Effects of Iron Limitation on the Degradation of Toluene by Pseudomonas Strains Carrying the TOL (pWWO) Plasmid

ABSTRACT Most aerobic biodegradation pathways for hydrocarbons involve iron-containing oxygenases. In iron-limited environments, such as the rhizosphere, this may influence the rate of degradation of hydrocarbon pollutants. We investigated the effects of iron limitation on the degradation of toluene by Pseudomonas putida mt2 and the transconjugant rhizosphere bacterium P. putidaWCS358(pWWO), both of which contain the pWWO (TOL) plasmid that harbors the genes for toluene degradation. The results of continuous-culture experiments showed that the activity of the upper-pathway toluene monooxygenase decreased but that the activity of benzyl alcohol dehydrogenase was not affected under iron-limited conditions. In contrast, the activities of three meta-pathway (lower-pathway) enzymes were all found to be reduced when iron concentrations were decreased. Additional experiments in which citrate was used as a growth substrate and the pathways were induced with the gratuitous inducer o-xylene showed that expression of the TOL genes increased the iron requirement in both strains. Growth yields were reduced and substrate affinities decreased under iron-limited conditions, suggesting that iron availability can be an important parameter in the oxidative breakdown of hydrocarbons.

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Iron Requirement for Mn(II) Oxidation by Leptothrix discophora SS-1

Applied and Environmental Microbiology ◽

10.1128/aem.02291-08 ◽

2008 ◽

Vol 75 (5) ◽

pp. 1229-1235 ◽

Cited By ~ 28

Author(s):

Iman A. El Gheriany ◽

Daniela Bocioaga ◽

Anthony G. Hay ◽

William C. Ghiorse ◽

Michael L. Shuler ◽

...

Keyword(s):

Complex Formation ◽

Temporal Variations ◽

Iron Limitation ◽

Gene Transcript ◽

Cellular Functions ◽

Transcript Levels ◽

Leptothrix Discophora ◽

Geochemical Cycling ◽

Iron Requirement

ABSTRACT A common form of biocatalysis of Mn(II) oxidation results in the formation of biogenic Mn(III, IV) oxides and is a key reaction in the geochemical cycling of Mn. In this study, we grew the model Mn(II)-oxidizing bacterium Leptothrix discophora SS-1 in media with limited iron (0.1 μM iron/5.8 mM pyruvate) and sufficient iron (0.2 μM iron/5.8 mM pyruvate). The influence of iron on the rate of extracellular Mn(II) oxidation was evaluated. Cultures in which cell growth was limited by iron exhibited reduced abilities to oxidize Mn(II) compared to cultures in medium with sufficient iron. While the extracellular Mn(II)-oxidizing factor (MOF) is thought to be a putative multicopper oxidase, Mn(II) oxidation in the presence of zero added Cu(II) was detected and the decrease in the observed Mn(II) oxidation rate in iron-limited cultures was not relieved when the medium was supplemented with Cu(II). The decline of Mn(II) oxidation under iron-limited conditions was not accompanied by siderophore production and is unlikely to be an artifact of siderophore complex formation with Mn(III). The temporal variations in mofA gene transcript levels under conditions of limited and abundant iron were similar, indicating that iron limitation did not interfere with the transcription of the mofA gene. Our quantitative PCR results provide a step forward in understanding the regulation of Mn(II) oxidation. The mechanistic role of iron in Mn(II) oxidation is uncertain; the data are consistent with a direct requirement for iron as a component of the MOF or an indirect effect of iron resulting from the limitation of one of many cellular functions requiring iron.

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Regulation of freA, acoA, lysF, and cycA Expression by Iron Availability in Aspergillus nidulans

Applied and Environmental Microbiology ◽

10.1128/aem.68.11.5769-5772.2002 ◽

2002 ◽

Vol 68 (11) ◽

pp. 5769-5772 ◽

Cited By ~ 19

Author(s):

Harald Oberegger ◽

Michelle Schoeser ◽

Ivo Zadra ◽

Markus Schrettl ◽

Walther Parson ◽

...

