Impacts of microgravity on the survival and growth kinetics of Salmonella on seeds and in plant nutrient solution

• Mathematical modeling developed to predict Salmonella Agona growth under microgravity. • Salmonella Agona had a longer lag phase, slower growth, and higher populations in microgravity. • Salmonella Agona persisted on seeds for 65 days, with fewer injured cells in microgravity. • No significant differences in microbial community between microgravity and Earth conditions. Foodborne pathogens, like Salmonella , present significant risks to space food safety and astronaut health, particularly given the limited medical resources available during missions. This study investigates the behavior of Salmonella Agona in plant nutrient solution (PNS) and on vegetable seeds under simulated microgravity conditions and explores microbial communities on seeds using 16S rRNA sequencing. Inoculated PNS and red cabbage seeds were stored at ambient temperature under microgravity and Earth gravity conditions. Microgravity conditions were simulated using a random positioning machine, and the PNS was prepared bubble-free to mitigate potential mixing effects. Predictive models, the Huang and no-lag phase models, were developed to predict the pathogen growth. These two models were validated with low root mean squared error values ranging from 0.43 to 0.55 log CFU/mL. Salmonella Agona exhibited an extended lag phase, slower growth rate, and higher maximum populations under microgravity compared to Earth gravity in PNS. On red cabbage seeds, Salmonella Agona persisted over the 65 days, with slight reductions (0.07-0.42 log CFU/g), and less injured cells under microgravity. The seed background microflora also persisted well, with no significant differences between microgravity and Earth gravity. These findings underscore the importance of microbial control in space environments. The developed models offer potential applications for assessing Salmonella Agona risk in space food systems. The bacterial community composition on seeds exhibited slight shifts, but no significant differences in bacterial taxa at the phylum, class, and order levels were observed between microgravity and Earth gravity, suggesting the resilience of the seed-associated microbiome.