Transformation of Triclosan by Trametes versicolor and Pycnoporus cinnabarinus

Abstract

We investigated the ability of Trametes versicolor and Pycnoporous cinnabarinus to metabolize triclosan. T. versicolor produced three metabolites, 2-O-(2,4,4-trichlorodiphenyl ether)-␤-D-xylopyranoside, 2-O-(2,4,4-trichlorodiphenyl ether)-␤-D-glucopyranoside, and 2,4-dichlorophenol. P. cinnabarinus converted triclosan to 2,4,4-trichloro-2-methoxydiphenyl ether and the glucoside conjugate known from T. versicolor. The conjugates showed a distinctly lower cytotoxic and microbicidal activity than triclosan did.Triclosan (2,4,4Ј-trichloro-2Ј-hydroxydiphenyl ether; synonym, Irgasan DP 300) has been used as an antimicrobial compound in deodorants (6), soaps, and dentifrices (2, 8, 36) for many years. The mode of action of triclosan has, however, remained unclear. Recently, it was shown that triclosan blocks one step in bacterial fatty acid synthesis (20,24,25). Due to its widespread use, triclosan and some of its derivatives can be detected in the environment (22,26,27). The chemical structure of triclosan is related to many compounds which are wellknown as xenobiotics, such as halogenated diphenyl ethers. Though some reports on the transformation of halogenated diphenyl ether compounds by bacteria are available (21, 30), triclosan itself was not metabolized by the strains tested (31) or by Rhodococcus chlorophenolicus, which can methylate several other chlorinated hydroxydiphenyl ethers (34). Several hydroxylated metabolites, as well as 2,4-dichlorophenol and 4-chlorocatechol, are formed from triclosan by rats (33), while guinea pigs mostly form glucuronide conjugates (3). No reports exist concerning the degradation of triclosan by fungi. The white rot fungi Trametes versicolor and Pycnoporus cinnabarinus are capable of transforming diphenyl ethers, like 4-chlorodiphenyl ether, up to ring cleavage (10, 11). Hydroxylated biarylic ethers are transformed to oligomerization products by laccases secreted by these strains (13). In this paper we describe some biotransformation reactions of triclosan by the white rot fungi T. versicolor and P. cinnabarinus.The strains T. versicolor SBUG-M 1050, T. versicolor DSM 11269, T. versicolor DSM 11309, and P. cinnabarinus SBUG-M 1044 were cultivated in a nitrogen-rich (8 mM) medium. The cultures for transformation were prepared with 0.25 mM (wt/ vol) triclosan (Mallinckrodt-Baker, Griesheim, Germany) and inoculated and incubated as described previously (10, 11).Cell extracts were prepared from a 3-day culture of T. versicolor, harvested by centrifugation, and washed twice with 50 mM ice-cold Tris-HCl buffer (pH 7.5). Cells were broken at 1,000 lb/in 2 using a French press (SLM Amnico, Rochester, N.Y.) and were immediately resuspended in Tris-HCl buffer. The cell extracts (4 ml, approximately 5 mg of protein ml Ϫ1 ) were incubated at 30°C for 24 h with 2.88 mg of triclosan and 1 mg each of UDP-xylose, UDP-glucose, and UDP-glucuronic acid (Sigma, Deisenhofen, Germany).Analysis of metabolites in culture supernatants and purification of intermediates were done by high-performance liquid ...

Soil bacteria Pseudomonas putida and Alcaligenes xylosoxidans subsp. denitrificans inactivate triclosan in liquid and solid substrates

“…No decrease in triclosan was seen in uninoculated samples or those inoculated with E. coli (data not shown). Conjugated products of triclosan, as previously identi¢ed in triclosan detoxi¢cation by T. versicolor and P. cinnabarinus [11], were not observed in P. putida TR1 or A. xylosoxidans TR1 culture extracts at 280 nm, since there was a single peak with the identical retention time of triclosan. Combined with the growth of P. putida TriRY and A. xylosoxidans TR1 in medium containing triclosan as a sole carbon source and the ability of these isolates to detoxify triclosan-containing media and plastics, degradation appears to be the mechanism of triclosan detoxi¢cation by these bacteria.…”

Identification and Characterization of TriABC-OpmH, a Triclosan Efflux Pump of Pseudomonas aeruginosa Requiring Two Membrane Fusion Proteins

“…strain RD1, where loss of the ability to mineralize triclosan resulted in susceptibility to this biocide (28). While the authors are not aware of any bacteria that can modify triclosan, O-glucosyation and O-xylosylation of this biocide have been demonstrated in at least two fungi (25), and we should not be too surprised to find similar modification mechanisms in bacteria. Biofilm-grown Salmonella enterica serovar Typhimurium was triclosan tolerant, and it was suggested that Salmonella bacteria within biofilms could experience reduced influx (64).…”

Novel Ring Cleavage Products in the Biotransformation of Biphenyl by the Yeast Trichosporon mucoides

“…There are no data available for the influence of 250 g of this mixture ml Ϫ1 on the growth of the yeast cells because of the limited amount of this mixture enriched by semipreparative HPLC. (18). In contrast, conjugates with hydroxylated intermediates were not found during biphenyl transformation by T. mucoides.…”