Deciphering the Enigmatic Function of Pseudomonas Metallothioneins

Habjanič, Jelena; Mathew, Anugraha; Eberl, Leo; Freisinger, Eva

doi:10.3389/fmicb.2020.01709

Cited by 20 publications

(11 citation statements)

References 40 publications

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“…The decrease in Cd accumulation in fish tissues observed after feeding on A. cepa-based diets could be attributed to its high flavonoid content, such as quercetin, which can increase the production of metallothioneins (Weng et al 2011;Sagar et al 2022). These proteins have substantial protective roles in detoxifying metals in aquatic animals (Habjanič et al 2020).…”

Section: Discussionmentioning

confidence: 99%

Onion (Allium cepa) improves Nile tilapia (Oreochromis niloticus) resistance to saprolegniasis (Saprolegnia parasitica) and reduces immunosuppressive effects of cadmium

et al. 2022

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The present study investigated the protective effects of dietary Allium cepa against Saprolegnia parasitica infections and the amelioration of cadmium-induced immunosuppression in Oreochromis niloticus. Saprolegnia isolates were recovered during an outbreak of saprolegniasis in farmed O. niloticus raised in a poor aquatic environment. Isolates were identified phenotypically as S. parasitica. Results were confirmed further by ITS gene sequencing. Four fish groups were kept in water with cadmium (1.5 mg/L) and fed for 30 days on a diet supplemented with crude or alcoholic extracts of A. cepa using two concentrations (0.5% or 1%). Positive (with Cd) and negative (without Cd) control fish groups were given the basal diet. The 96 h LC50 value of Cd in tilapia was (15.1 mg/L Cd). Fish exposed to Cd showed poor growth performance parameters, abnormal biochemical measurements, impaired immunological responses, and high oxidative stress indicators. Feeding tilapia on A. cepa-supplemented diets enhanced their growth performance (WG, SGR) and improved the nonspecific immune responses (WBCs, total protein, globulins, lysozyme, myeloperoxidase, and antiproteases). The inclusion of A. cepa in the diets reduced the oxidative stress (GST, SOD) and significantly decreased fish mortality after the challenge with S. parasitica. Dietary supplementation with A. cepa reduced cadmium accumulation in fish organs and up-regulated IL-1β and IFNɣ levels. The most favorable benefits were obtained by the addition of 0.5% A. cepa extract. Our results highlight the immunostimulatory properties of A. cepa dietary supplementation for farmed tilapia and recommend its use prophylactically to control saprolegniasis and mitigate cadmium adverse effects.

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Section: Discussionmentioning

confidence: 99%

Onion (Allium cepa) improves Nile tilapia (Oreochromis niloticus) resistance to saprolegniasis (Saprolegnia parasitica) and reduces immunosuppressive effects of cadmium

et al. 2022

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“…Analysis of the genomic organization of other prokaryotic MTs like Pseudomonas MT also revealed an absence of regulatory protein adjacent to the Pseudomonas fluorescens Q2-87 MT locus. Also, the genes adjacent to the Pseudomonas MT gene code for proteins of unknown function ( Habjanič et al, 2020 ). Genomic arrangement of MT and its regulator as operons apparently is not mandatory as such regulators function as trans -acting factors on cis- regulatory elements.…”

Section: Resultsmentioning

confidence: 99%

AzuR From the SmtB/ArsR Family of Transcriptional Repressors Regulates Metallothionein in Anabaena sp. Strain PCC 7120

Divya

Acharya

2022

Front. Microbiol.

