Mechanisms of bacterial resistance to chromium compounds |
| |
Authors: | Martha I Ramírez-Díaz César Díaz-Pérez Eréndira Vargas Héctor Riveros-Rosas Jesús Campos-García Carlos Cervantes |
| |
Institution: | (1) Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio B-3, Ciudad Universitaria, Morelia, Michoacan, 58030, Mexico;(2) Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico, D.F., Mexico |
| |
Abstract: | Chromium is a non-essential and well-known toxic metal for microorganisms and plants. The widespread industrial use of this
heavy metal has caused it to be considered as a serious environmental pollutant. Chromium exists in nature as two main species,
the trivalent form, Cr(III), which is relatively innocuous, and the hexavalent form, Cr(VI), considered a more toxic species.
At the intracellular level, however, Cr(III) seems to be responsible for most toxic effects of chromium. Cr(VI) is usually
present as the oxyanion chromate. Inhibition of sulfate membrane transport and oxidative damage to biomolecules are associated
with the toxic effects of chromate in bacteria. Several bacterial mechanisms of resistance to chromate have been reported.
The best characterized mechanisms comprise efflux of chromate ions from the cell cytoplasm and reduction of Cr(VI) to Cr(III).
Chromate efflux by the ChrA transporter has been established in Pseudomonas aeruginosa and Cupriavidus
metallidurans (formerly Alcaligenes eutrophus) and consists of an energy-dependent process driven by the membrane potential. The CHR protein family, which includes putative
ChrA orthologs, currently contains about 135 sequences from all three domains of life. Chromate reduction is carried out by
chromate reductases from diverse bacterial species generating Cr(III) that may be detoxified by other mechanisms. Most characterized
enzymes belong to the widespread NAD(P)H-dependent flavoprotein family of reductases. Several examples of bacterial systems
protecting from the oxidative stress caused by chromate have been described. Other mechanisms of bacterial resistance to chromate
involve the expression of components of the machinery for repair of DNA damage, and systems related to the homeostasis of
iron and sulfur. |
| |
Keywords: | Chromate resistance Chromate efflux Chromate reduction |
本文献已被 SpringerLink 等数据库收录! |
|