Degradation of phenol and m-toluate in Pseudomonas sp. strain EST1001 and its Pseudomonas putida transconjugants is determined by a multiplasmid system

Formation of new PHE plasmids in pseudomonads in a phenol-polluted environment

Several years ago, a laboratory-constructed plasmid with a single-component phenol monooxygenase gene (pheBA operon) flanked by two IS elements was released to a phenol-polluted area. During the following years, we found in the test area widely distributed pheBA operon-containing bacteria. The new pheBA⁺ strains belong predominantly to the Pseudomonas fluorescens group, and they did not arise via selection of the released PHE plasmid. On the contrary, the formation of several different types of PHE plasmids occurred, namely pPHE101 (60,958 bp) from the IncP-9 group, non-transferable plasmid pPHE69 (44,717 bp), mobilizable plasmid pPHE20 (39,609 bp) and the IncP-7 type plasmid pPHE24ΔpheBA (120,754 bp), in which the pheBA operon was translocated from the plasmid to the chromosome. In two cases, PHE plasmid-bearing strains exist in a multi-plasmid state, also containing the non-catabolic plasmids pG20 (133,709 bp) and pG69 (144,433 bp) with backbones sharing 97% DNA identity and with redundant genes for the initiation of replication, repA1and repA2, of which only one was active. Seemingly, several other plasmids and bacterial features besides the pheBA operon were involved in selective distribution of catabolic operons in the natural environment. The comparison of the genetic structure of plasmids and IS elements' functions, as well as resistance to heavy metals of seven completely sequenced plasmids, are discussed.

Narrative of a versatile and adept species Pseudomonas putida

Pseudomonas putidais a fast-growing bacterium found mostly in temperate soil and water habitats. The metabolic versatility ofP. putidamakes this organism attractive for biotechnological applications such as biodegradation of environmental pollutants and synthesis of added-value chemicals (biocatalysis). This organism has been extensively studied in respect to various stress responses, mechanisms of genetic plasticity and transcriptional regulation of catabolic genes.P. putidais able to colonize the surface of living organisms, but is generally considered to be of low virulence. A number ofP. putidastrains are able to promote plant growth. The aim of this review is to give historical overview of the discovery of the speciesP. putidaand isolation and characterization ofP. putidastrains displaying potential for biotechnological applications. This review also discusses some major findings inP. putidaresearch encompassing regulation of catabolic operons, stress-tolerance mechanisms and mechanisms affecting evolvability of bacteria under conditions of environmental stress.

Plasmid-Mediated Tolerance Toward Environmental Pollutants

The survival capacity of microorganisms in a contaminated environment is limited by the concentration and/or toxicity of the pollutant. Through evolutionary processes, some bacteria have developed or acquired mechanisms to cope with the deleterious effects of toxic compounds, a phenomenon known as tolerance. Common mechanisms of tolerance include the extrusion of contaminants to the outer media and, when concentrations of pollutants are low, the degradation of the toxic compound. For both of these approaches, plasmids that encode genes for the degradation of contaminants such as toluene, naphthalene, phenol, nitrobenzene, and triazine or are involved in tolerance toward organic solvents and heavy metals, play an important role in the evolution and dissemination of these catabolic pathways and efflux pumps. Environmental plasmids are often conjugative and can transfer their genes between different strains; furthermore, many catabolic or efflux pump genes are often associated with transposable elements, making them one of the major players in bacterial evolution. In this review, we will briefly describe catabolic and tolerance plasmids and advances in the knowledge and biotechnological applications of these plasmids.

Gene therapy: implications for craniofacial regeneration

Gene therapy in the craniofacial region provides a unique tool for delivery of DNA to coordinate protein production in both time and space. The drive to bring this technology to the clinic is derived from the fact that more than 85% of the global population may at one time require repair or replacement of a craniofacial structure. This need ranges from mild tooth decay and tooth loss to temporomandibular joint disorders and large-scale reconstructive surgery. Our ability to insert foreign DNA into a host cell has been developing since the early uses of gene therapy to alter bacterial properties for waste cleanup in the 1980s followed by successful human clinical trials in the 1990s to treat severe combined immunodeficiency. In the past 20 years, the emerging field of craniofacial tissue engineering has adopted these techniques to enhance regeneration of mineralized tissues, salivary gland, and periodontium and to reduce tumor burden of head and neck squamous cell carcinoma. Studies are currently pursuing research on both biomaterial-mediated gene delivery and more clinically efficacious, although potentially more hazardous, viral methods. Although hundreds of gene therapy clinical trials have taken place in the past 20 years, we must still work to ensure an ideal safety profile for each gene and delivery method combination. With adequate genotoxicity testing, we can expect gene therapy to augment protein delivery strategies and potentially allow for tissue-specific targeting, delivery of multiple signals, and increased spatial and temporal control with the goal of natural tissue replacement in the craniofacial complex.

