Influence on Growth and Physiology of Campylobacter jejuni Under Simulated Microgravity

Campylobacter jejuni is a major cause of gastrointestinal infections worldwide and commonly transmitted through the ingestion of undercooked, contaminated meat. Despite the extensive knowledge of pathogenic bacterium’s behavior on the Earth, there is no study with C. jejuni under spaceflight conditions. This study examines the influence of simulated microgravity on the growth, cell length, and virulence gene expression of C. jejuni. Microbial cultures were maintained under simulated microgravity using a Rotary Cell Culture System and compared with cultures grown under normal gravity conditions. No significant differences in bacterial growth were observed under simulated microgravity compared with normal gravity after 48 and 72 h of incubation. Cell length was shorter in both simulated microgravity and normal gravity (Falcon tubes) cultures than in the normal gravity (HARV) control, although differences were not significant based on mean cell-length values from biological replicates using a paired t-test. In contrast, mixed-effects analysis of individual cell-length measurements revealed significant differences between simulated microgravity and the normal gravity HARV control and between the normal gravity (Falcon tubes) and normal gravity (HARV) control conditions. Gene expression analysis using quantitative PCR was performed on selected virulence genes (cadF, ciaB, cdtA, luxS, and flaA) associated with adhesion, invasion, toxin production, quorum sensing, metabolism, and motility. This study found no significant differences in gene expression under simulated microgravity compared to normal gravity for the selected genes. Results indicated the limited influence of microgravity on Campylobacter physiology, but further investigation utilizing whole-genome transcriptomic and proteomic analyses is warranted to gain a deeper understanding.