Impact of phenazine-1-carboxylic acid upon biofilm development, Fe speciation, and the fate of microbial biomass in the rhizosphere of dryland and irrigated wheat
EMSL Project ID
48738
Abstract
Rhizobacterial biofilms are a major sink for plant-derived carbon, and a major source for microbially-derived soil organic matter (SOM). Bacteria residing within biofilm matrices, which restrict oxygen diffusion, may transfer electrons to ferric iron instead of oxygen, leading to mineral transformations. Because recalcitrance of SOM is influenced by interactions with mineral surfaces, alteration of soil mineral surfaces by Fe-reducing biofilms may influence the recalcitrance of SOM. 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, soil mineralogy, and recalcitrance of SOM is unkown. Without this knowledge, it is impossible to evaluate how redox-active metabolites and bacterial Fe reduction influence long-term sequestration of plant-derived carbon in microbially-derived SOM, or to incorporate widespread production of redox-active metabolites and bacterial Fe reduction into model predictions for carbon flux through SOM pools.Our objective is to investigate the impact of PCA upon biofilm development, Fe speciation, and the fate of microbial biomass in the rhizosphere of dryland and irrigated wheat. This research is significant because it will reveal the biogeochemical footprint of PCA and other microbial metabolites associated with bacterial iron reduction and biofilm development, improving resolution of biogeochemical models. Because standard macroscopic methods are insufficient to fully quantify and characterize these micro-scale processes, we will leverage the array of chemical and biological imaging tools available at EMSL combined with image analysis software to compare accumulation and structural and chemical characteristics of extracellular polymeric substances (EPS) in PCA-producing and non-PCA-producing biofilms. We will also use Mossbauer spectroscopy to identify Fe mineral phases favored by PCA, and NanoSIMS to track distribution and preservation of 15N-labelled microbial biomass and co-localization of SOM with Fe minerals. The combined results of these studies will reveal the relative significance of PCA, biofilm development, Fe mineralogy, and soil moisture as determinants of SOM accumulation and recalcitrance.
Project Details
Project type
Exploratory Research
Start Date
2015-03-10
End Date
2015-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
LeTourneau M.K., M.J. Marshall, J.B. Cliff, R.F. Bonsall, A. Dohnalkova, D.V. Mavrodi, and I. Devi, et al. 2018. "Phenazine-1-carboxylic acid and soil moisture influence biofilm development and turnover of rhizobacterial biomass on wheat root surfaces." Environmental Microbiology 20, no. 6:2178-2194. PNNL-SA-134049. doi:10.1111/1462-2920.14244
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.