Conjugal transfer and mobilization capacity of the completely sequenced naphthalene plasmid pNAH20 from multiplasmid strain Pseudomonas fluorescens PC20

The complete 83 042-bp nucleotide sequence of the IncP-9 naphthalene degradation plasmid pNAH20 from Pseudomonas fluorescens PC20 exhibits striking similarity in size and sequence to another naphthalene (NAH) plasmid pDTG1. However, the positions of insertion sequence (IS) elements significantly alter both catabolic and backbone functions provided by the two plasmids. In pDTG1, insertion of a pCAR1 ISPre1-like element disrupts expression of the lower naphthalene operon and this strain utilizes the chromosomal pathway for complete naphthalene degradation. In pNAH20, this operon is intact and functional. The transfer frequency of pNAH20 is 100 times higher than that of pDTG1 probably due to insertion of the pCAR1 ISPre2-like element into the mpfR gene coding for a putative repressor of the mpf operon responsible for mating pilus formation. We also demonstrate in situ plasmid transfer - we isolated a rhizosphere transconjugant strain of pNAH20, P. fluorescens NS8. The plasmid pNS8, a derivative of pNAH20, lacks the ability to self-transfer as a result of an additional insertion event of ISPre2-like element that disrupts the gene coding for VirB2-like major pilus protein MpfA. The characteristics of the strain PC20 and the conjugal transfer/mobilization capacity of pNAH20 (or its backbone) make this strain/plasmid a potentially successful tool for bioremediation applications.

Mineralization of 4-aminobenzenesulfonate (4-ABS) by Agrobacterium sp. strain PNS-1

A bacterial strain, PNS-1, isolated from activated sludge, could utilize sulphanilic acid (4-ABS) as the sole organic carbon and energy source under aerobic conditions. Determination and comparison of 16S r DNA sequences showed that the strain PNS-1 is closely related to the species of Agrobacterium genus. Growth on 4-ABS was accompanied with ammonia and sulfate release. TOC results showed complete mineralization of sulphanilic acid. This strain was highly specific for 4-ABS as none of the sulphonated aromatics used in the present study including other ABS isomers were utilized. Strain PNS-1 could, however, utilize all the tested monocyclic aromatic compounds devoid of a sulfonate group. No intermediates could be detected either in the growth phase or with dense cell suspensions. Presence of chloramphenicol completely inhibited 4-ABS degradation by cells pregrown on succinate, indicating that degradation enzymes are inducible. No plasmid could be detected in the Agrobacterium sp. Strain PNS-1 suggesting that 4-ABS degradative genes may be chromosomal encoded.

Phenol biodegradation by Pseudomonas putida DSM 548 in a batch reactor

Phenol biodegradation in a batch reactor using a pure culture of Pseudomonas putida DSM 548 was studied. The purpose of the experiments was to determine the kinetics of biodegradation by measuring biomass growth rates and phenol concentration as a function of time in a batch reactor. The Haldane equation µ=µ(m)S/((K(s)+S+S(2))/K(i)) adequately describes cell growth with kinetic constants µ(m)=0.436h(-1), K(s)=6.19mgl(-1), K(i)=54.1mgl(-1). These values are in the range of those published in literature for pure or mixed cultures degrading phenol.

