The “Little Iron Waltz”: The Ternary Response of Paracoccidioides spp. to Iron Deprivation

Paracoccidioides is a genus of thermodimorphic fungi that causes paracoccidioidomycosis. When in the host, the fungus undergoes several challenges, including iron deprivation imposed by nutritional immunity. In response to the iron deprivation triggered by the host, the fungus responds in a ternary manner using mechanisms of high affinity and specificity for the uptake of Fe, namely non-classical reductive iron uptake pathway, uptake of host iron proteins, and biosynthesis and uptake of siderophores. This triple response resembles the rhythmic structure of a waltz, which features three beats per compass. Using this connotation, we have constructed this review summarizing relevant findings in this area of study and pointing out new discoveries and perspectives that may contribute to the expansion of this “little iron waltz”.

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Ferrous Iron Uptake in Cryptococcus neoformans

Infection and Immunity ◽

10.1128/iai.66.9.4169-4175.1998 ◽

1998 ◽

Vol 66 (9) ◽

pp. 4169-4175 ◽

Cited By ~ 40

Author(s):

Eric S. Jacobson ◽

Asha Prasad Goodner ◽

Karin J. Nyhus

Keyword(s):

Cryptococcus Neoformans ◽

Iron Uptake ◽

Opportunistic Pathogen ◽

Metabolic Energy ◽

Yeast Cells ◽

Ferric Reductase ◽

High Affinity ◽

Steep Rise ◽

Uptake Pathway ◽

Uptake Activity

ABSTRACT Previous studies have implicated ferric reduction in the iron uptake pathway of the opportunistic pathogen Cryptococcus neoformans. Here we studied iron uptake directly, using55Fe in the presence of reductants. Uptake was linear with respect to time and number of yeast cells. The plot of uptake versus concentration exhibited a steep rise up to about 1 μM, a plateau between 1 and 25 μM, and a second steep rise above 25 μM, consistent with high- and low-affinity uptake systems. AKm for high-affinity uptake was estimated to be 0.6 μM Fe(II); 1 μM was used for standardized uptake assays. At this concentration, the uptake rate was 110 ± 3 pmol/106 cells/h. Iron repletion (15 μM) and copper starvation drastically decreased high-affinity iron uptake. Incubation at 0°C or in the presence of 2 mM KCN abolished high-affinity iron uptake, suggesting that uptake requires metabolic energy. When exogenous reducing agents were not supplied and the culture was washed free of secreted reductants, uptake was reduced by 46%; the remaining uptake activity presumably was dependent upon the cell membrane ferric reductase. Further decreases in free Fe(II) levels achieved by trapping with bathophenanthroline disulfonate or reoxidizing with potassium nitrosodisulfonate reduced iron uptake very drastically, suggesting that it is the Fe(II) species which is transported by the high-affinity transporter. The uptake of Fe was stimulated two- to threefold by deferoxamine, but this increment could be abolished by copper starvation or inhibition of the ferric reductase by Pt, indicating that Fe solubilized by this molecule also entered the reductive iron uptake pathway.

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The Fish Pathogen Vibrio ordalii Under Iron Deprivation Produces the Siderophore Piscibactin

Microorganisms ◽

10.3390/microorganisms7090313 ◽

2019 ◽

Vol 7 (9) ◽

pp. 313 ◽

Cited By ~ 3

Author(s):

Pamela Ruiz ◽

Miguel Balado ◽

Juan Carlos Fuentes-Monteverde ◽

Alicia E. Toranzo ◽

Jaime Rodríguez ◽

...

Keyword(s):

