TOM, a new aromatic degradative plasmid from Burkholderia (Pseudomonas) cepacia G4

Abstract

Burkholderia (Pseudomonas) cepacia PR1 23 has been shown to constitutively express a toluene catabolic pathway distinguished by a unique toluene ortho-monooxygenase (Tom). This strain has also been shown to contain two extrachromosomal elements of <70 and >100 kb. A derivative strain cured of the largest plasmid, PR1 23 Cure, was unable to grow on phenol or toluene as the sole source of carbon and energy, which requires expression of the Tom pathway. Transfer of the larger plasmid from strain G4 (the parent strain inducible for Tom) enabled PR1 23 Cure to grow on toluene or phenol via inducible Tom pathway expression. Conjugal transfer of TOM 23c from PR1 23 to an antibiotic-resistant derivative of PR1 23 Cure enabled the transconjugant to grow with either phenol or toluene as the sole source of carbon and energy through constitutive expression of the Tom pathway. A cloned 11.2-kb EcoRI restriction fragment of TOM 23c resulted in the expression of both Tom and catechol 2,3-dioxygenase in Escherichia coli, as evidenced by its ability to oxidize trichloroethylene, toluene, m-cresol, o-cresol, phenol, and catechol. The largest resident plasmid of PR1 was identified as the source of these genes by DNA hybridization. These results indicate that the genes which encode Tom and catechol 2,3-dioxygenase are located on TOM, an approximately 108-kb degradative plasmid of B. cepacia G4.

Identifying the genetic basis of ecologically and biotechnologically useful functions of the bacterium Burkholderia vietnamiensis

“…Phe TOM mutations were localized to a 31 172 bp contig of the draft G4 genome sequence which encoded the previously described toluene ortho-monooxygenase (tomA012345; TomA) and catechol 2,3-dioxygenase (tomB; TomB) enzymes (Shields et al, 1991). A putative partition protein (ParA) was encoded upstream of these catabolic genes indicating the contig represented part of the 108 kb catabolic plasmid pTOM (Shields et al, 1995). The contig carried 16 genes encoding the complete phenol catabolic pathway (tomA012345XBYDEFGHIZ; Fig.…”

“…Burkholderia vietnamiensis strain G4 (formerly Pseudomonas cepacia; Payne et al, 2005) can proficiently degrade trichloroethylene (TCE) as well as many other toxic aromatic hydrocarbons (Nelson et al, 1987). Its catabolic plasmid pTOM carries all the genes required to degrade phenol, toluene, o-cresol, m-cresol and benzene (Shields et al, 1995). G4 derivatives have been successfully used in field trial bioremediation of TCE in bioreactors (Lee et al, 2003) and groundwater (Steffan et al, 1999).…”

Engineering TCE-degrading rhizobacteria for heavy metal accumulation and enhanced TCE degradation

“…In addition, TOM can degrade other reductivedehalogenation products of TCE such as cis-DCE and trans-DCE (Canada et al, 2002;Shim et al, 2000), making TOM a promising candidate for bioremediation of TCE. Recombinant strains expressing TOM have been shown to effectively degrade a mixture of these chlorinated ethenes (Canada et al, 2002;Luu et al, 1995;Shields et al, 1995).…”

Biotechnological potential within the genus Burkholderia

“…Strain G4 co-metabolically degrades TCE in the presence of aromatic inducer molecules such as toluene or phenol (Nelson et al 1986). The key enzyme is toluene o-monooxygenease (Tom) which is the first enzyme of the TOM operon encoded on the catabolic plasmid pTOM (Shields et al 1995).…”