Molecular diversity of plasmids bearing genes that encode toluene and xylene metabolism in Pseudomonas strains isolated from different contaminated sites in Belarus

Twenty different Pseudomonas strains utilizing m-toluate were isolated from oil-contaminated soil samples near Minsk, Belarus. Seventeen of these isolates carried plasmids ranging in size from 78 to about 200 kb (assigned pSVS plasmids) and encoding the meta cleavage pathway for toluene metabolism. Most plasmids were conjugative but of unknown incompatibility groups, except for one, which belonged to the IncP9 group. The organization of the genes for toluene catabolism was determined by restriction analysis and hybridization with xyl gene probes of pWW0. The majority of the plasmids carried xyl-type genes highly homologous to those of pWW53 and organized in a similar manner (M. T. Gallegos, P. A. Williams, and J. L. Ramos, J. Bacteriol. 179:5024-5029, 1997), with two distinguishable meta pathway operons, one upper pathway operon, and three xylS-homologous regions. All of these plasmids also possessed large areas of homologous DNA outside the catabolic genes, suggesting a common ancestry. Two other pSVS plasmids carried only one meta pathway operon, one upper pathway operon, and one copy each of xylS and xylR. The backbones of these two plasmids differed greatly from those of the others. Whereas these parts of the plasmids, carrying the xyl genes, were mostly conserved between plasmids of each group, the noncatabolic parts had undergone intensive DNA rearrangements. DNA sequencing of specific regions near and within the xylTE and xylA genes of the pSVS plasmids confirmed the strong homologies to the xyl genes of pWW53 and pWW0. However, several recombinations were discovered within the upper pathway operons of the pSVS plasmids and pWW0. The main genetic mechanisms which are thought to have resulted in the present-day configuration of the xyl operons are discussed in light of the diversity analysis carried out on the pSVS plasmids.

Three types of phenol and p-cresol catabolism in phenol- and p-cresol-degrading bacteria isolated from river water continuously polluted with phenolic compounds

A total of 39 phenol- and p-cresol-degraders isolated from the river water continuously polluted with phenolic compounds of oil shale leachate were studied. Species identification by BIOLOG GN analysis revealed 21 strains of Pseudomonas fluorescens (4, 8 and 9 of biotypes A, C and G, respectively), 12 of Pseudomonas mendocina, four of Pseudomonas putida biotype A1, one of Pseudomonas corrugata and one of Acinetobacter genospecies 15. Computer-assisted analysis of rep-PCR fingerprints clustered the strains into groups with good concordance with the BIOLOG GN data. Three main catabolic types of degradation of phenol and p-cresol were revealed. Type I, or meta-meta type (15 strains), was characterized by meta cleavage of catechol by catechol 2,3-dioxygenase (C23O) during the growth on phenol and p-cresol. These strains carried C23O genes which gave PCR products with specific xylE-gene primers. Type II, or ortho-ortho type (13 strains), was characterized by the degradation of phenol through ortho fission of catechol by catechol 1,2-dioxygenase (C12O) and p-cresol via ortho cleavage of protocatechuic acid by protocatechuate 3,4-dioxygenase (PC34O). These strains carried phenol monooxygenase gene which gave PCR products with pheA-gene primers. Type III, or meta-ortho type (11 strains), was characterized by the degradation of phenol by C23O and p-cresol via the protocatechuate ortho pathway by the induction of PC34O and this carried C23O genes which gave PCR products with C23O-gene primers, but not with specific xylE-gene primers. In type III strains phenol also induced the p-cresol protocatechuate pathway, as revealed by the induction of p-cresol methylhydroxylase. These results demonstrate multiplicity of catabolic types of degradation of phenol and p-cresol and the existence of characteristic assemblages of species and specific genotypes among the strains isolated from the polluted river water.

Identification and characterization of IS1411, a new insertion sequence which causes transcriptional activation of the phenol degradation genes in Pseudomonas putida

A new insertion sequence (IS element), IS1411, was identified downstream of the phenol degradation genes pheBA that originated from plasmid DNA of Pseudomonas sp. strain EST1001. According to sequence analysis, IS1411 belongs to a new family of IS elements that has recently been named the ISL3 family (J. Mahillon and M. Chandler, Microbiol. Mol. Biol. Rev. 62:725-774, 1998). IS1411 generates 8-bp duplication of the target DNA and carries 24-bp inverted repeats (IRs), highly homologous to the IRs of other IS elements belonging to this family. IS1411 was discovered as a result of insertional activation of promoterless pheBA genes in Pseudomonas putida due to the presence of outward-directed promoters at the left end of IS1411. Both promoters located on the IS element have sequences that are similar to the consensus sequence of Escherichia coli sigma70. IS1411 can produce IS circles, and the circle formation is enhanced when two copies of the element are present in the same plasmid.

