Molecular characteristics of Pseudomonas rhodesiae strain KK1 in response to phenanthrene

Abstract

Radiorespirometric analysis revealed that Pseudomonas sp. strain KK1 isolated from a soil contaminated with petroleum hydrocarbons was able to catabolize polycyclic aromatic hydrocarbons such as phenanthrene and naphthalene. The rate and extent of phenanthrene mineralization was markedly enhanced when the cells were pregrown on either naphthalene or phenanthrene, compared to the cells grown on universal carbon sources (i.e., TSA medium). Deduced amino acid sequence of the Rieske-type iron-sulfur center of a putative phenanthrene dioxygenase (PhnA1) obtained from the strain KK1 shared significant homology with DxnA1 (dioxin dioxygenase) from Spingomonas sp. RW1, BphA1b (biphenyl dioxygenase) from Spingomonas aromaticivorans F 199, and PhnAc (phenanthrene dioxygenase) from Burkholderia sp. RP007 or Alcaligenes faecalis AFK2. Northern hybridization using the dioxygenase gene fragment cloned from KK1 showed that the expression of the putative phn dioxygenase gene reached the highest level in cells grown in the minimal medium containing phenanthrene and KNO3, and the expression of the phn gene was repressed in cells grown with glucose. In addition to the metabolic change, phospholipid ester-linked fatty acids (PLFA) analysis revealed that the total cellular fatty acid composition of KK1 was significantly changed in response to phenanthrene. Fatty acids such as 14:0, 16:0 3OH, 17:0 cyclo, 18: 1 omega7c, 19:0 cyclo increased in phenanthrene-exposed cells, while fatty acids such as 10:0 3OH, 12:0, 12:0 2OH, 12:0 3OH, 16:1omega7c, 15:0 iso 2OH, 16:0, 18:1 omega6c, 18:0 decreased.