Soil biogeochemistry environment is inherently heterogeneous and patchy. Active soil bacteria require an aquatic habitat for their life function, where aqueous phase is highly dynamic and fragmented. Soil water remaining in soil is often retained by capillary forces in corners and crevices between soil grains or adsorbed as thin liquid films on rough soil surfaces. In majority of soils, the thinness and patchiness of the liquid films restricts the dispersal of individual cells or populations on a microscopic scale. Contrary to bacteria, the habitat of fungi is not restricted to water films. Fungal hyphae easily breach through air-water interfaces and form dense networks within soil. Hydrophilic mycelial networks were found to act as “highways” as they may drastically accelerate bacterial dispersal by providing continuous liquid films around their hyphae. Numerous researches have drawn that conclusion on agar experiment. From views of physics and physiochemistry, the objectives of our research can be listed as follows: 1) to determine the effect of fungal hyphae on bacterial motility on agar surface under various abiotic conditions (water and nutrient), and to determine the roles of bacterial extracellular structures (including flagella, pili and EPS) in this process; 2) to investigate the interaction between two bacterial strains with the presence of fungal hyphae on agar surface under water limited condition; and 3) to quantify those processes by mathematical model.
Bacteriophages are among the most common and diverse entities in the biosphere, and contribute to manipulate and maintain microbial diversity and community structure, impacting element and energy cycling. Understanding of the bacteriophages-host interactions patterns is a key to uncovering the fundamental mechanisms shaping microbial diversity patterns and community structure and associating elements cycling of soil ecosystem, yet remains largely unknown. We propose to develop a soil micro-model experimental platform, coupling surface roughness ceramic soil model and micro-scale in-situ observation methodologies, and to quantify how soil pore-scale physics and associating hydro-physicochemical characteristics manipulate bacteriophages-host interactions processes. In addition, we would establish an individual-based and spatially resolved modeling platform that explicitly considers soil pore characteristics and aqueous phase configuration and associating biophysical processes (e.g., hydration dynamics, nutrient diffusion, bacterial motility, etc.) forming a virtual soil microcosm. The assembly of these complex ingredients into a computational platform will enable systematic hypotheses testing concerning fundamental mechanisms underlying bacteriophages-host interactions. Specifically, the project will provide quantitative insights into the effects of micro-scale hydro-physicochemical processes on shaping bacteriophage-host interactions and coexistence patterns, and impacts on microbial diversity and community structure, and ecological consequences on carbon and nitrogen cycling in soils
Microbial interaction largely determines the composition and function of microbial community in soil ecosystem, which is one of the sources of soil nutrient cycling. Soil phosphorus dissolving microorganisms can mineralize the insoluble and invalid phosphorus to form soluble available phosphorus that can be absorbed and utilized by crops, thus improving the soil available phosphorus content and promoting the utilization efficiency of soil phosphorus by plants. Therefore, phosphorus - solubilizing microorganisms have great application value and research significance in agricultural production. Soil has special spatial heterogeneity. Its pore structure, water and nutrient conditions always affect the growth, migration and interaction process of microorganisms, and then affect the functional expression of phosphorus solubilizing bacteria and the release process of available phosphorus. We propose to use Bacillus sp. N and Variovorax sp. N4, both strains of phosphorus nutrient symbiosis, to explore the effects of different soil physical conditions on the nutrient interaction of soil phosphorus microorganisms. Molecular biology and biochemistry techniques were used to determine the expression of phosphate-solubilizing function and the release of available phosphorus. In addition, we would establish an individual-based and spatially resolved modeling platform that clarifying the mechanism of the influence mechanism of hydration and spatial coordination on nutrient interaction of soil phosphorus solubilizing microorganisms.