Seasonal Bacterial Hand Prints

I have had the opportunity to work with several 4th grade classes doing handprints on large TSA plate.  Over the past two years I started noticing differences in the bacterial growth during different environmental conditions.  As can be seen in the images above warm dry weather flora was different from cold wet (cold being 13 degree's C) flora.  The warmer prints had an abundance of large spreading Bacillus spp (possible subtilis, cereus or megatarium), environmental yeast (orange/red Rhodotorula, yellow unknown).  The cold prints seemed to lack the large spreading colonies of Bacillus but replaced by a smaller mucoid species of Bacillus,  The rhizoid Bacillus mycodies (not seen on the warm weather plates) was seen with little to no environmental  Rhodotorula , yellow unidentified yeast was still seen but not as abundant.  Large TSA plates were grown for 24-48 hrs at 37 degree's C, then incubated at room room temperature for 48 + hrs then held at refrigerated temperature for up to month.  Each incubation temperature and time period allows the different bacteria and fungi to grow and develop pigmentation.  Most of the yellow and orange yeast develop better pigmentation and continue to grow at refrigerated temperatures.
 I

Enlarged Warm Bacterial Hand Print





Enlarged image of warm weather Bacillus spp seen on the finger tip.  Note that this Bacillus is spreading and mucoid.




Enlarge image of a different warm weather plate showing the vibrant coloration of the various yeast spp as well as possible Staph aureus/epidermidis.



 Rhodutrula was subcultured.  There was no growth at 37 degree's C but good growth seen at 4 degree's C







Light orange colonies were subcultured (a) and (b) gram stained.  Colonies grew at 37 degree's C after 24 hrs and had a G+ gram stain with showing thin G+ rods.

(a)


(b)







Enlarged cold weather plate.  Yellow colonies are possible Staphylococcus aureus as well as numerous colonies of Bacillus mycodies starting to show characteristic rhizoid branching growth.  The below image is a close up of a more mature colony of Bacillus mycodies.


Bacillus mycodies seen on cold weather print.  Note that this species is rhizoid and alway "swirls" in the same direction looking like a crooked finger, is beige and matt in texture.  There is yellow pigmentation seen in the environmental yeast, along with normal body flora (white colonies) of Staph spp.  This image was taken from a hand print in the warmer months and is unusual and more common in the cooler months.


Yellow colonies were (a) subcultured and grew at 37 degree's C as well as 4 degree's C and Gram stained (b).  Gram stain showed large oval budding cells, arrangement looked like Mickey mouse ears.

(a)



(b)







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All images copyright T. Sturm





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