The microbial communities of a tomato crop grown in Veggie under different lighting regimes on the International...

Customized lighting treatments are being investigated to help optimize space crop production. The VEG-05 experiment on the International Space Station (ISS) investigated the effect of red-rich and blue-rich lighting in the Veggie plant-growth chamber on the microbial communities of a dwarf tomato variety Solanum lycopersicum cv. Red Robin. The microbial communities were investigated using bacterial 16S rRNA and fungal internal transcribed spacer (ITS) sequencing methods to identify bacterial and fungal communities from tomato fruit, leaves, roots, rooting substrate, and Veggie chamber surfaces grown under red-rich or blue-rich lighting. The plants were also screened using culture-based methods for potential food-borne pathogens and plate counts for bacteria and fungi. Differences in microbial load were compared between lighting conditions, as well as between ISS and ground-control treatments. Fruit production was lower on ISS-grown plants, thus limiting the number of samples available for analyses from flight plants. These analyses determined the microbiological food safety for tomato plants grown under a red-rich or a blue-rich lighting treatment and microgravity conditions. The potential core microbiome for flight tomato plants included the genera Rhizobium, Azospirillum, Burkholderia, Dyadobacter, Methylobacterium/Methylorubrum, Sphingomonas, and the family Erwiniacea. Pseudomonas was the only genus common to all ground-control plants, due to low microbial diversity on leaf samples. Culture-based pathogen screening, corroborated by 16S rRNA and ITS sequencing, yielded negative results. Our results indicate flight microbial communities show increased colonization compared to ground controls, and this increase was associated with red-rich light treatment more so than blue-rich light treatment. This experiment provides valuable data for a fruiting crop grown on the ISS and how the plant microbial community may change due to different lighting conditions.