Regulation ofSalmonella entericaSerovar TyphimuriummntHTranscription by H2O2, Fe2+, and Mn2+

Kehres, David G.; Janakiraman, Anu; Slauch, James M.; Maguire, Michael E.

doi:10.1128/jb.184.12.3151-3158.2002

Cited by 143 publications

(174 citation statements)

References 45 publications

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“…This is consistent with misregulation of Mn uptake as a consequence of iron starvation, as has been found in other bacteria (36,37). Under iron-replete conditions, Fe-Fur represses not only iron acquisition genes but also a manganese import system (VC1688) (38) and the small RNA RyhB (32).…”

Section: ) Epv102 (Null) (B) Epv104 (Vfeo) (C) Epv115 (Vfbp) (D) supporting

confidence: 88%

“…ent within the V. cholerae genome, and mutation of other candidate iron-regulated iron transporter genes (32,34) has, thus far, not been successful in abrogating anaerobic growth. It is possible that a transporter for another metal, such as manganese, can also transport iron, as has been noted for the Salmonella Sit system (36) and S. flexneri MntH (54).…”

Section: Discussionmentioning

confidence: 88%

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Nonredundant Roles of Iron Acquisition Systems in Vibrio cholerae

et al. 2016

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Vibrio cholerae, the causative agent of the severe diarrheal disease cholera, thrives in both marine environments and the human host. To do so, it must encode the tools necessary to acquire essential nutrients, including iron, under these vastly different conditions. A number of V. cholerae iron acquisition systems have been identified; however, the precise role of each system is not fully understood. To test the roles of individual systems, we generated a series of mutants in which only one of the four systems that support iron acquisition on unsupplemented LB agar, Feo, Fbp, Vct, and Vib, remains functional. Analysis of these mutants under different growth conditions showed that these systems are not redundant. The strain carrying only the ferrous iron transporter Feo grew well at acidic, but not alkaline, pH, whereas the ferric iron transporter Fbp promoted better growth at alkaline than at acidic pH. A strain defective in all four systems (null mutant) had a severe growth defect under aerobic conditions but accumulated iron and grew as well as the wild type in the absence of oxygen, suggesting the presence of an additional, unidentified iron transporter in V. cholerae. In support of this, the null mutant was only moderately attenuated in an infant mouse model of infection. While the null mutant used heme as an iron source in vitro, we demonstrate that heme is not available to V. cholerae in the infant mouse intestine. The Gram-negative bacterium Vibrio cholerae has an absolute requirement for iron (1). Despite the prevalence of iron within its environmental niches and human host, most of this iron is not readily available. Iron occurs naturally as oxidized (ferric) or reduced (ferrous) iron (2). Ferric iron(III), found in oxygenated environments at neutral to alkaline pH, has very low water solubility and forms large insoluble complexes. Studies of ocean water have found iron to be the limiting nutrient for microbial growth (3). Soluble, ferrous iron(II) is more prevalent under the anoxic conditions that V. cholerae may encounter while colonizing the human host. However, access to iron in the host is limited due to competition with other microbes on host surfaces, as well as sequestration by high-affinity iron-binding host proteins such as transferrin and lactoferrin (4-7). Despite the challenges of obtaining iron in these various environments, V. cholerae is proficient in growth in both marine and host environments.The V. cholerae genome encodes multiple iron acquisition systems, which each transport a specific form of iron and may thus optimize iron acquisition in the various niches that V. cholerae inhabits (8-12). These include genes for the synthesis (vib) and utilization (viu) of vibriobactin, a siderophore that is secreted into the environment, where it binds ferric iron with extremely high affinity (9,(13)(14)(15). Ferrivibriobactin is bound by the outer membrane receptor ViuA (16,17) and is transported across the outer membrane in a process that requires either of two energy transduction systems, To...

