Microbial Profiles of Rhizosphere and Bulk Soil Microbial Communities of Biofuel Crops Switchgrass (Panicum virgatumL.) and Jatropha (Jatropha curcasL.)

Abstract

The production of biofuels from the low-input energy crops, switchgrass (Panicum virgatumL.) and jatropha (Jatropha curcasL.), is a sustainable approach that can provide more usable energy and environmental benefits than food-based biofuels. Plant rhizosphere affects the microbial community structure due to variations in root exudation rates and residue chemistry. The objective of this investigation was to determine the profiles of microbial communities associated with rhizosphere and bulk soils of switchgrass or jatropha using phospholipid fatty acid (PLFA) analysis and length heterogeneity PCR (LH-PCR). Switchgrass soil contained a significantly (P<0.05) higher abundance of Gram-positive (i14:0, i15:0, a15:0), Gram-negative (16:1ω5c, 16:1ω7c, 18:1ω5c), and saturated (14:0, 15:0) PLFAs compared to jatropha soil, whereas jatropha had a higher abundance of fungal (18:2ω6, 9c), 18:1ω9c, 20:1ω9c, and 18:0 PLFAs compared to switchgrass soil. Irrespective of plant type, rhizosphere soil contained a significantly (P<0.05) higher abundance of saturated PLFAs (16:0, 18:0, 20:0), actinomycetes (10Me17:0), and fungal (18:2ω6, 9c) PLFAs compared to bulk soil; whereas bulk soil had higher abundance of saturated (14:0), Gram-negative (16:1ω9c, 16:1ω5c, 16:1ω7c), and 18:1ω9c PLFAs compared to rhizosphere soil. Multivariate principle component analysis of PLFAs and LH-PCR percent relative peak areas successfully differentiated the microbial communities of rhizosphere and bulk soils of switchgrass and jatropha.