Abstract

The aims of this study are isolating arsenite-resistant bacteria from arsenic contaminated soil and the investigation of arsenite bioremediation efficiency by the most resistant isolates. Isolation of arsenite-resistant bacteria and the minimum inhibitory concentration (MIC) were conducted by spread plate method and the agar dilution method on PHG-II agar plates supplemented with sodium arsenite respectively. The results showed that, 69 and 25% of arsenite resistant isolates were geram positive and negative bacilli, respectively. Its maximum MIC was 128 mM/L, which is related to such bacteria asBacillus macerans, Bacillus megaterimand Corynebacterium vitarumen. There is a significant difference (P< 0.01) between three isolates in arsenite removal potential and arsenite bioaccumulation. The maximum percentage of arsenite removal potential (92%) and arsenite bioaccumulation (36%) were related to B. macerans. The removal efficiency of arsenite for B. macerans, C. (vitaromen) and B. megaterim were 60, 43 and 38% after 48 h of growth, respectively, while after 144 h of Bacillus macerans, Corynebacterium(vitaromen) growth  and 120 h of Bacillus megaterimgrowth were 92, 80 and 73% respectively. The results also were shown the highest percentage of arsenite in biomass (36%), arsenate from oxidation (27%) were related to B. macerans, B. megaterium and B. megaterium. These results express the probability of finding more arsenic accumulating bacteria from the contaminated soil environment and can be concluded that arsenic resistant and/or accumulating bacteria, such as Bacillus sp., are widespread in the polluted soils and are valuable candidates for bioremediation of arsenic contaminated ecosystems.

Key words: Arsenite, bacteria, bioremediation, MIC.