Department of Botany and Microbiology and Department of Chemistry and Biochemistry, The University of Oklahoma, Norman, Oklahoma 73019.
Appl Environ Microbiol. 1993 Jul;59(7):2251-6. doi: 10.1128/aem.59.7.2251-2256.1993.
The anaerobic biodegradation of picloram (3,5,6-trichloro-4-amino-2-pyridinecarboxylic acid) in freshwater sediment was favored under methanogenic conditions but not when sulfate or nitrate was available as a terminal electron acceptor. Under the former conditions, more than 85% of the parent substrate (340 muM) was removed from nonsterile incubations in 30 days, following a 50-day acclimation period. Concomitant with substrate decay, an intermediate transiently accumulated in the sediment slurries. By liquid chromatography-mass spectrometry, the intermediate was identified as an isomer of dichloro-4-amino-2-pyridinecarboxylic acid. Proton nuclear magnetic resonance evidence suggested that a chlorine was reductively removed from the parent substrate at the position meta to the nitrogen heteroatom. Upon continued incubation, the dechlorinated product was transformed into an unidentified compound which accumulated and resisted further decay. The addition of sulfate or bromoethanesulfonic acid to sediment slurries inhibited picloram dehalogenation, but molybdate reversed the inhibitory effect of sulfate on pesticide metabolism. These findings help clarify the fate of a halogenated nitrogen heterocyclic herbicide in anaerobic environments.
在产甲烷条件下， picloram（3,5,6-三氯-4-氨基-2-吡啶羧酸）在淡水沉积物中的厌氧生物降解得到促进，但在硫酸盐或硝酸盐可用作末端电子受体时则不然。在前一种情况下，在 50 天的适应期后，30 天内未灭菌培养物中超过 85％的母体基质（340 μM）被去除。伴随着基质的衰减，一种中间产物在沉积物悬浮液中短暂积累。通过液相色谱-质谱联用仪，鉴定出中间产物是二氯-4-氨基-2-吡啶羧酸的异构体。质子核磁共振证据表明，母体底物上位于氮杂原子间位的氯被还原去除。随着进一步的孵育，脱氯产物被转化为一种未知的化合物，该化合物积累并抵制进一步降解。向沉积物悬浮液中添加硫酸盐或溴乙磺酸盐会抑制 picloram 脱卤，但钼酸盐会逆转硫酸盐对农药代谢的抑制作用。这些发现有助于阐明卤代含氮杂环除草剂在厌氧环境中的命运。
