Pyrene biodegradation and proteomic analysis in Achromobacter xylosoxidans, PY4 strain

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants from incomplete combustion and petroleum products. As the molecular weight increases, PAHs become more recalcitrant to biodegradation. A bacterial strain capable of metabolizing the four fused aromatic ring PAH pyrene was isolated and characterized. The analysis of 16S rRNA gene revealed that it belongs to Achromobacter xylosoxidans species. A. xylosoxidans PY4 can utilize pyrene as the sole source of carbon. PY4 has a doubling time (dt) of less than 1 day when it grows in the presence of 1-5 mg l(-1) pyrene, a dt range similar to that of the most efficient pyrene biodegrading bacteria described so far. The optimal pyrene degradation conditions are at pH 7-9, 37-40 degrees C, and 0-2.5% NaCl. PY4 also utilizes salicylic acid, catechol, naphthalene, anthracene and phenanthrene. PY4 degrades more than 50% of 100 mgl(-1) of pyrene, within the first 15 days, at a rate of 0.069 day(-1), R-2 = 0.99. The metabolites include monohydroxypyrene, 1-methoxy1-2-H-benzo[h]chromene-2-carboxylic acid, 9,10-phenanthrenequinone, 1-methoxyl-trans-2'-carboxybenzalpyruvate, and dibutyl-phthalate. Up-expressed proteins in response to pyrene are involved in cell homeostasis, genetic information synthesis and storage, and chemical stress. Among these proteins are 4-hydroxyphenylpyruvate dioxygenase and homogentisate 1,2-dioxygenase, involved in the lower pyrene degradation pathway.