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

Telias A, White JR, Pahl DM, Ottesen AR, Walsh CS - BMC Microbiol. (2011)

Bottom Line: The 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.Despite 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Plant Science and Landscape Architecture Department, University of Maryland, College Park, MD 21201, USA. atelias@umd.edu

ABSTRACT

Background: Tomato (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.

Results: The 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.

Conclusions: Despite 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.

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Related in: MedlinePlus

Neighbor-joining phylogenetic tree of reads mapping to members of the Enterobacteriaceae family. Screening our dataset for putative E. coli/Shigella/Salmonella species we discovered most hits were from the fruit surface samples. We found that by including 16S rRNA reference sequences from members of other related genera including Citrobacter and Cronobacter, we could not confidently assign any sequences from our dataset to Salmonella due to poor phylogenetic resolution. However, we did determine that no reads mapping to the Enterobacteriaceae family were from E. coli/Shigella. The E. coli/Shigella monophyletic clade is colored in red, the Staphylococcus aureus outgroup is purple, and monophyletic clades of sequences from our dataset are colored in green.
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Figure 7: Neighbor-joining phylogenetic tree of reads mapping to members of the Enterobacteriaceae family. Screening our dataset for putative E. coli/Shigella/Salmonella species we discovered most hits were from the fruit surface samples. We found that by including 16S rRNA reference sequences from members of other related genera including Citrobacter and Cronobacter, we could not confidently assign any sequences from our dataset to Salmonella due to poor phylogenetic resolution. However, we did determine that no reads mapping to the Enterobacteriaceae family were from E. coli/Shigella. The E. coli/Shigella monophyletic clade is colored in red, the Staphylococcus aureus outgroup is purple, and monophyletic clades of sequences from our dataset are colored in green.

Mentions: We created a phylogenetic tree in order to compare the Enterobacteriaceae species present in the different samples (Figure 7). By populating the tree with several genera we could not confidently assign sequences to pathogenic species within the family. Based on our tree, the 527 bp segment of the 16S rRNA gene used is not enough to distinguish between several members of the Enterobacteriaceae family.


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

Telias A, White JR, Pahl DM, Ottesen AR, Walsh CS - BMC Microbiol. (2011)

Neighbor-joining phylogenetic tree of reads mapping to members of the Enterobacteriaceae family. Screening our dataset for putative E. coli/Shigella/Salmonella species we discovered most hits were from the fruit surface samples. We found that by including 16S rRNA reference sequences from members of other related genera including Citrobacter and Cronobacter, we could not confidently assign any sequences from our dataset to Salmonella due to poor phylogenetic resolution. However, we did determine that no reads mapping to the Enterobacteriaceae family were from E. coli/Shigella. The E. coli/Shigella monophyletic clade is colored in red, the Staphylococcus aureus outgroup is purple, and monophyletic clades of sequences from our dataset are colored in green.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108269&req=5

Figure 7: Neighbor-joining phylogenetic tree of reads mapping to members of the Enterobacteriaceae family. Screening our dataset for putative E. coli/Shigella/Salmonella species we discovered most hits were from the fruit surface samples. We found that by including 16S rRNA reference sequences from members of other related genera including Citrobacter and Cronobacter, we could not confidently assign any sequences from our dataset to Salmonella due to poor phylogenetic resolution. However, we did determine that no reads mapping to the Enterobacteriaceae family were from E. coli/Shigella. The E. coli/Shigella monophyletic clade is colored in red, the Staphylococcus aureus outgroup is purple, and monophyletic clades of sequences from our dataset are colored in green.
Mentions: We created a phylogenetic tree in order to compare the Enterobacteriaceae species present in the different samples (Figure 7). By populating the tree with several genera we could not confidently assign sequences to pathogenic species within the family. Based on our tree, the 527 bp segment of the 16S rRNA gene used is not enough to distinguish between several members of the Enterobacteriaceae family.

Bottom Line: The 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.Despite 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Plant Science and Landscape Architecture Department, University of Maryland, College Park, MD 21201, USA. atelias@umd.edu

ABSTRACT

Background: Tomato (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.

Results: The 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.

Conclusions: Despite 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.

Show MeSH
Related in: MedlinePlus