AME 76:243-255 (2016)  -  DOI:

Organic contamination versus mineral properties: competing selective forces shaping bacterial community assembly in aquifer sediments

Michael Grösbacher1, Carolin Spicher1, Anne Bayer2, Martin Obst3, Clemens Karwautz1, Giovanni Pilloni1,6, Martin Wachsmann4, Hagen Scherb5, Christian Griebler1,*

1Institute of Groundwater Ecology, Helmholtz Zentrum München, 85764 Neuherberg, Germany
2Bayerisches Landesamt für Umwelt, 82407 Wielenbach, Germany
3Center for Applied Geosciences, Institute for Geosciences, Eberhard Karls Universität Tübingen, 72074 Tübingen, Germany
4Ludwig-Maximilians-Universität München, Department of Earth and Environmental Sciences, Section for Mineralogy, Petrology and Geochemistry, 80333 München, Germany
5Institute of Computational Biology, Helmholtz Zentrum München, 85764 Neuherberg, Germany
6Present address: ExxonMobil Research and Engineering, Corporate Strategic Research, Annandale, NJ 08801, USA
*Corresponding author:

ABSTRACT: Multiple factors have been shown to influence the assembly of sediment microbial communities. We hypothesized that in an organically polluted aquifer, the degree of contamination controls bacterial distribution patterns, superimposing other selective forces such as sediment and mineral properties. Groundwater and sediment samples were analyzed from distinct zones of a petroleum hydrocarbon contaminated sandy aquifer that correspond to different degrees of contamination: Zone 1, with a high concentration of dissolved contaminants (benzene, toluene, ethylbenzene, and xylenes); Zone 2, with high concentrations of sediment-bound polycyclic aromatic hydrocarbons (PAHs); and Zone 3, with only minor PAH contamination. Sediment analysis concentrated on 2 mineral fractions differing in many sediment properties, i.e. translucent quartz (TQ) and mica. Sediment bacterial communities were analyzed by DNA fingerprinting (terminal restriction fragment length polymorphism) and total cell counts. While Zone 1 exhibited highly similar communities on TQ and mica, the selective sorption of PAHs to mica revealed sediment bacterial communities with hardly any taxonomic units shared in Zone 2. Typical selective forces active in sediments of oligotrophic habitats, such as sediment mineral content and surface roughness, only gained influence in Zone 3. Similarly, the least contamination revealed the most pronounced differences in Shannon diversity, evenness, and total cell counts between the mineral fractions tested, with mica characterized by highest biomass and bacterial diversity. The role of contamination as a selective force is also underlined by the zone-specific dominance of key microbes involved in petroleum hydrocarbon degradation. Our results demonstrate that typical selective forces shaping aquifer sediment microbial communities are outcompeted by organic contamination.

KEY WORDS: Aquifer microbiology · Groundwater · Petroleum hydrocarbons · Sediment community assembly · Selective forces · Quartz · Mica

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Cite this article as: Grösbacher M, Spicher C, Bayer A, Obst M and others (2016) Organic contamination versus mineral properties: competing selective forces shaping bacterial community assembly in aquifer sediments. Aquat Microb Ecol 76:243-255.

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