Adaptation of Comamonas testosteroni TA441 to utilize phenol: organization and regulation of the genes involved in phenol degradation

Comamonas testosteroni TA441 was not able to grow on phenol as a sole carbon and energy source, but it gained the ability to utilize phenol after a 2-3-week incubation in a medium containing phenol. Phenol hydroxylase (PH) and catechol 2,3-dioxygenase (C230) were highly induced by phenol in the adapted strain designated as strain P1, suggesting that phenol was degraded via the meta-pathway. Gene clusters for phenol degradation were isolated from both strains TA441 and P1. The structural genes encoding multi-component PH and C230 (aphKLMNOPQB), and a regulatory gene of the NtrC family (aphR), were located in a divergent transcriptional organization. The cloned aphKLMNOPQB genes from either strain TA441 or strain P1 produced active PH and C230 enzymes in strain TA441. No difference was found between the strains in the sequences of aphR and the intergenic promoter region of aphK and aphR. However, the transcriptional activities of the aphK and aphR promoters were higher in strain P1 than in strain TA441. The aphK-promoter activity was not observed in aphR mutant strains and these strains could not grow on phenol. The aphR mutant of strain P1 was able to grow on phenol after transformation with a recombinant aphR gene but strain TA441 was not, suggesting that the expression of the aph genes is silenced by an unidentified repressor in strain TA441 and that this repressor is modified in strain P1.

Acquisition of a deliberately introduced phenol degradation operon, pheBA, by different indigenous Pseudomonas species

Horizontal transfer of genes of selective value in an environment 6 years after their introduction into a watershed has been observed. Expression of the gene pheA, which encodes phenol monooxygenase and is linked to the pheBA operon (A. Nurk, L. Kasak, and M. Kivisaar, Gene 102:13-18, 1991), allows pseudomonads to use phenol as a growth substrate. Pseudomonas putida strains carrying this operon on a plasmid were used for bioremediation after an accidental fire in the Estonia oil shale mine in Estonia in 1988. The water samples used for studying the fate of the genes introduced were collected in 1994. The same gene cluster was also detected in Pseudomonas strains isolated from water samples of a nearby watershed which has been continuously polluted with phenols due to oil shale industry leachate. Together with the more frequently existing counterparts of the dmp genes (V. Shingler, J. Powlowski, and U. Marklund, J. Bacteriol. 174:711-724, 1992), the pheA gene was also represented in the phenol-degrading strains. The area where the strains containing the pheA gene were found was restricted to the regular route of phenolic leachate to the Baltic Sea. Nine Pseudomonas strains belonging to four different species (P. corrugata, P. fragi, P. stutzeri, and P. fluorescens biotypes B, C, and F) and harboring horizontally transferred pheBA operons were investigated. The phe genes were clustered in the same manner in these nine phe operons and were connected to the same promoter as in the case of the original pheBA operon. One 10.6-kb plasmid carrying a pheBA gene cluster was sequenced, and the structure of the rearranged pheBA operon was described. This data indicates that introduced genetic material could, if it encodes a beneficial capability, enrich the natural genetic variety for biodegradation.

Activation of the catBCA promoter: probing the interaction of CatR and RNA polymerase through in vitro transcription

The soil bacterium Pseudomonas putida is capable of degrading many aromatic compounds, including benzoate, through catechol as an intermediate. The catabolism of catechol is mediated by the catBCA operon, whose induction requires the pathway intermediate cis,cis-muconate as an inducer and the regulatory protein, CatR. CatR also regulates the plasmid-borne pheBA operon of P. putida PaW85, which is involved in phenol catabolism. We have used an in vitro transcription system to study the roles of CatR, cis,cis-muconate, Escherichia coli RNA polymerase, and promoter sequences in expression of the cat and phe operons. The assay confirmed the requirement of both CatR and cis,cis-muconate for transcript formation. We also examined the in vitro transcription of three site-directed mutants of the catBCA promoter; the results obtained compared favorably with previous in vivo data. The requirement of the alpha subunit of RNA polymerase for expression of the catBCA and the pheBA transcripts was also examined. The C-terminal region of the alpha subunit of RNA polymerase has been implicated in direct protein-protein contact with transcriptional regulatory proteins and/or direct contact with the DNA. We show that the carboxyl terminus of the alpha subunit is required for the expression of the catBCA and the pheBA operons because RNA polymerases with truncated alpha subunits were deficient in activation. Further experiments demonstrated the arginine at position 265 and the asparagine at position 268 of the alpha subunit as possible amino acids involved in activation. On the basis of these and previous results, we propose a model to explain the interaction of the different regulatory components leading to CatR-dependent activation of the catBCA operon.

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

Burkholderia (Pseudomonas) cepacia PR1(23) has been shown to constitutively express to 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 TOM23c 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 TOM23c 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.

Catabolic transposons

The structure and function of transposable elements that code for catabolic pathways involved in the biodegradation of organic compounds are reviewed. Seven of these catabolic transposons have structural features that place them in the Class I (composite) or Class II (Tn3-family) bacterial elements. One is a conjugative transposon. Another three have been found to have properties of transposable elements but have not been characterized sufficiently to assign to a known class. Structural features of the toluene (Tn4651/Tn4653) and naphthalene (Tn4655) elements that illustrate the enormous potential for acquisition, deletion and rearrangement of DNA within catabolic transposons are discussed. The recently characterized chlorobenzoate (Tn5271) and chlorobenzene (Tn5280) catabolic transposons encode different aromatic ring dioxygenases, however they both illustrate the constraints that must be overcome when recipients of catabolic transposons assemble and regulate complete metabolic pathways for environmental pollutants. The structures of the chlorobenzoate catabolic transposon Tn5271 and the related haloacetate dehalogenase catabolic element of plasmid pUO1 are compared and a hypothesis for their formation is discussed. The structures and activities of catabolic transposons of unknown class coding for the catabolism of halogenated alkanoic acids (DEH) and chlorobiphenyl (Tn4371) are also reviewed.

Molecular mechanisms of genetic adaptation to xenobiotic compounds

Microorganisms in the environment can often adapt to use xenobiotic chemicals as novel growth and energy substrates. Specialized enzyme systems and metabolic pathways for the degradation of man-made compounds such as chlorobiphenyls and chlorobenzenes have been found in microorganisms isolated from geographically separated areas of the world. The genetic characterization of an increasing number of aerobic pathways for degradation of (substituted) aromatic compounds in different bacteria has made it possible to compare the similarities in genetic organization and in sequence which exist between genes and proteins of these specialized catabolic routes and more common pathways. These data suggest that discrete modules containing clusters of genes have been combined in different ways in the various catabolic pathways. Sequence information further suggests divergence of catabolic genes coding for specialized enzymes in the degradation of xenobiotic chemicals. An important question will be to find whether these specialized enzymes evolved from more common isozymes only after the introduction of xenobiotic chemicals into the environment. Evidence is presented that a range of genetic mechanisms, such as gene transfer, mutational drift, and genetic recombination and transposition, can accelerate the evolution of catabolic pathways in bacteria. However, there is virtually no information concerning the rates at which these mechanisms are operating in bacteria living in nature and the response of such rates to the presence of potential (xenobiotic) substrates. Quantitative data on the genetic processes in the natural environment and on the effect of environmental parameters on the rate of evolution are needed.

Complete nucleotide sequence of tbuD, the gene encoding phenol/cresol hydroxylase from Pseudomonas pickettii PKO1, and functional analysis of the encoded enzyme

The gene (tbuD) encoding phenol hydroxylase, the enzyme that converts cresols or phenol to the corresponding catechols, has been cloned from Pseudomonas pickettii PKO1 as a 26.5-kbp BamHI-cleaved DNA fragment, designated pRO1957, which allowed the heterogenetic recipient Pseudomonas aeruginosa PAO1c to grow on phenol as the sole source of carbon. Two subclones of pRO1957 carried in trans have shown phenol hydroxylase activity in cell extracts of P. aeruginosa. The nucleotide sequence was determined for one of these subclones, a 3.1-kbp HindIII fragment, and an open reading frame that would encode a peptide of 73 kDa was found. The size of this deduced peptide is consistent with the size of a novel peptide that had been detected in extracts of phenol-induced cells of P. aeruginosa carrying pRO1959, a partial HindIII deletion subclone of pRO1957. Phenol hydroxylase purified from phenol-plus-Casamino Acid-grown cells of P. aeruginosa carrying pRO1959 has an absorbance spectrum characteristic of a simple flavoprotein; moreover, the enzyme exhibits a broad substrate range, accommodating phenol and the three isomers of cresol equally well. Sequence comparisons revealed little overall homology with other flavoprotein hydroxylases, supporting the novelty of this enzyme, although three conserved domains were apparent.

Sequence of the gene (pheA) encoding phenol monooxygenase from Pseudomonas sp. EST1001: expression in Escherichia coli and Pseudomonas putida

The plasmid pEST1412 contains the genes, pheA and pheB, encoding phenol monooxygenase (PMO) and catechol 1,2-dioxygenase (C12]), respectively. Thse were originally cloned from the plasmid DNA of Pseudomonas sp. EST1001 [Kivisaar et al., Plasmid 24 (1990) 25-36]. Although pheA and pheB are cotranscribed using the promoter sequences derived from Tn4652 and the level of expression of C120 activities from pEST1412 was equal both in Escherichia coli and in Pseudomonas putida, the level of PMO activity measured in the cell-free extracts of E. coli was lower than that in P. putida. The nucleotide sequence of the 2.0-kb PstI-HindIII fragment of pEST1412 carrying pheA was determined. A 1821-bp ORF was found in this DNA. The structural gene (tfdB) encoding 2,4-dichlorophenol hydroxylase from pJP4 has been sequenced [Perkins et al., J. Bacteriol. 172 (1990) 2351-2359]. Comparison of the deduced amino acid sequences of tfdB and pheA revealed highly conserved regions in the protein products of these genes.

Molecular cloning, characterization, and regulation of a Pseudomonas pickettii PKO1 gene encoding phenol hydroxylase and expression of the gene in Pseudomonas aeruginosa PAO1c

A 26-kilobase BamHI restriction endonuclease DNA fragment was cloned from Pseudomonas pickettii PKO1, a strain isolated from a soil microcosm that had been amended with benzene, toluene, and xylene. This DNA fragment, cloned into vector plasmid pRO1727 and designated pRO1957, allowed Pseudomonas aeruginosa PAO1c to grow on phenol as the sole source of carbon. Physical and functional restriction endonuclease maps have been derived for the cloned DNA fragment. Two DNA fragments carried in trans and derived from subclones of pRO1957 show phenol hydroxylase activity in cell extracts of P. aeruginosa. Deletion and subcloning analyses of these fragments indicated that the gene encoding phenol hydroxylase is positively regulated. Phenol and m-cresol were shown to be inducers of the enzyme. o-Cresol and p-cresol did not induce enzymatic activity but could be metabolized by cells that had been previously exposed to phenol or m-cresol; moreover, the enzyme exhibited a rather broad substrate specificity and was sensitive to thiol-inhibiting reagents. A novel polypeptide with an estimated molecular mass of 80,000 daltons was detected in extracts of phenol-induced cells of P. aeruginosa carrying plasmid pRO1959.

Selection of independent plasmids determining phenol degradation in Pseudomonas putida and the cloning and expression of genes encoding phenol monooxygenase and catechol 1,2-dioxygenase

Long-term cultivation of the Pseudomonas putida multiplasmid strain EST1020 on phenol resulted in the formation of individual PHE plasmids determining phenol degradation. Four types of PHE plasmids, pEST1024, pEST1026, pEST1028, and pEST1029, are characterized. They all contain a transferrable replicon similar to pWWO-8 with a partly duplicated DNA sequence of the 17-kb transposable element of this plasmid and include various amounts of DNA that carry genes encoding phenol degradation (phe genes). We cloned the genes determining phenol monooxygenase and catechol 1,2-dioxygenase from the Pseudomonas sp. parent strain plasmid DNA into the broad host range vector pAYC32 and studied the expression of the cloned DNA. The formation of a new hybrid metabolic plasmid, pEST1354, was demonstrated in P. putida PaW85 as the result of transposition of the 17-kb genetic element from the chromosome of PaW85 into the plasmid carrying cloned phe genes. The target site for the 17-kb transposon was localized in the vector DNA, just near the cloning site. In subcloning experiments we found two regions in the 17-kb DNA stretch that are involved in the expression of the cloned phe genes.