Principal Investigator:
Brian
D. Lanoil
Assistant Professor and Assistant Environmental Microbiologist
Department of Environmental Sciences
University of California
Riverside, CA 92521
Duration of Project: 2 years
In order to understand the processes governing the storage of
carbon in soils, quantify the impacts of anthropogenic inputs on soil carbon
dynamics, and assess the roles of soils in greenhouse gas flux, we need to
understand the activities and compositions of microbial communities that underlie
many of these processes. For example, we do not know which microbial species
are involved in the catabolism of soil acetate, primarily due to our inability
to culture 99% or more of environmental organisms. Acetate is central to soil
organic matter degradation under anaerobic conditions, which arise in soils
under conditions of transient (e.g. irrigation) or permanent (e.g. rice paddies)
flooding. Acetate is a product of anaerobic fermentation and homoacetogenesis
and serves as a substrate for a variety of anaerobic metabolisms. It is one
of the most important substrates for denitrification, metal reduction, sulfate
reduction, and methanogenesis in soils. In fact, acetate is the carbon and
energy source responsible for as much as 80% of methane flux from soils to
the atmosphere. In the proposed project, we will use a recently published
method, stable isotope probing (SIP), to link the activity of acetate catabolism
with the identity of the organisms performing this process. This method combines
stable isotope labeling with 16S rRNA methods to identify the acetate catabolizers.
We will evaluate SIP with pure and defined mixed cultures, both in the presence
and absence of a soil matrix. Once the method is optimized, we will use the
approach to identify the components of the microbial community that are critical
for acetate consumption in soil microcosms. We will also evaluate how the
microbial communities change with changes in the water content (and therefore
O2 content) of the soil.