Development in Altered Gravity Influences Height in Dictyostelium

We investigated the effects of altered gravity on the life cycle of Dictyostelium discoideum after and during life-long exposure to one of three altered gravity ( g) environments: (1) substrate inverted, parallel to and facing the surface of the Earth; (2) hyper- g ; (3) reduced- g . To this end, we measured the height of the final stage of the life cycle, the mature spore-bearing sorocarp. Typically, the sorocarp stands erect and perpendicular to the substrate. In the case of each altered g environment, the control cultures were produced and treated identically to the experimental cultures except for the conditions of their exposure to altered g . Inverted cultures developing and growing in the same direction as the gravity vector had a mean height of 1.84 mm. Their counterpart control cultures had a mean height of 1.64 mm being therefore statistically significantly shorter. Cultures chronically exposed to a hyper (10) g environment produced sorocarps with a mean height of 1.13 mm. These were statistically significantly shorter than their 1 g controls whose mean height was 2.06 mm. Clinorotated (simulated reduced g ) sorocarp heights (mean equal to 2.12 mm) were statistically significantly taller compared to their 1 g controls (mean equal to 1.79 mm). The significance level for all the statistical analyses is p < 0.05. Therefore, measurements of the mature stage after life-long exposure to simulated altered gravity show that the final height of the sorocarp is ultimately determined, at least partially, by the gravity environment in which development occurs.