Transmissible plasmid coding early enzymes of naphthalene oxidation in Pseudomonas putida

Plasmid- and chromosome-mediated dissimilation of naphthalene and salicylate in Pseudomonas putida PMD-1

Pseudomonas putida PMD-1 dissimilates naphthalene (Nah), salicylate (Sal), and benzoate (Ben) via catechol which is metabolized through the meta (or alpha-keto acid) pathway. The ability to utilize salicylate but not naphthalene was transferred from P. putida PMD-1 to several Pseudomonas species. Agarose gel electrophoresis of deoxyribonucleic acid (DNA) from PMD-1 and Sal+ exconjugants indicated that a plasmid (pMWD-1) of 110 megadaltons is correlated with the Sal+ phenotype; restriction enzyme analysis of DNA from Sal+ exconjugants indicated that plasmid pMWD-1 was transmitted intact. Enzyme analysis of Sal+ exconjugants demonstrated that the enzymes required to oxidize naphthalene to salicylate are absent, but salicylate hydroxylase and enzymes of the meta pathway are present. Thus, naphthalene conversion to salicylate requires chromosomal genes, whereas salicylate degradation is plasmid encoded. Comparison of restriction digests of plasmid pMWD-1 indicated that it differs considerably from the naphthalene and salicylate degradative plasmids previously described in P. putida.

Selective enrichment of Pseudomonas spp. defective in catabolism after exposure to halogenated substrates

Significant selective enrichments of mutants defective in catabolic pathways can be achieved by exposure of pseudomonad cells to halogenated analogs of growth substrates. Between 3 and 95% of viable clones rescued from such enrichments have been defective in specific catabolic pathways. This has been demonstrated for eight different catabolic pathways for aromatic compounds in pseudomonads, in which the genes are located on plasmids or on the chromosome. The plasmid-encoded pathways studied include those for the catabolism of p-cymene (CYM), m- and p-xylenes (TOL), naphthalene (NAH), salicylate (SAL), and 4-methylphthalate (MOP), and the chromosome-encoded pathways include those for p-hydroxybenzoate, monohydric phenols, and p-anisate utilization. The recalcitrance of halogenated compounds may, in part, be explained by these observations, which introduce an as yet not widely recognized factor in assessment of biodegradability of halogenated compounds and their effects on the transformation of the natural substrates.

Catabolism of 3- and 4-hydroxyphenylacetate by the 3,4-dihydroxyphenylacetate pathway in Escherichia coli

Various strains of Escherichia coli (but not strain K-12) were found to grow on 3-hydroxyphenylacetate and 4-hydroxyphenylacetate. Both compounds were catabolized by the same pathway, with 3,4-dihydroxyphenylacetate as a substrate for fission of the benzene nucleus, and with pyruvate and succinate as products. All the necessay enzymes were demonstrated in cell extracts prepared from induced cells but were essentially absent from uninduced cells. Mutants unable to grow on 3- and 4-hydroxyphenylactetate were defective in particular enzymes of the pathway. The characteristics of certain mutants indicated that either uptake or hydroxylation of 3- and 4-hydroxyphenylacetate may involve a common protein component. E. coli also grew on 3,4-hydroxyphenylacetate, with induction of the enzyme necessary for its degradation but not those for the uptake-hydroxylation of 3- and 4-hydroxyphenylacetate.

Mapping of the loci involved in the catabolic oxidation of L-hydroxyproline in Pseudomonas aeruginosa PAO

Genes specifying the oxidative utilization of hydroxyproline (Hyp) in P. aeruginosa PAO were located on the chromosome, around 19th minute by conjugation experiments. A map order of his-68-his-07-Hyp was assigned. Confirmation of this gene order was also demonstrated by transductional mapping studies. All the genes determining the enzymes of Hyp dissimiliatory pathway were closely linked.

Compatibility and sex specific phage plating characteristics of the TOL and NAH catabolic plasmids

The sex specific bacteriophage PR4 has been found to plate onP. aeruginosastrains harbouring the TOL catabolic plasmid or the plasmid pND2 derived from TOL. Based on this, attempts were made to place TOL into aPseudomonasplasmid incompatibility group and by showing that pND2 is incompatible with the R plasmid R2, TOL has been placed into the P-9 group. The NAH catabolic plasmid has been reported to be incompatible with TOL, pND2 and a variety of other plasmids derived from TOL. Thus, these plasmids also would appear to belong to the P-9 incompatibility group.

