Characterization of Methane Producing Bacteria from Ricefield Soil and Rice Roots

Abstract

One of the emission sources of methane in the atmosphere causing the world warming comesfrom paddy fields which are the habitats of methane producing bacteria. Rhizospheric soil samplesand rice roots cv. Supanburi 90 and Homsupanburi grown at the Rice Research Center, PathumthaniProvince were analyzed for the presence of methane producing bacteria. The samples were incubatedin basal broth medium in serum vials under anaerobic condition at 37°C for 40 days. Methaneconcentration in the head space vials was determined by gas chromatography. The results showedthat the methane was released from the producing bacteria from the rhizospheric soil of the paddyfield of the rice root samples cv. Homsupanburi and Supanburi 90 could produce methane at themaximum concentration of 21.55 and 24.67 micromole/g dry weight /day at 24 and 22 days ofincubation, respectively. The microorganisms from the rice root cv. Supanburi 90 and Homsupanburicould produce methane at maximum rate of 19.92 and 23.23 micromole/g dry weight/day at 28 daysof incubation, respectively. From the experiments of determination on the type of methane producingbacteria by Fluorescent In Situ Hybridization (FISH) technique, it was found that the microbacteriafrom rice root was characterized to be Methanosarcina sp. while the microbacteria from the soil wascharacterized to be Methanosatae sp. The number of the methanogenic bacteria from the soil and riceroot of the rice was determined by most probable number (MPN) method. The results showed thatmethane production rate depended on the number of the methanogenic bacteria.

Key Words : Methane / Methanogenic Bacteria / Rice / Root