Usage of metals as the terminal electron acceptors by the sulfate-reducing bacteria

Reduction of sulfate, nitrate and nitrite ions by Desulfovibrio sp. under the influence of ferrum (III) citrate

“…When sulfate ions reduction by the bacteria in the presence of 1.74−10.41 mM FeC 6 H 5 O 7 decreased 2.0−4.7 times, the nitrate ions reduction − 1.3−1.9 times, nitrite ions − 1. nitrate and nitrite reductases of the investigated strains are less sensitive to negative influence of ferrum (III) citrate than the cytoplasmic enzymes involved in sulfate respiration of these bacteria -ATP sulfurylase, pyrophosphatase, APS reductase, sulfite reductase, as described [16,21,27]. This can be explained by the fact that at high concentrations in the medium Fe(III) can interact not only with functional groups of a number of bacteria cellular metabolites, but also cause an oxidative stress [10,28]. Despite the fact that the reduction of 1.74−10.41 mM Fe(ІІІ) by cells in the media with Na 2 SO 4 ×10 H 2 O, NaNO 3 or NaNO 2 decreased by 1.1−2.1, 1.6−2.7 and 1.1−2.5 times, respectively, compared with its reduction in the medium with only FeC 6 H 5 O 7 , the obtained results suggest that the investigated strains of bacteria are adapted to high concentrations of trivalent ferrum compounds (up to 10.41 mM) and, therefore, can survive in environments contaminated by heavy metals.…”

“…In the bacteria cells, ferrum is an essential trace element that participates in the processes of photosynthesis, N 2 fixation, methanogenesis, H 2 synthesis, respiration, regulation of gene expression and DNA biosynthesis [19]. The toxic effect of ferrum, as well as other metals, on the bacterial cell is its binding with the surface structures of the cell wall, the change in the electrophysiological properties of the cytoplasmic membrane, the blocking of transport systems, the replacement of the nece ssary ions from active centers of the enzymes, binding with functional groups of cell metabolites [27,28]. Because the Fe(ІІІ)/Fe(ІІ) pair at pH 7.0 has a very high oxidation-reduction potential (E 0 ′ = +0.77 V), which, however, is highly dependent on the acidity of the medium [7,8,16], at high concentrations in the cytoplasm the Fe(ІІІ) is the catalyst of Fenton and Haber-Weiss reactions that result a formation of toxic forms of oxygen [10,19,27].…”