Keyword(s):

Aspergillus Nidulans ◽

Iron Homeostasis ◽

Regulatory Mechanism ◽

Growth Conditions ◽

Iron Limitation ◽

Transcriptional Level ◽

Iron Availability ◽

Gata Factor ◽

Genes Encoding ◽

Encoding Gene

ABSTRACT In the filamentous fungus Aspergillus nidulans, iron homeostasis is regulated at the transcriptional level by the negative-acting GATA factor SREA. In this study the expression of a putative heme-containing metalloreductase-encoding gene, freA, was found to be upregulated by iron limitation independently of SREA, demonstrating the existence of an iron-regulatory mechanism which does not involve SREA. In contrast to freA, various other genes encoding proteins in need of iron-containing cofactors—acoA, lysF, and cycA—were downregulated in response to iron depletion. Remarkably, SREA deficiency led to increased expression of acoA, lysF, and cycA under iron-replete growth conditions.

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Simultaneous Growth on Citrate Reduces the Effects of Iron Limitation during Toluene Degradation in Pseudomonas

Microbial Ecology ◽

10.1007/s00248-002-2023-y ◽

2003 ◽

Vol 45 (1) ◽

pp. 97-107 ◽

Cited By ~ 16

Author(s):

I.J.T. Dinkla ◽

D.B. Janssen

Keyword(s):

Iron Limitation ◽

Toluene Degradation ◽

Simultaneous Growth

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Iron acquisition inLeishmaniaand its crucial role in infection

Parasitology ◽

10.1017/s0031182016000858 ◽

2016 ◽

Vol 143 (11) ◽

pp. 1347-1357 ◽

Cited By ~ 9

Author(s):

QINWANG NIU ◽

SHIHONG LI ◽

DALI CHEN ◽

QIWEI CHEN ◽

JIANPING CHEN

Keyword(s):

Free Radicals ◽

Iron Metabolism ◽

Metabolic Pathways ◽

Crucial Role ◽

Iron Acquisition ◽

Iron Limitation ◽

Iron Availability ◽

Acquisition Strategies ◽

Dual Character ◽

Pathogenic Microbes

SUMMARYIron is an essential cofactor for many basic metabolic pathways in pathogenic microbes and their hosts. It is also dangerous as it can catalyse the production of reactive free radicals. This dual character makes the host can either limit iron availability to invading microbes or exploit iron to induce toxicity to pathogens. Successful pathogens, includingLeishmaniaspecies, must possess mechanisms to circumvent host's iron limitation and iron-induced toxicity in order to survive. In this review, we discuss the regulation of iron metabolism in the setting of infection and delineate the iron acquisition strategies used byLeishmaniaparasites and their subversions to host iron metabolism to overcome host's iron-related defences.

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High Stability and Fast Recovery of Expression of the TOL Plasmid-Carried Toluene Catabolism Genes of Pseudomonas putida mt-2 under Conditions of Oxygen Limitation and Oscillation

Applied and Environmental Microbiology ◽

10.1128/aem.01039-10 ◽

2010 ◽

Vol 76 (20) ◽

pp. 6715-6723 ◽

Cited By ~ 16

Author(s):

Paula M. MartÃ¯Â¿Â½nez-Lavanchy ◽

Christina MÃ¯Â¿Â½ller ◽

Ivonne Nijenhuis ◽

Uwe Kappelmeyer ◽

Marieke Buffing ◽

...

Keyword(s):

Pseudomonas Putida ◽

Tricarboxylic Acid Cycle ◽

Oxygen Depletion ◽

Toluene Degradation ◽

Tol Plasmid ◽

Reverse Transcription Pcr ◽

Catabolic Genes ◽

Genes Encoding ◽

The Media ◽

Tricarboxylic Acid Cycle Intermediates

ABSTRACT Pseudomonas putida mt-2 harbors the TOL plasmid (pWWO), which contains the genes encoding the enzymes necessary to degrade toluene aerobically. The xyl genes are clustered in the upper operon and encode the enzymes of the upper pathway that degrade toluene to benzoate, while the genes encoding the enzymes of the lower pathway (meta-cleavage pathway) that are necessary for the conversion of benzoate to tricarboxylic acid cycle intermediates, are encoded in a separate operon. In this study, the effects of oxygen availability and oscillation on the expression of catabolic genes for enzymes involved in toluene degradation were studied by using P. putida mt-2 as model bacterium. Quantitative reverse transcription-PCR was used to detect and quantify the expression of the catabolic genes xylM (a key gene of the upper pathway) and xylE (a key gene of the lower pathway) in cultures of P. putida mt-2 that were grown with toluene as a carbon source. Toluene degradation was shown to have a direct dependency on oxygen concentration, where gene expression of xylM and xylE decreased due to oxygen depletion during degradation. Under oscillating oxygen concentrations, P. putida mt-2 induced or downregulated xylM and xylE genes according to the O2 availability in the media. During anoxic periods, P. putida mt-2 decreased the expression of xylM and xylE genes, while the expression of both xylM and xylE genes was immediately increased after oxygen became available again in the medium. These results suggest that oxygen is not only necessary as a cosubstrate for enzyme activity during the degradation of toluene but also that oxygen modulates the expression of the catabolic genes encoded by the TOL plasmid.

