Microbiota in ground water and alternative irrigation water, and spinach microbiota impacted by irrigation with different type of water

Authors: GU, GANYU - Virginia Tech; YIN, HSIN-BAI - University Of Maryland; OTTESEN, ANDREA - Food And Drug Administration(FDA); BOLTEN, SAMANTHA - University Of Maryland; Patel, Jitu; RIDEOUT, STEVEN - Virginia Tech; Nou, Xiangwu

Submitted to: Phytobiomes Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2019
Publication Date: 4/15/2019
Citation: Gu, G., Yin, H., Ottesen, A., Bolten, S., Patel, J.R., Rideout, S., Nou, X. 2019. Microbiota in ground water and alternative irrigation water, and spinach microbiota impacted by irrigation with different type of water. Phytobiomes Journal. https://doi.org/10.1094/PBIOMES-09-18-0037-R .
DOI: https://doi.org/10.1094/PBIOMES-09-18-0037-R

Interpretive Summary: Due to worsening fresh water scarcity and increasing global food demands, alternative water sources need to be explored for agricultural use, and the potential health risks also need to be assessed. In this study, we compared the microbial composition in three different types of irrigation water, including ground water (control), reclaimed waste water, and urban storm runoff water; and investigated the shift in bacterial communities on spinach in field before and after irrigation. The results indicated that the most abundant bacterial species on spinach retained dominant presence after irrigation with different types of irrigation water, while irrigation resulted in a transient increase of multiple bacterial species on spinach, including species of potential opportunistic pathogens. This study provided information on the potential risks of non-conventional water source for produce irrigation. This research findings can benefit research community for understanding the impacts of using unconventional irrigation water, and fresh produce growers in water restricted regions for exploring alternative water sources.

Technical Abstract: Irrigation water, particularly if applied overhead, could be an important source of bacterial contamination to fresh produce. The colonization, survival and proliferation of exogenous bacterial pathogens can be strongly influenced by the produce microbiota. In this study, spinach grown in an organic field was irrigated with ground water (Gr) and potential alternative irrigation water including reclaimed-waste (Wa), and urban storm runoff (Rf) water, over a period of two weeks. Water and spinach samples were collected before and after irrigation for bacterial plate count, qPCR, and community profiling using 16S rDNA sequencing analyses. The average bacterial population densities on spinach (6.50 ± 0.04 log CFU/g, 7.40 ± 0.10 log 16S copies/g) were significantly higher than those in irrigation water (3.61 ± 0.12 log CFU/ml, 4.94 ± 0.13 log 16S copies/ml). The composition and relative abundance of spinach microbiome varied with different types of irrigation waters, however, the most abundant microbial taxa on spinach were not significantly affected by the irrigation with different types of water. Shigella, Salmonella, Listeria, Campylobacter spp. and pathogenic Escherichia coli were not detected in this study. This study provides information on the microbial ecology of diverse bacterial community on spinach after irrigation by different types of water, which can benefit future studies on the interaction of microbes on produce, and the prevention of foodborne pathogens and plant disease.