Construction and characterization of heavy metal-resistant haloaromatic-degrading Alcaligenes eutrophus strains

Springael, Dirk; Diels, Ludo; Hooyberghs, L.; Kreps, Sabine; Mergeay, Max

doi:10.1128/aem.59.1.334-339.1993

Cited by 80 publications

(17 citation statements)

References 30 publications

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“…Bacteria belonging to the genus Alcaligenes express not only metal resistance genes (cnr, czc, chr, cup) but also various xenocatabolic plasmids which are involved in the degradation of polychlorobiphenyl (PCB) [25] or the herbicide 2,4-D (pJP4) [26]. These xenobiotics may be used as sole carbon sources, even in the presence of high concentrations of heavy metals [26]. This observation is of particular relevance for the treatment of heterogenous mixed sources of pollution (heavy metals-organic pollutants) which correspond to more than a third of the polluted areas.…”

Section: Treatment Of Mixed Pollutionsmentioning

confidence: 99%

Plasmids for heavy metal resistance in Alcaligenes eutrophus CH34: Mechanisms and applications

Collard¹

1994

FEMS Microbiology Reviews

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Alcaligenes eutrophus CH34 is the main representative of a group of strongly related strains (mostly facultative chemolithotrophs) that are well adapted to environments containing high levels of heavy metals. It harbors the megaplasmids pMOL28 and pMOL30 which carry resistance determinants to Co2+, Ni2+, CrO(4)2-, Hg2+, Tl+, Cd2+, Cu2+ and Zn2+. Among the best characterized determinants are the cnr operon (resistance to Co, Ni) on pMOL28 and the czc operon on pMOL30 (resistance to Co, Cd and Zn). Although the two systems reveal a significant degree of amino acid similarity in the structural genes, the regulation of the operons is different. The resistance mechanism in both cases is based on efflux. The efflux mechanism leads to a pH increase outside of the cytoplasmic membrane. Metals are sequestered from the external medium through the bioprecipitation of metal carbonates formed in the saturated zone around the cell. This latter phenomenon can be exploited in bioreactors designed to remove metals from effluents. The bacteria are immobilized on composite membranes in a continuous tubular membrane reactor (CTMR). The effluent continuously circulates through the intertubular space, while the external surface of the tubes is in contact with the growth medium. Metal crystals are eventually removed by the effluent stream and collected on a glass bead column. The system has been applied to effluents containing Cd, Zn, Co, Ni and Cu. By introducing catabolic plasmids involved in the aerobic degradation of PCBs and 2,4-D into metal-resistant A. eutrophus strains, the application range was widened to include effluents polluted with both organic and inorganic substances. Biosensors have been developed which are based on the fusion of genes induced by metals to a reporter system, the lux operon of Vibrio fischeri. Bacterial luciferases produce light through the oxidation of fatty aldehydes. The gene fusions are useful both for the study of regulatory genes and for the determination of heavy metal concentrations in the environment.

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Section: Treatment Of Mixed Pollutionsmentioning

confidence: 99%

Plasmids for heavy metal resistance in Alcaligenes eutrophus CH34: Mechanisms and applications

Collard¹

1994

FEMS Microbiology Reviews

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“…Conjugation experiments, the isolation and characterization of R‐prime plasmids [10,65], the construction of a cosmid library [39], and the development of electroporation [66] allowed the circularity of the chromosome to be established and various loci to be mapped [10,16,65,67,68]. Genetic and physical maps of the pMOL28 plasmid and its conjugation‐proficient derivative pMOL50 were produced [14].…”

Section: Introduction:ralstonia Metallidurans: General Description Amentioning

confidence: 99%

Ralstonia metallidurans, a bacterium specifically adapted to toxic metals: towards a catalogue of metal-responsive genes

et al. 2003

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Ralstonia metallidurans, formerly known as Alcaligenes eutrophus and thereafter as Ralstonia eutropha, is a beta-Proteobacterium colonizing industrial sediments, soils or wastes with a high content of heavy metals. The type strain CH34 carries two large plasmids (pMOL28 and pMOL30) bearing a variety of genes for metal resistance. A chronological overview describes the progress made in the knowledge of the plasmid-borne metal resistance mechanisms, the genetics of R. metallidurans CH34 and its taxonomy, and the applications of this strain in the fields of environmental remediation and microbial ecology. Recently, the sequence draft of the genome of R. metallidurans has become available. This allowed a comparison of these preliminary data with the published genome data of the plant pathogen Ralstonia solanacearum, which harbors a megaplasmid (of 2.1 Mb) carrying some metal resistance genes that are similar to those found in R. metallidurans CH34. In addition, a first inventory of metal resistance genes and operons across these two organisms could be made. This inventory, which partly relied on the use of proteomic approaches, revealed the presence of numerous loci not only on the large plasmids pMOL28 and pMOL30 but also on the chromosome. It suggests that metal-resistant Ralstonia, through evolution, are particularly well adapted to the harsh environments typically created by extreme anthropogenic situations or biotopes.

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“…Conventional remediation of these sites is often costly and ineffective [2]. Bioremediation may be a lower cost alternative, but several studies have shown that metal toxicity inhibits organic pollutant biodegradation in co-contaminated systems [1,[3][4][5][6][7][8][9]. Several approaches to mitigating metal toxicity in co-contaminated systems have been proposed including the use of metal-resistant bacteria [10], treatment additives [11], and chelating agents [7].…”

Section: Introductionmentioning

confidence: 99%

Effect of pH on cadmium toxicity, speciation, and accumulation during naphthalene biodegradation

Sandrin

Maier

2002

Enviro Toxic and Chemistry

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Lowering pH of a microbiological medium from 7 to 4 decreased cadmium toxicity during naphthalene biodegradation by a Burkholderia sp. Cadmium speciation and cadmium accumulation in the system were studied to explain this effect. Cadmium speciation was determined by direct measurement and by geochemical modeling. Previous studies have implicated the monovalent hydroxylated cadmium (CdOH+) species in the effect of pH on cadmium toxicity. Modeling analysis predicted CdOH+ formation only at very low concentrations (< or = 0.0128 microM), while the measured concentration of divalent ionic cadmium (Cd2+) was at least three orders of magnitude greater, suggesting that Cd2+ is the more significant metal form. With respect to cadmium accumulation, cells contained in media adjusted to pH 4 accumulated only 2.76 +/- 0.76 mg Cd/g cells, whereas cells in media adjusted to pH 7 accumulated 8.52 +/- 0.71 mg Cd/g cells. These data suggest that cadmium toxicity is correlated with increased cadmium accumulation rather than the formation of CdOH as pH is increased. At low pH, the decrease in cadmium accumulation may be caused by increased competition between hydrogen and cadmium ions for binding sites on the cell surface or by an increase in metal efflux pump activity due to an increase in the proton gradient that drives the efflux pump.

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Construction and characterization of heavy metal-resistant haloaromatic-degrading Alcaligenes eutrophus strains

Cited by 80 publications

References 30 publications

Plasmids for heavy metal resistance in Alcaligenes eutrophus CH34: Mechanisms and applications

Plasmids for heavy metal resistance in Alcaligenes eutrophus CH34: Mechanisms and applications

Ralstonia metallidurans, a bacterium specifically adapted to toxic metals: towards a catalogue of metal-responsive genes

Effect of pH on cadmium toxicity, speciation, and accumulation during naphthalene biodegradation

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