Bacterial Metabolism of para - and meta -Xylene: Oxidation of a Methyl Substituent

Abstract

Pseudomonas Pxy was isolated on p -xylene as sole source of carbon and energy. Substrates that supported growth were toluene, p -methylbenzyl alcohol, p -tolualdehyde, p -toluic acid, and the analogous m -methyl derivatives, including m -xylene. Cell extracts prepared from Pseudomonas Pxy after growth with either p -xylene or m -xylene oxidized the p - and m -isomers of tolualdehyde as well as p -methylbenzyl alcohol. The same cell extracts also catalyzed a “meta” fission of both 3- and 4-methylcatechol. Treatment of Pseudomonas Pxy with N -methyl- N ′-nitro- N -nitrosoguanidine led to the isolation of two mutant strains. Pseudomonas Pxy-40, when grown on succinate in the presence of p -xylene, accumulated p -toluic acid in the culture medium. Under the same conditions Pseudomonas Pxy-82 accumulated p -toluic acid and also 4-methylcatechol. When Pseudomonas Pxy-82 was grown on succinate in the presence of m -xylene, 3-methylcatechol and 3-methylsalicylic acid were excreted into the culture medium. A pathway is proposed for the initial reactions utilized by Pseudomonas Pxy to oxidize p - and m -xylene.