The complete general secretory pathway in gram-negative bacteria

The intent of this review is to provide an outline of the microbial degradation of polycyclic aromatic hydrocarbons. A catabolically diverse microbial community, consisting of bacteria, fungi and algae, metabolizes aromatic compounds. Molecular oxygen is essential for the initial hydroxylation of polycyclic aromatic hydrocarbons by microorganisms. In contrast to bacteria, filamentous fungi use hydroxylation as a prelude to detoxification rather than to catabolism and assimilation. The biochemical principles underlying the degradation of polycyclic aromatic hydrocarbons are examined in some detail. The pathways of polycyclic aromatic hydrocarbon catabolism are discussed. Studies are presented on the relationship between the chemical structure of the polycyclic aromatic hydrocarbon and the rate of polycyclic aromatic hydrocarbon biodegradation in aquatic and terrestrial ecosystems.

Biodegradation of polycyclic aromatic hydrocarbons

Recent advances in molecular biology have extended our understanding of the metabolic processes related to microbial transformation of petroleum hydrocarbons. The physiological responses of microorganisms to the presence of hydrocarbons, including cell surface alterations and adaptive mechanisms for uptake and efflux of these substrates, have been characterized. New molecular techniques have enhanced our ability to investigate the dynamics of microbial communities in petroleum-impacted ecosystems. By establishing conditions which maximize rates and extents of microbial growth, hydrocarbon access, and transformation, highly accelerated and bioreactor-based petroleum waste degradation processes have been implemented. Biofilters capable of removing and biodegrading volatile petroleum contaminants in air streams with short substrate-microbe contact times ( 2 S and sulfoxides from petrochemical waste streams. Microbes also have potential for use in removal of nitrogen from crude oil leading to reduced nitric oxide emissions provided that technical problems similar to those experienced in biodesulfurization can be solved. Enzymes are being exploited to produce added-value products from petroleum substrates, and bacterial biosensors are being used to analyze petroleum-contaminated environments.

Recent Advances in Petroleum Microbiology

The terms 'antioxidant', 'oxidative stress' and 'oxidative damage' are widely used but rarely defined. This brief review attempts to define them and to examine the ways in which oxidative stress and oxidative damage can affect cell behaviour both in vivo and in cell culture, using cancer as an example.

Biochemistry of oxidative stress

Polycyclic aromatic hydrocarbons: environmental pollution and bioremediation

A 25-kb DNA SalI fragment cloned from the chromosomal DNA of Pseudomonas putida OUS82, which utilizes phenanthrene (Phn+) and naphthalene (Nah+), carried all of the genes necessary for upper naphthalene catabolism. Cosmid recombinant pIP7 complemented both the Nah- and Phn- defects of OUS8211 (Trp-Nah-Phn-Sal+[salicylate utilizing]Hna+[1-hydroxy-2-naphthoate utilizing]) and only the Phn- defect of OUS8212 (Trp-Nah-Phn-Sal-Hna+). The results indicate that strain OUS82 uses different pathways after o-hydroxycarboxylic aromatics in the catabolism of naphthalene and phenanthrene.

Cloning and characterization of a chromosomal gene cluster, pah, that encodes the upper pathway for phenanthrene and naphthalene utilization by Pseudomonas putida OUS82.

Naphthalene and phenanthrene are transformed by enzymes encoded by the pah gene cluster of Pseudomonas putida OUS82. The pahA and pahB genes, which encode the first and second enzymes, dioxygenase and cis-dihydrodiol dehydrogenase, respectively, were identified and sequenced. The DNA sequences showed that pahA and pahB were clustered and that pahA consisted of four cistrons, pahAa, pahAb, pahAc, and pahAd, which encode ferredoxin reductase, ferredoxin, and two subunits of the iron-sulfur protein, respectively.

Identification and characterization of genes encoding polycyclic aromatic hydrocarbon dioxygenase and polycyclic aromatic hydrocarbon dihydrodiol dehydrogenase in Pseudomonas putida OUS82.

We determined the entire nucleotide sequence of the Klebsiella aerogenes W70 pullulanase gene (pulA) contained on a 4.2-kilobase-pair fragment of plasmid pPB174. The amino acid composition deduced from an open reading frame of 3,288 base pairs agreed closely with that determined for the intracellular pullalanase. The precursor enzyme consisted of 1,096 amino acid residues and contained a hydrophobic N-terminal signal peptide and the consensus sequence for the bacterial prelipoprotein signal peptide cleavage site.

Entire nucleotide sequence of the pullulanase gene of Klebsiella aerogenes W70.

Three strains of Pseudomonas pickettii that can grow with 2,4,6-trichlorophenol (2,4,6-TCP) as the sole source of carbon and energy were isolated from different mixed cultures of soil bacterial populations that had been acclimatized to 2,4,6-TCP. These strains released 3 mol of chloride ion from 1 mol of 2,4,6-TCP during the complete degradation of the TCP. Of these strains, P. pickettii DTP0602 in high-cell-density suspension cultures dechlorinated various chlorophenols (CPs). Cells that were preincubated with 2,4,6-TCP converted isomers of 4-CP to the corresponding chloro-p-hydroquinones, but those preincubated with 4-CP converted CPs lacking a chlorine atom(s) at the o position to isomers of chlorocatechol. The ability of DTP0602 to dechlorinate 2,4,6-TCP was induced by 2,6-dichlorophenol, 2,3,6- and 2,4,6-TCP, and 2,3,4,6-tetrachlorophenol and was repressed in the presence of succinate or glucose.

Isolation of Pseudomonas pickettii strains that degrade 2,4,6-trichlorophenol and their dechlorination of chlorophenols.

A locus of Pseudomonas pickettii DTP0602, had, that encodes 2,4,6-trichlorophenol-4-dechlorinase with hydroxylase activity, and hydroxylation of various chlorophenols by the enzyme

Noboru Takizawa

Papers

Cloning and characterization of a chromosomal gene cluster, pah, that encodes the upper pathway for phenanthrene and naphthalene utilization by Pseudomonas putida OUS82.

Identification and characterization of genes encoding polycyclic aromatic hydrocarbon dioxygenase and polycyclic aromatic hydrocarbon dihydrodiol dehydrogenase in Pseudomonas putida OUS82.

Entire nucleotide sequence of the pullulanase gene of Klebsiella aerogenes W70.

Isolation of Pseudomonas pickettii strains that degrade 2,4,6-trichlorophenol and their dechlorination of chlorophenols.

A locus of Pseudomonas pickettii DTP0602, had, that encodes 2,4,6-trichlorophenol-4-dechlorinase with hydroxylase activity, and hydroxylation of various chlorophenols by the enzyme