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Iron effects on colonization behavior, motility, and enzymatic activity of marine bacteria

Canadian Journal of Microbiology ◽

10.1139/w07-059 ◽

2007 ◽

Vol 53 (8) ◽

pp. 968-974 ◽

Cited By ~ 4

Author(s):

Kam W. Tang ◽

Hans-Peter Grossart

Keyword(s):

Marine Bacteria ◽

Laboratory Experiments ◽

Large Fraction ◽

Iron Limitation ◽

Colonization Rate ◽

Particle Interactions ◽

Iron Availability ◽

Free Living ◽

Attached Bacteria ◽

Colonization Behavior

Iron availability in the ocean has been shown to affect the growth and production of phytoplankton and free-living bacteria. A large fraction of marine bacteria are specialized in colonizing and living on particles and aggregates, but the effects of iron limitation on these bacteria are not fully known. We conducted laboratory experiments to study the effects of iron availability on particle colonization behavior, motility, and enzymatic activities of 4 strains of marine bacteria. Iron depletion reduced the bacterial particle colonization rate by 1.7%–43.1%, which could be attributed to reduced swimming speeds in 2 of the 4 strains. Protease activity was not affected by iron availability. However, attached bacteria did show higher protease activities than their free counterparts. Our results suggest that iron limitation in the ocean could in some cases reduce bacteria–particle interactions by reducing bacterial motility and colonization rate.

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ntn Genes Determining the Early Steps in the Divergent Catabolism of 4-Nitrotoluene and Toluene in Pseudomonas sp. Strain TW3

Journal of Bacteriology ◽

10.1128/jb.180.8.2043-2049.1998 ◽

1998 ◽

Vol 180 (8) ◽

pp. 2043-2049 ◽

Cited By ~ 32

Author(s):

Keith D. James ◽

Peter A. Williams

Keyword(s):

Alcohol Dehydrogenase ◽

Benzyl Alcohol ◽

Open Reading Frame ◽

Pseudomonas Sp ◽

Tol Plasmid ◽

Reading Frame ◽

Toluene Monooxygenase ◽

Dehydrogenase Gene ◽

Amino Acid Levels ◽

Benzaldehyde Dehydrogenase

ABSTRACT Pseudomonas sp. strain TW3 is able to oxidatively metabolize 4-nitrotoluene and toluene via a route analogous to the upper pathway of the TOL plasmids. We report the sequence and organization of five genes, ntnWCMAB*, which are very similar to and in the same order as the xyl operon of TOL plasmid pWW0 and present evidence that they encode enzymes which are expressed during growth on both 4-nitrotoluene and toluene and are responsible for their oxidation to 4-nitrobenzoate and benzoate, respectively. These genes encode an alcohol dehydrogenase homolog (ntnW), an NAD+-linked benzaldehyde dehydrogenase (ntnC), a two-gene toluene monooxygenase (ntnMA), and part of a benzyl alcohol dehydrogenase (ntnB*), which have 84 to 99% identity at the nucleotide and amino acid levels with the corresponding xylWCMABgenes. The xylB homolog on the TW3 genome (ntnB*) appears to be a pseudogene and is interrupted by a piece of DNA which destroys its functional open reading frame, implicating an additional and as-yet-unidentified benzyl alcohol dehydrogenase gene in this pathway. This conforms with the observation that the benzyl alcohol dehydrogenase expressed during growth on 4-nitrotoluene and toluene differs significantly from the XylB protein, requiring assay via dye-linked electron transfer rather than through a nicotinamide cofactor. The further catabolism of 4-nitrobenzoate and benzoate diverges in that the former enters the hydroxylaminobenzoate pathway as previously reported, while the latter is further metabolized via the β-ketoadipate pathway.

