Parallel Microbial Ecology of Pasteuria and Nematode Species in Scottish Soils

Abstract

Pasteuria spp. are endospore forming bacteria which act as natural antagonists to many of the most economically significant plant parasitic nematodes (PPNs). Highly speciesspecific nematode suppression may be observed in soils containing a sufficiently high density of Pasteuria spp. spores. This suppression is enacted by the bacteria via inhibition of root invasion and sterilization of the nematode host. Molecular methods for the detection of Pasteuria spp. from environmental DNA (eDNA) have been described; however, these methods are limited in both scale and in depth. We report the use of small subunit rRNA gene metabarcoding to profile Pasteuria spp. and nematode communities in parallel. We have investigated Pasteuria spp. population structure in Scottish soils using eDNA from two sources: soil extracted DNA from the second National Soil Inventory of Scotland (NSIS2); and nematode extracted DNA collected from farms in the East Scotland Farm Network (ESFN). We compared the Pasteuria spp. community culture to both nematode community structure and the physiochemical properties of soils. Our results indicate that Pasteuria spp. populations in Scottish soils are broadly dominated by two sequence variants. The first of these aligns with high identity to Pasteuria hartismeri, a species first described parasitizing Meloidogyne ardenensis, a nematode parasite of woody and perennial plants in northern Europe. The second aligns with a Pasteuria-like sequence which was first recovered from a farm near Edinburgh which was found to contain bacterial feeding nematodes and Pratylenchus spp. encumbered by Pasteuria spp. endospores. Further, soil carbon, moisture, bulk density, and pH showed a strong correlation with the Pasteuria spp. community composition. These results indicate that metabarcoding is appropriate for the sensitive, specific, and semi-quantitative profiling of Pasteuria species from eDNA.

Plant Root-Exudates Recruit Hyperparasitic Bacteria of Phytonematodes by Altered Cuticle Aging: Implications for Biological Control Strategies

“…and the Grampositive endospore forming bacterial micro-parasite Pasteuria ramosa Metchnikoff has become a valuable model for studying co-evolutionary relationships where it is reported that the binding of endospores, a key stage in the infection process, is genetic and under negative frequency-dependent selection (also known as "Red Queen dynamics") and not linked to environmental factors (Decaestecker et al, 2007;Ebert et al, 2016). However, meta-barcoding studies in Scottish soils suggest that Pasteuria communities are structured and correlate with environmental factors including soil carbon, moisture and pH (Orr et al, 2020) suggesting and environmental component to this nematode hyperparasite interaction.…”

Impact of land use and management practices on soil nematode communities of Machair, a low-input calcareous ecosystem of conservation importance

“…More recently, Vink et al (2014) assessed the temporal and land use effects on soil bacterial community structure from a range of Machair habitats throughout the Outer Hebrides archipelago. Orr et al (2020) included Machair soil in their study of Pasteuria, endospore forming bacteria that are considered natural antagonists to soilborne nematodes.…”