scholarly journals A Ferrous Iron Exporter Mediates Iron Resistance in Shewanella oneidensis MR-1

2015 ◽  
Vol 81 (22) ◽  
pp. 7938-7944 ◽  
Author(s):  
Brittany D. Bennett ◽  
Evan D. Brutinel ◽  
Jeffrey A. Gralnick
Keyword(s):  
Escherichia Coli ◽  
Ferrous Iron ◽  
Ferric Iron ◽  
Shewanella Oneidensis ◽  
Cation Diffusion ◽  
Content Type ◽  
Increased Sensitivity ◽  
Iron Respiration ◽  
Inner Membrane Protein ◽  
Excess Fe

ABSTRACTShewanella oneidensisstrain MR-1 is a dissimilatory metal-reducing bacterium frequently found in aquatic sediments. In the absence of oxygen,S. oneidensiscan respire extracellular, insoluble oxidized metals, such as iron (hydr)oxides, making it intimately involved in environmental metal and nutrient cycling. The reduction of ferric iron (Fe3+) results in the production of ferrous iron (Fe2+) ions, which remain soluble under certain conditions and are toxic to cells at higher concentrations. We have identified an inner membrane protein inS. oneidensis, encoded by the gene SO_4475 and here called FeoE, which is important for survival during anaerobic iron respiration. FeoE, a member of the cation diffusion facilitator (CDF) protein family, functions to export excess Fe2+from the MR-1 cytoplasm. Mutants lackingfeoEexhibit an increased sensitivity to Fe2+. The export function of FeoE is specific for Fe2+, as anfeoEmutant is equally sensitive to other metal ions known to be substrates of other CDF proteins (Cd2+, Co2+, Cu2+, Mn2+, Ni2+, or Zn2+). The substrate specificity of FeoE differs from that of FieF, theEscherichia colihomolog of FeoE, which has been reported to be a Cd2+/Zn2+or Fe2+/Zn2+exporter. A complementedfeoEmutant has an increased growth rate in the presence of excess Fe2+compared to that of the ΔfeoEmutant complemented withfieF. It is possible that FeoE has evolved to become an efficient and specific Fe2+exporter in response to the high levels of iron often present in the types of environmental niches in whichShewanellaspecies can be found.

scholarly journals Survival of Anaerobic Fe2+Stress Requires the ClpXP Protease

2018 ◽  
Vol 200 (8) ◽  
Author(s):  
Brittany D. Bennett ◽  
Kaitlyn E. Redford ◽  
Jeffrey A. Gralnick
Keyword(s):  
Escherichia Coli ◽  
Shewanella Oneidensis ◽  
Oxygenic Photosynthesis ◽  
Ferrous Ions ◽  
Content Type ◽  
Stratified Lakes ◽  
Increased Sensitivity ◽  
Oxide Minerals ◽  
High Concentrations ◽  
Living Organisms

ABSTRACTShewanella oneidensisstrain MR-1 is a versatile bacterium capable of respiring extracellular, insoluble ferric oxide minerals under anaerobic conditions. The respiration of iron minerals results in the production of soluble ferrous ions, which at high concentrations are toxic to living organisms. It is not fully understood how Fe2+is toxic to cells anaerobically, nor is it fully understood howS. oneidensisis able to resist high levels of Fe2+. Here we describe the results of a transposon mutant screen and subsequent deletion of the genesclpXandclpPinS. oneidensis, which demonstrate that the protease ClpXP is required for anaerobic Fe2+resistance. Many cellular processes are known to be regulated by ClpXP, including entry into stationary phase, envelope stress response, and turnover of stalled ribosomes. However, none of these processes appears to be responsible for mediating anaerobic Fe2+resistance inS. oneidensis. Protein trapping studies were performed to identify ClpXP targets inS. oneidensisunder Fe2+stress, implicating a wide variety of protein targets.Escherichia colistrains lackingclpXorclpPalso display increased sensitivity to Fe2+anaerobically, indicating Fe2+resistance may be a conserved role for the ClpXP protease system. Hypotheses regarding the potential role(s) of ClpXP during periods of high Fe2+are discussed. We speculate that metal-containing proteins are misfolded under conditions of high Fe2+and that the ClpXP protease system is necessary for their turnover.IMPORTANCEPrior to the evolution of cyanobacteria and oxygenic photosynthesis, life arose and flourished in iron-rich oceans. Today, aqueous iron-rich environments are less common, constrained to low-pH conditions and anaerobic systems such as stratified lakes and seas, digestive tracts, subsurface environments, and sediments. The latter two ecosystems often favor dissimilatory metal reduction, a process that produces soluble Fe2+from iron oxide minerals. Dissimilatory metal-reducing bacteria must therefore have mechanisms to tolerate anaerobic Fe2+stress, and studying resistance in these organisms may help elucidate the basis of toxicity.Shewanella oneidensisis a model dissimilatory metal-reducing bacterium isolated from metal-rich sediments. Here we demonstrate a role for ClpXP, a protease system widely conserved in bacteria, in anaerobic Fe2+resistance in bothS. oneidensisandEscherichia coli.

