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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/12294

Title: Biodegradation of phenanthrene by Psuedomonas sp strain PP2: novel metabolic pathway, role of biosurfactant and cell surface hydrophobicity in hydrocarbon assimilation
Authors: PRABHU, Y
PHALE, PS
Keywords: polycyclic aromatic-hydrocarbons
pseudomonas-putida ous82
rhamnolipid biosurfactant
microbial surfactants
escherichia-coli
gene-cluster
degradation
aeruginosa
kp7
enhancement
Issue Date: 2003
Publisher: SPRINGER-VERLAG
Citation: APPLIED MICROBIOLOGY AND BIOTECHNOLOGY, 61(4), 342-351
Abstract: Pseudomonas sp. strain PP2 isolated in our laboratory efficiently metabolizes phenanthrene at 0.3% concentration as the sole source of carbon and energy. The metabolic pathways for the degradation of phenanthrene, benzoate and p-hydroxybenzoate were elucidated by identifying metabolites, biotransformation studies, oxygen uptake by whole cells on probable metabolic intermediates, and monitoring enzyme activities in cell-free extracts. The results obtained suggest that phenanthrene degradation is initiated by double hydroxylation resulting in the formation of 3,4-dihydroxyphenanthrene. The diol was finally oxidized to 2-hydroxymuconic semialdehyde. Detection of 1-hydroxy-2-naphthoic acid, a-naphthol, 1,2-dihydroxy naphthalene, and salicylate in the spent medium by thin layer chromatography; the presence of 1,2-dihydroxynaphthalene dioxygenase, salicylaldehyde dehydrogenase and catechol-2,3-dioxygenase activity in the extract; 02 uptake by cells on alpha-naphthol, 1,2-dihydroxynaphthalene, salicylaldehyde, salicylate and catechol; and no 02 uptake on o-phthalate and 3,4-dihydroxybenzoate supports the novel route of metabolism of phenanthrene via 1-hydroxy-2-naphthoic acid --> [alpha-naphthol] --> 1,2-dihydroxy naphthalene --> salicylate --> catechol. The strain degrades benzoate via catechol and cis,cis-muconic acid, and p-hydroxybenzoate via 3,4-dihydroxybenzoate and 3-carboxy-cis,cis-muconic acid. Interestingly, the culture failed to grow on naphthalene. When grown on either hydrocarbon or dextrose, the culture showed good extracellular biosurfactant production. Growth-dependent changes in the cell surface hydrophobicity, and emulsification activity experiments suggest that: (1) production of biosurfactant was constitutive and growth-associated, (2) production was higher when cells were grown on phenanthrene as compared to dextrose and benzoate, (3) hydrocarbon-grown cells were more hydrophobic and showed higher affinity towards both aromatic and aliphatic hydrocarbons compared to dextrose-grown cells, and (4) mid-log-phase cells were significantly (2-fold) more hydrophobic than stationary phase cells. Based on these results, we hypothesize that growth-associated extracellular biosurfactant production and modulation of cell surface hydrophobicity plays an important role in hydrocarbon assimilation/uptake in Pseudomonas sp. strain PP2.
URI: http://dx.doi.org/10.1007/s00253-002-1218-y
http://dspace.library.iitb.ac.in/xmlui/handle/10054/12294
http://hdl.handle.net/10054/12294
ISSN: 0175-7598
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