Aromatic compounds of both natural and man-made sources abound in the environment. The degradation of such chemicals is mainly accomplished by microorganisms. This review provides key background information but centres on recent developments in the bacterial degradation of selected man-made aromatic compounds. An aromatic compound can only be considered to be biodegraded if the ring undergoes cleavage, and this is taken as the major criteria for inclusion in this review (although the exact nature of the enzymic ring-cleavage has not been confirmed in all cases discussed).

The biodegradation of aromatic hydrocarbons by bacteria

Is bioaugmentation a feasible strategy for pollutant removal and site remediation

Recent trends in biodegradable polymers indicate significant developments in terms of novel design strategies and engineering to provide advanced polymers with comparably good performance. However, there are several inadequacies in terms of either technology or cost of production especially in the case of applications in environmental pollution. So, there is a need to have a fresh perspective on the design, properties and functions of these polymers with a view to developing strategies for future developments. The paper reviews the present state-of-art on biodegradable polymers and discusses the salient features of the design and properties of biodegradable polymers. Special emphasis is given to the problems and prospects of (1) approaches adopted to make non-biodegradable synthetic polymers such as polyethylene biodegradable and (2) biodegradable polymers and copolymers made from renewable resources especially poly(lactic acid) based polymers and copolymers which are emerging as the candidate biodegradable materials for the future.

Biodegradable Polymers- A Review on Recent Trends and Emerging Perspectives

Pseudomonas stutzeri is a nonfluorescent denitrifying bacterium widely distributed in the environment, and it has also been isolated as an opportunistic pathogen from humans. Over the past 15 years, much progress has been made in elucidating the taxonomy of this diverse taxonomical group, demonstrating the clonality of its populations. The species has received much attention because of its particular metabolic properties: it has been proposed as a model organism for denitrification studies; many strains have natural transformation properties, making it relevant for study of the transfer of genes in the environment; several strains are able to fix dinitrogen; and others participate in the degradation of pollutants or interact with toxic metals. This review considers the history of the discovery, nomenclatural changes, and early studies, together with the relevant biological and ecological properties, of P. stutzeri.

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Biology of Pseudomonas stutzeri

Phytochemicals: The Chemical Components of Plants H.L. Brielmann Jr., W.N. Setzer, P.B. Kaufman, A. Kirakosyan, and L.J. Cseke How and Why These Compounds Are Synthesized by Plants L.J. Cseke, C.R. Lu, A. Kornfeld, P.B. Kaufman, and A. Kirakosyan Regulation of Metabolite Synthesis in Plants L.J. Cseke and P. B. Kaufman Plant Natural Products in the Rhizosphere Bhinu, V.S., K. Narasimhan, and S. Swarup Molecular Biology of Plant Natural Products Sheela Reuben, L.J. Cseke, Bhinu, V.S., K. Narasimhan, M. Jeyakumar and S. Swarup The Study of Natural Product Biosynthesis in the Pregenomics and Genomics Eras F. Chen, L.J. Cseke, H. Lin, A. Kirakosyan, J.S. Yuan, and P. Kaufman Plant Biotechnology for the Production of Natural Products A. Kirakosyan Traditional, Analytical, and Preparative Separations of Natural Products L.J. Cseke, W.N. Setzer, B. Vogler, A. Kirakosyan, and P.B. Kaufman Characterization of Natural Products B. Vogler and W.N. Setzer Bioassays for Activity W.N. Setzer and B. Vogler Modes of Action at Target Sites S. Warber, E.M. Seymour, P. Kaufman, A. Kirakosyan, and L.J. Cseke The Uses of Plant Natural Products by Humans and Risks Associated with Their Use P.B. Kaufman, A. Kirakosyan, M. McKenzie, P. Dayanandan, J.E. Hoyt, and C. Li The Synergy Principle at Work with Plants, Pathogens, Insects, Herbivores, and Humans K. Spelman, J.A. Duke and M.J. Bogenschutz-Godwin Plant Conservation M.J. Bogenschutz-Godwin, J.A. Duke, M. McKenzie, and P.B. Kaufman Relationship Between People and Plants S. Warber and K. Irvine Appendix:Information Retrieval on Natural Products in Plants Indexes: Chemicals, Plant Species and Common Names, and Subject

Natural Products from Plants

A Pseudomonas stutzeri strain capable of growing on o-xylene was isolated from enrichment cultures. The organism grew on 2,3- and 3,4-dimethylphenol but not on 2-methylbenzyl alcohol, o-tolualdehyde, or o-toluate. P. stutzeri was not able to utilize m-xylene, p-xylene, or 1,2,4-trimethylbenzene, but growth was observed in the presence of the corresponding alcohols and acids. From the Pseudomonas cultures supplied with o-xylene, 2,3-dimethylphenol was isolated and identified. When resting P. stutzeri cells were incubated with 2,3-dimethylphenol, the reaction mixture turned greenish yellow and showed spectral properties identical to those of the 3,4-dimethylcatechol meta ring fission product. Catechol 2,3-oxygenase was induced by growth on o-xylene or on 2,3- or 3,4-dimethylphenol. The suggested hypothesis is that the first metabolic steps of growth on o-xylene involve the direct oxygenation of the aromatic nucleus, followed by meta pathway reactions.