scholarly journals Vibrio cholerae VciB Mediates Iron Reduction

2017 ◽  
Vol 199 (12) ◽  
Author(s):  
Eric D. Peng ◽  
Shelley M. Payne
Keyword(s):  
Electron Transport ◽  
Vibrio Cholerae ◽  
Ferrous Iron ◽  
Electron Transport Chain ◽  
Iron Reduction ◽  
Iron Transport ◽  
Ferric Iron ◽  
Transport Systems ◽  
Content Type ◽  
Transport Chain

ABSTRACT Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. V. cholerae thrives within the human host, where it replicates to high numbers, but it also persists within the aquatic environments of ocean and brackish water. To survive within these nutritionally diverse environments, V. cholerae must encode the necessary tools to acquire the essential nutrient iron in all forms it may encounter. A prior study of systems involved in iron transport in V. cholerae revealed the existence of vciB, which, while unable to directly transport iron, stimulates the transport of iron through ferrous (Fe2+) iron transport systems. We demonstrate here a role for VciB in V. cholerae in which VciB stimulates the reduction of Fe3+ to Fe2+, which can be subsequently transported into the cell with the ferrous iron transporter Feo. Iron reduction is independent of functional iron transport but is associated with the electron transport chain. Comparative analysis of VciB orthologs suggests a similar role for other proteins in the VciB family. Our data indicate that VciB is a dimer located in the inner membrane with three transmembrane segments and a large periplasmic loop. Directed mutagenesis of the protein reveals two highly conserved histidine residues required for function. Taken together, our results support a model whereby VciB reduces ferric iron using energy from the electron transport chain. IMPORTANCE Vibrio cholerae is a prolific human pathogen and environmental organism. The acquisition of essential nutrients such as iron is critical for replication, and V. cholerae encodes a number of mechanisms to use iron from diverse environments. Here, we describe the V. cholerae protein VciB that increases the reduction of oxidized ferric iron (Fe3+) to the ferrous form (Fe2+), thus promoting iron acquisition through ferrous iron transporters. Analysis of VciB orthologs in Burkholderia and Aeromonas spp. suggest that they have a similar activity, allowing a functional assignment for this previously uncharacterized protein family. This study builds upon our understanding of proteins known to mediate iron reduction in bacteria.

scholarly journals Tail-Anchored Inner Membrane Protein ElaB Increases Resistance to Stress While Reducing Persistence in Escherichia coli

2017 ◽  
Vol 199 (9) ◽  
Author(s):  
Yunxue Guo ◽  
Xiaoxiao Liu ◽  
Baiyuan Li ◽  
Jianyun Yao ◽  
Thomas K. Wood ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Membrane Proteins ◽  
Membrane Protein ◽  
Stationary Phase ◽  
Transmembrane Domain ◽  
Inner Membrane ◽  
Content Type ◽  
E Coli ◽  
Inner Membrane Protein

