Community composition of bacteria isolated from Swiss banknotes varies depending on collection environment

Humans interact constantly with surfaces and associated microbial
communities in the environment. The factors shaping the composition of
these communities are poorly understood: some proposed explanations
emphasize the influence of local habitat conditions (niche-based
explanations), while others point to geographic structure and the distance
among sampled locations (dispersal-based explanations). However, the
relative roles of these different drivers for microbial community assembly
on human-associated surfaces are not clear. Here, we used a combination of
sampling, sequencing (16S rRNA) and culturing to show that the
composition of banknote-associated bacterial communities varies depending
on the local collection environment. Using banknotes collected from
various locations and types of shops across Switzerland, we found
taxonomic diversity dominated by families such
as Pseudomonadaceae and Staphylococcaceae, but
with banknote samples from particular types of shops (especially butcher
shops) having distinct community structure. By contrast, we found no
evidence of geographic structure: similarity of community composition did
not decrease with increasing distance among sampled locations. These
results show that microbial communities associated with banknotes, one of
the most commonly encountered and exchanged human-associated surfaces, can
reflect the local environmental conditions (in this case, the type of
shop), and the signal for this type of variation was stronger than that
for geographic structure among the locations sampled here.