Bacteria resist copper (Cu) stress
by implementing several metabolic
mechanisms. However, these mechanisms are not fully understood. We
investigated the mechanism of Cu resistance in Cupriavidus
gilardii CR3, a Cu-resistant bacterium with a fully sequenced,
annotated genome. The growth of CR3 was inhibited by higher Cu concentrations
(≥1.0 mM) but not by lower ones (≤0.5 mM). CR3 accumulated
Cu intracellularly (ratios of intercellular to extracellular Cu were
11.6, 4.24, and 3.9 in 0.1, 0.5, and 1.5 mM Cu treatments, respectively).
A comparative transcriptome analysis of CR3 respectively revealed
310 and 413 differentially expressed genes under 0.5 and 1.5 mM Cu
stress, most of which were up-regulated under Cu treatment. Gene Ontology
and Kyoto Encyclopedia of Genes and Genomes functional enrichment
analyses uncovered several genotype-specific biological processes
related to Cu stress. Besides revealing known Cu resistance-related
genes, our global transcriptomics approach indicated that sulfur metabolism,
iron–sulfur cluster, and cell secretion systems are involved
in mediating Cu resistance in strain CR3. These results suggest that
bacteria collectively use multiple systems to cope with Cu stress.
Our findings concerning the global transcriptome response to Cu stress
in CR3 provide new information for understanding the intricate regulatory
network of Cu homeostasis in prokaryotes.