Efflux of chromate by Pseudomonas aeruginosa cells expressing the ChrA protein

Pimentel, Bruna Maria Fia

doi:10.1016/s0378-1097(02)00755-3

Cited by 26 publications

(36 citation statements)

References 14 publications

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“…This chromate resistance system operates by maintaining low cellular chromium levels even in the presence of millimolar extracellular chromate concentrations. Decreased accumulation of chromate has been associated with chromate resistance in other microorganisms (3,29,31,33). ChrA proteins from C. metallidurans (29) and Pseudomonas aeruginosa (10) have been functionally characterized as chromate efflux pumps.…”

Section: Discussionmentioning

confidence: 99%

The Chromate-Inducible chrBACF Operon from the Transposable Element Tn OtChr Confers Resistance to Chromium(VI) and Superoxide

et al. 2008

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Large-scale industrial use of chromium(VI) has resulted in widespread contamination with carcinogenic chromium(VI). The abilities of microorganisms to survive in these environments and to detoxify chromate require the presence of specific resistance systems. Here we report identification of the transposon-located (TnOtChr) chromate resistance genes from the highly tolerant strain Ochrobactrum tritici 5bvl1 surviving chromate concentrations of >50 mM. The 7,189-bp-long TnOtChr of the mixed Tn21/Tn3 transposon subfamily contains a group of chrB, chrA, chrC, and chrF genes situated between divergently transcribed resolvase and transposase genes. The chrB and chrA genes, but not chrF or chrC, were essential for establishment of high resistance in chromium-sensitive O. tritici. The chr promoter was strongly induced by chromate or dichromate, but it was completely unresponsive to Cr(III), oxidants, sulfate, or other oxyanions. Plasmid reporter experiments identified ChrB as a chromate-sensing regulator of chr expression. Induction of the chr operon suppressed accumulation of cellular Cr through the activity of a chromate efflux pump encoded by chrA. Expression of chrB, chrC, or chrF in an Escherichia coli sodA sodB double mutant restored its aerobic growth in minimal medium and conferred resistance to superoxide-generating agents menadione and paraquat. Nitroblue tetrazolium staining on native gels showed that ChrC protein had superoxide dismutase activity. TnOtChr appears to represent a mobile genetic system for the distribution of the chromate-regulated resistance operon. The presence of three genes protecting against superoxide toxicity should provide an additional survival advantage to TnOtChr-containing cells in the environments with multiple redox-active contaminants.Chromium(VI) is one of the major environmental contaminants, which reflects its numerous high-volume industrial applications and poor environmental practices in the disposal of chromium-containing waste products (42). High solubility and tetrahedral conformation of the chromate anion promote its rapid transport across biological membranes (11), and once internalized by cells, Cr(VI) exhibits a variety of toxic, mutagenic, and carcinogenic effects (43). Formation of DNA damage is a major cause of toxic and mutagenic responses in both human and bacterial cells, as evidenced by their increased sensitivity to chromate in the absence of DNA repair (16, 36). Human and other mammalian cells lack any detectable extrusion of chromate, and DNA repair is their main cellular defense mechanism against chromate toxicity. Because bacterial cells are less proficient in repair of chromium-DNA adducts compared to human cells (35), their ability to survive in the environment with heavy chromate contamination required selection of alternative resistance mechanisms. Genes conferring resistance to chromate have been found in Pseudomonas spp. (7,27), Streptococcus lactis (13), and Cupriavidus metallidurans (28). Unlike other metal resistance systems that allow survival at...

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Section: Discussionmentioning

confidence: 99%

The Chromate-Inducible chrBACF Operon from the Transposable Element Tn OtChr Confers Resistance to Chromium(VI) and Superoxide

et al. 2008

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“…The identification of a Neurospora gene showing homology to the ChrA chromate resistance gene of Pseudomonas aeruginosa (and Acetobacter aceti), which functions by chromate efflux (616), is intriguing. No significant homology to any eukaryotic genes is observed for this putative member of the chromate ion transporter (TC 2.A.51.1.3) family (Table 33), and this may represent another potential case of horizontal gene transfer.…”

Section: Sulfur Metabolismmentioning

confidence: 99%

Lessons from the Genome Sequence ofNeurospora crassa: Tracing the Path from Genomic Blueprint to Multicellular Organism

Borkovich

Alex

Yarden

et al. 2004

Microbiol Mol Biol Rev

598

618

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We present an analysis of over 1,100 of the ∼10,000 predicted proteins encoded by the genome sequence of the filamentous fungus Neurospora crassa. Seven major areas of Neurospora genomics and biology are covered. First, the basic features of the genome, including the automated assembly, gene calls, and global gene analyses are summarized. The second section covers components of the centromere and kinetochore complexes, chromatin assembly and modification, and transcription and translation initiation factors. The third area discusses genome defense mechanisms, including repeat induced point mutation, quelling and meiotic silencing, and DNA repair and recombination. In the fourth section, topics relevant to metabolism and transport include extracellular digestion; membrane transporters; aspects of carbon, sulfur, nitrogen, and lipid metabolism; the mitochondrion and energy metabolism; the proteasome; and protein glycosylation, secretion, and endocytosis. Environmental sensing is the focus of the fifth section with a treatment of two-component systems; GTP-binding proteins; mitogen-activated protein, p21-activated, and germinal center kinases; calcium signaling; protein phosphatases; photobiology; circadian rhythms; and heat shock and stress responses. The sixth area of analysis is growth and development; it encompasses cell wall synthesis, proteins important for hyphal polarity, cytoskeletal components, the cyclin/cyclin-dependent kinase machinery, macroconidiation, meiosis, and the sexual cycle. The seventh section covers topics relevant to animal and plant pathogenesis and human disease. The results demonstrate that a large proportion of Neurospora genes do not have homologues in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. The group of unshared genes includes potential new targets for antifungals as well as loci implicated in human and plant physiology and disease

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“…The efflux of chromate from cytoplasm through membrane transporter in bacterial cells was encoded on the genes present on plasmids. The chromate reduction strategies like free-radical detoxifying activities, repairing of DNA damage, specific or unspecific Cr (VI) reduction are under the control of genes, which are present on chromosome (Pimentel et al 2002). The strains B. cereus-TA2 and B. cereus-TA4 also reduced selenite to elemental selenium aerobically at an initial selenite concentration of 200 µg mL -1 .…”

Section: Discussionmentioning

confidence: 99%

Characterization and Metal Detoxification Potential of Moderately Thermophilic Bacillus cereus from Geothermal Springs of Himalaya

Ghalib¹,

Yasin²,

Faisal³

2014

Braz. arch. biol. technol.

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Efflux of chromate by Pseudomonas aeruginosa cells expressing the ChrA protein

Abstract: The ChrA protein of Pseudomonas aeruginosa plasmid pUM505 confers resistance to chromate. Using an in vitro system, we reported [Alvarez, A.H. et al. (1999)

Cited by 26 publications

References 14 publications

The Chromate-Inducible chrBACF Operon from the Transposable Element Tn OtChr Confers Resistance to Chromium(VI) and Superoxide

The Chromate-Inducible chrBACF Operon from the Transposable Element Tn OtChr Confers Resistance to Chromium(VI) and Superoxide

Lessons from the Genome Sequence ofNeurospora crassa: Tracing the Path from Genomic Blueprint to Multicellular Organism

Characterization and Metal Detoxification Potential of Moderately Thermophilic Bacillus cereus from Geothermal Springs of Himalaya

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