2-Keto-4-methylthiobutyric acid-dependent biosynthesis of ethylene in soil

2-Keto-4-methylthiobutyric acid (KMBA) has been identified as an intermediate in methionine-derived ethylene (C2H4) biosynthesis by microbial cultures. This study was designed to assess the effectiveness of KMBA as an C2H4 precursor in soil. Gas chromatographic analysis indicated that amendment with KMBA (up to 10 mM) stimulated the biosynthesis of C2H4 in two Pakistani soils. Results also revealed that substrate- (KMBA)-dependent C2H4 production was inhibited when the soils were amended either with glucose (as a C source), NH4NO3 (N source) or antibiotics. The KMBA-derived C2H4 biosynthesis in both soils was maximum when the soil suspension was amended with 10 mM substrate and incubated at pH 7.5 for a period of 120 h at 35°C with shaking. Comparison of soils revealed that C2H4 production was relatively greater in a silty clay loam S1 (containing 1.15% organic C) soil compared to a loamy S2 (containing 0.54% organic C) soil. KMBA was found to be an equally effective substrate of C2H4 when compared with another intermediate, 1-aminocyclopropane-1-carboxylic acid (ACC), whereas, α-ketglutaric acid failed to serve as an C2H4 substrate in soil. As far as we know, this is the first study reporting KMBA-dependent C2H4 production in soil.