Efficient removal of hexavalent chromium by a tolerant Streptomyces sp. affected by the toxic effect of metal exposure.
OBJECTIVE
To isolate and analyse chromium-resistant micro-organisms suitable for bioremediation.


RESULTS
Strain CG252, with a minimal inhibitory concentration of 500 microg ml(-1), was isolated from contaminated soils and identified as a Streptomyces sp. by 16S rDNA sequence analysis. Assays carried out at various Cr(VI) concentrations indicated that chromium removal was more efficient at lower concentrations and that this activity resulted in accumulation of Cr(III). Atomic adsorption analysis indicated that the chromium removed was not associated with cell mass and activity assays showed that the capacity to reduce Cr(VI) was most probably due to a soluble cytosolic enzyme. Cells grown as biofilms showed enhanced removal of Cr(VI) with respect to planktonic cells, while analysis of growth and colony morphology indicated that Cr(VI) had a toxic effect on this strain.


CONCLUSIONS
Streptomyces sp. CG252 tolerated heavy metals and elevated levels of chromium, despite its negative effect on growth and development, and was efficient at removing Cr(VI) by promoting reduction to Cr(III).


CONCLUSIONS
Strain CG252's capacity to tolerate heavy metals and to reduce Cr(VI) to the less toxic Cr(III), especially when forming biofilms, makes it a promising candidate for detoxification of sites containing this heavy metal.
Morales
D K
DK
Corporación Corpogen, Bogotá, Colombia.
Ocampo
W
W
Zambrano
M M
MM
D001673:Biodegradation, Environmental; D018441:Biofilms; D002857:Chromium / Q000633:toxicity; D004783:Environmental Microbiology; D007220:Industrial Waste; D019216:Metals, Heavy; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability; D021521:Ribotyping; D012988:Soil Microbiology; D012989:Soil Pollutants; D013302:Streptomyces / Q000187:drug effects / Q000302:isolation & purification* / Q000378:metabolism
D007220:Industrial Waste; D019216:Metals, Heavy; D012989:Soil Pollutants; D002857:Chromium; C074702:chromium hexavalent ion