TU Berlin

UmweltmikrobiologieInterurban

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Interurban

Molecular characterization of soil microorganisms from urban habitats: Role of biofilm-producing bacteria in urban soils until April 2007 (DFG Interdisciplinary Research Group FOR 409 INTERURBAN)

In the second period of the project we focus on the influence of microbial communities on soil texture and dynamics of organic matter. The main emphasis will be put on investigations with regard to the impact of microorganisms on water repellence of urban soil and microbial immobilization and mobilization of soil components and organic pollutants. The research topics are:

i. characterization of the active microbial communities with regard to biotransformations in soil transformation of organic pollutants (subproject MOBIL)

ii. adsorption characteristics of microorganisms to soil particles microbial impact on development of hydrophilic and hydrophobic areas (subproject HUMUS)

ad i. Analyses of microbial communities active in degradation of organic pollutants characteristic for the sampling site sewage field Berlin Buch will be performed by stable-isotope probing (SIP). For selected bacterial degraders FISH probes will be designed to prove their presence in situ and to localize them in the urban habitat.

ad ii) Two different reactor types will be used to produce abundant microbial biomass for interdisciplinary investigations.

Homogenous biofilms will be grown in upflow fixed bed reactors.
To simulate conditions at the sampling sites downstream percolation reactors periodically fed with medium will be set up. The microorganisms in this reactor system will be exposed to various periods of water and heat stress.

Samples from the percolation reactor will be analysed to determine the sorption kinetics of

  • selected bacterial soil isolates with known hydrophobicity/hydrophilicity
  • defined mixed soil communities (isolates from the sampling sites)
  • undefined mixed soil communities (extracted from the sampling sites) on different kinds of surfaces:
  • defined surfaces (glass, Teflon, PE) - defined soil fractions (clay, quartz, feldspar) as well as
  • real soil suspensions

These experiments shall help to define the microbial influence on development of hydrophobic and hydrophilic areas in anthropogenic soils.

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