Leucobacter chromiireducens CRB2, a new strain with high Cr(VI) reduction potential isolated from tannery-contaminated soil (Fez, Morocco)

Abstract

A new chromate-reducing bacterial strain was isolated from soil contaminated with tannery waste. Based on 16S rRNA gene sequence analyses, this strain was identified as Leucobacter chromiireducens CRB2. This bacterium had high multiresistance against heavy metals with a MIC of 700 mg/L Cr(VI) and was able to reduce Cr(VI) both aerobically and anaerobically. The optimum pH and temperature for Cr(VI) reduction were pH 8.0 and 30°C, respectively. Glycerol (10 mM) was the most efficient carbon source for Cr(VI) reduction by the strain followed by glucose. Moreover, Cr(VI) reduction by L. chromiireducens CRB2 was unaltered in the presence of other oxyanions. Bacterial cells immobilized in Na-alginate beads showed a high Cr(VI) reduction rates and exhibited an ability to repeatedly reduce Cr(VI). Therefore, immobilized cells were more effective than free cells in Cr(VI) reduction. Resting and permeabilized cell assays provided the better evidence of the presence of an enzymatic chromate reduction in L. chromiireducens CRB2. Assays conducted with cytosolic and particulate fractions of L. chromiireducens confirmed the role of cytosolic proteins in Cr(VI) reduction. Cr(VI) reduction by L. chromiireducens was mediated by a soluble enzyme contained in the cytoplasm after its adsorption on the cell surface. To the best of our knowledge, this is the first report studying parameters affecting Cr(VI) reduction and describing Cr(VI) removal mechanism by strain of L. chromiireducens.

Biogenic Silver Nanoparticles Produced by Soil Rare Actinomycetes and Their Significant Effect on Aspergillus-derived mycotoxins

“…In this context, it has been reported that metal-resistant G. nicotianae MSSRFPD35 exhibited the potential to grow and degrade phenol in the presence of several heavy metals such as Pb, Ni, Cd, Co, and Cu [49]. Likewise, various species of the genus Leucobacter, which belongs to the phylum Actinobacteria, can tolerate a wide variety of heavy metals such as Cd, Cr, Cu, As, and Pb [50][51][52]. In agreement with our findings, the biomass extract from the Ag-tolerant actinobacterium Nocardiopsis dasonvillei KY772427 was used as a reducing agent for the biosynthesis of bioactive AgNPs [53].…”

Leucobacter chromiisoli sp. nov., isolated from chromium-containing chemical plant soil

“…Strain CSA1 T grew in medium containing 5.8 m Cr(VI). When the concentration of Cr(VI) was 3.8 mM, the strain could reduce 5 % Cr(VI) within 48 h. Some members of the genus Leucobacter are reported to be able to resist Cr(VI) with a concentration of 5–300 mM and have a certain reduction ability [29–32].…”