Pseudomonas putida naphthalene degradation

An issue of particular relevance in the context of bioremediation is illustrated by the increased rate of cell death in an established naphthalene-degrading Pseudomonas putida G7 brought about by the substrate (naphthalene) under conditions of oxygen (or combined oxygen and nitrogen) limitation (Ahn et al. 1998). 

The enzymes of alternative pathways may be induced in a given strain by growth with different substrates for example, growth of Pseudomonas putida R1 with salicylate induces enzymes of the extradiol fission pathway, whereas growth with benzoate induces those of the intradiol pathway (Chakrabarty 1972). As a broad generalization, the extradiol fission is preferred for the degradation of more complex compounds such as toluene, naphthalene, and biphenyl (Furukawa et al. 1983). 

Guerin WF, SA Boyd (1992) Maintenance and induction of naphthalene degradation activity in Pseudomonas putida and an Alcaligenes sp under different culture conditions. Appl Environ Microbiol 61 4061-4068. 

Kniper I, LV Kravchenko, GV Bloemberg, BJJ Lugtenberg (2002) Pseudomonas putida strain PC L1444, selected for efficient root colonization and naphthalene degradation, effectively utilizes root exudate components. Mol Plant-Microbe Interact 15 734-741. 

A recent experiment compared for the first time pollutant degradation by chemotactic bacteria and nonchemotactic mutants [54]. The result suggested an important role of chemotaxis in the bioremediation of contaminated soils. In a heterogeneous system, in which naphthalene was supplied from a microcapillary, a 90% reduction in the initial amount of naphthalene took six hours with the chemotactic wild-type Pseudomonas putida PpG7, while a similar reduction with either a chemotaxis-negative or a nonmotile mutant strain took about five times longer. Only the systems inoculated with the chemotactic strain exhibited degradation rates in excess of the rate of naphthalene diffusion from the... 

The reactions, described so far, are derived from tiie most extensively studied catabolic pathway for naphthalene, which is encoded by the NAH7 plasmid of Pseudomonas putida. But, the same sequence of reactions seems to take place in all naphthalene-degrading bacteria, which means that salicylate is a common intmmiediate in naphthalene catabolism. With respect to the enzymes involved in the breakdown of naphthalene, there seem to exist differences between the bacterial species, that can grow on naphtiialene-containing media. A recently isolated and described Rhodococcus sp., for example, seems to have a 1,2-dihydroxynaphthalene oxygenase that requires NADH [38]. 

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