Evidence for a transmissible catabolic plasmid in Pseudomonas putida encoding the degradation of p-cresol via the protocatechuate ortho cleavage pathway

Evidence is presented that a strain ofPseudomonas putidaharbours a catabolic plasmid which encodes for the degradation ofp-cresol through the protocatechuateorthocleavage pathway. This plasmid can transfer giving approximately 10−3transconjugants per donor cell, can be cured with mitomycin C, belongs to the P-9 plasmid incompatibility group and can be transduced with the bacteriophage pf16.

TOL is a broad-host-range plasmid

We readily isolated insertions of the carbenicillin resistance element Tn401 into the TOL plasmid in Pseudomonas putida. Hybrid TOL::Tn401 plasmids stably express the Cbr phenotype in Pseudomonas aeruginosa and Escherichia coli. Whereas the replicative and conjugative functions are expressed in both hosts, the ability to grow on m-toluate is only expressed in the Pseudomonas species.

Molecular relationships of degradative plasmids determined by in situ hybridisation of their endonuclease-generated fragments

Plasmid inter-relationships were studied by hybridisation of a radioactively labelled DNA probe to endonuclease-derived fragmentation patterns of plasmids bound to a nitrocellulose filter. The degradative plasmids SAL and NAH were found to be very closely related, but probably one did not give rise to the other by just a single deletion or insertion. Relationships between SAL and other degradative plasmids are complex; substantial homology was found with TOL and other plasmids encoding toluate dissimilation and significant homology was found with OCT.

Evidence for transductional shortening of the plasmid obtained by recombination between the TOL catabolic plasmid and the R91 R plasmid

The previously isolated plasmid pND3, arising from recombination between the TOL catabolic plasmid and the R plasmid R91, was transduced by pf16 inPseudomonas putida. Apparent transductional shortening was evident in 25% of the transduced pND3 plasmids. Transductants were isolated which had segregated the antibiotic resistance marker, transfer ability and some of the catabolic functions of the parent plasmid.

2-Hydroxypyridine metabolism and pigment formation in three Arthrobacter species

Three species of the genus Arthrobacter, A. crystallopoietes, A. pyridinolis, and A. viridescens, have the capabilities to utilize 2-hydroxypyridine (2-HP) as the sole source of carbon and nitrogen for growth and to produce an extracellular crystalline pigment from this substrate. Degradation of 2-HP by cell-free extracts requires the presence of both reduced nicotinamide adenine dinucleotide and molecular oxygen and is stimulated by flavin mononucleotide, suggesting the presence of a monooxygenase activity in the extract. Loss of the ability to produce pigment at a high spontaneous frequency, 0.26% loss per generation, is observed only with A. crystallopoietes and can be visualized by the presence of sectored and fully nonpigmented colonies on solid media containing 2-HP. Concomitant with the loss of pigment-producing character are both loss of ability to utilize 2-HP for growth and oxidation of 2-HP by cell-free extracts. These three 2-HP-associated characteristics also are lost simultaneously by treating cultures of A. crystallopoietes with curing agents, such as acridine orange and mitomycin C, but are not curable in A. pyridinolis or A. viridescens. All nonpigmented strains of A. crystallopoietes are nonrevertible for these properties. These data suggest that 2-HP-related characteristics are plasmid determined in A. crystallopoietes but not in A. pyridinolis and A. viridescens. A survey for the presence of plasmids in these three species and two physiologically unrelated species, A. globiformis and A. atrocyaneus, revealed plasmid material only in A. globiformis and A. crystallopoietes.

XYL, a nonconjugative xylene-degradative plasmid in Pseudomonas Pxy

Pseudomanas 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 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 wit- 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 presumable by xylene as well.

Combined chromosomal and plasmid encoded control for the degradation of phenol in Pseudomonas putida

The TOL(M1) metabolic plasmid was transferred fromPseudomonas arvillamt-2 to a mutant ofPseudomonas putida. Although neither the donor nor the recipient could grow on phenol, the transconjugants could grow slowly on this carbon source. In these transconjugants phenol was converted to catechol by chromosomal encoded phenol hydroxylase followed by degradation of catechol by low uninduced levels of the plasmid encoded catecholmetacleavage pathway. A mutant, which grew well on phenol, was isolated from one of the transconjugants and it was found that phenol could now act as an inducer for themetacleavage pathway.

