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Plasmids for heavy metal resistance in Alcaligenes eutrophus CH34: Mechanisms and applications
Collard, Jean-Marc; Corbisier, Philippe; Diels, Ludo et al.
1994In FEMS Microbiology Reviews, 14, p. 405-414
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Keywords :
Heavy metal resistance; CH34; plasmids; Alcaligenes eutrophus
Abstract :
[en] 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+, CrO42-, Hg2+, Tl+, Cd2+, Cu2+ and Zn2+. Among the best characterized determinants are the cnr operon (resistance to Co, Ni) an 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.
Disciplines :
Microbiology
Author, co-author :
Collard, Jean-Marc
Corbisier, Philippe
Diels, Ludo
Dong, Q.
Jeanthon, Christian
Mergeay, Max ;  Université de Liège - ULiège > Département Argenco : Secteur GeMMe > Génie minéral et recyclage
Taghavi, S.
Van Der Lelie, Daniel
Wilmotte, Annick  ;  Université de Liège - ULiège > Département des sciences de la vie > Physiologie et génétique bactériennes
Wuertz, Stefan
Language :
English
Title :
Plasmids for heavy metal resistance in Alcaligenes eutrophus CH34: Mechanisms and applications
Publication date :
1994
Journal title :
FEMS Microbiology Reviews
ISSN :
0168-6445
eISSN :
1574-6976
Publisher :
Blackwell Publishing, Oxford, United Kingdom
Volume :
14
Pages :
405-414
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 21 July 2011

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