Salicylate hydroxylase was purified from the soil yeast Trichosporon cutaneum. The enzyme contained flavin adenine dinucleotide and was monomeric, with a molecular weight of 45,300. In addition to salicylate, the four isomeric hydroxysalicylates were oxidatively decarboxylated without significant formation of hydrogen peroxide. One of these isomers, gentisate, was rapidly oxidized to hydroxyquinol (HQ) by the enzyme but did not serve as an effective single carbon source for T. cutaneum; however, when growing with salicylate, cells also readily utilized gentisate for growth. Hydroxyquinol 1,2-dioxygenase is a newly investigated enzyme which was purified from T. cutaneum grown with 4-hydroxybenzoate (pHB). The enzyme was red, contained ferric iron, and was specific for HQ; catechol and pyrogallol were oxidized at less than 1% of the rate for HQ, and no activity could be detected against seven other catechols. The enzyme was composed of two nonidentical subunits having molecular weights of 39,600 and 38,200, and was apparently dimeric. A strain of Acinetobacter lwoffii was isolated from soil by elective culture on 4-hydroxy-3-methoxymandelate (VMA). The organism could also grow on 4-hydroxymandelate and degraded the compound via pHB and the meta-fission pathway of protocatechuate (PCA). VMA was metabolized to vanillate which, by a novel metabolic reaction, was hydrozylated to give 3-0-methylgallate. Using C-13 NMR spectroscopy with whole cells, (methoxyl-('13)C)3-0-methylgallte was found to be oxidatively cleaved by a meta-fission dioxygenase to give an open-chain methyl ester which was further catabolized to Krebs cycle intermediates with release of methanol. The ester could also spontaneously cyclize to form 2-pyrone-4,6-dicarboxylate and methanol. However, when 3,4,5-trimethoxybenzoate grown P. putida TMC cells were used instead, the ester could not be observed, while with pHB grown P. testosteroni cells a different methyl ester, formed by a 2-hydrogen reduction of the previous ester, was produced. The degradation of cresols by another soil yeast was studied. The organism degraded o- and m-cresol via methylhydroquinone and ortho-fission of 2,3,5-trihydroxytoluene; p-cresol was first oxidized to pHB, then to PCA, to be degraded by the eukaryotic (beta)-ketoadipate pathway. These pathways are very different from those previously investigated in T. cutaneum and bacteria.