus called “MRSA”is one of the emerging pathogens that have become resistant to an entire class of antibiotics and shows increased resistance to other classes of antibiotics. This poses a huge problem in hospitals, as healthcare professionals struggle to treat MRSA with their limited antimicrobial toolkit. Luckily for me, this is unlikely to be MRSA.

Pseudomona AHH-rugenosa

Picture taken by Kevin Hunter
Picture taken by Kevin Hunter

This agar art was made on Pseudomonas Isolation Agar using Pseudomonas aeruginosa. Glycerol is used as the primary carbohydrate source, which helps promote the production of a ghastly green pigment called phycocyanin. Antibiotics present in the agar prevent growth from other species outside of the Pseudomonas family.

Pseudomonas aeruginosa produces a metabolite that is fluorescent under ultraviolet light, causing it to glow a distinct aqua green. Pseudomonas is weird in a way where it gives off a pleasant fruity smell which I would describe as either pear or grape. I cannot confirm if it tastes any good, so maybe stick to Halloween candy this year!

Happy Halloween!