Principal Investigator:
Lisa Y. Stein
Assistant Professor
Department of Environmental Sciences
University of California
Riverside, CA
Duration of the Project: 2 years
The proposed project is significant to the mission of the Kearney Foundation
by assessing the roles of soils, microorganisms, management strategies, and
nutrient availability in the flux of carbon-based and other greenhouse gases
into and out of soils. The goal of the proposed research is to determine the
physiological mechanism of greenhouse gas production by methane-oxidizing bacteria
(MOB) and ammonia-oxidizing bacteria (AOB) in agricultural soils by 1) characterizing
the physiological responses of pure cultures to changes in CH4, NH3, NO2, and
O2 concentrations, 2) developing molecular tools for quantifying changes in
populations of MOB, AOB, and their functional genes, and 3) applying both the
physiology and molecular tools developed above to soil microcosms to assess
how MOB and AOB respond within a soil matrix when perturbed by changes in nutrient
composition. Objective 1 will be accomplished by assaying the production or
consumption of CH4, CO2, and N2O by known numbers of MOB or AOB provided with
the appropriate substrates. In objective 2, we will use web-based tools to develop
specific molecular probes for conducting real-time quantitative PCR, and we
will test them with pure cultures. Objective 3 will combine the data and methodologies
from objectives 1 and 2 to analyze both the physiology and populations of MOB,
AOB and their functional genes within soil microcosms. Here, we wish to correlate
changes in greenhouse gas flux with specific gene populations and changes in
nutrient composition in soils. We expect to observe increases in MOB or AOB
populations when they are provided with their preferred metabolic substrate.
Decreases or changes in populations are expected when co-substrates compete
with the preferred substrates for access to metabolic enzymes, or when a toxic
agent is detected. The populations of functional genes should correlate with
measured changes in gas composition as predicted from the characterized physiology
of the MOB and AOB cultures.