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Resilience of the rhizosphere Pseudomonas and ammonia‐oxidizing bacterial populations during phytoextraction of heavy metal polluted soil with poplar
Author(s) -
Frey Beat,
Pesaro Manuel,
Rüdt Andreas,
Widmer Franco
Publication year - 2008
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2007.01556.x
Subject(s) - rhizosphere , biology , temperature gradient gel electrophoresis , phytoremediation , pseudomonas , bulk soil , soil water , ralstonia , soil microbiology , pseudomonas fluorescens , botany , phylotype , 16s ribosomal rna , bacteria , ecology , genetics
Summary We assessed the effects of phytoextraction on the dynamics of Pseudomonas spp. and ammonia‐oxidizing bacterial populations in a heavy metal (HM) polluted soil. Hybrid poplars were grown in two‐compartment root containers with a medium history (> 4 years) of HM pollution for 13 weeks. Bulk and poplar rhizosphere soils were analysed by denaturing gradient gel electrophoresis (DGGE) of Pseudomonas ( sensu stricto ) 16S rRNA and amoA gene fragments. DGGE patterns revealed that Pseudomonas and amoA ‐containing populations in the contaminated soils were markedly different from those in the uncontaminated soils. Pseudomonas and amoA profiles appeared to be stable over time in the bulk soils. In contrast, contaminated rhizosphere soils revealed a clear shift of populations with removal of HM becoming similar or at least shifted to the populations of the uncontaminated soils. The effect of phytoextraction was, however, not evident in the bulk samples, which still contained large amounts of HM. Cloning and sequencing of dominant DGGE bands revealed that Pseudomonas were phylogenetically related to the Pseudomonas fluorescens cluster and the amoA sequences to Nitrosospira spp. At the last sampling, major prominent band sequences from contaminated rhizosphere soils were identical to sequences obtained from uncontaminated rhizosphere soils, indicating that the populations were dominated by the same phylotypes. This study suggests that two taxonomically different populations are able to recover after the relief of HM stress by phytoextraction practices, whereas bulk microbial activities still remained depressed.