Microbial interactions with chromium: basic biological processes and applications in environmental biotechnology

Abstract

Chromium (Cr) is a highly toxic metal for microorganisms as well as plants and animal cells. Due to its widespread industrial use, Cr has become a serious pollutant in diverse environmental settings. The hexavalent form of the metal, Cr(VI), is considered a more toxic species than the relatively innocuous and less mobile Cr(III) form. The study of the interactions between microorganisms and Cr has been helpful to unravel the mechanisms allowing organisms to survive in the presence of high concentrations of Cr(VI) and to detoxify and remove the oxyanion. Various mechanisms of interactions with Cr have been identified in diverse species of bacteria and fungi, including biosorption, bioaccumulation, reduction of Cr(VI) to Cr(III), and chromate efflux. Some of these systems have been proposed as potential biotechnological tools for the bioremediation of Cr pollution using bioreactors or by in situ treatments. In this review, the interactions of microorganisms with Cr are summarised, emphasising the importance of new research avenues using advanced methodologies, including proteomic, transcriptomic, and metabolomic analyses, as well as the use of techniques based on X-ray absorption spectroscopy and electron paramagnetic resonance spectroscopy.

Gut microbiota and gut morphology of gilthead sea bream (Sparus aurata) juveniles are not affected by chromic oxide as digestibility marker

“…Furthermore, it is known that Pseudomonas sp. can reduce hexavalent Cr (VI), which is considered the most toxic form of Cr, to trivalent Cr (III) without compromising its viability (Gutiérrez‐Corona, Romo‐Rodríguez, Santos‐Escobar, Espino‐Saldaña, & Hernández‐Escoto, ). Thus, it seems unlikely that Cr (III), which is the form present in Cr 2 O 3 would induce negative effects on Gram‐negative bacteria.…”

Heavy metal pollution – A mini review

“…4,13 These siderophore-metal complexes are incapable to enter into the bacterial cells, thereby reducing free toxic metal concentrations in the heavy metal polluted environment. 20 This capability suggests utility of siderophores or siderophore-producing microbes to remediate heavy metal-contaminated environments. 11 Thus, use of metal-tolerant bacteria can be an efficient strategy to reduce metal pollution in contaminated areas, thus, enabling us to use natural tools for reducing heavy metal toxicity in the environment.…”

Confluence of montmorillonite and Rhizobium towards the adsorption of chromium(vi) from aqueous medium

“…Due to its high mobility the hexavalent form is highly toxic, entering the cell and interfering with the functioning of proteins, lipids and DNA by producing reactive oxygen species (ROS). 2,3 Hence, USEPA has categorized stipulated hexavalent chromium under group A carcinogen and the chromium permissible limit in drinking water is less than 0.1 mg L À1 . 4 Therefore, development of various remediation methods for chromium is necessary.…”