title: Chromium(VI) bioremoval by Pseudomonas bacteria: role of microbial exudates for natural attenuation and biotreatment of Cr(VI) contamination.
abstract: Laboratory batch and column experiments were conducted to investigate the role of microbial exudates, e.g., exopolymeric substance (EPS) and alginic acid, on microbial Cr(VI) reduction by two different Pseudomonas strains (P. putida P18 and P. aeuroginosa P16) as a method for treating subsurface environment contaminated with Cr(VI). Our results indicate that microbial exudates significantly enhanced microbial Cr(VI) reduction rates by forming less toxic and highly soluble organo-Cr(III) complexes despite the fact Cr(III) has a very low solubility under the experimental conditions studied (e.g., pH 7). The formation of soluble organo-Cr(III) complexes led to the protection of the cells and chromate reductases from inactivation. In systems with no organic ligands, soluble organo-Cr(III) end products were formed between Cr(III) and the EPS directly released by bacteria due to cell lysis. Our results also provide evidence that cell lysis played an important role in microbial Cr(VI) reduction by Pseudomonas bacteria due to the release of constitutive reductases that intracellularly and/or extracellularly catalyzed the reduction of Cr(VI) to Cr(III). The overall results highlight the need for incorporation of the release and formation of organo-Cr(III) complexes into reactive transport models to more accurately design and monitor in situ microbial remediation techniques for the treatment of subsurface systems contaminated with Cr(VI).
authors.affiliation: Faculty of Arts and Science, Department of Biology, Pamukkale University, Denizli, Turkey.
authors.forename: Nazime Mercan
authors.initials: NM
authors.lastname: Dogan
authors.forename: Cetin
authors.initials: C
authors.lastname: Kantar
authors.forename: Sibel
authors.initials: S
authors.lastname: Gulcan
authors.forename: Cleveland J
authors.initials: CJ
authors.lastname: Dodge
authors.forename: Banu Coskun
authors.initials: BC
authors.lastname: Yilmaz
authors.forename: Mehmet Ali
authors.initials: MA
authors.lastname: Mazmanci
mesh_terms: D001673:Biodegradation, Environmental; D002857:Chromium / Q000032:analysis / Q000378:metabolism*; D005122:Exudates and Transudates / Q000378:metabolism*; D011549:Pseudomonas / Q000378:metabolism*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*
chemical_list: D012989:Soil Pollutants; D002857:Chromium; C074702:chromium hexavalent ion