Convergent and divergent points in catabolic pathways involved in utilization of fluoranthene, naphthalene, anthracene, and phenanthrene by Sphingomonas paucimobilis var. EPA505

Catabolic pathways for utilization of naphthalene (NAP), anthracene (ANT), phenanthrene (PHE), and fluoranthene (FLA) by Sphingomonas paucimobilis EPA 505 were identified. Accumulation of catabolic intermediates was investigat ed with three classes of Tn5 mutants with the following polycyclic aromatic hydrocarbon (PAH)-negative phenotypes; (class I NAP(-) PHE- FLA(-), class II NAP- PHE-, and class III FLA-). Class I mutant 200pbhA had a Tn5 inserti on within a meta ring fission dioxygenase (pbhA), and a ferredoxin subunit gene (pbhB) resided directly downstream. Mutant 200pbhA and other class I m utants lost the ability to catalyze the initial dilhydroxylation step and d id not transform NAP, ANT, PHE, or FLA. Class I mutant 401 accumulated sali cylic acid, 2-hydroxy-3-naphthoic acid, 1-hydroxy-2-naphthoic acid, and hyd roxyacenaphthoic acid during incubation with NAP, ANT, PHE, or FLA, respect ively. Class II mutant 132pbhC contained the Tn5 insertion in an aldolase h ydratase (pbhC) and accumulated what appeared to be meta ring fission produ cts: trans-o-hydroxybenzylidene pyruvate, trans-o-hydroxynaphylidene pyruva te, and trans-o-hydroxynaphthyl-oxobutenoic acid when incubated with NAP, A NT, and PHE, respectively. When mutant 132pbhC was incubated with 1-hydroxy -2-naphthoic acid, it accumulated trans-o-hydroxylbenzylidene pyruvate. Cla ss III mutant 104ppdk had a Tn5 insertion in a pyruvate phosphate dikinase gene that affected expression of a FLA-specific gene and accumulated a prop osed meta ring fission product; trans-o-hydroxyacenaphyloxobutenoic acid du ring incubation with FLA. Trans-o-hydroxyacenaphyl-oxobutenoic acid was deg raded to acenaphthenone that accumulated with class III mutant 611. Acenaph thenone was oxidized via incorporation of one molecule of dioxygen by anoth er oxygenase. 2,3-Dihydroxybenzoic acid was the final FLA-derived catabolic Intermediate detected. Analysis of PAH utilization mutants revealed that t here are convergent and divergent points involved in NAP, ANT, PHE, and FLA utilization by S. paucimobilis EPA505.