Isolation and Characterization of Hexavalent Chromium-Reducing Rhizospheric Bacteria From a Wetland

• Published in: International journal of phytoremediation Vol. 12; no. 4; pp. 317 - 334
• Main Authors: Mauricio Gutierrez, Amparo, Pena Cabriales, Juan Jose, Maldonado Vega, Maria
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis Group 01.04.2010; Taylor & Francis Ltd
• Subjects: Adaptation, Physiological - drug effects; Bacteria; Bacteria - genetics; Bacteria - growth & development; Bacteria - isolation & purification; Bacteria - metabolism; bacterial consortia; Biodegradation, Environmental - drug effects; Bioremediation; Cadmium; Chromium; Chromium - isolation & purification; Chromium - metabolism; Chromium - toxicity; Culture Media - pharmacology; Cyperaceae - microbiology; Environmental cleanup; Flowers & plants; Hydrogen-Ion Concentration - drug effects; hyperaccumulators; Industrial Waste - analysis; industrial wastes; microbial activity; Microorganisms; nutrient uptake; Oxidation-Reduction - drug effects; Phylogeny; phytoremediation; Plant Roots - drug effects; Plant Roots - metabolism; Plant Roots - microbiology; pollution control; ponds; Pseudomonas; quantitative analysis; Reduction; rhizosphere bacteria; roots; Salinity; Scirpus; Scirpus americanus; Scirpus americanus Pers; Sodium; Sodium Chloride - pharmacology; soil bacteria; soil pollution; Strain; Waste disposal; Waste Disposal, Fluid; wastewater treatment; water pollution; wetland soils; Wetlands; Mexico; Guanajuato Mexico
• ISSN: 1522-6514; 1549-7879
• DOI: 10.1080/15226510902968118

Scirpus americanus Pers. occurs naturally in "San Germán," a pond that serves as a receptor of industrial wastewater in Guanajuato, México. This plant accumulates metals mainly in the root: concentrations (mg/kg) of Cr, As, Cd and Se were 970, 49, 41, and 85 respectively. Analysis of rhizosphere samples indicated bacterial population of 10 8 cfu g −1 in media with 0.2 mM Cr(VI) and 10 mM sodium gluconate. Thirteen isolates were obtained and phylogenetic analyses (16S rRNA) indicated they corresponded to genera of Agrobacterium, Arthrobacter, Microbacterium, Curtobacterium, Rhodococcus, Xanthomonas and Pseudomonas. Cr(VI) reduction was evaluated using the diphenyl carbazide method. The isolates accomplished 5-40% (20 μM) of reduction in assays of resting cell and tolerated 0.5-5.0 mM Cr(VI). Eight strains used nitrate and thirteen used iron and chromium as electron acceptors to grow under anaerobic conditions. Cr(VI) reduction by five strains occurred at pH values (7-9) and NaCl concentrations (0.5-1.0 M) in basal medium. A mixed culture of strains (S17 and S28) reached a chromium removal of 100% at 0.2 mM Cr(VI) initial concentration. Aerobically, this consortium was capable of 93.8% Cr(VI) reduction of 81 μgL −1 Cr(VI) of the industrial effluent, indicating their possible use in environmental cleanup.