Phosphate inhibits acetotrophic methanogenesis on rice roots

The contribution of acetate- and H-2/CO2-dependent methanogenesis to total CH4 production was determined in excised washed rice roots by radiolabeling , methyl fluoride inhibition, and stable carbon isotope fraction ation. Add ition of greater than or equal to 20 mM phosphate inhibited methanogenesis, which then was exclusively from H-2/CO2. Otherwise, acetate contributed ab out 50 to 60% of the total methanogenesis, demonstrating that phosphate spe cifically inhibited acetotrophic methanogens on rice roots.