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

Abstract

Catabolic pathways for utilization of naphthalene (NAP), anthracene (ANT), phenanthrene (PHE), and fluoranthene (FLA) by Sphingomonas paucimobilis EPA505 were identified. Accumulation of catabolic intermediates was investigated 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 insertion within a meta ring fission dioxygenase (pbhA), and a ferredoxin subunit gene (pbhB) resided directly downstream. Mutant 200pbhA and other class I mutants lost the ability to catalyze the initial dihydroxylation step and did not transform NAP, ANT, PHE, or FLA. Class I mutant 401 accumulated salicylic acid, 2-hydroxy-3-naphthoic acid, 1-hydroxy-2-naphthoic acid, and hydroxyacenaphthoic acid during incubation with NAP, ANT, PHE, or FLA, respectively. Class II mutant 132pbhC contained the Tn5 insertion in an aldolase hydratase (pbhC) and accumulated what appeared to be meta ring fission products: trans-o-hydroxybenzylidene pyruvate, trans-o-hydroxynaphylidene pyruvate, and trans-o-hydroxynaphthyl-oxobutenoic acid when incubated with NAP, ANT, and PHE, respectively. When mutant 132pbhC was incubated with 1-hydroxy-2-naphthoic acid, it accumulated trans-o-hydroxybenzylidene pyruvate. Class III mutant 104ppdk had a Tn5 insertion in a pyruvate phosphate dikinase gene that affected expression of a FLA-specific gene and accumulated a proposed meta ring fission product; trans-o-hydroxyacenaphyl-oxobutenoic acid during incubation with FLA. Trans-o-hydroxyacenaphyl-oxobutenoic acid was degraded to acenaphthenone that accumulated with class III mutant 611. Acenaphthenone was oxidized via incorporation of one molecule of dioxygen by another oxygenase. 2,3-Dihydroxybenzoic acid was the final FLA-derived catabolic intermediate detected. Analysis of PAH utilization mutants revealed that there are convergent and divergent points involved in NAP, ANT, PHE, and FLA utilization by S. paucimobilis EPA505.

A Polyomic Approach To Elucidate the Fluoranthene-Degradative Pathway in Mycobacterium vanbaalenii PYR-1

“…The formation of 8-hydroxy-7-methoxyfluoranthene by catechol-O-methyltransferase was also reported in strain PYR-1 (26). Since then, additional metabolites have been identified in other degraders (38,54), proving the productive extradiol ring cleavage pathway for further degradation of 7,8-dihydroxyfluoranthene (V). In the genome analysis, the putative cyclohexanone monooxygenase (gi:119956901) and the putative hydrolase (gi:119955392) were found to have 33% and 67% identities with those identified functionally from P. fluorescens ACB (20) and Acinetobacter calcoaceticus F46 (15), respectively.…”

“…2 and Table 2) is accounted for by additional actions of a ring-hydroxylating oxygenase on the benzylic methyne groups of the naphthenoaromatic metabolites (29,51). The C-7,8 dioxygenation of fluoranthene followed by intradiol ring cleavage giving acenaphthylene-type metabolites would proceed into the ␤-ketoadipate pathway via 1,2,3-benzenetricarboxylic acid (XXV) (38,54).…”

“…strain EPA505, Pseudomonas alcaligenes PA-10, and Alcaligenes denitrificans WW1, with a possible monooxygenation reaction, resulting in the production of monohydroxyfluoranthenes in Sphingomonas sp. strain LB126 (7,54,58,62). Despite these efforts, there are crucial gaps in the fluoranthene degradation pathway.…”

Recent Advances in Petroleum Microbiology

“…This is especially evident when novel dead-end metabolites, such as the methoxylated 1-methoxy-2-hydroxyanthracene from anthracene metabolism (641) and the dicarboxylic acid 6,6Ј-dihydroxy-2,2Ј-biphenyl dicarboxylic acid from pyrene metabolism (437), are detected with strains simultaneously employing multiple degradative routes for a single substrate. This is also the case in strains that have degradative pathways for multiple aromatic substrates (588,519). For example, in Sphingomonas aromaticivorans strain F199, induction studies have indicated that naphthalene and toluene mineralization may be higher in the presence of both substrates, as greater gene expression can be achieved (519).…”

Identification and Functional Analysis of Two Aromatic-Ring-Hydroxylating Dioxygenases from a Sphingomonas Strain That Degrades Various Polycyclic Aromatic Hydrocarbons

“…In recent years, sphingomonad species have been described for their ability to degrade a wide range of aromatic hydrocarbons, including mono-and polycyclic aromatic hydrocarbons (13,32,40,48), naphthalene sulfonate (39), dibenzo-p-dioxin (1), dibenzothiophene, and methylated PAHs (29). The sequences and organization of catabolic genes responsible for PAH degradation were found to be remarkably similar in several sphingomonads (31), but these genes differed from those previously described for pseudomonads (46).…”