ABSTRACT Host-associated bacteria, such as Escherichia coli, often encounter various host-related stresses, such as nutritional deprivation, oxidative stress, and temperature shifts. There is growing interest in searching for small endogenous proteins that mediate stress responses. Here, we characterized the small C-tail-anchored inner membrane protein ElaB in E. coli. ElaB belongs to a class of tail-anchored inner membrane proteins with a C-terminal transmembrane domain but lacking an N-terminal signal sequence for membrane targeting. Proteins from this family have been shown to play vital roles, such as in membrane trafficking and apoptosis, in eukaryotes; however, their role in prokaryotes is largely unexplored. Here, we found that the transcription of elaB is induced in the stationary phase in E. coli and stationary-phase sigma factor RpoS regulates elaB transcription by binding to the promoter of elaB. Moreover, ElaB protects cells against oxidative stress and heat shock stress. However, unlike membrane peptide toxins TisB and GhoT, ElaB does not lead to cell death, and the deletion of elaB greatly increases persister cell formation. Therefore, we demonstrate that disruption of C-tail-anchored inner membrane proteins can reduce stress resistance; it can also lead to deleterious effects, such as increased persistence, in E. coli. IMPORTANCE Escherichia coli synthesizes dozens of poorly understood small membrane proteins containing a predicted transmembrane domain. In this study, we characterized the function of the C-tail-anchored inner membrane protein ElaB in E. coli. ElaB increases resistance to oxidative stress and heat stress, while inactivation of ElaB leads to high persister cell formation. We also demonstrated that the transcription of elaB is under the direct regulation of stationary-phase sigma factor RpoS. Thus, our study reveals that small inner membrane proteins may have important cellular roles during the stress response.

scholarly journals Ferrous Iron Is a Significant Component of Bioavailable Iron in Cystic Fibrosis Airways

mBio ◽  
2013 ◽  
Vol 4 (4) ◽  
Author(s):  
Ryan C. Hunter ◽  
Fadi Asfour ◽  
Jozef Dingemans ◽  
Brenda L. Osuna ◽  
Tahoura Samad ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Ferrous Iron ◽  
Ferric Iron ◽  
Relative Proportion ◽  
Iron Oxidation ◽  
The United States ◽  
Environmental Parameter ◽  
Content Type

ABSTRACTChronic, biofilm-like infections by the opportunistic pathogenPseudomonas aeruginosaare a major cause of mortality in cystic fibrosis (CF) patients. While much is known aboutP. aeruginosafrom laboratory studies, far less is understood about what it experiencesin vivo. Iron is an important environmental parameter thought to play a central role in the development and maintenance ofP. aeruginosainfections, for both anabolic and signaling purposes. Previous studies have focused on ferric iron [Fe(III)] as a target for antimicrobial therapies; however, here we show that ferrous iron [Fe(II)] is abundant in the CF lung (~39 µM on average for severely sick patients) and significantly correlates with disease severity (ρ = −0.56,P= 0.004), whereas ferric iron does not (ρ = −0.28,P= 0.179). Expression of theP. aeruginosagenesbqsRS, whose transcription is upregulated in response to Fe(II), was high in the majority of patients tested, suggesting that increased Fe(II) is bioavailable to the infectious bacterial population. Because limiting Fe(III) acquisition inhibits biofilm formation byP. aeruginosain various oxicin vitrosystems, we also tested whether interfering with Fe(II) acquisition would improve biofilm control under anoxic conditions; concurrent sequestration of both iron oxidation states resulted in a 58% reduction in biofilm accumulation and 28% increase in biofilm dissolution, a significant improvement over Fe(III) chelation treatment alone. This study demonstrates that the chemistry of infected host environments coevolves with the microbial community as infections progress, which should be considered in the design of effective treatment strategies at different stages of disease.IMPORTANCEIron is an important environmental parameter that helps pathogens thrive in sites of infection, including those of cystic fibrosis (CF) patients. Ferric iron chelation therapy has been proposed as a novel therapeutic strategy for CF lung infections, yet until now, the iron oxidation state has not been measured in the host. In studying mucus from the infected lungs of multiple CF patients from Europe and the United States, we found that ferric and ferrous iron change in concentration and relative proportion as infections progress; over time, ferrous iron comes to dominate the iron pool. This information is relevant to the design of novel CF therapeutics and, more broadly, to developing accurate models of chronic CF infections.

scholarly journals Secreted Pyomelanin of Legionella pneumophila Promotes Bacterial Iron Uptake and Growth under Iron-Limiting Conditions

2013 ◽  
Vol 81 (11) ◽  
pp. 4182-4191 ◽  
Author(s):  
Huaixin Zheng ◽  
Christa H. Chatfield ◽  
Mark R. Liles ◽  
Nicholas P. Cianciotto
Keyword(s):  
Legionella Pneumophila ◽  
Ferrous Iron ◽  
Iron Uptake ◽  
Iron Transport ◽  
Ferric Iron ◽  
Iron Acquisition ◽  
Ferric Hydroxide ◽  
Supernatant Fraction ◽  
Content Type ◽  
Ferrous Iron Transport

