Biodegradation of Atrazine by Bacteria Isolated from Lotic Water

Abstract

Background: The persistence of toxic herbicides in water and soil has been considered to be potential environmental concern. As atrazine is still used in Nigeria as a major herbicide, a continuous search for atrazine degrading microorganisms is required. Objectives: The effects of incubation period on growth and atrazine degradation by bacteria isolated from a lotic water in the Niger Delta were evaluated and also determined were the effects of temperature and anaerobic incubation on atrazine removal by the most efficient isolate.    Methods: The bacteria capable of degrading atrazine were isolated from the lotic water using enrichment technique. The optimal incubation period for growth and atrazine degradation by the isolates was assessed by growing the isolates in Mineral salts medium containing 100 mg/L atrazine for 30 days at 35ºC. The flasks inoculated with the most efficient isolate were also incubated anaerobically and at varying temperatures (25, 30, 35 and 40ºC). Cultures were withdrawn every 5 days and growth and atrazine concentration measurements were carried out using standard plate count and HPLC respectively.   Results: Atrazine degrading bacteria of the genera Pseudomonas, Bacillus and Micrococcus were isolated with Pseudomonas sp. as the most efficient isolate. Incubation time of 20 days was observed as optimum for growth of the three isolates. Pseudomonas sp. gave the highest atrazine degradation rate of 82.67% followed by Bacillus sp. (75.33%) and Micrococcus sp. (69.33%) at the end of 30 days. Atrazine was degraded at reduced rate under anaerobic condition and temperature of 35ºC was optimum for atrazine degradation by Pseudomonas sp. Conclusion: These atrazine degrading strains may be useful in bioremediation of contaminated wastewater.