SELECTION AND DEVELOPMENT OF CADMIUM RESISTANCE IN BACTERIAL CONSORTIA

摘要

The effects of Cadmium (Cd) toxicity on bacterial consortia originating from anaerobic sewage sludge and cultivated under a variety of physiological conditions were studied. Cultures were enriched in minimal media developed specifically for Cd stress studies. At inoculation all Cd was soluble in free ion or chelated form. Electron donors and acceptors were varied to obtain each physiological enrichment type. Adaptation leading to higher levels of Cd resistance of the consortia over time was observed under all physiological conditions. Initial and increased Cd tolerances were greatest under multiphysiological (MPH) followed by sulfate reducing (SRB) and methanogenic (MET) conditions. Fermentative (FRM) enrichments had the least ability to tolerate and adapt to Cd. The Cd remained soluble as free Cd in MPH and FRM conditions and was precipitated in SRB and MET conditions. The 16S rRNA profiles of the consortia under SRB, MPH, and FRM conditions were followed over time. The consortia underwent succession under all physiological conditions when compared with the profile of the inoculum. Microbial population diversity decreased as the consortia were sub-cultured. The effects of chelators in the MPH media were also evaluated. The addition of chelators transiently decreased toxicity.