Ubiquity of plasmids in coding for toluene and xylene metabolism in soil bacteria: evidence for the existence of new TOL plasmids

Thirteen bacteria have been isolated from nine different soil samples by selective enrichment culture on m-toluate (m-methylbenzoate) minimal medium. Eight of these were classified as Pseudomonas putida, one as a fluorescent Pseudomonas sp., and four as nonfluorescent Pseudomonas sp. All 13 strains appeared to carry TOL plasmids superficially similar to that previously described in P. putida mt-2 in that: (i) all the wild-type strains could utilize toluene, m-xylene, and p-xylene as sole carbon and energy sources, (ii) these growth substrates were metabolized through the corresponding alcohols and aldehydes to benzoate, m-toluate, and p-toluate, respectively, and thence by the divergent meta (or alpha-ketoacid) pathway, and (iii) the isolates could simultaneously and spontaneously lose their ability to utilize the hydrocarbons, alcohols, aldehydes, and acids, particularly during growth on benzoate, giving rise to cured strains which could grow only on benzaldehyde and benzoate of the aromatic substrates by the alternative ortho (or beta-ketoadipate) pathway. Eight of the isolates were able to transfer their TOL plasmids into their own cured strains, but only five were able to transfer them in interstrain conjugation into the cured strains, but only five were able to transfer them in interstrain conjugation into the cured derivative of P. putida mt-2. However, P. putida mt-2 was able to transfer its TOL plasmid into 11 of the cured isolates, and eight of these were able to retransmit this foreign plasmid in intrastrain conjugation with their own cured derivatives. Three of the isolates, MT 14, MT 15, and MT 20, differed significantly from the others in that the wild-type strains dissimilated the p-methyl-substituted substrates poorly, and also, during growth on benzoate, in addition to the cured derivatives, they gave rise to derivatives with a phenotype intermediate between the cured and wild-type strains, the biochemical and genetic nature of which has not been elucidated.

Role and regulation of the ortho and meta pathways of catechol metabolism in pseudomonads metabolizing naphthalene and salicylate

The enzymes of naphthalene metabolism are induced in Pseudomonas putida ATCC 17484, PpG7, NCIB 9816, and PG and in Pseudomonas sp. ATCC 17483 during growth on naphthalene or salicylate; 2-aminobenzoate is a gratuitous inducer of these enzymes. The meta-pathway enzymes of catechol metabolism are induced in ATCC 17483 and PPG7 during growth on naphthalene or salicylate or during growth in the presence of 2-aminobenzoate, but in ATCC 17484 and NCIB 9816 the ortho-pathway enzymes of catechol metabolism are induced during growth on naphthalene or salicylate. 2-Aminobenzoate does not induce any enzymes of catechol metabolism in the latter two organisms. In Pseudomonas PG the meta-pathway enzymes are present at high levels under all conditions of growth, but this organism and PpG7 can induce ortho-pathway enzymes during naphthalene or salicylate metabolism. Salicylate appears to be the inducer of the enzymes of naphthalene metabolism in all of the organisms studied and, where they are inducible, of the meta-pathway enzymes, but the properties of Pseudomonas PG suggest that separate, regulatory systems may exist.

Metabolism of toluene and xylenes by Pseudomonas (putida (arvilla) mt-2: evidence for a new function of the TOL plasmid

Pseudomonas putida (arvilla) mt-2 carries genes for the catabolism of toluene, m-xylene, and p-xylene on a transmissible plasmid, TOL. These compounds are degraded by oxidation of one of the methyl substituents via the corresponding alcohols and aldehydes to benzoate and m- and p-toluates, respectively, which are then further metabolised by the meta pathway, also coded for by the TOL plasmid. The specificities of the benzyl alcohol dehydrogenase and the benzaldehyde dehydrogenase for their three respective substrates are independent of the carbon source used for growth, suggesting that a single set of nonspecific enzymes is responsible for the dissimilation of the breakdown products of toluene and m- and p-xylene. Benzyl alcohol dehydrogenase and benzaldehyde dehydrogenase are coincidently and possible coordinately induced by toluene and the xylenes, and by the corresponding alcohols and aldehydes. They are not induced in cells grown on m-toluate but catechol 2,3-oxygenase can be induced by m-xylene.

