| title: | Molecular structure of the plasmids of five Pseudomonas strains before and after bioaugmentation of microcosms and field semi-coke test plots |
|---|---|
| reg no: | ETF6621 |
| project type: | Estonian Science Foundation research grant |
| subject: |
1.9. Genetics, Physiology and Microbiology |
| status: | accepted |
| institution: | TU Faculty of Biology and Geography |
| head of project: | Eve Vedler |
| duration: | 01.01.2006 - 31.12.2008 |
| description: | Plasmids are extrachromosomal mobile genetic elements (MGEs), largely responsible for horizontal gene transfer (HGT) in nature. Plasmids play a major role in the ability of bacterial populations to degrade a wide variety of chemical compounds, and also in their adaptation to novel substances. The molecular structure of plasmids is a subject to frequent changes (e.g. integration and excision of IS elements, transposons and other DNA elements) reflecting the events taking place during HGT. Studying such changes gives us very valuable knowledge about the evolution in nature. This in turn helps us to better design technologies exploiting HGT, for example bioremediation of polluted soils using bioaugmentation. More than 70 years of oil shale thermal processing has resulted in huge dump sites of semi-coke in the areas surrounding oil shale chemical industry plants in the northeastern part of Estonia. In July 2001, our research group established four phytoremediation test plots at one of these semi-coke dump sites. In July 2002, we conducted the bioaugmentation experiment in these test plots using the set of bacteria consisting of three strains, Pseudomonas mendocina PC1, P. fluorescens PC18 and PC24. In June 2005, we performed bioaugmentation of other parts of our test plots using the same three strains plus P. fluorescens PC20 and P. corrugata PC17. Introduced microbial strains are often not able to adapt to new environmental conditions and to compete with indigenous microorganisms. As the result, they rapidly vanish from the microbial community. However, the well adapted local microorganisms may acquire the necessary genetic information from the introduced microorganisms by HGT. Strong evidence has been provided that MGEs play an important role in the horizontal spread of existing catabolic pathways, as well as in the natural construction of novel ones. The positive effect of bioaugmentation observed in our test plots could be attributed either to the activity of the introduced bacterial strains or to horizontal transfer of the genetic information encoding degradation of pollutants from the inoculated strains to indigenous bacterial populations. Four of the five strains used in bioaugmentation were revealed to contain plasmid DNA - PC17 (1 plasmid), PC18 (4 plasmids), PC20 (2 plasmids) and PC24 (1 plasmid). It is possible that the strain PC1 contains very large plasmid(s) not detected so far. The first aim of this project is to analyze the plasmids of the five strains used in bioaugmentation – to determine their incompatibility group and find out which catabolic transposons and/or genes and other important elements (e.g. genes necessary for HGT) they carry. The second aim of this project is to analyze the structure of the above mentioned plasmids after inoculation of the strains carrying these molecules into soil microbial communities residing in our semi-coke test plots. In order to do that we are planning to perform both microcosm (using soils from our test plots) and field (in our test plots in semi-coke mounds) bioaugmentation experiments. For that purpose the most promising strains are selected based on the results obtained so far and the introduced strains and their plasmids are labeled with detectable markers. During these experiments we will first monitor the fate of the introduced strains and their plasmids (MGEs) in these soils and then we will isolate bacteria carrying the labeled plasmids, both/either the original introduced strains and/or the indigenous strains which have acquired these plasmids through HGT. Finally, we will analyze the molecular structure of the isolated plasmids and compare these structures with the original ones. |
| project group | ||||
|---|---|---|---|---|
| no | name | institution | position | |
| 1. | Eve Vedler | Tartu Ülikool | ||