Abstract

Microgravity is known to have an effect on various plants, animals, and bacteria, but little research has been done to see how it affects bacteriophages. Bacteriophages (phages) are viruses that infect bacterial hosts. There are two classifications of phages based on their life cycle: lytic and temperate. Lytic phages infect a bacterial host, replicate and lyse the cell releasing new phages. Temperate phages are able to integrate their genome within that of the host bacteria, so when the host replicates, the viral DNA replicates with it. The phage genome will remain integrated until it is triggered to form phage particles and lyse the cell. We propose that microgravity may stimulate temperate phages to switch to the lytic cycle, resulting in increased bacterial lysis in microgravity environments like the International Space Station. Using a temperate Mycobacterium phage named GreaseLightnin and a high aspect ratio vessel (HARV) to simulate microgravity, the effect of microgravity on integrated phages was measured. Our results suggest that microgravity may increase the switch to the lytic cycle. Phages play a key role in the environment by limiting the amount of bacteria present. If lysis of bacterial cells increases due to microgravity in the space environment, then the composition of the spacecraft microbiome and the astronauts’ microbiomes may be affected, impacting their overall health.