Bacterial community diversity and variation in spray water sources and the tomato fruit surface

Abstract

BackgroundTomato (Solanum lycopersicum) consumption has been one of the most common causes of produce-associated salmonellosis in the United States. Contamination may originate from animal waste, insects, soil or water. Current guidelines for fresh tomato production recommend the use of potable water for applications coming in direct contact with the fruit, but due to high demand, water from other sources is frequently used. We sought to describe the overall bacterial diversity on the surface of tomato fruit and the effect of two different water sources (ground and surface water) when used for direct crop applications by generating a 454-pyrosequencing 16S rRNA dataset of these different environments. This study represents the first in depth characterization of bacterial communities in the tomato fruit surface and the water sources commonly used in commercial vegetable production.ResultsThe two water sources tested had a significantly different bacterial composition. Proteobacteria was predominant in groundwater samples, whereas in the significantly more diverse surface water, abundant phyla also included Firmicutes, Actinobacteria and Verrucomicrobia. The fruit surface bacterial communities on tomatoes sprayed with both water sources could not be differentiated using various statistical methods. Both fruit surface environments had a high representation of Gammaproteobacteria, and within this class the genera Pantoea and Enterobacter were the most abundant.ConclusionsDespite the major differences observed in the bacterial composition of ground and surface water, the season long use of these very different water sources did not have a significant impact on the bacterial composition of the tomato fruit surface. This study has provided the first next-generation sequencing database describing the bacterial communities living in the fruit surface of a tomato crop under two different spray water regimes, and therefore represents an important step forward towards the development of science-based metrics for Good Agricultural Practices.

The Growing Season, but Not the Farming System, Is a Food Safety Risk Determinant for Leafy Greens in the Mid-Atlantic Region of the United States

“…Trickle (drip) irrigation is considered to have a lower risk for contaminating produce since water does not contact the edible parts of produce; previous research has shown internalization and persistence of E. coli O157:H7 in lettuce leaves following spray irrigation with contaminated water (90). In contrast, a study using groundwater or surface water for pesticide mixing and application to tomatoes revealed no significant impacts to tomato fruit microbial communities (82).…”

“…However, evidence also supports the notion that selection for phyllospheric microbial community members is largely plant regulated and less influenced by environmental factors such as water type (82) or airborne migration (83), which might explain why soiled leaves did not harbor significantly higher indicator bacterial counts. In any case, field surroundings and activities close to harvest are of concern in small-to medium-size farms, which tend to have larger production areas exposed to such risk factors.…”

Diversity of enterobacteria associated with tomato (Lycopersicum sculentum Mill) fruits and greenhouse soils

“…La presencia del enteropató-geno ETEC detectado en este trabajo (Tabla 3), se relaciona con lo reportado por Telias et al (2011), quienes afirman que la inocuidad del tomate se compromete ante la existencia de las enterobacterias mencionadas sobre la superficie del fruto. Lo anterior debido a que el fruto de tomate se consume habitualmente en forma cruda incluyendo su pericarpio.…”

An Investigation on Performance and Structure of Ecological Revetment in a Sub-Tropical Area: A Case Study on Cuatien River, Vinh City, Vietnam

“…The Shannon index and Simpson index were used to estimate the microbial community diversity in the samples. According to Shannon index and Simpson index values, the diversity of microbial community in the samples were ranked as #3 > #2 > #1 from high to low [35,36]. The results showed that the total number and diversity of microorganisms attached on the gabion and riprap revetments were much higher than that of the suspended microorganisms in the water.…”

“…Among them, Polynuclebacter, Menicius, Mssila, Geobacter, Gemmatimonas, Albidiferax, Ramlibacter, Janthino bacterium, Sphaerotilus, Clostridium sensu stricto, pauludibacter, Dechoromonas, Sphingomonas, and Dechloromonas were significantly higher. Previous studies have shown that Polynuclebacter, Geobacter, Gemmatimonas, Ramlibacter, Clostridium sensu strict, pauludibacter, Dechoromonas, and Sphingomonas have a strong ability to reduce pollutant levels in river water [36]. Its main role is to uptake nutrient in river water to form a biofilm.…”