ABSTRACTIron acquisition is critical to the growth and virulence ofLegionella pneumophila. Previously, we found thatL. pneumophilauses both a ferrisiderophore pathway and ferrous iron transport to obtain iron. We now report that two molecules secreted byL. pneumophila, homogentisic acid (HGA) and its polymerized variant (HGA-melanin, a pyomelanin), are able to directly mediate the reduction of various ferric iron salts. Furthermore, HGA, synthetic HGA-melanin, and HGA-melanin derived from bacterial supernatants enhanced the ability ofL. pneumophilaand other species ofLegionellato take up radiolabeled iron. Enhanced iron uptake was not observed with a ferrous iron transport mutant. Thus, HGA and HGA-melanin mediate ferric iron reduction, with the resulting ferrous iron being available to the bacterium for uptake. Upon further testing ofL. pneumophilaculture supernatants, we found that significant amounts of ferric and ferrous iron were associated with secreted HGA-melanin. Importantly, a pyomelanin-containing fraction obtained from a wild-type culture supernatant was able to stimulate the growth of iron-starved legionellae. That the corresponding supernatant fraction obtained from a nonpigmented mutant culture did not stimulate growth demonstrated that HGA-melanin is able to both promote iron uptake and enhance growth under iron-limiting conditions. Indicative of a complementary role in iron acquisition, HGA-melanin levels were inversely related to the levels of siderophore activity. Compatible with a role in the ecology and pathogenesis ofL. pneumophila, HGA and HGA-melanin were effective at reducing and releasing iron from both insoluble ferric hydroxide and the mammalian iron chelates ferritin and transferrin.

scholarly journals Growth Inhibition by External Potassium of Escherichia coli Lacking PtsN (EIIANtr) Is Caused by Potassium Limitation Mediated by YcgO

2016 ◽  
Vol 198 (13) ◽  
pp. 1868-1882 ◽  
Author(s):  
Ravish Sharma ◽  
Tomohiro Shimada ◽  
Vinod K. Mishra ◽  
Suchitra Upreti ◽  
Abhijit A. Sardesai
Keyword(s):  
Escherichia Coli ◽  
Membrane Protein ◽  
Phosphorylation Site ◽  
Phosphotransferase System ◽  
Inner Membrane ◽  
Content Type ◽  
E Coli ◽  
External Potassium ◽  
Inner Membrane Protein ◽  
External K

ABSTRACTThe absence of PtsN, the terminal phosphoacceptor of the phosphotransferase system comprising PtsP-PtsO-PtsN, inEscherichia coliconfers a potassium-sensitive (Ks) phenotype as the external K+concentration ([K+]e) is increased above 5 mM. A growth-inhibitory increase in intracellular K+content, resulting from hyperactivated Trk-mediated K+uptake, is thought to cause this Ks. We provide evidence that the Ksof the ΔptsNmutant is associated with K+limitation. Accordingly, the moderate Ksdisplayed by the ΔptsNmutant was exacerbated in the absence of the Trk and Kup K+uptake transporters and was associated with reduced cellular K+content. Conversely, overproduction of multiple K+uptake proteins suppressed the Ks. Expression of PtsN variants bearing the H73A, H73D, and H73E substitutions of the phosphorylation site histidine of PtsN complemented the Ks. Absence of the predicted inner membrane protein YcgO (also called CvrA) suppressed the Ks, which was correlated with elevated cellular K+content in the ΔptsNmutant, but the ΔptsNmutation did not alter YcgO levels. Heterologous overexpression ofycgOalso led to Ksthat was associated with reduced cellular K+content, exacerbated by the absence of Trk and Kup and alleviated by overproduction of Kup. Our findings are compatible with a model that postulates that Ksin the ΔptsNmutant occurs due to K+limitation resulting from activation of K+efflux mediated by YcgO, which may be additionally stimulated by [K+]e, implicating a role for PtsN (possibly its dephosphorylated form) as an inhibitor of YcgO activity.IMPORTANCEThis study examines the physiological link between the phosphotransferase system comprising PtsP-PtsO-PtsN and K+ion metabolism inE. coli. Studies on the physiological defect that renders anE. colimutant lacking PtsN to be growth inhibited by external K+indicate that growth impairment results from cellular K+limitation that is mediated by YcgO, a predicted inner membrane protein. Additional observations suggest that dephospho-PtsN may inhibit and external K+may stimulate K+limitation mediated by YcgO. It is speculated that YcgO-mediated K+limitation may be an output of a response to certain stresses, which by modulating the phosphotransfer capacity of the PtsP-PtsO-PtsN phosphorelay leads to growth cessation and stress tolerance.

