A novel degradation pathway in the assimilation of phenanthrene by Staphylococcus sp. strain PN/Y via meta-cleavage of 2-hydroxy-1-naphthoic acid: formation of trans-2,3-dioxo-5-(2′-hydroxyphenyl)-pent-4-enoic acid

Abstract

Staphylococcus sp. strain PN/Y, capable of utilizing phenanthrene as a sole source of carbon and energy, was isolated from petroleum-contaminated soil. In the degradation of phenanthrene by strain PN/Y, various metabolites, isolated and identified by a combination of chromatographic and spectrometric analyses, revealed a novel phenanthrene assimilation pathway involving 2-hydroxy-1-naphthoic acid. Metabolism of phenanthrene was initiated by the dioxygenation on the 1,2-position of phenanthrene followed by meta-cleavage of phenanthrene-1,2-diol, leading to 2-hydroxy-1-naphthoic acid, which was then processed via a novel meta-cleavage pathway, leading to the formation of trans-2,3-dioxo-5-(29-hydroxyphenyl)-pent-4-enoic acid and subsequently to salicylic acid. In the lower pathway, salicylic acid was transformed to catechol, which was then metabolized by catechol-2,3-dioxygenase to 2-hydroxymuconaldehyde acid, ultimately forming TCA cycle intermediates. The catabolic genes involved in phenanthrene degradation were found to be plasmid-encoded. This detailed study of polycyclic aromatic hydrocarbon (PAH) metabolism by a Gram-positive species involving a unique ring-cleavage dioxygenase in a novel phenanthrene degradation pathway provides a new insight into the microbial degradation of PAHs. INTRODUCTIONPolycyclic aromatic hydrocarbons (PAHs) constitute a group of priority environmental pollutants, which are ubiquitous contaminants in soils and sediments and are of environmental concern because of their toxic, mutagenic and/or carcinogenic effects (Mastrangelo et al., 1996;Marston et al., 2001;Xue & Warshawsky, 2005). In recent years, the biodegradation of PAHs has received considerable attention and a variety of micro-organisms have been reported to play important roles in the process (Pothuluri & Cerniglia, 1994;Shuttleworth & Cerniglia, 1995;Kanaly & Harayama, 2000;Habe & Omori, 2003;Tortella et al., 2005). Bioremediation technologies have increasingly been proposed to decontaminate PAH-contaminated sites (Harayama, 1997;Samanta et al., 2002;Parrish et al., 2004;Vinas et al., 2005).Phenanthrene, a PAH with three condensed rings fused in angular fashion, has a 'bay-region' and a 'K-region' and is often used as a model substrate for studies on the metabolism of carcinogenic PAHs. Over the last 60 years, a number of studies on phenanthrene degradation by several Gram-negative and Gram-positive bacterial species have been reported (Evans et al., 1965;Kiyohara et al., 1976Kiyohara et al., , 1982Kiyohara & Nagao, 1978;Barnsley, 1983;Gibson & Subramanian, 1984;Houghton & Shanley, 1994;Adachi et al., 1999;Samanta et al., 1999), where various pathways and metabolic diversity involved in phenanthrene degradation were documented. In general, the metabolic pathway is initiated by the double hydroxylation of the bay-region of phenanthrene by a dioxygenase enzyme to form cis-3,4-phenanthrenedihydrodiol. The resultant dihydrodiol is then converted by the action of dihydrodiol dehydrogenase to 3,4-dihydroxyphenanthrene, which und...

meta-Cleavage of hydroxynaphthoic acids in the degradation of phenanthrene by Sphingobium sp. strain PNB

“…Enrichment of cultures was started by inoculating a 1 g municipal waste-contaminated soil sample (Dhapa, Kolkata, India) in liquid mineral salt medium (MSM; Mallick et al, 2007) supplemented with solid phenanthrene (1 g l 21 ) as the sole carbon and energy source, and incubated at 28 uC on a rotary shaker (180 r.p.m.). When growth was observed, the enrichment process was repeated with several transfers under the same conditions and the enriched cultures were subsequently purified by plating on nutrient agar (2 %, w/v) medium.…”

“…for different periods of time. Resting cell incubations, individually with phenanthrene and pathway intermediates (concentrations of 0.2-1 g l 21 ), were done as described previously (Mallick et al, 2007). Unless stated otherwise, each experimental set was performed in triplicate.…”

“…Suspensions of cells grown individually on phenanthrene, 2-hydroxy-1-naphthoic acid and 1-hydroxy-2-naphthoic acid were prepared as described previously (Mallick et al, 2007) and were loaded into a pre-cooled French press (Constant Cell Disruption System, One Shot model) fitted with a 8.0 ml cell followed by lysis at 30 000 p.s.i. (#207 MPa) for two cycles.…”

“…These two intermediates were proposed to be transformed and converged into naphthalene-1,2-diol, which was further metabolized via either salicylic acid (Pinyakong et al, 2000) or phthalic acid or both (Seo et al, , 2007. Dioxygenation exclusively at the 1,2-position of phenanthrene, forming phenanthrene cis-1,2-dihydrodiol, has also been reported, where the dihydrodiol is subsequently metabolized to 2-hydroxy-1-naphthoic acid, which was further degraded by a meta-cleavage dioxygenase, ultimately leading to TCA cycle intermediates via salicylic acid and catechol (Mallick et al, 2007;Ghosal et al, 2010).…”

Biodegradation of malodorous mercaptans by a novel Staphylococcus capitis strain isolated from gas-washing wastewaters of the Tunisian Chemical Group

“…The Staphylococcus sp. strain PN/Y, isolated from petroleum-contaminated soils, was also described to have the ability to grow on phenanthrene as the sole carbon and energy source (Mallick et al 2007;Mallick and Dutta 2008). Moreover, Staphylococcus arlettae strain VN-11, which was isolated from an activated sludge of a textile industry, was reported to decolorize four different azo dyes under microaerophilic conditions (Elisangela et al 2009).…”