Survival and Growth in the Presence of Elevated Copper: Transcriptional Profiling of Copper-Stressed Pseudomonas aeruginosa

Abstract

Transcriptional profiles of Pseudomonas aeruginosa exposed to two separate copper stress conditions were determined. Actively growing bacteria subjected to a pulse of elevated copper for a short period of time was defined as a "copper-shocked" culture. Conversely, copper-adapted populations were defined as cells actively growing in the presence of elevated copper. Expression of 405 genes changed in the copper-shocked culture, compared to 331 genes for the copper-adapted cultures. Not surprisingly, there were genes identified in common to both conditions. For example, both stress conditions resulted in up-regulation of genes encoding several active transport functions. However, there were some interesting differences between the two types of stress. Only copper-adapted cells significantly altered expression of passive transport functions, down-regulating expression of several porins belonging to the OprD family. Copper shock produced expression profiles suggestive of an oxidative stress response, probably due to the participation of copper in Fenton-like chemistry. Copper-adapted populations did not show such a response. Transcriptional profiles also indicated that iron acquisition is fine-tuned in the presence of copper. Several genes induced under iron-limiting conditions, such as the siderophore pyoverdine, were up-regulated in copper-adapted populations. Interesting exceptions were the genes involved in the production of the siderophore pyochelin, which were down-regulated. Analysis of the copper sensitivity of select mutant strains confirmed the array data. These studies suggest that two resistance nodulation division efflux systems, a P-type ATPase, and a two-component regulator were particularly important for copper tolerance in P. aeruginosa.

Heavy Metal Resistance Strategies of Acidophilic Bacteria and Their Acquisition: Importance for Biomining and Bioremediation

“…Thus the properties of OMP40 would not only be a passive strategy as already mentioned but would function together with other envelope proteins such as a new RND-type effl ux pump and a putative periplasmic disulfi de isomerase, both being apparently regulated copper-resistance determinants in this extremophile (Almárcegui et al, 2013b). A similar result has been observed in Pseudomonas aeruginosa, in which a reduced expression of eight diff erent porins was seen when cells were exposed to copper (Teitzel et al, 2006).…”

CtpA, a Copper-translocating P-type ATPase Involved in the Biogenesis of Multiple Copper-requiring Enzymes

“…This indicates that CtpA is not required for copper tolerance and suggests that other pumps involved in this process exist in these bacteria to respond to excess copper. In Pseudomonas aeruginosa, which possesses two operons encoding cbb 3 and a homologue of ctpA (PA1549), the PA1549 mutant did not show any phenotype in excess copper (27). More recently, expression of ctpA (PA1549) in the copper-sensitive strain of E. coli (GG44) did not restore resistance to copper (28).…”

“…The only available supporting argument is provided by the copper transcriptome of P. aeruginosa. CtpA (PA1549) was not induced by excess copper, whereas CopA (PA3920) and other heavy metal trans- locating P-type ATPases involved in copper tolerance were induced more than 5-fold (27). Therefore, it will be interesting to constitutively express the ctpA gene in a copA Ϫ background of R. gelatinosus to test whether it can restore growth in excess copper.…”

Pseudomonas Aeruginosa AmpR Transcriptional Regulatory Network

“…The most strongly downregulated genes were the iron acquisition genes, mostly those repressed by Fur, the iron-uptake regulator. One of the downregulated transcriptional regulators, PA3410, encodes a probable extracellular sigma factor (157). The upregulated genes included mostly hypothetical genes, and a bacterioferritin involved in iron storage.…”

“…genes; (157)]. Genes involved in active efflux of copper included transporters, copper oxidase, periplasmic thiol-disulfide interchange proteins, lyases, and transcriptional regulators.…”