N-218. Diversity of Acetate-Utilizing Bacteria in California Soils by Comparative Stable Isotope Probing

S. Han, B. D. Lanoil;
Univ. of California, Riverside, CA.

Acetate is central to the soil carbon cycle due to the fact that acetate is a non-fermentable end product of fermentation, and acts as the primary electron donor for anaerobic respirations such as metal reduction, sulfate reduction, and methanogenesis. Our goal was to determine which microbes utilize acetate under acetate-limiting conditions, where competition for substrate is fierce. To better understand the communities involved in acetate utilization, we incubated soil microcosms in the presence of various concentrations of 13C-labelled acetate as a carbon source. In total, 32 soil samples were collected representing 7 different soil sequences (climo, chrono, or bio) from around the state of California. The average acetate utilization rate (AUR) under aerobic conditions was 13.7 ± 9.5 μmol g soil-1 day-1 and under anaerobic conditions was 8.6 ± 8.4 μmol g soil-1 day-1. The DGGE banding patterns of bacterial composition were complex for all soils, indicating the presence of a diverse acetate utilizing community in all soils. Major DGGE bands were excised and sequenced to identify and searched the nearest neighbor by BLAST search. Most 13C-DGGE band’s sequences were affiliated with Firmicutes and Delta and Gamma Proteobacteria.