Spatial Characterization of Microbial Communities on Multi-Species Leafy Greens Grown Simultaneously in the Vegetable Production Systems on the International Space Station.

Mary E Hummerick,Gioia D Massa,Lashelle E Spencer,Jason A Fischer,Christina L M Khodadad,Jennifer L Gooden,Trent M Smith,Matthew W Romeyn,Cory J Spern,Gretchen J Maldonado-Vasquez,Anirudha R Dixit,Ye Zhang,Nicole Dufour,Raymond M Wheeler

doi:10.3390/life11101060

Abstract

The establishment of steady-state continuous crop production during long-term deep space missions is critical for providing consistent nutritional and psychological benefits for the crew, potentially improving their health and performance. Three technology demonstrations were completed achieving simultaneous multi-species plant growth and the concurrent use of two Veggie units on the International Space Station (ISS). Microbiological characterization using molecular and culture-based methods was performed on leaves and roots from two harvests of three leafy greens, red romaine lettuce (Lactuca sativa cv. ‘Outredgeous’); mizuna mustard, (Brassica rapa var japonica); and green leaf lettuce, (Lactuca sativa cv. Waldmann’s) and associated rooting pillow components and Veggie chamber surfaces. Culture based enumeration and pathogen screening indicated the leafy greens were safe for consumption. Surface samples of the Veggie facility and plant pillows revealed low counts of bacteria and fungi and are commonly isolated on ISS. Community analysis was completed with 16S rRNA amplicon sequencing. Comparisons between pillow components, and plant tissue types from VEG-03D, E, and F revealed higher diversity in roots and rooting substrate than the leaves and wick. This work provides valuable information for food production-related research on the ISS and the impact of the plant microbiome on this unique closed environment.

Highlights

Future space missions and habitats will likely include crop production systems designed to provide a fresh, nutritious component to the crew diet
In Veg-03D, we found that the more rapidly growing mizuna plants overshadowed adjacent lettuce plants, causing watering and accessibility issues for plant maintenance
These experiments were performed by the crew in a semi-autonomous manner; the water volume was adequate for maintaining plant health, but may not have been optimal, and may have varied among the crew members who tended these plants

Summary

Introduction

Future space missions and habitats will likely include crop production systems designed to provide a fresh, nutritious component to the crew diet. Understanding the complexities of plant growth systems designed with the unique challenges of space exploration missions and the associated plant microbiome is essential for sustaining the health of crop systems as well as the human consumer [1,2]. Molecular biology methods to characterize whole microbial communities through omics approaches have led to the understanding of organism and habitat-specific microbiomes. Plants and their associated microbiota exist in a complex association with important functions critical to plant growth and health. Microbes are recruited and assembled on or in plant tissues and organs from reservoirs such as the soil, rhizosphere, and phyllosphere [3,4,5,6].

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