Study of the degradation activity and the strategies to promote the the bioavailability of phenanthrene by Sphingomonas paucimobilis strain 20006FA

COPPOTELLI BIBIANA M.; IBARROLAZA AGUSTÍN; DIAS ROMINA; DEL PANNO MARÍA T.; BERTHE-CORTI LUISE; MORELLI IRMA S.

MICROBIAL ECOLOGY

Springer Science

Lugar: New York; Año: 2010 vol. 59 p. 266 - 276

0095-3628

The present study describes the characterization of phenanthrene-degrading activity and the cell ability to promote the bioavailability of phenanthrene, of a PAH-degrading bacterial strain Sphingomonas paucimobilis 20006FA, isolated from a phenanthrene-contaminated soil-microcosm. The strain was able to grow in liquid mineral medium saturated with phenanthrene as the sole carbon source, showing high phenanthrene elimination (76% of the supplied phenanthrene within 20 days). The accumulation of 1-hydroxy-2-naphthoic acid and salicylic acid as major phenanthrene metabolites and the capacity of the strain to grow with sodium salicylate as the sole source of carbon and energy indicated that the S. paucimobilis 20006FA possesses a complete phenanthrene degradation pathway. However, in the studied conditions, the strain was able to mineralize only the 7.1% of the eliminated phenanthrene. Investigations on the cell ability to promote bioavailability of phenanthrene showed that the S. paucimobilis strain 20006FA exhibited low cell hydrophobicity (0.13), a pronounced chemotaxis towards phenanthrene and it was able to reduce the surface tension of mineral liquid medium supplemented with phenanthrene as sole carbon source. Scanning electron micrographs revealed that: i) in suspension cultures cells formed flocks and showed small vesicles on the cell surface; ii) the strain was also able to adhere to phenanthrene crystals and to produce biofilms. Clearly the strain seems to exhibit two different mechanisms to enhance phenanthrene bioavailability:  biosurfactant production and adhesion to the phenanthrene crystals.