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Effects of iron on the elemental stoichiometry during EIFEX and in the diatoms <i>Fragilariopsis kerguelensis</i> and <i>Chaetoceros dichaeta</i>

Biogeosciences Discussions ◽

10.5194/bgd-4-249-2007 ◽

2007 ◽

Vol 4 (1) ◽

pp. 249-275 ◽

Cited By ~ 1

Author(s):

L. J. Hoffmann ◽

I. Peeken ◽

K. Lochte

Keyword(s):

Laboratory Experiments ◽

Iron Limitation ◽

Iron Availability ◽

Diatom Species ◽

Fertilization Experiment ◽

High Iron ◽

Iron Fertilization ◽

Elemental Stoichiometry ◽

Fertilization Experiments

Abstract. The interaction between iron availability and the phytoplankton elemental composition was investigated during the in situ iron fertilization experiment EIFEX and in laboratory experiments with the Southern Ocean diatom species Fragilariopsis kerguelensis and Chaetoceros dichaeta. Contrary to other in situ iron fertilization experiments we observed an increase in the bPSi : POC, bPSi : PON, and bPSi : POP ratios within the iron fertilized patch during EIFEX. This is possibly caused by a relatively stronger increase in diatom abundance compared to other phytoplankton groups and does not necessarily represent the amount of silicification of single diatom cells. In laboratory experiments with F. kerguelensis and C. dichaeta no changes in the POC : PON, PON : POP, and POC : POP ratios were found with changing iron availability in both species. BPSi : POC, bPSi : PON, and bPSi : POP ratios were significantly lower in the high iron treatments compared to the controls. In F. kerguelensis this is caused by a decrease in cellular bPSi concentrations and therefore possibly less silicification. In C. dichaeta no change in cellular bPSi concentration was found. Here lower bPSi : POC, bPSi : PON, and bPSi : POP ratios were caused by an increase in cellular C, N, and P under high iron conditions. We therefore assume that iron limitation does not generally increase silicification of diatoms and that changes in the bPSi : POC, bPSi : PON, and bPSi : POP ratios under iron fertilization in the field are caused by a variety of different mechanisms. These results imply that the effect of iron on nutrient uptake is more complex than hitherto assumed.

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Effects of Iron Limitation on Adherence and Cell Surface Carbohydrates of Corynebacterium diphtheriae Strains

Applied and Environmental Microbiology ◽

10.1128/aem.69.10.5907-5913.2003 ◽

2003 ◽

Vol 69 (10) ◽

pp. 5907-5913 ◽

Cited By ~ 38

Author(s):

Lílian de Oliveira Moreira ◽

Arnaldo Feitosa Braga Andrade ◽

Márcio Damasceno Vale ◽

Sônia Maria Silva Souza ◽

Raphael Hirata ◽

...

Keyword(s):

Sialic Acid ◽

Lectin Binding ◽

Iron Concentration ◽

Corynebacterium Diphtheriae ◽

Host Cells ◽

Iron Limitation ◽

Iron Availability ◽

Virulence Determinants ◽

Adhesive Properties ◽

Bacterial Surface

ABSTRACT Iron limitation may cause bacterial pathogens to grow more slowly; however, it may also stimulate these microorganisms to produce greater tissue damage, given that many virulence factors are controlled by the iron supply in the environment. The present study investigated the influence of low iron availability on the expression of proteins and surface sugar residues of two toxigenic strains of Corynebacterium diphtheriae subsp. mitis and evaluated their adherence to human group B erythrocytes and HEp-2 cells. A comparison was made between bacteria grown in (i) Trypticase soy broth (TSB), (ii) TSB treated with dipyridyl to deplete free iron, and (iii) TSB enriched with FeCl3. The effects of iron concentration on adhesive properties were different for strains 241 and CDC-E8392, of the sucrose-fermenting and non-sucrose-fermenting biotypes, respectively. Iron-limited conditions enhanced interaction of strain 241 with erythrocytes and HEp-2 cells. Inhibition assays suggested the involvement of nonfimbrial protein combination 67-72p on hemagglutination of diphtheria bacilli grown under iron-limited conditions. Conversely, iron limitation inhibited adherence to glass and expression of electron-dense material on the bacterial surface. Lectin binding assays demonstrated a reduction in the number of sialic acid residues and an increase in d-mannose and d-galactose residues on the surfaces of both strains. Thus, iron exerts a regulatory role on adhesive properties of diphtheria bacilli, and low iron availability modulates the expression of C. diphtheriae surface carbohydrate moieties. The significant changes in the degree of lectin binding specific for d-mannose, d-galactose and sialic acid residues may have an effect on binding of host cells. The expression of dissimilar microbial virulence determinants may be coordinately controlled by common regulatory systems. For C. diphtheriae, the present results imply regulation of adherence and slime production as part of a global response to iron-limited environmental conditions that includes derepression of genes for the synthesis of cytotoxin and siderophores and for transport of the Fe(III)-siderophore complexes.

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