Fe(III), Cr(VI), and Fe(III) mediated Cr(VI) reduction in alkaline media using a Halomonas isolate from Soap Lake, Washington

Hexavalent chromium is one of the most widely distributed environmental contaminants. Given the carcinogenic and mutagenic consequences of Cr(VI) exposure, the release of Cr(VI) into the environment has long been a major concern. While many reports of microbial Cr(VI) reduction are in circulation, very few have demonstrated Cr(VI) reduction under alkaline conditions. Since Cr(VI) exhibits higher mobility in alkaline soils relative to pH neutral soils, and since Cr contamination of alkaline soils is associated with a number of industrial activities, microbial Cr(VI) reduction under alkaline conditions requires attention. Soda lakes are the most stable alkaline environments on earth, and contain a wide diversity of alkaliphilic organisms. In this study, a bacterial isolate belonging to the Halomonas genus was obtained from Soap Lake, a chemically stratified alkaline lake located in central Washington State. The ability of this isolate to reduce Cr(VI) and Fe(III) was assessed under alkaline (pH = 9), anoxic, non-growth conditions with acetate as an electron donor. Metal reduction rates were quantified using Monod kinetics. In addition, Cr(VI) reduction experiments were carried out in the presence of Fe(III) to evaluate the possible enhancement of Cr(VI) reduction rates through electron shuttling mechanisms. While Fe(III) reduction rates were slow compared to previously reported rates, Cr(VI) reduction rates fell within range of previously reported rates

New Findings on Aromatic Compounds’ Degradation and Their Metabolic Pathways, the Biosurfactant Production and Motility of the Halophilic Bacterium Halomonas sp. KHS3

The study of the aromatic compounds’ degrading ability by halophilic bacteria became an interesting research topic, because of the increasing use of halophiles in bioremediation of saline habitats and effluents. In this work, we focused on the study of aromatic compounds’ degradation potential of Halomonas sp. KHS3, a moderately halophilic bacterium isolated from hydrocarbon-contaminated seawater of the Mar del Plata harbour. We demonstrated that H. sp. KHS3 is able to grow using different monoaromatic (salicylic acid, benzoic acid, 4-hydroxybenzoic acid, phthalate) and polyaromatic (naphthalene, fluorene, and phenanthrene) substrates. The ability to degrade benzoic acid and 4-hydroxybenzoic acid was analytically corroborated, and Monod kinetic parameters and yield coefficients for degradation were estimated. Strategies that may enhance substrate bioavailability such as surfactant production and chemotactic responses toward aromatic compounds were confirmed. Genomic sequence analysis of this strain allowed us to identify several genes putatively related to the metabolism of aromatic compounds, being the catechol and protocatechuate branches of β-ketoadipate pathway completely represented. These features suggest that the broad-spectrum xenobiotic degrader H. sp. KHS3 could be employed as a useful biotechnological tool for the cleanup of aromatic compounds-polluted saline habitats or effluents.Fil: Corti Monzón, Georgina de la Paz. Universidad Nacional de Mar del Plata; Argentina. Instituto de Ciencia y Tecnología de Alimentos y Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Nisenbaum, Melina. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Herrera Seitz, Karina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Murialdo, Silvia Elena. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentin