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Pseudomonas putida B2 is able to grow on o-nitrophenol (ONP) as the sole source of carbon and nitrogen. ONP was converted by a nitrophenol oxygenase to nitrite and catechol. Catechol was then attacked by a catechol 1,2-dioxygenase and further degraded through an ortho-cleavage pathway. ONP derivatives which were para-substituted with a methyl-, chloro-, carboxy-, formyl- or nitro-group failed to support growth of strain B2. Relevant catabolic enzymes were characterized to analyze why these derivatives were not mineralized. Nitrophenol oxygenase of strain B2 is a soluble, NADPH-dependent enzyme that is stimulated by magnesium, manganese, and calcium ions. It is active toward ONP, 4-methyl-, 4-chloro-, and to a lesser extent, 4-formyl-ONP but not toward 4-carboxy- or 4-nitro-ONP. In addition, 4-formyl-, 4-carboxy-, and 4-nitro-ONP failed to induce the formation of nitrophenol oxygenase. Catechol 1,2-dioxygenase of strain B2 is active toward catechol and 4-methyl-catechol but only poorly active toward chlorinated catechols. 4-Methyl-catechol is likely to be degraded to methyl-lactones, which are often dead-end metabolites in bacteria. Thus, of the compounds tested, only unsubstituted ONP acts as an inducer and substrate for all of the enzymes of a productive catabolic pathway.

DNA fragments containing the xylD and xylL genes of TOL plasmid pWW0 -161 of Pseudomonas putida, which code for the catabolic enzymes toluate 1,2-dioxygenase and dihydrodihydroxybenzoic acid dehydrogenase, respectively, and the nahG gene of the NAH plasmid NAH7 , which codes for salicylate hydroxylase, were cloned in pBR322 vector plasmid. Deletion and insertion mutagenesis were used to localize these genes with respect to crucial endonuclease cleavage sites. The pBR322-based plasmids were ligated to the broad host range cloning vector pKT231 , or derivatives of it, and the hybrid plasmids were introduced into Pseudomonas sp. B13( WR1 ), a bacterium able to degrade 3-chlorobenzoate but not 4-chlorobenzoate, 3,5- dichlorobenzoate , salicylate, or chlorosalicylates . The cloned xylD gene expanded the catabolic range of WR1 to include 4-chlorobenzoate, whereas the cloned xylD - xylL genes enabled the isolation of derivatives of WR1 that degraded 3-chlorobenzoate, 4-chlorobenzoate, and 3,5- dichlorobenzoate . The cloned nahG gene extended the catabolic range of WR1 to include salicylate and 3-, 4-, and 5- chlorosalicylate .

Host-vector systems have been developed for gene cloning in the metabolically versatile bacterial genus Pseudomonas. They comprise restriction-negative host strains of Pseudomonas aeruginosa and P. putida and new cloning vectors derived from the high-copy-number, broad-host-range plasmid RSF1010, which are stably maintained in a wide range of Gram-negative bacteria. These plasmids contain EcoRI, SstI, HindIII, XmaI, XhoI, SalI, BamHI, and ClaI insertion sites. All cloning sites, except for BamHI and ClaI, are located within antibiotic-resistance genes' insertional inactivation of these genes during hybrid plasmid formation provides a readily scored phenotypic change for the rapid identification of bacterial clones carrying such hybrids. One of the new vector plasmids is a cosmid that may be used for the selective cloning of large DNA fragments by in vitro lambda packaging. An analogous series of vectors that are defective in their plasmid-mobilization function, and that exhibit a degree of biological containment comparable to that of current Escherichia coli vector plasmids, are also described.

The Pseudomonas putida TOL plasmid pWWO carries an operon that specifies a meta-cleavage pathway for the catabolism of benzoate and toluates whose transcription is positively regulated by the xylS gene product. Stimulation of transcription of the operon is thought to result from activation of this protein by pathway substrates/effectors. In the present study, overexpression of the xylS gene has led to identification of the regulator as a 33 kDa protein. Overexpression of xylS also resulted in partially constitutive, i.e. effector-independent expression of the meta-cleavage operon. Determination of the polynucleotide sequence of the xylS gene revealed amino acid sequence homology with several DNA binding proteins, particularly with the araC products of Escherichia coli and Salmonella typhimurium and with the nifA and ntrC products of Klebsiella pneumoniae. Homologous sequences were mainly located in an alpha-helix-turn-alpha-helix domain of the polypeptide. Interestingly, amino acid sequence homology was also found with sigma factors of E. coli (ntrA and htpR products) and Bacillus subtilis (spoIIG and phage SPOI Gp34 products) and other RNA polymerase core-interacting proteins, such as the E. coli nusA product.

Stimulation of transcription from positively regulated promoters involves regulatory proteins that have been activated, generally as a consequence of binding low molecular weight effector molecules. To define essential structural features of effectors for one positively acting gene regulator, the xylS-encoded protein, which activates the TOL plasmid meta-cleavage pathway operon promoters, effector activities of a wide range of benzoate derivatives have been systematically analyzed, and mutant xylS-encoded proteins exhibiting altered effector specificities have been generated and characterized. Cloned mutant xylS genes were trans dominant in partial diploids containing the wild-type xylS allele and could therefore be used to effect expansion of the range of aromatic compounds completely or partially degraded by Pseudomonas bacteria. The method developed to isolate mutant xylS-encoded proteins has general applicability and could in principle be used to isolate gene regulator specificity mutants of any inducible regulatory system.

The role of plasmids in the virulence of Shigella dysenteriae 1 W30864, which contains at least five species, was investigated. By means of a standard plasmid-curing procedure, that is, bacterial cultivation at an elevated temperature, five virulence-deficient derivatives were obtained. One of these lacked a small, 6-megadalton plasmid, designated pHW400, exhibited reduced invasiveness for HeLa cells, and failed to produce the somatic antigen. Transposon tagging of the pHW400 plasmid to produce pHW401 and the transfer of this derivative into a variant of strain W30864 lacking pHW400 confirmed the conclusion that the pHW400 plasmid encodes one or more functions involved in O antigen (lipopolysaccharide) biosynthesis and bacterial virulence. A plasmid of similar size was detected in all of the three other strains of S. dysenteriae 1 examined.

The genetic organization of the Pseudomonas putida plasmid pWWO-161, which encodes enzymes for the degradation of toluene and related aromatic hydrocarbons, has been investigated by transposition mutagenesis and gene cloning. Catabolic genes were localized to two clusters, one for upper pathway (hydrocarbon leads to carboxylic acid) enzymes and the other for lower pathway (carboxylic acid leads to tricarboxylic acid cycle) enzymes, that are separated by a 14-kilobase DNA segment. The physical organization of the catabolic genes thus reflects their functional organization into two regulatory blocks. The pWWO-161 DNA fragments Sst I fragment C and fragment D were cloned in a broad host range vector to produce plasmid pKT530. This hybrid encodes toluate oxygenase and all meta cleavage pathway enzymes, and it enables P. putida mt-2 and Escherichia coli K-12 cells to grow on m-toluate as sole carbon source. The pKT530 plasmid also carries xylS (a gene whose product has been postulated to regulate expression of the lower pathway genes) and the control sequences of the pathway that interact with this product, because catechol 2,3-oxygenase synthesis is specifically induced by m-toluate in both P. putida and E. coli. Evidence is presented that suggests the promoter operator of the meta pathway gene functions less effectively with the RNA polymerase or xylS product of E. coli than with the enzyme or product of P. putida.

Colicin D-CA23, obtained by sonic treatment of mitomycin C-induced cells of Escherichia coli K-12 W1485 (colD), was purified by ammonium sulfate precipitation, gel filtration on Sephadex G200, ion-exchange chromatography on diethylaminoethyl cellulose, and isoelectrofocusing. Polyacrylamide-gel electrophoresis, sedimentation velocity analysis, and antigenic analysis indicated that the preparation was homogeneous. Colicin D is composed entirely of amino acids and hence is a simple protein uncomplexed with lipid or lipopolysaccharide. It contains six residues of cysteine per molecule. The molecular weight of colicin D is approximately 92,000, as determined by sodium dodecyl sulfate-polyacrylamide-gel electrophoresis and gel filtration on Sephadex G200. Its sedimentation coefficient is 4.41S. The behavior of colicin D in solutions of sodium dodecyl sulfate and 2-mercaptoethanol indicates that it does not consist of subunits and exists as a single polypeptide chain. Its high molecular weight and presence of six cysteine residues per molecule distinguish colicin D from all colicins previously described. Although colicins D and E3 have similar modes of action, their gross molecular properties are entirely different.

Reproducible yields of covalently closed circular (plasmid) deoxyribonucleic acid were obtained from mutants defective for extracellular nuclease but not from the corresponding wild-type strain of Serratia marcescens