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Microbial Biodiversity of Cell Phones and Shoes
The results are in!
So, what lives on reporters’ cell phones and shoes, you ask? As, you can see from the graph at left, quite a lot! Each vertical bar is one shoe or cell phone, and each color represents a different species of bacteria. The larger the colored block, the more prevalent the species. The most predominant species include:
Mycoplasma (beige) – one of the smallest cells (0.1 μm diameter), also characterized by its resistance to antibiotics and role in respiratory illnesses including pneumonia.
Moraxellaceae (fuchsia) – this family includes the causative agent of pink eye in cattle and human respiratory tract antibiotic-resistant pathogens.
Sphingomonadaceae (orange) – widespread family of bacteria which can be found in both marine and terrestrial habitats. Some species are able to rapidly degrade plastics in landfills.
Streptophyta (purple) – a cyanobacterium, this microbe uses photosynthesis in a manner similar to plants.
Flavobacteriaceae (pink) – a group associated with diseases in fish, such as rainbow trout fry syndrome and bacterial cold water disease
You can click here to download detailed taxonomy counts and high-resolution images of this visualization.
*Note: The above descriptions of bacterial groups serve to highlight interesting features of very broad and diverse lineages; finding Mycoplasma and Moraxellaceae in these samples does not indicate an outbreak of pneumonia and pink eye.
Interestingly, many of the bacteria from these samples were unidentifiable; the light blue and red sections at the bottom of each bar represent species which could only be classified as “Bacteria” (as opposed to Archean or Eukarya) or which could not be classified at all.
You may also have noticed the alternating trends in this figure – that if you numbered the bars from left to right, that the even-numbered bars are different from the odd-numbered bars. This is because the odd-numbered bars represent bacteria from shoe soles and the even-numbered bars represent bacteria from cell phones! When you can see these trends with the unaided eye, you know you are onto something. And indeed, interrogating thebeta diversity of these samples using principle coordinate analysis tools (at right) reveals that bacterial populations group according to the surface they were sampled from.
These groupings belie that fact that some species are more common to cell phones and others are more common to shoes – to such a degree that you can take a “mystery swab” and, by examining the bacteria it contains, determine if it was used on a cell phone or shoe. So, you might ask, how are these communities different? What bacteria live on a shoe but not on a cell phone? From this study, there appear to be 56 species which statistically favor one environment over the other. Oddly, only four of the 56 prefer the cell phone environment. They are:
Mycoplasma – 52% of phone bacteria vs 20% of shoe bacteria (q-value = 1E-8)
Streptococcaceae – 2.44% vs 0.94% (q-value = 0.016) – some subspecies are responsible for strep throat and meningitis.
Fusobacteriaceae – 0.26% vs 0.07% (q-value = 0.027) – pathogenic bacterium of the throat.
Neisseriaceae – 0.55% vs 0.11% (q-value = 0.040) – can cause gonorrhea and meningitis.
The four most abundant species that favored growing on shoes were:
Moraxellaceae – 6.8% of shoe bacteria vs 2.9% of phone bacteria (q-value = 8E-5) – as described above.
Unidentified Gammaproteobacteria – 2.7% vs 1.6% (q-value = 5E-4) – very diverse class of bacteria – includes E. coli, Vibrio, and Salmonella.
Unidentified Actinomycetales – 2.8% vs 1.4% (q-value = 5E-3) – a group of gram-positive bacteria used in the production of drugs for treating cancer and infections.
In summary, the cell phone in your pocket and the shoes on your feet are home to a diverse collection of bacteria. What’s more, the bacteria on your cell phone look a lot like the bacteria on other people’s cell phones, and the bacteria on your shoes are similar to those on the shoes of those around you. However, the microbial communities on your cell phone are distinct from the ones on your shoes. And although many of the bacteria that call you home are closely related to disease-causing pathogens, these microbes are in fact defending you from their more dangerous cousins. So next time you see something sticky on the ground, instead of walking around it, go ahead and give them a treat ;-)
Major components of this analysis were conducted using QIIME, a free and open-source software package available from http://www.qiime.org/. Funding for this project was provided by the Alfred P. Sloan Foundation through the University of Chicago and Argonne National Laboratory. Questions about this study may be directed to Daniel Smith at firstname.lastname@example.org or posted in the comment section below.