Biology subjects

Bordi, C.

Publications and source records attributed to Bordi, C..

3 recordsLinked to original sources

bioRxiv2025

Atypical thioredoxin Patrx2 enhances alginate production in mucoid Pseudomonas aeruginosa

Pseudomonas aeruginosa, an opportunistic human pathogen, is known for its ability to respond and adapt to its environment, employing intricate adaptation mechanisms that can lead to the formation of complex biofilms. Redox processes play a pivotal role in bacterial adaptation mechanisms. The cytoplasm of most organisms is recognized for maintaining a reducing environment through thiol-disulfide oxidoreductases. In Pseudomonas aeruginosa, we have identified an unusual cytoplasmic thioredoxin named Patrx2. What sets Patrx2 apart is its active site, which contains a consensus sequence, CGHC, identical to the characteristic motif of protein disulfide isomerases (PDIs) found in eukaryotic cells. Our investigations have unveiled that Patrx2, unlike canonical thioredoxins, exhibits disulfide isomerase activity in vitro and displays physicochemical properties, as well as a structural conformation of its catalytic site, reminiscent of PDIs. Using a mutant transposon library, we found that the expression of patrx2 is regulated by the alternative sigma factor AlgU, which plays a crucial role in the formation of alginate biofilms in P. aeruginosa. We further demonstrated strong patrx2 expression in a mucoid strain we constructed, carrying the clinically relevant mucA22 mutation frequently found in cystic fibrosis patients. Furthermore, our results showed a significant decrease in alginate synthesis in a patrx2 mutant in this mucoid strain, which we attributed to its catalytic activity in a C34S variant. The study of Patrx2, an atypical thioredoxin expressed within an alginate biofilm, underscores the importance of redox regulation in adaptation mechanisms. Patrx2s involvement in alginate biosynthesis opens new pathway for inhibiting biofilm synthesis. HighlightsO_LIThe patrx2 gene is regulated by the alternative sigma factor AlgU C_LIO_LIPatrx2 is strongly produced in mucoid P. aeruginosa C_LIO_LIPatrx2 is an atypical thioredoxin with disulfide isomerase activity C_LIO_LIPatrx2 impacts alginate production in the mucoid P. aeruginosa mucA22 strain, likely through redox regulation of alginate biosynthesis. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=128 SRC="FIGDIR/small/667166v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@14f304forg.highwire.dtl.DTLVardef@1ecc15eorg.highwire.dtl.DTLVardef@8b18d9org.highwire.dtl.DTLVardef@c71b7_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2025

Pseudopaline-mediated zinc uptake by Pseudomonas aeruginosa determines specific clinically relevant phenotypes and infection outcome

AUTHOR SUMMARYThe host-pathogen interface is a biological niche in which two entities competes for essential resources. The hosts nutritional immunity restrict access to metals, while a successful pathogen overcomes these restrictions using dedicated uptake pathways. Pseudopaline is a high-affinity metallophore allowing Pseudomonas aeruginosa to acquire zinc in chelated environments. We demonstrate that this pathway is the last-resort solution to acquire zinc for this dreadful pathogen. The capacity to provide this metal to zinc-metalloproteins drives clinically relevant phenotypes, such as the capacity to form a mature and antibiotic-tolerant biofilm, or to affect the outcome of an infection. These results place pseudopaline as a potential drug target for blocking P. aeruginosa pathogenic capacity and resensitizing established biofilm to classic antibiotic treatment. ABSTRACTBiological metals are essential trace elements which are required by metalloproteins, involved in virtually every cellular, structural and catalytic function of the bacterial cell. Bacterial pathogenesis involves a tug-of-war between the host nutritional immunity, sequestering essential metals and the invading pathogens that deploy high-metal affinity uptake strategies in order to overcome these defence mechanisms. Metallophores are high-affinity, low-molecular mass metal chelators produced and secreted by bacteria to access chelated metals from the environment. Pseudopaline is a metallophore produced and secreted by Pseudomonas aeruginosa to acquire zinc when the bioavailability of this metal is severely restricted, as in the presence of a strong metal chelator such as EDTA, or during infections when the nutritional immunity of the host is active, in mammals through the production of the zing binding protein calprotectin. We show that under the conditions of metal deprivation, a pseudopaline-deficient P. aeruginosa strain exhibit a severe intracellular zinc deficiency, establishing that the pseudopaline pathway is the last-resort and unique pathway for the bacteria to acquire zinc under these restricted growth conditions. The present study explores the pleiotropic role of pseudopaline-mediated zinc acquisition on several clinically relevant phenotypes and its capacity to drive infection outcomes, placing this machinery as a promising therapeutic target for P. aeruginosas infection, acting synergistically as a pathogenicity determinant as well as an adaptative trait allowing the establishment of a mature and antibiotic resistance biofilm necessary for recalcitrant chronic infections.

microbiology↗

bioRxiv2017

c-di-GMP-linked phenotypes are modulated by the interaction between a diguanylate cyclase and a polar hub protein

c-di-GMP is a major player in the decision between biofilm and motile lifestyles. Several bacteria present a large number of c-di-GMP metabolizing proteins, thus a fine-tuning of this nucleotide levels may occur. It is hypothesized that some c-di-GMP metabolizing proteins would provide the global c-di-GMP levels inside the cell whereas others would maintain a localized pool, with the resulting c-di-GMP acting at the vicinity of its production. Although attractive, this hypothesis has yet to be proven in Pseudomonas aeruginosa. We found that the diguanylate cyclase DgcP interacts with the cytosolic region of FimV, a peptidoglycan-binding protein involved in type IV pilus assembly. Moreover, DgcP is located at the cell poles in wild type cells, but scattered in the cytoplasm of cells lacking FimV. Overexpression of DgcP leads to the classical phenotypes of high c-di-GMP levels (increased biofilm and impaired motilities) in the wild-type strain, but not in a AfimV background. Therefore, our findings strongly suggest that DgcP is regulated by FimV and may provide the local c-di-GMP pool that can be sensed by other proteins at the cell pole, bringing to light a specialized function for a specific diguanylate cyclase.

microbiology↗