Farshid Kafilzadeh, Younes Moghtaderi, Abbasali Rezaeian Jahromi
Biological uptake is one of the most effective ways to remove heavy metals from contaminated areas. Bacteria in contaminated areas get resistant to cadmiumby many ways and become able to remove cadmium. Sultan Abad River, due to its proximity to agricultural land, urban sewage and industrial town of Shiraz suffers from various contaminationswith heavy metals such as cadmium. The purpose of this study is isolation and identification of cadmium-resistant bacteriain Soltan Abad River sediments and determination of MIC and MBC ranges of resistance by those indigenous bacteria. In this study, sediment samples from three stations were taken during two consecutive seasons from Sultanabad River (Autumn and Winter,2012 and 2013). Sediment samples were preparedand studied according to standard methods in the two groups, The first group was used to measure the amount of cadmium by atomic absorption spectrophotometry and the values of pH and temperatureand the second group was used for enrichment and isolation of cadmium-resistant bacteria.LB medium was used for the enrichment and solid nutrient agar medium was used for separation. Bacteria were identified by conventional biochemical tests and tolerance of isolated bacteria by MIC and MBC were evaluated at different concentrations of cadmium chloride. By morphology and biochemical tests, eight Gram-negative bacteria and four Gram-positive cadmium-resistant bacteria were
isolated and indentified. The average bacteria counts at all stations show that as compared with other stations, station 3 has more bacteria and the averagebacteria counts was reduced in the presence of 1 mM cadmium chloride (p<0/001). The most abundant isolated in this study that were Escherichia cloi and Bacillus, were observed at all stations and the rarest one wasKlebsiella pneumoniaethat was only observed at station 1 and in autumn. The Maximum resistance to cadmium was observed in bacteria Klebsiella pneumoniae with MIC 9 and MBC 10 mM andnext to it, the resistant bacteria Pseudomonas aeruginosa and Bacillus cereus were reported as the most resistant, respectively, with MIC 8 and 6 and MBC 9 and 7 mM. Isolated bacteria, especially bacteria Klebseilla pneumoniae, Pseudomonas aeruginosa and Bacillus cereus are good candidates for treatment and elimination of the
cadmium present in polluted rivers.
