Degradation of Organic Matter by Ecologically Distinct Microbiomes Uniformly Promotes Growth of Brachypodium distachyon

In this study, we explore the relationship between ecologically distinct soil/compost microbiomes and their role in plant growth promotion through organic matter (OM) decomposition. Using a controlled experimental system, we tested whether living microbiomes from geographically and ecologically distinct environments impact plant biomass when provided with OM in the form of dried, ground leaves sourced from pre-flowering Avena barbata to mimic cover cropping conditions with annual grasses. Results showed a consistent threefold increase in plant biomass when a living microbiome and organic matter were present, regardless of the microbiome's origin, which included agricultural fields, desert soil, and pine-oak forest soil, municipal compost, and the microbiome on unautoclaved organic matter. Bacterial community profiling based on 16S amplicon sequencing revealed genera, e.g. Massilia, that were significantly associated with decomposition and subsequent plant growth promotion. This suggests a conserved functional capacity within specific taxa for plant growth promotion via organic matter decomposition across diverse microbiomes, likely due to evolutionary pressures to efficiently break down plant material for nutrient acquisition. The study provides a framework for further investigation into microbial consortia that enhance plant growth via decomposition, offering a robust experimental system to identify microbes and microbial processes that could be harnessed to improve nutrient uptake from organic inputs like cover crops.