Microbiomes in Ground Water and Alternative Irrigation Water, and Spinach Microbiomes Impacted by Irrigation with Different Types of Water

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 and potential alternative irrigation water including reclaimed wastewater, and urban runoff water, over a period of 2 weeks. Water and spinach samples were collected before and after irrigation for bacterial plate count, qPCR, and community profiling using 16S rDNA high-throughput 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 microbiomes 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 communities on spinach surface 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.

Prevalence of Salmonella and Listeria monocytogenes in non-traditional irrigation waters in the Mid-Atlantic United States is affected by water type, season, and recovery method

“…Lower levels of both S. enterica and L. monocytogenes (Figs 2 an d3; Table 3) recovered from reclaimed water compared to river water sites are not surprising since it has undergone physical and chemical treatments to remove contaminants (Table 1) [34].Reclaimed water was analyzed from a holding pond after treatment, which may have allowed low levels of Salmonella and L. monocytogenes to be introduced to the pond through animal intrusions or soil runoff. Other studies did not find the presence of Salmonella or L. monocytogenes in reclaimed wastewater but used non-culture-based methods and smaller volumes in their detection methods [35]. Lower prevalence of Salmonella and L. monocytogenes indicate that the microbial quality of reclaimed wastewater from this site may be suitable for agricultural irrigation.…”

Correlation of Salmonella enterica and Listeria monocytogenes in Irrigation Water to Environmental Factors, Fecal Indicators, and Bacterial Communities

“…and L. monocytogenes in irrigation ponds, respectively. The diverse and complex composition of microbial communities in irrigation water are associated with environmental conditions and water sources ( Gu et al, 2019b ; Chung et al, 2020 ). The sample size ( n = 96) performed for high-throughput sequencing in this study might be limited to cover the comprehensive microbial communities.…”

“…S. enterica serovar Newport was implicated in the recurring outbreaks associated with tomato in this agricultural region ( Greene et al, 2008 ; Bennett et al, 2015 ). Diverse S. enterica serotypes were identified from irrigation water, poultry litter, and field soil samples in this region ( Gu et al, 2019a , b ). However, serovar Newport was identified to be the dominant serotype in sampled irrigation water (35% in tested pond water and 65% in well water), but not in poultry litter (2%) or poultry litter amended field soil (6%) samples.…”

“…A most probable number (MPN) method was used to assess S. enterica concentration in collected water samples as described previously ( Luo et al, 2014 ; Gu et al, 2019a , b ).…”

Persistence of Escherichia coli O157:H12 and Escherichia coli K12 as Non-pathogenic Surrogates for O157:H7 on Lettuce Cultivars Irrigated With Secondary-Treated Wastewater and Roof-Collected Rain Water in the Field

“…Water characteristics such as total organic carbon, hardness, ion composition, pH, and indigenous microflora influenced the survival of E. coli O157:H7 in different water sources (Williams et al, 2007;Avery et al, 2008). Spray irrigation of spinach with wastewater and roof-collected rain water significantly altered its microbiome compositions (Gu et al, 2019). Effects of alternative irrigation waters on the transference and persistence of nonpathogenic E. coli surrogates from the water to the lettuce cultivars at farm levels need further investigation.…”