Impact of phenazine-1-carboxylic acid upon biofilm development in the rhizosphere of dryland and irrigated wheat
EMSL Project ID
48737
Abstract
Rapid access is necessary for completion of six months work required for an Office of Science Graduate Student Research award by the end of the award period lasting from January 21, 2015 to July 21, 2015. July, 2015 is also the anticipated completion date for the award recipient’s PhD dissertation, which will include the results of this work. Access for the latter portion of the award period will be pursued through a parallel general user proposal.This proposed work also meets the rapid-access “proof of principle” criteria, as it will test the feasibility of a high-resolution imaging and image-analysis approach for quantification and characterization of rhizobacterial biofilms, which are important sinks for plant-derived carbon and sources of microbially-derived soil organic matter. Extracellular polymeric substances in rhizobacterial biofilms cannot be unambiguously quantified or characterized using current bulk extraction methods, which are non-selective, incomplete, and disruptive to biofilm matrices. Development of an imaging approach for quantification and characterization of minimally-disturbed biofilms attached to root and soil mineral surfaces will enable incorporation of rhizobacterial carbon as a factor in carbon-cycling models, and will enhance the impact of future studies concerning carbon sequestration in rhizobacterial biofilms.
Phenazine-1-carboxylic acid (PCA) is a redox-active bacterial metabolite known to promote biofilm development via reduction of Fe oxides in culture, and has been discovered in high concentrations throughout the low-precipitation zone of the Columbia Plateau. However, the impact of PCA and other redox-active metabolites upon rhizobacterial biofilms is unknown. Without this knowledge, it is impossible to evaluate how redox-active metabolites influence sequestration of plant-derived carbon in microbially-derived SOM, or to incorporate widespread production of redox-active metabolites into model predictions for carbon flux through SOM pools.
Our objective is to investigate the impact of PCA upon biofilm development in the rhizosphere of dryland and irrigated wheat. This research is significant because it will reveal the potential of PCA to improve carbon storage in rhizobacterial biofilms under variable soil moisture regimes, improving resolution of biogeochemical models. Because current chemical extraction methods are insufficient to fully quantify and characterize these micro-scale processes, we will study intact biofilms on root surfaces using the FIB/SEM and HIM at EMSL, ImageJ analysis, and ANOVA comparisons to quantitatively compare accumulation and morphological and nano-structural characteristics of extracellular polymeric substances (EPS) in PCA-producing and non-PCA-producing biofilms under dry and irrigated conditions. The results will reveal the relative significance of PCA, biofilm development, and soil moisture as determinants of SOM accumulation in the rhizosphere.
Project Details
Project type
Limited Scope
Start Date
2015-03-16
End Date
2015-04-16
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
LeTourneau MK, MJ Marshall, L Thomashow, and JB Harsh. 2015. "Impact of Phenazine-1-carboxylic acid upon Biofilm Development in the Rhizosphere of Dryland and Irrigated Wheat. ." Presented by Melissa LeTourneau (Invited Speaker) at Oregon Convention Center , Portland , OR on August 2, 2015. PNNL-SA-113970.