Screening and characterization of novel methane oxidizing bacterial strains from oil contaminated soils in Khuzestan, Iran

Based on information about the types and numbers of microorganisms in the surface soil samples, the distribution range of underlying oil and gas reservoirs can be judged. In the present study, methane oxidizing bacteria were isolated and characterized from oil contaminated soils in Khuzestan, Iran and their growth was optimized in the presence of methane as sole carbon and energy sources. 

Materials & Methods:

Bacteria were isolated in nitrate mineral salt (NMS) medium in the presence of 50% air and 50% methane. The cultures were incubated on a shaker for 10 days at 30°C in dark place, and every two days, the gas mixture was replaced. The isolated bacteria were characterized based on biochemical and molecular identification tests. Then the optimum growth conditions was detected in different pH values and incubation temperatures in NMS medium containing methane.

Three Gram-negative rods were isolated from soil samples that were able to grow in isolation condition. The isolates were characterized as Achromobacter and Sphingomonas spp. The strains could also grow in the NMS medium with a high methanol concentration (3%). The optimal pH and temperature for the isolates were 7.4 and 30°C respectively.

Methanotrophic strains that were isolated in the present study were able to grow and oxidize methane in high ranges of temperature and pH and can be proposed for the removal of mono-carbon compounds such as methane and as biological detectors for prospecting for oil and gas reservoirs