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Use of transcriptome data to study the c-di-GMP signaling network in Pseudomonas aeruginosa clinical isolates

ABSTRACT: In the Pseudomonas aeruginosa type strain PA14, 40 genes are known to encode for diguanylate cyclases (DGCs) and/or phosphodiesterases (PDEs), which modulate the intracellular pool of the nucleotide second messenger c-di-GMP. While in general, high levels of c-di-GMP drive the switch from highly motile phenotypes towards a sessile lifestyle, the different c-di-GMP modulating enzymes are responsible for smaller and in parts non-overlapping phenotypes. In this study, we sought to utilize previously recorded P. aeruginosa gene expression datasets on 414 clinical isolates to uncover transcriptional changes as a result of a high expression of genes encoding diguanylate cyclases. We demonstrate that the selection of sub-groups of clinical isolates with high versus low expression of regulatory genes served the identification of their downstream regulons. Thus, analyzing transcriptional profiles of clinical isolates with variant expression of diguanylate cyclase genes might provide a unique opportunity to bypass the problem that for many c-di-GMP modulating enzymes it is not known under which conditions their expression is activated. However, because the high c-di-GMP associated phenotypes were rapidly lost in the clinical isolates, we were unable to confirm diguanylate specific gene regulation. It is possible that the elevated c-di-GMP concentrations observed in the clinical P. aeruginosa isolates were due to a memory response, in which the bacteria maintain a certain level of c-di-GMP even after being removed from the conditions that induced the production of c-di-GMP. Further studies would be needed to determine the specific mechanisms underlying this memory response in P. aeruginosa.

ORGANISM(S): Pseudomonas aeruginosa Pseudomonas aeruginosa PAO1 Pseudomonas aeruginosa UCBPP-PA14

PROVIDER: GSE233207 | GEO | 2023/08/21

REPOSITORIES: GEO

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Project description:Bacterial lifestyles are dictated by the conditions encountered during colonization of a specific ecological niche or host. A wide range of environmental stimuli triggers sensory modules, that modify activity of proteins, or/and initiate a transfer of information in complex regulatory networks, which modulate gene expression, and therefore adaptation. The transition between planktonic and biofilm growth is dependent on the homeostasis of the intracellular second messenger c-di-GMP. High c-di-GMP levels driven by diguanylate cyclase (DGC) activity favor biofilm while low levels maintained by phosphodiesterase (PDE) enzymes encourage planktonic style or biofilm dispersal. In Pseudomonas aeruginosa over 40 PDE/DGC are involved in c-di-GMP homeostasis, including 16 dual enzymes possessing both canonical DGC and PDE motifs, i.e. GGDEF and EAL, respectively. It has been previously reported that the deletion of the PDE/DGC dual enzyme PA0285, one of 5 c-di-GMP-related enzymes conserved across all Pseudomonas species, impacts biofilms and causes elevated c-di-GMP levels in P. aeruginosa. Here we confirm that this role is conserved in various P. aeruginosa (PAO1, PA14 and PAK) and Pseudomonas putida strains. Deletion of PA0285 has the highest impact during the early stage of surface colonization, and RNA-seq analysis in biofilm context indicates that it may be associated with upregulation of cupA fimbrial genes. We demonstrate that the C-terminal portion of PA0285 encompassing the GGDEF and EAL domains binds the respective GTP (GGDEF) and c-di-GMP (EAL) substrates but only exhibits PDE activity in vitro. Both GGDEF and EAL domains are important for PA0285 PDE activity in vivo as suggested by site-directed mutants in each of the key motifs. Complementation of the PA0285 mutant strain with the C-terminal GGDEF/EAL portion in trans is not as effective as with the full-length gene suggesting that the transmembrane region and PAS domains contained in PA0285’s N-terminal portion influence its PDE activity in vivo. We speculate that the transmembrane portion or/and PAS domains of PA0285 impede its PDE activity in vivo through modulating the conformation of the enzyme, as shown for P. aeruginosa RbdA, in response to an unknown stimulus.

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Use of transcriptome data to study the c-di-GMP signaling network in Pseudomonas aeruginosa clinical isolates

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