scholarly journals The Aminoglycoside Antibiotic Kanamycin Damages DNA Bases in Escherichia coli: Caffeine Potentiates the DNA-Damaging Effects of Kanamycin while Suppressing Cell Killing by Ciprofloxacin in Escherichia coli and Bacillus anthracis

2012 ◽  
Vol 56 (6) ◽  
pp. 3216-3223 ◽  
Author(s):  
Tina Manzhu Kang ◽  
Jessica Yuan ◽  
Angelyn Nguyen ◽  
Elinne Becket ◽  
Hanjing Yang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Bacillus Anthracis ◽  
Gene Knockout ◽  
Aminoglycoside Antibiotic ◽  
Double Strand Breaks ◽  
Repair Capacity ◽  
Content Type ◽  
Strand Breaks ◽  
Knockout Mutants ◽  
Increased Sensitivity

ABSTRACTThe distribution of mutants in the Keio collection ofEscherichia coligene knockout mutants that display increased sensitivity to the aminoglycosides kanamycin and neomycin indicates that damaged bases resulting from antibiotic action can lead to cell death. Strains lacking one of a number of glycosylases (e.g., AlkA, YzaB, Ogt, KsgA) or other specific repair proteins (AlkB, PhrB, SmbC) are more sensitive to these antibiotics. Mutants lacking AlkB display the strongest sensitivity among the glycosylase- or direct lesion removal-deficient strains. This perhaps suggests the involvement of ethenoadenine adducts, resulting from reactive oxygen species and lipid peroxidation, since AlkB removes this lesion. Other sensitivities displayed by mutants lacking UvrA, polymerase V (Pol V), or components of double-strand break repair indicate that kanamycin results in damaged base pairs that need to be removed or replicated past in order to avoid double-strand breaks that saturate the cellular repair capacity. Caffeine enhances the sensitivities of these repair-deficient strains to kanamycin and neomycin. The gene knockout mutants that display increased sensitivity to caffeine (dnaQ,holC,holD, andpriAknockout mutants) indicate that caffeine blocks DNA replication, ultimately leading to double-strand breaks that require recombinational repair by functions encoded byrecA,recB, andrecC, among others. Additionally, caffeine partially protects cells of bothEscherichia coliandBacillus anthracisfrom killing by the widely used fluoroquinolone antibiotic ciprofloxacin.

scholarly journals Cj1386, an Atypical Hemin-Binding Protein, Mediates Hemin Trafficking to KatA in Campylobacter jejuni

2014 ◽  
Vol 197 (5) ◽  
pp. 1002-1011 ◽  
Author(s):  
Annika Flint ◽  
Alain Stintzi
Keyword(s):  
Escherichia Coli ◽  
Campylobacter Jejuni ◽  
Biochemical Properties ◽  
Wild Type ◽  
Visible Spectroscopy ◽  
Content Type ◽  
Increased Sensitivity ◽  
Uv Visible

Catalase enzymes detoxify H2O2by the dismutation of H2O2into O2and H2O through the use of hemin cofactors. While the structure and biochemical properties of catalase enzymes have been well characterized over many decades of research, it remained unclear how catalases acquire hemin. We have previously reported that Cj1386 is essential for ensuring proper hemin content inCampylobacter jejunicatalase (KatA) (A. Flint, Y. Q. Sun, and A. Stintzi, J Bacteriol194:334–345, 2012). In this report, an in-depth molecular characterization of Cj1386 was performed to elucidate the mechanistic details of this association. Coimmunoprecipitation assays revealed that KatA-Cj1386 transiently interactin vivo, and UV-visible spectroscopy demonstrated that purified Cj1386 protein binds hemin. Furthermore, hemin titration experiments determined that hemin binds to Cj1386 in a 1:1 ratio with hexacoordinate hemin binding. Mutagenesis of potential hemin-coordinating residues in Cj1386 showed that tyrosine 57 was essential for hemin coordination when Cj1386 was overexpressed inEscherichia coli. The importance of tyrosine 57 in hemin traffickingin vivowas confirmed by introducing thecj1386Y57Aallele into aC. jejuniΔcj1386mutant background. Thecj1386Y57Amutation resulted in increased sensitivity toward H2O2relative to the wild type, suggesting that KatA was not functional in this strain. In support of this finding, KatA immunoprecipitated from the Δcj1386+cj1386Y57Amutant had significantly reduced hemin content compared to that of thecj1386WTbackground. Overall, these findings indicate that Cj1386 is involved in directly trafficking hemin to KatA and that tyrosine 57 plays a key role in this function.

