Leveraging aquatic-terrestrial interfaces to capture putative habitat generalists

Abstract

Habitat type is a strong determinant of microbial composition. Habitat interfaces, such as the boundary between aquatic and terrestrial systems, present unique combinations of abiotic factors for microorganisms to contend with. Aside from the spillover of certain harmful microorganisms from agricultural soils into water (e.g. fecal coliform bacteria), we know little about the extent of soil-water habitat switching across microbial taxa. In this study, we developed a proof-of-concept system to facilitate the capture of putatively generalist microorganisms that can colonize and persist in both soil and river water. We aimed to examine the phylogenetic breadth of putative habitat switchers and how this varies across different source environments. Microbial composition was primarily driven by recipient environment type, with the strongest phylogenetic signal seen at the order level for river water colonizers. We also identified more microorganisms colonizing river water when soil was collected from a habitat interface (i.e. soil at the side of an intermittently flooded river, compared to soil collected further from water sources), suggesting that environmental interfaces could be important reservoirs of microbial habitat generalists. Continued development of experimental systems that actively capture microorganisms that thrive in divergent habitats could serve as a powerful tool for identifying and assessing the ecological distribution of microbial generalists.

Autoclaving is at least as effective as gamma irradiation for biotic clearing and intentional microbial recolonization of soil

“…For bacteria in each soil, and fungi in Soil 1, we observed no significant differences between the wash treatments. These data agree with our previous observations that the pool of recolonizing microorganisms is usually quite distinct from the bulk soil ( 14 , 50 ). However, for Soil 2 and for fungi, we did observe a significant difference (H = 18, P ≤ 0.001) which was primarily driven by a greater similarity between the unsterilized soil and the washed soils for each sterilization method (average Bray-Curtis dissimilarity: autoclave wash = 0.81; autoclave no wash = 0.98, gamma wash = 0.87; gamma no wash = 0.99; q-values: autoclave wash vs no wash = 0.002, gamma wash vs no wash = 0.02).…”