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Metallothioneins (MTs) are cysteine-rich, metal-sequestering cytosolic proteins that play a key role in maintaining metal homeostasis and detoxification. We had previously characterized NmtA, a MT from the heterocystous, nitrogen-fixing cyanobacterium Anabaena sp. strain PCC 7120 and demonstrated its role in providing protection against cadmium toxicity. In this study, we illustrate the regulation of Anabaena NmtA by AzuR (Alr0831) belonging to the SmtB/ArsR family of transcriptional repressors. There is currently no experimental evidence for any functional role of AzuR. It is observed that azuR is located within the znuABC operon but in the opposite orientation and remotely away from the nmtA locus. Sequence analysis of AzuR revealed a high degree of sequence identity with Synechococcus SmtB and a distinct α5 metal binding site similar to that of SmtB. In order to characterize AzuR, we overexpressed it in Escherichia coli and purified it by chitin affinity chromatography. Far-UV circular dichroism spectroscopy indicated that the recombinant AzuR protein possessed a properly folded structure. Glutaraldehyde cross-linking and size-exclusion chromatography revealed that AzuR exists as a dimer of ∼28 kDa in solution. Analysis of its putative promoter region [100 bp upstream of nmtA open reading frame (ORF)] identified the presence of a 12–2–12 imperfect inverted repeat as the cis-acting element important for repressor binding. Electrophoretic mobility shift assays (EMSAs) showed concentration-dependent binding of recombinant dimeric AzuR with the promoter indicating that NmtA is indeed a regulatory target of AzuR. Binding of AzuR to DNA was disrupted in the presence of metal ions like Zn2+, Cd2+, Cu2+, Co2+, Ni2+, Pb2+, and Mn2+. The metal-dependent dissociation of protein–DNA complexes suggested the negative regulation of metal-inducible nmtA expression by AzuR. Overexpression of azuR in its native strain Anabaena 7120 enhanced the susceptibility to cadmium stress significantly. Overall, we propose a negative regulation of Anabaena MT by an α5 SmtB/ArsR metalloregulator AzuR.

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“…Instead, the predicted operon includes two genes, one with unknown function and putatively short-chain dehydrogenase (Mao et al, 2009). In addition, Habjanič et al (2020) noted that PflQ2 MT expression was elevated during stationary phase with or without the addition of metals in P. fluorescens Q2-87. The addition of metals at exponential phase did not induce transcription of MT, and increasing metal concentrations resulted in a decline in growth.…”

Section: Discussionmentioning

confidence: 99%

PmtA Regulates Pyocyanin Expression and Biofilm Formation in Pseudomonas aeruginosa

et al. 2021

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The opportunistic pathogen Pseudomonas aeruginosa expresses a small molecular weight, cysteine-rich protein (PmtA), identified as a metallothionein (MT) protein family member. The MT family proteins have been well-characterized in eukaryotes as essential for zinc and copper homeostasis, protection against oxidative stress, and the ability to modify a variety of immune activities. Bacterial MTs share sequence homology, antioxidant chemistry, and heavy metal-binding capacity with eukaryotic MTs, however, the impact of bacterial MTs on virulence and infection have not been well-studied. In the present study, we investigated the role of PmtA in P. aeruginosa PAO1 using a PmtA-deficient strain (ΔpmtA). Here we demonstrated the virulence factor, pyocyanin, relies on the expression of PmtA. We showed that PmtA may be protective against oxidative stress, as an alternative antioxidant, glutathione, can rescue pyocyanin expression. Furthermore, the expression of phzM, which encodes a pyocyanin precursor enzyme, was decreased in the ΔpmtA mutant during early stationary phase. Upregulated pmtA expression was previously detected in confluent biofilms, which are essential for chronic infection, and we observed that the ΔpmtA mutant was disrupted for biofilm formation. As biofilms also modulate antibiotic susceptibility, we examined the ΔpmtA mutant susceptibility to antibiotics and found that the ΔpmtA mutant is more susceptible to cefepime and ciprofloxacin than the wild-type strain. Finally, we observed that the deletion of pmtA results in decreased virulence in a waxworm model. Taken together, our results support the conclusion that PmtA is necessary for the full virulence of P. aeruginosa and may represent a potential target for therapeutic intervention.

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Deciphering the Enigmatic Function of Pseudomonas Metallothioneins

Cited by 20 publications

References 40 publications

Onion (Allium cepa) improves Nile tilapia (Oreochromis niloticus) resistance to saprolegniasis (Saprolegnia parasitica) and reduces immunosuppressive effects of cadmium

Onion (Allium cepa) improves Nile tilapia (Oreochromis niloticus) resistance to saprolegniasis (Saprolegnia parasitica) and reduces immunosuppressive effects of cadmium

AzuR From the SmtB/ArsR Family of Transcriptional Repressors Regulates Metallothionein in Anabaena sp. Strain PCC 7120

PmtA Regulates Pyocyanin Expression and Biofilm Formation in Pseudomonas aeruginosa

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