abstracts der vorträge und poster - Technisches Büro für Ökologie

Hödl Iris, Dep. Freshwater Ecology, Uni.Vienna; iris.hoedl@univie.ac.at
Hödl Josef, Helenenstrasse 73, 2500 Baden; josef@hoedl.cc
Singer Gabriel, Dep. Freshwater Ecology, Uni.Vienna; gabriel.singer@univie.ac.at
Besemer, Katharina, Dep. Freshwater Ecology, katharina.besemer@univie.ac.at
Battin, Tom, WasserCluster Lunz GmbH, 3293 Lunz am See; tom.battin@univie.ac.at
INTERACTIONS GENERATE NON-RANDOM SPATIAL DISTRIBUTION OF LOW-
ABUNDANCE CELLS DURING INITIAL BIOFILM FORMATION
Spatial configuration plays a fundamental role in defining the structural and functional properties of
biological systems, therefore it is of paramount importance to quantify the spatial organization of
these systems. In this study, we investigated the spatial configuration of post-adhesive nonreproducing
cells in a nascent stream biofilm. We conducted experiments in artificial streams
continuously fed with natural streamwater and contained inoculum where we exposed sterile slides to
microhabitats exposed to different flow environments. Attached cells were monitored microscopically
over 12 hours for their spatial arrangement using Voronoi tessellation. This is a geometrical method
that partitions space between attached cells by assigning space to the nearest neighboring cells,
resulting in an area-wide coverage with concave polygons. We found that already after 0.5 h the
distribution of cells significantly differed from uniform-random distribution, and did so increasingly
over 12 h. Using a simple mechanistic model assuming cell-cell signalling and chemical surface
conditioning as candidate mechanisms, we could simulated the deviation from uniform-random
Hörtnagl, Paul, Inst. für Ökologie, Universität Innsbruck, paul.hoertnagl@uibk.ac.at
Pérez, Maria, Teresa, Inst. für Ökologie, Universität Innsbruck, maria.perez@uibk.ac.at
Sommaruga, Ruben, Inst. für Ökologie, Universität Innsbruck, ruben.sommaruga@uibk.ac.at
EFFECT OF ULTRAVIOLET RADIATION ON THE GROWTH EFFICIENCY OF
FRESHWATER BACTERIAL ISOLATES
Five bacterial strains of the taxonomical groups Alphaproteobacteria, Betaproteobacteria,
Gammaproteobacteria, and Actinobacteria were isolated from different freshwater habitats and used to
test the effect of ultraviolet radiation (UVR) on heterotrophic bacterial production, respiration, and
growth efficiency. Bacterial carbon production (BCP) was assessed by measuring leucine bulk
incorporation rates, whereas bacterial respiration (BR) was calculated from oxygen consumption rates
after exposing the strains to simulated PAR and PAR+UVR for 4 hours. Although BCP was not
significantly different between the dark control and the PAR treatment, it decreased significantly after
exposure to the PAR+UVR treatment in three out of five strains. Moreover, BR rates of two strains
also decreased significantly after exposure to PAR+UVR. The bacterial growth efficiency of the
different strains ranged between 0.2% and 42.3% under dark conditions. In three out of five strains,
the BGE was significantly lower after exposure to PAR+UV than in the dark, but it increased
significantly in one strain. Our results indicate that freshwater bacterial strains strongly differ in their
BGE and that UVR can inhibit as well as stimulate their growth efficiencies.
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