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Presentation Oral presentation
Title The diversity and activity of bacterial communities in Namibian semiarid savanna soils – anthropogenic determinants and feedback loops

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Short title Bacteria in Namibian savanna soils

Author(s) Zul, D.(1,2); Fösel, B.U.(1); Romann, E.(1); Mayer, M.(1); Overmann, J.(1)

Presenting author Overmann, J. (1)

Institution(s) (1) Section Microbiology, Department Biology I, University of Munich, 80638 München, Germany; (2) Dept. Biology, Faculty of Mathematics and Natural Sciences, University of Riau, Kampus Bina Widya Km 12.5 Simpang Baru, Pekanbaru, Indonesia

Keywords Soil Bacteria; Acidobacteria; Land use pressure; Key species; Bacterial diversity

Abstract To date, the interdependence between land use, soil properties and bacterial populations are poorly understood. The role of soil microorganisms in land degradation and restoration was studied in 29 arenosols from the Kavango region in north-eastern Namibia using enzymatic assays, nutrient liberation experiments and molecular methods. Bacterial cell numbers (0.4-3.9•109 cells g-1 soil) and soil respiration rates (4.0-23.7 nmol O2 g-1 soil) correlated with soil type rather than land use. Exoenzyme activities greatly varied among sites, but did not show a clear correlation any one of the two factors. Quantitative PCR with group specific primers identified Acidobacteria and Actinobacteria as the most abundant phyla (30 and 20% of all bacteria, respectively). Subsequent high-resolution DGGE-fingerprinting for both bacterial groups did only show minor differences in composition of bacterial communities among sampling sites. Stable isotope probing with 13C-labeled substrates demonstrated that Acidobacteria not only represented the most abundant group but also an active fraction of the soil bacterial community, preferentially utilizing sugar compounds. Cloning and sequencing of 16S rRNA genes from the most active soil site revealed an unexpectedly high bacterial diversity with an estimated number of 6000 types. Our study provides the first estimates for the species richness, information on the active fraction of bacterial communities and their anthropogenic determinants in subtropical sandy soils on the African continent.

Congress Topic Microbiology

Topic No. 7.2
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Ref. No. 516