Gene Cluster ◽

Iron Uptake ◽

Peptide Mass Fingerprinting ◽

Iron Limitation ◽

Fish Pathogen ◽

Fish Pathogens ◽

Iron Deprivation ◽

Peptide Mass ◽

Photobacterium Damselae ◽

Vibrio Ordalii

Vibrio ordalii is the causative agent of vibriosis, mainly in salmonid fishes, and its virulence mechanisms are still not completely understood. In previous works we demonstrated that V. ordalii possess several iron uptake mechanisms based on heme utilization and siderophore production. The aim of the present work was to confirm the production and utilization of piscibactin as a siderophore by V. ordalii. Using genetic analysis, identification by peptide mass fingerprinting (PMF) of iron-regulated membrane proteins and chemical identification by LC-HRMS, we were able to clearly demonstrate that V. ordalii produces piscibactin under iron limitation. The synthesis and transport of this siderophore is encoded by a chromosomal gene cluster homologous to another one described in V. anguillarum, which also encodes the synthesis of piscibactin. Using β-galactosidase assays we were able to show that two potential promoters regulated by iron control the transcription of this gene cluster in V. ordalii. Moreover, biosynthetic and transport proteins corresponding to piscibactin synthesis and uptake could be identified in membrane fractions of V. ordalii cells grown under iron limitation. The synthesis of piscibactin was previously reported in other fish pathogens like Photobacterium damselae subsp. piscicida and V. anguillarum, which highlights the importance of this siderophore as a key virulence factor in Vibrionaceae bacteria infecting poikilothermic animals.

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Pyoverdine-Mediated Iron Uptake in Pseudomonas aeruginosa: the Tat System Is Required for PvdN but Not for FpvA Transport

Journal of Bacteriology ◽

10.1128/jb.188.9.3317-3323.2006 ◽

2006 ◽

Vol 188 (9) ◽

pp. 3317-3323 ◽

Cited By ~ 39

Author(s):

Romé Voulhoux ◽

Alain Filloux ◽

Isabelle J. Schalk

Keyword(s):

Pseudomonas Aeruginosa ◽

Outer Membrane ◽

Iron Uptake ◽

Cytoplasmic Membrane ◽

Signal Sequence ◽

Iron Release ◽

Outer Membrane Receptor ◽

Uptake Pathway ◽

Uptake Process ◽

Tat System

ABSTRACT Under iron-limiting conditions, Pseudomonas aeruginosa PAO1 secretes a fluorescent siderophore called pyoverdine (Pvd). After chelating iron, this ferric siderophore is transported back into the cells via the outer membrane receptor FpvA. The Pvd-dependent iron uptake pathway requires several essential genes involved in both the synthesis of Pvd and the uptake of ferric Pvd inside the cell. A previous study describing the global phenotype of a tat-deficient P. aeruginosa strain showed that the defect in Pvd-mediated iron uptake was due to the Tat-dependent export of proteins involved in Pvd biogenesis and ferric Pvd uptake (U. Ochsner, A. Snyder, A. I. Vasil, and M. L. Vasil, Proc. Natl. Acad. Sci. USA 99:8312-8317, 2002). Using biochemical and biophysical tools, we showed that despite its predicted Tat signal sequence, FpvA is correctly located in the outer membrane of a tat mutant and is fully functional for all steps of the iron uptake process (ferric Pvd uptake and recycling of Pvd on FpvA after iron release). However, in the tat mutant, no Pvd was produced. This suggested that a key element in the Pvd biogenesis pathway must be exported to the periplasm by the Tat pathway. We located PvdN, a still unknown but essential component in Pvd biogenesis, at the periplasmic side of the cytoplasmic membrane and showed that its export is Tat dependent. Our results further support the idea that a critical step of the Pvd biogenesis pathway involving PvdN occurs at the periplasmic side of the cytoplasmic membrane.

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Regulation of Copper Metabolism by Nitrogen Utilization in Saccharomyces cerevisiae

Journal of Fungi ◽

10.3390/jof7090756 ◽

2021 ◽

Vol 7 (9) ◽

pp. 756

Author(s):

Suzie Kang ◽

Hyewon Seo ◽

Min-Gyu Lee ◽

Cheol-Won Yun

Keyword(s):