Isolation of a Pseudomonas stutzeri strain that degrades o-xylene.

Styrene Catabolism by a Strain of Pseudomonas fluorescens.

A selected mixed culture and a strain of Alcaligenes eutrophus TCP were able to totally degrade 2,4,6-TCP with stoichiometric release of Cl - . In cultures of Alc. eutrophus TCP, a dioxygenated dichlorinated metabolite was detected after 48 h of incubation. Experiments conducted with soil microcosms gave evidence that : the degradative process had a biotic nature and was accompanied by microbial growth; the soil used presented an intrinsic degradative capacity versus 2,4,6-TCP; the specialized organism used as inoculum was effective in degrading 2,4,6-TCP in a short time. These results could be utilized for the adoption of appropriate remediation techniques for contaminated soil.

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Degradation of 2,4,6‐trichlorophenol by a specialized organism and by indigenous soil microflora: bioaugmentation and self‐remediability for soil restoration

1. Two Pseudomonas strains capable of utilizing 2-phenylbutane, 3-phenylpentane and 4-phenylheptane as the sole carbon and energy source were isolated. 2. Two Nocardia strains capable of utilizing only 3-phenyldodecane as the sole carbon and energy source were isolated. 3. All the isolated strains were unable to grow on the corresponding phenylalkane-p-sulphonates. 4. From liquid cultures of Pseudomonas strains utilizing 2-phenylbutane, 2-(2,3-dihydro-2,3-dihydroxyphenyl)butane was isolated and identified. Evidence for a meta cleavage of the benzene ring was also obtained. 5. From liquid cultures of Pseudomonas strains utilizing 3-phenylpentane, 3-(2,3-dihydro-2,3-dihydroxyphenyl)pentane and 2-hydroxy-7-ethyl-6-oxonona-2,4-dienoic acid were isolated and identified. 6. Evidence for the formation of both a diol and a meta-cleavage compound was obtained from liquid cultures of both Pseudomonas strains utilizing 4-phenylheptane. 7. Liquid cultures of both Nocardia strains utilizing 3-phenyldodecane never formed a diol or a semialdehyde-related compound. 2-Phenylbutyric acid, 3-phenylvaleric acid and 4-phenylhexanoic acid were shown to be present in these cultures.

The microbial degradation of phenylalkanes. 2-Phenylbutane, 3-phenylpentane, 3-phenyldodecane and 4-phenylheptane

A study was made of the metabolic and co-metabolic intermediates of 2- and 3-chlorobenzoate, 2,3- and 3,5-dichlorobenzoate to elucidate the mechanism(s) involved in the negative effects observed on the growth of a chlorobenzoate-degrading microbial consortium in the presence of mixed chlorobenzoates. 2-Chloro-muconate accumulated as the end-product in the cultural broths of the microbial consortium during growth on 2-chlorobenzoate; the same 2-chloromuconate was identified in the reaction mixtures of resting cells pre-grown on 2-chlorobenzoate and exposed to 3-chloro- and 2,3-dichlorobenzoate, while in similar experiments 1,2-dihydroxy-3,5-dichloro-cyclohexa-3,5-dienoate was detected as dead-end product of 3,5-dichlorobenzoate co-metabolism. These results suggest an initial degradative attack by 2-chlorobenzoate induced dioxygenase(s). The role of 3,5-dichlorobenzoate as an antagonist of 2-chlorobenzoate degradation was also studied: in the presence of mixed 2-chloro- and 3,5-dichlorobenzoate, the 3,5-dichlorobenzoate preferential uptake by the resting cells of the chlorobenzoate-degrading consortium was observed. 2-Chlorobenzoate entered the cells only after the complete removal of the co-substrate. In growing cells experiments, the addition of 1,2-dihydroxy-3,5-dichloro-cyclohexa-3,5-dienoate, the 3,5-dichlorobenzoate co-metabolite, to 2-chlorobenzoate exerted the same antagonistic effect of the parent compound, inhibiting both the microbial growth and the degradative process. These data are discussed, allowing us to attribute the inhibitory effects observed to a substrate/co-substrate competition, though other additional causes may not be totally excluded.

3-chloro-, 2,3- and 3,5-dichlorobenzoate co-metabolism in a 2-chlorobenzoate-degrading consortium: role of 3,5-dichlorobenzoate as antagonist of 2-chlorobenzoate degradation. Metabolism and co-metabolism of chlorobenzoates.

Grazia Baggi

Papers

Isolation of a Pseudomonas stutzeri strain that degrades o-xylene.

Styrene Catabolism by a Strain of Pseudomonas fluorescens.

Degradation of 2,4,6‐trichlorophenol by a specialized organism and by indigenous soil microflora: bioaugmentation and self‐remediability for soil restoration

The microbial degradation of phenylalkanes. 2-Phenylbutane, 3-phenylpentane, 3-phenyldodecane and 4-phenylheptane

3-chloro-, 2,3- and 3,5-dichlorobenzoate co-metabolism in a 2-chlorobenzoate-degrading consortium: role of 3,5-dichlorobenzoate as antagonist of 2-chlorobenzoate degradation. Metabolism and co-metabolism of chlorobenzoates.