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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Foodborne Toxin Detection and Prevention Research » Research » Publications at this Location » Publication #315941
Title: Bacterial populations on the surfaces of organic and conventionally grown almond drupes

Author
item McGarvey, Jeffery - Jeff
item Hnasko, Robert
item Stanker, Larry
item HAN, RUYANG - University Of California
item CONNEL, JOSEPH - University Of California

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2015
Publication Date: 7/21/2015
Publication URL: http://handle.nal.usda.gov/10113/61370
Citation: Mcgarvey, J.A., Hnasko, R.M., Stanker, L.H., Han, R., Connel, J. 2015. Bacterial populations on the surfaces of organic and conventionally grown almond drupes. Journal of Applied Microbiology. 119:529-538.

Interpretive Summary: We investigated the types of bacteria found on the surfaces of almonds grown under organic and conventional farming practices. We found that there were significant differences in the types of bacteria found on the almonds. Specifically we observed more bacteria belonging to the group Gammaproteobacteria on the conventionally grown almonds and more bacteria associated with the Alphaproteobacteria on the organically grown almonds. Our data suggests that the different growing practices affects the type of bacteria on the almonds.

Technical Abstract: Aims: To compare the bacterial populations on organically and conventionally grown almond drupes before and after hull split. Methods and Results: We constructed 16S rRNA gene libraries containing approximately 3,000 sequences each from the bacteria from organically and conventionally grown drupes before and after hull split. We observed that before hull split both conventionally and organically grown drupes were colonized by relatively few types of bacteria that were mostly common phyllosphere-associated Proteobacteria. However, the organically grown drupes contained significantly more Alphaproteobacteria and the conventionally grown drupes contained significantly more Gammaproteobacteria. The conventionally grown drupes also contained significantly more sequences associated with the phylum Actinobacteria. After hull split, we observed a significant increase in bacterial diversity, with many newly appearing sequences that were not normally associated with the phyllosphere. Conclusions: Organic and conventional growing methodologies influence the types of bacteria on the pyllosphere and hull split results in a burst of microbial diversification. Significance and Impact of the Study: Production of organic produce is increasing due to consumer preferences, but it was unknown how this methodology affects the bacterial populations on the phyllosphere. This is the first study to compare the bacterial populations of organically and conventionally grown almond drupes.