PLASMID BORNE BIODEGRADATION OF 1,3 -DINITROBENZENE BY ACHROMOBACTER

Abstract

A pure culture of Achromobacter, designated YD, was isolated from mixed soil microflora that could utilize 1,3 -dinitrobenzene (m-DNB) as a sole carbon source. A small amount of yeast extract (10 ppm) is required to maintain the organism on selective medium. Growth in strain selective broth is logarithmic and reaches a level of 2.5 X 10⁷CFU/mL in 24 hours. Mineralization studies with m-DNB revealed that the entire mDNB molecule is degraded by YD, 36 % being released as carbon dioxide. Warburg studies have shown that this organism is metaspecific for the dinitrobenzene molecule but the elucidation of biochemical pathway of mDNB degradation remains evasive. Treating YD with Mitomycin C cured the bacteria of the trait for mDNB degradation and thus revealed evidence of a plasmid. The YD organism was conjugated with several Pseudomonas species. In these conjugation experiments, YD transferred the m-DNB degradation plasmid to the recipient Pseudomonas strains. The plasmid in YD encoding for m-DNB degradation was isolated by chemical extraction, as well as, from the Pseudomonas conjugates, after growth in selective media.