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Section: ) Epv102 (Null) (B) Epv104 (Vfeo) (C) Epv115 (Vfbp) (D) supporting

confidence: 88%

Section: Discussionmentioning

confidence: 88%

Nonredundant Roles of Iron Acquisition Systems in Vibrio cholerae

et al. 2016

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“…Growth of an Escherichia coli iron-transport mutant is inhibited in an mntH background, suggesting that manganese may substitute for iron in cells (6). The mntH and sitABCD genes are transcriptionally regulated by iron as well as by manganese in the model organisms E. coli, Salmonella enterica, and Bacillus subtilis (7)(8)(9). However, a regulatory role for manganese in controlling cellular processes other than its own transport is less well understood, and is addressed in the present study.…”

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confidence: 88%

Control of bacterial iron homeostasis by manganese

Puri

Hohle

O’Brian

2010

Proc. Natl. Acad. Sci. U.S.A.

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Perception and response to nutritional iron availability by bacteria are essential to control cellular iron homeostasis. The Irr protein from Bradyrhizobium japonicum senses iron through the status of heme biosynthesis to globally regulate iron-dependent gene expression. Heme binds directly to Irr to trigger its degradation. Here, we show that severe manganese limitation created by growth of a Mn 2+ transport mutant in manganese-limited media resulted in a cellular iron deficiency. In wild-type cells, Irr levels were attenuated under manganese limitation, resulting in reduced promoter occupancy of target genes and altered iron-dependent gene expression. Irr levels were high regardless of manganese availability in a heme-deficient mutant, indicating that manganese normally affects heme-dependent degradation of Irr. Manganese altered the secondary structure of Irr in vitro and inhibited binding of heme to the protein. We propose that manganese limitation destabilizes Irr under low-iron conditions by lowering the threshold of heme that can trigger Irr degradation. The findings implicate a mechanism for the control of iron homeostasis by manganese in a bacterium.Bradyrhizobium | heme | regulated degradation | oxidative stress

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“…Ogawa et al, 2002;Yamaguchi et al, 2002;Chandler et al, 2003;Guedon et al, 2003). The expression of the MntH-type proteins is also determined by iron status, because these transporters, although more selective for Mn 21 , do include Fe 21 among the substrates they handle (Kehres et al, 2002).…”

mentioning

confidence: 99%

Manganese Deficiency in Chlamydomonas Results in Loss of Photosystem II and MnSOD Function, Sensitivity to Peroxides, and Secondary Phosphorus and Iron Deficiency

et al. 2006

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For photoheterotrophic growth, a Chlamydomonas reinhardtii cell requires at least 1.7 × 107 manganese ions in the medium. At lower manganese ion concentrations (typically <0.5 μ m), cells divide more slowly, accumulate less chlorophyll, and the culture reaches stationary phase at lower cell density. Below 0.1 μ m supplemental manganese ion in the medium, the cells are photosynthetically defective. This is accompanied by decreased abundance of D1, which binds the Mn4Ca cluster, and release of the OEE proteins from the membrane. Assay of Mn superoxide dismutase (MnSOD) indicates loss of activity of two isozymes in proportion to the Mn deficiency. The expression of MSD3 through MSD5, encoding various isoforms of the MnSODs, is up-regulated severalfold in Mn-deficient cells, but neither expression nor activity of the plastid Fe-containing superoxide dismutase is changed, which contrasts with the dramatically increased MSD3 expression and plastid MnSOD activity in Fe-deficient cells. Mn-deficient cells are selectively sensitive to peroxide but not methyl viologen or Rose Bengal, and GPXs, APX, and MSRA2 genes (encoding glutathione peroxidase, ascorbate peroxidase, and methionine sulfoxide reductase 2) are slightly up-regulated. Elemental analysis indicates that the Mn, Fe, and P contents of cells in the Mn-deficient cultures were reduced in proportion to the deficiency. A natural resistance-associated macrophage protein homolog and one of five metal tolerance proteins were induced in Mn-deficient cells but not in Fe-deficient cells, suggesting that the corresponding gene products may be components of a Mn2+-selective assimilation pathway.

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Regulation ofSalmonella entericaSerovar TyphimuriummntHTranscription by H₂O₂, Fe²⁺, and Mn²⁺

Cited by 143 publications

References 45 publications

Nonredundant Roles of Iron Acquisition Systems in Vibrio cholerae

Nonredundant Roles of Iron Acquisition Systems in Vibrio cholerae

Control of bacterial iron homeostasis by manganese

Manganese Deficiency in Chlamydomonas Results in Loss of Photosystem II and MnSOD Function, Sensitivity to Peroxides, and Secondary Phosphorus and Iron Deficiency

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