Saccharomyces Cerevisiae ◽

Iron Uptake ◽

Nitrogen Starvation ◽

Copper Metabolism ◽

Nitrogen Utilization ◽

Deletion Mutants ◽

Uptake System ◽

Wild Type ◽

High Affinity ◽

Uptake Activity

To understand the relationship between carbon or nitrogen utilization and iron homeostasis, we performed an iron uptake assay with several deletion mutants with partial defects in carbon or nitrogen metabolism. Among them, some deletion mutants defective in carbon metabolism partially and the MEP2 deletion mutant showed lower iron uptake activity than the wild type. Mep2 is known as a high-affinity ammonia transporter in Saccharomyces cerevisiae. Interestingly, we found that nitrogen starvation resulted in lower iron uptake activity than that of wild-type cells without downregulation of the genes involved in the high-affinity iron uptake system FET3/FTR1. However, the gene expression of FRE1 and CTR1 was downregulated by nitrogen starvation. The protein level of Ctr1 was also decreased by nitrogen starvation, and addition of copper to the nitrogen starvation medium partially restored iron uptake activity. However, the expression of MAC1, which is a copper-responsive transcriptional activator, was not downregulated by nitrogen starvation at the transcriptional level but was highly downregulated at the translational level. Mac1 was downregulated dramatically under nitrogen starvation, and treatment with MG132, which is an inhibitor of proteasome-dependent protein degradation, partially attenuated the downregulation of Mac1. Taken together, these results suggest that nitrogen starvation downregulates the high-affinity iron uptake system by degrading Mac1 in a proteasome-dependent manner and eventually downregulates copper metabolism.

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Yeast protective response to arsenate involves the repression of the high affinity iron uptake system

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research ◽

10.1016/j.bbamcr.2012.12.018 ◽

2013 ◽

Vol 1833 (5) ◽

pp. 997-1005 ◽

Cited By ~ 7

Author(s):

Liliana Batista-Nascimento ◽

Michel B. Toledano ◽

Dennis J. Thiele ◽

Claudina Rodrigues-Pousada

Keyword(s):

Iron Uptake ◽

Uptake System ◽

Protective Response ◽

High Affinity ◽

Iron Uptake System

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Modulation of Symbiotic Compatibility by Rhizobial Zinc Starvation Machinery

mBio ◽

10.1128/mbio.03193-19 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Pan Zhang ◽

Biliang Zhang ◽

Jian Jiao ◽

Shi-Qi Dai ◽

Wen-Xin Chen ◽

...

Keyword(s):

Sustainable Agriculture ◽

Host Range ◽

Zinc Transporter ◽

Zinc Homeostasis ◽

Broad Host Range ◽

Host Immune System ◽

High Affinity ◽

Nutritional Immunity ◽

Accessory Genes ◽

Legume Symbiosis

ABSTRACT Pathogenic bacteria need high-affinity zinc uptake systems to counteract the nutritional immunity exerted by infected hosts. However, our understanding of zinc homeostasis in mutualistic systems such as the rhizobium-legume symbiosis is limited. Here, we show that the conserved high-affinity zinc transporter ZnuABC and accessory transporter proteins (Zip1, Zip2, and c06450) made cumulative contributions to nodulation of the broad-host-range strain Sinorhizobium fredii CCBAU45436. Zur acted as a zinc-dependent repressor for the znuC-znuB-zur operon, znuA, and c06450 by binding to the associated Zur box, but did not regulate zip1 and zip2. ZnuABC was the major zinc transporter. Combined mutants lacking znuA and one of the three accessory genes had more severe defects in nodulation and growth under zinc starvation conditions than the znuA mutant, though rhizoplane colonization by these mutants was not impaired. In contrast to the elite strain CCBAU45436, more drastic symbiotic defects were observed for the znuA mutants of other Sinorhizobium strains, which lack at least one of the three accessory genes in their genomes and are characterized by their limited host range and geographical distribution. The znu-derived mutants showed a higher expression level of nod genes involved in Nod factor biosynthesis and a reduced expression of genes encoding a type three secretion system and its effector NopP, which can interfere with the host immune system. Application of exogenous zinc restored the nodulation ability of these znu-derived mutants. Therefore, the conserved ZnuABC and accessory components in the zinc starvation machinery play an important role in modulating symbiotic compatibility. IMPORTANCE The rhizobium-legume symbiosis contributes around 65% of biological nitrogen fixation in agriculture systems and is critical for sustainable agriculture by reducing the amount of chemical nitrogen fertilizer being used. Rhizobial inocula have been commercialized for more than 100 years, but the efficiency of inoculation can vary among legume cultivars, field sites, and years. These long-lasting challenging problems impede the establishment of a sustainable agriculture, particularly in developing countries. Here, we report that rhizobial zinc starvation machinery containing a conserved high-affinity zinc transporter and accessory components makes cumulative contributions to modulating rhizobial symbiotic compatibility. This work highlights a critical role of largely unexplored nutritional immunity in the rhizobium-legume symbiosis, which makes zinc starvation machinery an attractive target for improving rhizobial symbiotic compatibility.

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