Chromium(V) complexes generated in Arthrobacter oxydans by simulation analysis of EPR spectra

Effect of Zn(II) on the reduction and accumulation of Cr(VI) by Arthrobacter species

“…According to ESR measurements, in bacterial systems the Cr(V) ESR line is characterized by a g-factor of 1.980 and a line width of 12 G (corresponding to Cr(V) diols) and the Cr(III) ESR signal is characterized by a g-factor of 2.02 and a line width of 650 G (corresponding to Cr(III) hydroxide) [4,9]. Thus, the presence of Zn(II) ions did not change the nature of Cr(V) and Cr(III) complexes generated during the reduction of Cr(VI) by this bacterial strain.…”

“…In our recent studies we established that the Gram-positive bacterial strains of Arthrobacter genera isolated from basalt samples which were taken from the most polluted regions of the USA and the Republic of Georgia can reduce and detoxify Cr(VI) with a high efficiency under aerobic conditions [4,9,22,23]. Our electron spin resonance (ESR) experiments revealed that Cr(VI) is reduced to less toxic Cr(III) compounds through the formation of oxo Cr(V) diols at the surface of bacteria [4,9]. Later, the decomposition of Cr(V) diols to Cr(III) complexes was also investigated [23].…”

Biosorption of Heavy Metals – New Perspectives

“…bacteria in the biotreatment of Cr VI solutions has been reported by several authors. Tsibakhashvili et al have based their studies on the mechanism of Cr VI bioreduction with Arthrobacter oxydans [28,57,[63][64][65] on the detection of Cr v intermediaries by ESR spectroscopy. Isolation of Arthrobacter crystallopoietes from Cr VI contaminated sites was reported by Camargo et al, whom also used molecular biology to understand the biological processes that related to Cr VI reduction and bioaccumulation [66].…”

Chromate reduction by Arthrobacter CR47 in biofilm packed bed reactors

“…has been elucidated in recent studies with A. oxydans. It has been reported [3,4,18] that the mechanism responsible for chromate resistance in A. oxydans is a positively charged surface protein and a capsule that plays a role in the entrapment and chemical transformation of Cr(VI).…”

“…The most widely accepted hypothesis of the mechanisms of Cr(VI) toxicity involved entry into the cells by the sulfate transport channels and subsequent intracellular reduction to Cr(V) and reactive oxygen species. However According to recent data [3,4], extracellular reduction of Cr(VI) in animals may occur in the initial steps of Cr(VI) metabolism. Evidence is mounting that observed long lived Cr(V) complexes are stabilized by a combination of extracellular and intracellular species.…”