Data for: Can heavy metal pollution induce soil bacterial community resistance to antibiotics in boreal forests?

The emergence of microbial antibiotic resistance is a central threat to
global health, food security, and development. It has been shown that
heavy metal pollution can give rise to microbial resistance to
antibiotics, but how wide-spread this phenomenon is remains an open
question that urgently needs filling to enable appropriate environmental
risk assessments. Here, we determined whether long-term differences in
heavy metal pollution in boreal forests had affected soil microbial
communities such that they had increased microbial resistance to
antibiotics. First, we assessed variation in metal concentrations in
samples collected across a distance trajectory from the pollution source,
and also the microbial rates and levels of bacterial community resistance
to the heavy metal Cu and the antibiotics tetracycline and vancomycin in
those samples. Second, we tested if the exposure to Cu or tetracycline
could increase bacterial community resistance to Cu and to antibiotics in
soils with high versus low background levels of metal contamination. Metal
pollution had affected microbial community structures and suppressed
decomposer functioning. Importantly, bacterial community Cu resistance
increased with higher metal concentrations, which coincided with an
induced bacterial community resistance to tetracycline, but not to
vancomycin. Laboratory experiments revealed that bacterial community Cu
resistance could be further induced in both the low and high end of the
pollution gradient, but also that these short-term inductions of community
metal tolerance did not coincide with enhanced antibiotic resistance. This
yielded a surprising negative correlation between long-term and short-term
effects by metals on microbial metal and antibiotic resistances. One
mechanism that could provide protection against both metal cations and
tetracycline is the small multidrug resistance (SMR) family, which is an
energy demanding physiological mechanism that may take time to confer
protection. This may explain the different microbial responses to
long-term gradients and metal addition experiments. Policy implications.
We show that metal pollution in boreal forests will promote antibiotic
resistance in soil bacterial communities, revealing an overlooked
reservoir of antibiotic resistance. We recommend that environmental risk
assessments for any activity giving rise to increased soil metal
concentrations need to also consider the induction of microbial antibiotic
resistance.