scholarly journals Extracellular Electron Transfer: Respiratory or Nutrient Homeostasis?

2020 ◽  
Vol 202 (7) ◽  
Author(s):  
Lars J. C. Jeuken ◽  
Kiel Hards ◽  
Yoshio Nakatani
Keyword(s):  
Electron Transfer ◽  
Iron Reduction ◽  
Ferric Iron ◽  
Shewanella Oneidensis ◽  
Geobacter Sulfurreducens ◽  
Extracellular Electron Transfer ◽  
Gram Positive ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Nutrient Homeostasis

ABSTRACT Exoelectrogens are able to transfer electrons extracellularly, enabling them to respire on insoluble terminal electron acceptors. Extensively studied exoelectrogens, such as Geobacter sulfurreducens and Shewanella oneidensis, are Gram negative. More recently, it has been reported that Gram-positive bacteria, such as Listeria monocytogenes and Enterococcus faecalis, also exhibit the ability to transfer electrons extracellularly, although it is still unclear whether this has a function in respiration or in redox control of the environment, for instance, by reducing ferric iron for iron uptake. In this issue of Journal of Bacteriology, Hederstedt and colleagues report on experiments that directly compare extracellular electron transfer (EET) pathways for ferric iron reduction and respiration and find a clear difference (L. Hederstedt, L. Gorton, and G. Pankratova, J Bacteriol 202:e00725-19, 2020, https://doi.org/10.1128/JB.00725-19), providing further insights and new questions into the function and metabolic pathways of EET in Gram-positive bacteria.

scholarly journals Lon-Mediated Proteolysis of the FeoC Protein Prevents Salmonella enterica from Accumulating the Fe(II) Transporter FeoB under High-Oxygen Conditions

2014 ◽  
Vol 197 (1) ◽  
pp. 92-98 ◽  
Author(s):  
Hyunkeun Kim ◽  
Hwiseop Lee ◽  
Dongwoo Shin
Keyword(s):  
Ferrous Iron ◽  
Oxygen Sensor ◽  
Environmental Changes ◽  
High Oxygen ◽  
Lon Protease ◽  
Low Oxygen ◽  
Anaerobic Conditions ◽  
Content Type ◽  
Oxygen Conditions ◽  
Inner Membrane Protein

TheSalmonellaFeo system consists of the FeoA, FeoB, and FeoC proteins and mediates ferrous iron [Fe(II)] import. FeoB is an inner membrane protein that, along with contributions from two small hydrophilic proteins, FeoA and FeoC, transports Fe(II). We previously reported that FeoC binds to and protects the FeoB transporter from FtsH-mediated proteolysis. In the present study, we report proteolytic regulation of FeoC that occurs in an oxygen-dependent fashion. While relatively stable under low-oxygen conditions, FeoC was rapidly degraded by the Lon protease under high-oxygen conditions. The putative Fe-S cluster of FeoC seemed to function as an oxygen sensor to control FeoC stability, as evidenced by the finding that mutation of the putative Fe-S cluster-binding site greatly increased FeoC stability under high-oxygen conditions.Salmonellaectopically expressing thefeoBandfeoCgenes was able to accumulate FeoB and FeoC only under low-oxygen conditions, suggesting that FeoC proteolysis preventsSalmonellafrom accumulating the FeoB transporter under high-oxygen conditions. Finally, we propose that Lon-mediated FeoC proteolysis followed by FtsH-mediated FeoB proteolysis helpsSalmonellato avoid uncontrolled Fe(II) uptake during the radical environmental changes encountered when shifting from low-iron anaerobic conditions to high-iron aerobic conditions.

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