Daphné Golaz
Department of Plant and Microbial Biology, University of Zürich

Abstract
Establishing self-sustainable colonies on another stellar object demands implementing space farming. Yet, the lower gravity and the availability of nutrients necessary for crop growth make the production of an adequate yield a challenge. A solution to this issue is to use the symbiosis between nitrogen-fixing bacteria (rhizobia) and legumes. Rhizobia play a key role in the nitrogen cycle on Earth and are responsible for about 60% of the total global nitrogen fixation. Hence, they could be used to improve the growth of crops in space. Yet, little is known about the impact of microgravity on mutualistic systems. Thus, we have been studying the effects of simulated microgravity (s0-g) on the growth and symbiotic performance on the rhizobial strain Paraburkholderia phymatum. We have phenotypically characterized the rhizobia in s0-g using a random positioning machine (RPM) to induce simulated microgravity. No differences in resistance to antibiotic or oxidative stress could be observed in the samples grown in 1g and s0-g. Yet, the rhizobia displayed higher levels of vesicle formation and root attachment to the common bean root in s0-g compared to 1g. Also, an RNA sequencing analysis performed on P. phymatum free-living cells showed that key genes for osmolarity maintenance, stress resistance and nitrogen fixation are upregulated in s0-g compared to 1g, hinting that rhizobia can survive and establish a successful symbiosis with legumes in s0-g. Finally, the use of the RPM revealed that P. phymatum's genes involved in iron uptake are downregulated in simulated microgravity, which permitted us to reach a better understanding of iron transporters in nitrogen-fixing bacteria.

2023 January 19, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto