XYL, a nonconjugative xylene-degradative plasmid in Pseudomonas Pxy

Abstract

Pseudomonas Pxy metabolizes p-or m-xylene through intermediate formation of the corresponding methylbenzyl alcohol and toluic acid via the meta pathway. The strain Pseudomonas Pxy spontaneously loses its ability to grow with xylene or toluate, and the rate of loss of this ability is greatly enhanced by treatment of the cells with mitomycin C. The assay of a number of enzymes involved in xylene degradation in xylene-negative Pxy cells indicates the loss of the entire enzyme complement of the pathway. The genes specifying all the xylene-degradative enzymes, including those of the meta pathway, appear to be borne on a nonconjugative plasmid and can be transferred to xylene-negative Pxy or P. putida strain PpG1 cells only in the presence of a transfer plasmid termed factor K. When transferred to strain PpG1, the xylene-degradative plasmid, termed XYL, coexists stably with factor K, but transduction of XYL is not accompanied by a cotransfer of factor K. XYL appears to be compatible with all the other known degradative plasmids in P. putida. The xylene pathway is inducible in wild-type Pxy as well as in Pxy and PpG1 exconjugants, suggesting the cotransfer of regulatory genes along with the plasmid. The enzymes converting xylene to toluate are induced by xylene, methylbenzyl alcohol, or the aldehyde derivatives but not significantly by toluate, whereas catechol dioxygenase and other enzymes are induced by toluates and presumably by xylene as well.

Plasmid specifying total degradation of 3-chlorobenzoate by a modified ortho pathway

“…Other P. putida and P. aeruginosa strains have been described elsewhere (3,13). The composition of the synthetic minimal medium used for propagation of the strains (PAS medium) is given below ("Isolation of plasmid DNA").…”

Catabolism of pseudocumene and 3-ethyltoluene by Pseudomonas putida (arvilla) mt-2: evidence for new functions of the TOL (pWWO) plasmid

“…strain Pxy was also reported to carry a plasmid isofunctionalwith TOL (pWWO). This plasmid, however, was shown to be nonconjugative and was originally designated the XYL plasmid, distinguishing it from the conjugative plasmid in P. putida mt-2 (11).…”

Plasmid-borne catechol dissimilation in Rhizobium sp.

“…The transfer frequency was 2.6 x 10 -e transo conjugants/donor cell. The transconjugants had identical plasmid profiles and catechol 1,2-dioxygenase activity was comparable to that of wild type cells, Self-transmission and enhanced loss in the presence of a curing agent are common features of dissimilatory plasmids, Pseudomonas Pxy metabolized p or m-xylene through catechol by meta-fission [23], This property was encoded on a plasmid which was cured by mitomycin C treatment. In Acinetobacter caicoaceticus, genes for resorcinol utilization were encoded on a transmissible plasmid [25], in P. putida, a 68-MDa pAC2$ transmissible plasmid was responsible for 3chlorobenzoate dissimilation.…”