Isolation and identification of arsenic eliminating bacteria from Lake Maharloo and evaluation of the pattern of their antibiotic resistance

Arsenic is one of the most dangerous heavy metals in the environment that is harmful for organisms such as human beings. Due to this treat economic approach for elimination of arsenic from water and wastewater is necessary. In this research arsenic-resistant bacteria from water and sediments of Lake Maharloo were isolated and identified then their antibiotic resistance was evaluated. Methods and Materials: Sampling was done from water and sediments of four stations in Maharloo Lake in three seasons. Bacteria were isolated and purified after cultivation and enriching samples in LB broth medium containing 5mg/L arsenic oxide. Isolated bacteria were identified by usual and standard microbiological tests. Then antibiotic sensitivity was determined by antibiogram method and Muller Hinton Agar culture medium. Bacteria such as Bacillus sp, Vibrio sp, Staphylococcus sp, Corynebacterium sp, Micrococcus sp, Pseudomonas sp and E. coli were isolated in different seasons from water and sediments of Lake Maharloo. The maximum and minimum abundance percentage of arsenic-resistant bacteria was found in sediments of spring (56.25%) and winter (12.50%) (P<0.05) respectively. Also The maximum and minimum abundance percentage of arsenic-resistant bacteria in total of water and sediment related to Khoshk river in winter and the middle of lake in autumn (P<0.05) respectively. Antibiotics resistance patterns evaluation revealed that isolated bacteria had the most antibiotic resistance to penicillin and the lowest to amikacin in all seasons. In this research indigenous arsenic resistant bacteria of Lake Maharloo were identified. Entrance of arsenic metal and different antibiotics to Lake Maharloo have caused an increase in the arsenic resistant bacteria and their antibiotic resistance.