Introduction

     When in microgravity, biological processes are affected, and an understanding of these effects will help with present and future excursions in space. With longer and longer trips into space planned, the health of astronauts must be considered because microgravity creates muscular atrophy, reduced calcium levels in the skeletal system, and fluid redistribution. The natural cycles of plants are thrown off by microgravity, in particular gravitropism, the process that determines which direction roots and shoots grow. Microgravity has a large impact on bacteria, as shown in recent experiments with salmonella. Salmonella in microgravity becomes more deadly and more resistant to antibiotics. Many biological processes are influenced by microgravity, and the changes should be understood before long duration space flights are made in order to reduce the risk of illness on board and ensure a reliable food supply.