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Microbiological and molecular analysis of bacterial communities of an urban soil
Zitatschlüssel Braun2007
Autor Braun, Burga
Jahr 2007
Schule Technische Universität Berlin, FG Umweltmikrobiologie
Zusammenfassung Soil water repellency is a common phenomenon which occurs throughout the world and is influenced by physical, chemical and biological factors. It prevents water from infiltrating into the soil and influences soil properties. Changes in soil wettability may represent a significant source of stress for microbial communities and affect bacterial composition and soil microbial processes. Up till now, little is known about the effects of water repellency on soil bacterial communities and vice versa. The aim of this study was to gain a more profound insight into the bacterial community structure of wettable and water repellent soils. The horizontal and vertical distribution of the bacterial population was analyzed with regard to soil water repellency. Furthermore, the molecular diversity and active bacterial population subjected to water stress was monitored in microcosm experiments. Finally, the effects of hydrophilic and hydrophobic bacterial biofilms on soil wettability were investigated. For determination of alterations in the bacterial structure and their metabolic potential cultivation- and molecular methods were combined. The application of cultivation independent methods did not allow to distinguish between water repellent and wettable soil samples. Whereas determination of CFU and metabolic fingerprints resulted in differences between wettable and water repellent soil areas. Variations in community structure as well as in community function and activity were observed within the soil profile. These data indicated that water repellency did not have a significant effect on the total genetic diversity present but affected the physiological status, so that the bacteria capable of responding to laboratory culture methods were altered in activity without changes in phylogenetic distribution. Therefore, the bacterial communities of this urban soil seemed to be adapted to different moisture conditions by regulating their physiological cell activity. Microcosm experiments revealed no effects of water stress on the bacterial community, as no moisture related changes in the bacterial population were observed. To gain insights how biofilms may affect surface properties of soil, soil samples were inoculated with bacteria of different cell surface hydrophobicity: Bacillus sphaericus (hydrophilic), Variovorax paradoxus (hydrophobic) and an ?- Proteobacterium (hydrophobic). The results demonstrated the effect that bacterial biofilms can have on soil wettability, as biofilms were able to hydrophilize or hydrophobize soil samples.
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