Bioaugmentation with Pseudomonas sp. strain MHP41 promotes simazine attenuation and bacterial community changes in agricultural soils

Bioremediation is an important technology for the removal of persistent organic pollutants from the environment. Bioaugmentation with the encapsulated Pseudomonas sp. strain MHP41 of agricultural soils contaminated with the herbicide simazine was studied. The experiments were performed in microcosm trials using two soils: soil that had never been previously exposed to s-triazines (NS) and soil that had >20 years of s-triazine application (AS). The efficiency of the bioremediation process was assessed by monitoring simazine removal by HPLC. The simazine-degrading microbiota was estimated using an indicator for respiration combined with most-probable-number enumeration. The soil bacterial community structures and the effect of bioaugmentation on these communities were determined using 16S RNA gene clone libraries and FISH analysis. Bioaugmentation with MHP41 cells enhanced simazine degradation and increased the number of simazine-degrading microorganisms in the two soils. In highly contaminated NS soil, bioaugmentation with strain MHP41 was essential for simazine removal. Comparative analysis of 16S rRNA gene clone libraries from NS and AS soils revealed high bacterial diversity. Bioaugmentation with strain MHP41 promoted soil bacterial community shifts. FISH analysis revealed that bioaugmentation increased the relative abundances of two phylogenetic groups (Acidobacteria and Planctomycetes) in both soils. Although members of the Archaea were metabolically active in these soils, their relative abundance was not altered by bioaugmentation. © 2009 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.We gratefully acknowledge financial support from the Milenio P04/007-F (ICM, MIDEPLAN-Chile), USM 130522, USM 130836, USM 130948, CIT Nanotechnology and Systems Biology, PBCT Red 12 and INCO ICA4-CT-2002-10011 (European Union) grants. V.M. gratefully acknowledges MECESUP-UCV-0206 and Milenio EMBA fellowships. R.R.-M. and A.L.-L. acknowledge the financial support of the projects CE-CSD2007-0005 (Consolider Ingenio 2010) and CLG2006-12714-C02-02 of the Spanish Ministry of Science and Innovation, and the exchange project 2006CL0032 between the Spanish Council (CSIC) and the University of Chile.Peer Reviewe