Genes for ribitol and D-arabitol catabolism in Escherichia coli: their loci in C strains and absence in K-12 and B strains

Escherichia coli C strains can grow at the expense of the two natural pentitols ribitol and D-arabitol, sugar alcohols previously thought not to be utilized by E. coli. E. coli strains K-12 and B cannot utilize either compound. The genetic loci responsible for pentitol catabolism in E. coli C, designated rtl and atl, are separate and closely linked. Each lies between metG and his and is highly co-transducible with metG and with a P2 prophage attachment site. rtl and atl readily can be transduced into E. coli K-12 or B strains, in which they integrate at, or very near, their E. coli C location. Transduction also can be used to insert rtl and atl into certain E. coli K-12 F' plasmids. No recombination between E. coli C strains and either K-12 or B strains occurs within the rtl-atl genetic region after interstrain conjugations or transductions. No cryptic rtl or atl genes in K-12 or B strains can be detected by complementation, recombination, or mutagenesis. These results are consistent with the view that the rtl-atl portion of the E. coli C chromosome has no counterpart in E. coli K-12 or B and may have been obtained from an extrageneric source. Detailed biochemical and genetic comparisons of penitol utilization in E. coli and Klebsiella aerogenes are in progress. The ability to catabolize xylitol is conferred upon E. coli C strains by a mutation at or adjacent to the rtl locus, whereas in E. coli K-12 or B strains harboring rtl an additional mutation at a separate locus is required for xylitol utilization.

Metabolism of benzoate and the methylbenzoates by Pseudomonas putida (arvilla) mt-2: evidence for the existence of a TOL plasmid

Mutant strains of Pseudomonas putida (arvilla) mt-2 which have lost the ability to grow at the expense of m- or p-toluate (methylbenzoate) but retain the ability to grow with benzoate arise spontaneously during growth on benzoate; this genetic loss occurs to a lesser extent during growth on nonaromatic carbon sources in the presence of mitomycin C. The mutants have totally lost the activity of the enzymes of the divergent meta pathway with the possible exception of 2-oxopent-4-enoate hydratase and 4-hydroxy-2-oxovalerate aldolase; unlike the wild type they utilize benzoate by the ortho pathway. Evidence is presented that these mutants have lost a plasmid coding for the enzymes of the meta pathway, which may be transmitted back to them or into other P. putida strains. Preliminary results from these mutants and from a mutant defective in the regulation of the plasmid-carried pathway suggest that the wild type contains two benzoate oxidase systems, one on the plasmid which is nonspecific in both its catalysis and its induction and one on the chromosome which is more specific to benzoate as substrate and is specifically induced by benzoate.

Fusion and compatibility of camphor and octane plasmids in Pseudomonas

The octane (OCT) plasmid in Pseudomonas putida derived from the omega-hydroxylase-carrying strain of Coon and coworkers is transferable to the camphor (CAM) plasmid-bearing strain by conjugation or by transduction. While the majority of the Cam (+)Oct(+) exconjugants segregate Cam(+) or Oct(+) cells, exconjugants with stable Cam (+)Oct(+) phenotype (CAM-OCT) can be detected at a low frequency. The transductants are all of the CAM-OCT phenotype. In the stable Cam (+)Oct(+) strains, the OCT plasmid resembles the CAM plasmid with respect to curing by mitomycin C, transfer in conjugation, and reaction to ts (temperature-sensitive) mutation specifically affecting CAM plasmid replication. Therefore, it is suggested that certain regions of homology exist between the CAM and OCT plasmids that enable them to recombine to form a single plasmid, and to overcome the incompatibility barrier that prevents their coexisting.

Transmissible plasmid coding for the degradation of benzoate and m-toluate in Pseudomonas arvilla mt-2

Pseudomonas arvillamt-2 (ATCC 23073) has been shown to harbour a transmissible plasmid which codes for the degradation of benzoate andm-toluate. Plasmid-borne genetic information codes for the conversion of these compounds to catechol then the assimilation of catechol via themetacleavage pathway.

Camphor plasmid-mediated chromosomal transfer in Pseudomonas putida

Camphor-utilizing strains of Pseudomonas putida have been shown to carry the genetic information required for camphor degradation on a plasmid. The plasmid-carrying strains can serve as donors of both plasmid-borne and chromosomal genes. As recipients, plasmid-deleted strains are much superior to those carrying the camphor pathway genes. The transfer frequency of chromosomal, but not plasmid-borne, genes is markedly enhanced if the donor cells are irradiated with ultraviolet light followed by 3-h of growth on a rich medium in the dark. Recombinants selected for prototrophy are stable and most acquire the camphor (CAM) plasmid concomitantly; only a few of the Cam(+) recombinants inherit the donor's ability to transfer chromosomal genes at a high frequency. Transfer-defective mutations occur on the CAM plasmid, affecting both CAM and chromosomal gene transfer.