Pollution induced community tolerance (PICT) to Cu2þ, and co-tolerance to nanoparticulate Cu, ionic
silver (Agþ), and vancomycin were measured in field soils treated with Cu2þ 15 years previously. EC50
values were determined using substrate induced respiration and correlations made against soil physicochemical
properties, microbial community structure, physiological status (qCO2; metabolic quotient),
and abundances of genes associated with metal and antibiotic resistance. Previous level of exposure to
copper was directly (P < 0.05) associated with tolerance to addition of new Cu2þ, and also of nanoparticle
Cu. However, Cu-exposed communities had no co-tolerance to Agþ and had increased susceptibly to
vancomycin. Increased tolerance to both Cu correlated (P < 0.05) with increased metabolic quotient,
potentially indicating that the community directed more energy towards cellular maintenance rather
than biomass production. Neither bacterial or fungal community composition nor changes in the
abundance of genes involved with metal resistance were related to PICT or co-tolerance mechanisms.