Inoculation of soil microcosms with Sphingomonas paucimobilis. Impact of inoculation protocol on phenanthrene degradation and soil community

DEL PANNO M.T., COPPOTELLI B., MORELLI I.S. AND BERTHE-CORTI L

Madrid, España

Simposio; 13th International Biodeterioration and Biodegradation Symposium; 2005

Inoculation of soil Microcosms with SPHINGOMONAS PAUCIMOBILIS. Impact of the Inoculation Protocol On PhEnanthrene degradation and Soil community Del Panno, M.T. 1, Coppotelli, B.1, Morelli, I.S.1, and Berthe­Corti, L.2 1CINDEFI, UNLP­CONICET. La Plata, Argentina, e­mail: lbmh@biol.unlp.edu.ar. 2 ICBM, University of Oldenburg, Oldenburg, Germany, e-mail: luise.berthe.corti@uni-oldenburg.de.   Bioaugmentation by inoculating microorganisms into soil has been considered to be a valuable tool for increasing rate and extent of polyaromatic hydrocarbon (PAH)-biodegradation. However, the positive effect of inoculation is not always proved. In this study, soil microcosms artificially contaminated with phenanthrene were inoculated with the PAH-degrading bacterium Sphingomonas paucimobilis strain 20006FA. Phenanthrene concentration, structure (DGGE) and activity (CO2-production) of the microbial soil community were monitored. Microcosms containing garden soil were freshly contaminated with phenanthrene or had been pre-contaminated for several weeks. Both systems were inoculated with free-living or adsorbed cells of S. paucimobilis 20006FA according to different inoculation protocols with varying number and frequency of inoculations.   Freshly contaminated microcosms revealed a significant increase in the population density of heterotrophic soil bacteria after the first inoculation; subsequent inoculations did not produce further increase. Pre-contaminated microcosms revealed no changes in the population density after inoculation. CO2-production in inoculated microcosms was higher than in non-inoculated controls, indicating a higher biological activity. Phenanthrene elimination was highest in microcosms inoculated weekly during three weeks. Immediately after the first inoculation till the end of the experiment, we observed a strong DNA band corresponding to S. paucimobilis in all inoculated microcosms. A similar but weak band was detected in the 24day-old non-inoculated microcosms indicating that S. paucimobilis may also be an indigenous bacterium of the soil used. The results indicate that S. paucimobilis was able to survive in freshly and pre-contaminated soil under different inoculation conditions. It enhanced phenanthrene biodegradation significantly when successive inoculations were realized.