Michael T. Ganger, Victoria L. Holmes, Christopher M. Dempsey, Russell L. Minton
American Fern Journal 115 (2), 95-108, (12 May 2025) https://doi.org/10.1640/0002-8444-115.2.95
KEYWORDS: core microbiome, rhizosphere, soil microbiome
Much of our understanding of root-microbe interactions derives from angiosperm studies where root microbiomes are likely driven by root exudates. Much less is known about the root microbiomes of seedless vascular plants even though this plant group evolved much earlier and was the first to develop roots. Single field horsetails (Equisetum arvense) and surrounding soils were collected from eight roadside sites in Erie County, Pennsylvania. Bacterial DNA was extracted from E. arvense roots and soil samples and the 16S rRNA V4 region was sequenced. Soil physio-chemical measures including pH, dissolved organic carbon, and ammonia content were determined at each site. Root and soil bacterial microbiomes were significantly different from one another, and both were significantly correlated with the soil physio-chemistry at each site. The three most abundant bacterial families on E. arvense roots, Streptomycetaceae, Comamonadaceae, and Chitinophagaceae, are well-known root microbes. There were nine core amplified sequence variants associated with E. arvense roots including four genera of nitrogen-fixing bacteria. These results suggest that the root bacterial microbiome of E. arvense is influenced by the environment, and that horsetail roots host bacterial communities that are separate from those in adjacent soil bacterial microbiomes. As with published studies of bryophyte rhizoids and spermatophyte roots, Proteobacteria, Actinobacteria, and Acidobacteria were highly abundant on E. arvense roots.