Two bacteria have been isolated that are capable of oxidizing N-methylisonicotinate, a photodegradation product of Paraquat (1.1′-dimethyl-4,4′-bipyridylium ion). N-Methylisonicotinate-grown cells of strain 4C1, a Gram-positive rod, oxidized 2-hydroxy-N-methylisonicotinate without lag. Cell-free extracts of these cells converted 2-hydroxyisonicotinate into 2,6-dihydroxyisonicotinate; the reaction did not require molecular oxygen. Maleamate was deamidated and maleate isomerized to fumarate by soluble enzyme systems. [14C]Formaldehyde was isolated as the dimedone derivative from the supernatant of a cell suspension oxidizing N-[14C]methylisonicotinate, and no [14C]-methylamine was detected. Whole cells incubated with N-methyl[carboxy-14C]isonicotinate released 95% of the radioactivity as 14CO2. The second bacterium, strain 4C2, a Gram-negative rod, did not oxidize any of the mono- or di-hydroxypyridines or their N-methyl derivatives that were available or could be synthesized; nor did cell-free extracts oxidize any of these compounds. Methylamine was oxidized by whole cells without lag; cell-free extracts converted methylamine into formaldehyde when a soluble enzyme system requiring an electron acceptor was used; formaldehyde was oxidized to formate and formate to CO2 by enzyme systems requiring NAD+.
- © 1972 London: The Biochemical Society