Methods for Gravitational Biology Research

To study the impact of gravity on living systems on the cellular up to the organismic level, a variety of experimental platforms are available for gravitational biology and biomedical research providing either an almost stimulus-free microgravity environment (near weightlessness) of different duration and boundary conditions. The spectrum of real-microgravity research platforms is complemented by devices which are used to either increase the gravity level (centrifuges) or modify the impact of gravity on biological systems (clinostats and random-positioning machines) the so-called ground-based facilities. Rotating biological samples horizontally or in a two- or three-dimensional mode is often used to randomize the effect of gravity in the attempt to eliminate the gravity effect on sensing mechanisms and gravity-related responses. Sophisticated centrifuges have been designed allowing studies from cells up to humans, either on ground under hypergravity conditions (> 1 g) or in space, where they offer the chance to stepwise increase the acceleration force from 0 g (microgravity) to 1 g or higher and vice versa. In such a way, centrifuges are used to determine threshold values of gravisensitivity and to unravel molecular and cellular mechanisms of gravity sensing and gravity-related responses. By using the whole spectrum of experimental platforms, gravitational biologists gain deep insight into gravity-related biological processes and continuously increase our knowledge of how gravity affects life on Earth

Impact of spatial organization on a novel auxotrophic interaction among soil microbes

A key prerequisite to achieve a deeper understanding of microbial communities and to engineer synthetic ones is to identify the individual metabolic interactions among key species and how these interactions are affected by different environmental factors. Deciphering the physiological basis of species-species and species-environment interactions in spatially organized environment requires reductionist approaches using ecologically and functionally relevant species. To this end, we focus here on a specific defined system to study the metabolic interactions in a spatial context among a plant-beneficial endophytic fungus Serendipita indica, and the soil-dwelling model bacterium Bacillus subtilis. Focusing on the growth dynamics of S. indica under defined conditions, we identified an auxotrophy in this organism for thiamine, which is a key co-factor for essential reactions in the central carbon metabolism. We found that S. indica growth is restored in thiamine-free media, when co-cultured with B. subtilis. The success of this auxotrophic interaction, however, was dependent on the spatial and temporal organization of the system; the beneficial impact of B. subtilis was only visible when its inoculation was separated from that of S. indica either in time or space. These findings describe a key auxotrophic interaction in the soil among organisms that are shown to be important for plant ecosystem functioning, and point to the potential importance of spatial and temporal organization for the success of auxotrophic interactions. These points can be particularly important for engineering of minimal functional synthetic communities as plant-seed treatments and for vertical farming under defined conditions