Global Analysis of the Zinc Homeostasis Network in Pseudomonas aeruginosa and Its Gene Expression Dynamics

Abstract

Zinc is one of the most important trace elements for life and its deficiency, like its excess, can be fatal. In the bacterial opportunistic pathogen Pseudomonas aeruginosa, Zn homeostasis is not only required for survival, but also for virulence and antibiotic resistance. Thus, the bacterium possesses multiple Zn import/export/storage systems. In this work, we determine the expression dynamics of the entire P. aeruginosa Zn homeostasis network at both transcript and protein levels. Precisely, we followed the switch from a Zn-deficient environment, mimicking the initial immune strategy to counteract bacterial infections, to a Zn-rich environment, representing the phagocyte metal boost used to eliminate an engulfed pathogen. Thanks to the use of the NanoString technology, we timed the global silencing of Zn import systems and the orchestrated induction of Zn export systems. We show that the induction of Zn export systems is hierarchically organized as a function of their impact on Zn homeostasis. Moreover, we identify PA2807 as a novel Zn resistance component in P. aeruginosa and highlight new regulatory links among Zn-homeostasis systems. Altogether, this work unveils a sophisticated and adaptive homeostasis network, which complexity is key in determining a pathogen spread in the environment and during host-colonization.

Activity of N -Acetylcysteine Alone and in Combination with Colistin against Pseudomonas aeruginosa Biofilms and Transcriptomic Response to N -Acetylcysteine Exposure

“…Analysis of DEGs revealed that NAC mainly acted as Zn 2+ chelator, inducing a strong Zn 2+ starvation response. DEGs associated with such response were consistent with data reported in previous studies addressing zinc homeostasis in P. aeruginosa and other bacteria ( Table 2 ) ( 17 – 22 ). In particular, 31 of the 46 upregulated DEGs belonged to the zur regulon and are known to be activated in response to Zn 2+ starvation ( Table 2 ) ( 17 – 22 ).…”

“…DEGs associated with such response were consistent with data reported in previous studies addressing zinc homeostasis in P. aeruginosa and other bacteria ( Table 2 ) ( 17 – 22 ). In particular, 31 of the 46 upregulated DEGs belonged to the zur regulon and are known to be activated in response to Zn 2+ starvation ( Table 2 ) ( 17 – 22 ). Such genes mainly included operons involved in zinc uptake (e.g., the PA4063-PA4064-PA4065-PA4066 operon, cntOLMI operon, and znuABC operon) and genes encoding zinc-independent paralogs of cellular proteins (i.e., type B 50S ribosomal proteins L31 and L36, RNA polymerase-binding protein DksA2, adn GTP-cyclohydrolase FolE2) ( Table 2 ) ( 17 – 23 ).…”

“…In particular, 31 of the 46 upregulated DEGs belonged to the zur regulon and are known to be activated in response to Zn 2+ starvation ( Table 2 ) ( 17 – 22 ). Such genes mainly included operons involved in zinc uptake (e.g., the PA4063-PA4064-PA4065-PA4066 operon, cntOLMI operon, and znuABC operon) and genes encoding zinc-independent paralogs of cellular proteins (i.e., type B 50S ribosomal proteins L31 and L36, RNA polymerase-binding protein DksA2, adn GTP-cyclohydrolase FolE2) ( Table 2 ) ( 17 – 23 ). Upregulated DEGs belonging to the zur regulon also included genes encoding an N -acetylmuramoyl- l -alanine amidase (AmiA, involved in splitting of septal peptidoglycan during cell division), a γ-carbonic anhydrase (Cam, involved in reversible hydration of carbon dioxide and important for growth under low-CO 2 conditions), and three modulators of the membrane FtsH protease (i.e., HflC and HflK family modulators) ( Table 2 ).…”

A Zur-mediated transcriptional regulation of the zinc export system

“…It is vital for cells and must always be present in sufficient amounts, but can become toxic as soon as it exceeds a threshold (17). In the bacterium P. aeruginosa , eight zinc import and four zinc export systems have been described (4). In case of zinc excess, the Zur protein represses the expression of many import systems, thus preventing too much Zn from entering the cell.…”

“…In the Gram-negative bacterium Pseudomonas aeruginosa , several systems are involved in Zn homeostasis (4,5). Zn import into the periplasm is mediated by TonB-dependent importers such as ZnuD.…”