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.
Highlights
Tomato (Solanum lycopersicum) consumption has been one of the most common causes of produceassociated salmonellosis in the United States
Our research has generated the first culture-independent next-generation sequencing data set for the bacterial microbiology associated with the phyllosphere of a tomato crop under agricultural management
There are a myriad of agricultural practices that may play a role in the contamination of tomatoes by human pathogenic bacteria
Summary
Tomato (Solanum lycopersicum) consumption has been one of the most common causes of produceassociated salmonellosis in the United States. An increasing number of epidemic outbreaks caused by contamination of produce by human pathogens have been observed in the United States [1]. The phyllosphere has found itself at an intersection of food safety concerns and research that examines the microbial ecology of agricultural environments [4,5,6]. Human pathogens find their way to this environment via diverse channels that remain poorly understood. An extremely important component of agricultural management that remains to be comprehensively examined with culture-independent methods is the microbial ecology associated with water sources used in irrigation and pesticide applications
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