Abstract:
Numbers, of microorganism and rate of methane production from microorganisms from soil and 70 days of age rice root cv. Supanburi 90 were studied in this research. Most Probable Number Technique (MPN) was used for counting of methanogenic bacteria (MTB). 16SrDNA cloning and Fluorescent In Situ Hybridization Technique (FISH) were constructed to determine MTB. Methane and carbondioxide productions of microorganisms from soil and rice root cv. Supanburi 90 were determined by gas chromatography.Methane production of microorganisms from soil and rice root cv. Supanburi 90 was determined from the cultivation in the basal medium in the serum vial under anaerobic condition at 37 OC for 40 days. From scanning electron microscopic study, microorganisms from the soil and rice root were found to be cocci in the size of 1-2 ?m. The numbers of MTB were 3.49 ?108 cell/g soil (dry weight), 1.02?103 cell/g soil (dry weight) and 2.01?103 cell/g rice root (dry weight) for root zone soil, unplanted soil and rice root, respectively. MTBs from root zone soil, unplanted soil and rice root classified by Phylogenetic analysis to be Methanosarcina barkeri, Methanosaeta sp., Methanospirillum hungatei and uncultured archaeon. MTBs were cultured in the medium containing 0.86 and 1.72 mM acetic acid and characterized by FISH. MTBs from unplanted soil, enriched by 0.86 mM acetic acid were characterized to be Methanosaeta sp. MTBs from root zone soil, enriched by 0.86 mM acetic acid were characterized to be Methanosaeta sp. and Methanosarcina sp. But when enrichment by 1.72 mM acetic acid, MTB from root zone soil wasfound to be only Methanosarcina sp. MTB from rice root, enriched by 0.86 or 1.72 mM acetic acidwas found to be only Methanosarcina sp. Methane production of MTBs from soil near rice rootbegun at the 4 th day of incubation in basal medium under anaerobic condition in serum vial was0.07 mg/gdw?????-1/d-1. MTBs from unplanted soil begun at the 6 th day of incubation produced methane0.02 mg/gdw?????-1/d-1. The highes methane production was found at 32 th, 24 th and 28 th day of incubation to be 0.33, 0.44 and 0.29 mg/gdw?????for MTBs from unplanted soil, soil near rice root and rice root, respectively. Carbondioxide produced at the 4 th day of incubation was 0.03, 0.01 mg/gdw?????-1/d?????for soil near rice root and rice root, respectively and carbon dioxide produced at the 6 th day of incubation was 0.04 mg/gdw-1/d?????-1 for unplanted soil. The highest carbon dioxide produced at the 12 th , 18 th and 22 th day of incubation was 0.28,0.22 and 0.24 mg/gdw-1/d-1 for microorganisms from soil near rice root, rice root and unplanted soil, respectively.