In this work, we have used a metataxonomic analysis to study the bacterial biodiversity in three types of commercial dressing and ingredients habitually used in table olive packaging. The bioinformatics analysis showed that salt samples (marine and spring) had the highest biodiversity indexes, followed by the aromatic herbs (thyme, oregano, and fennel) and finally by fermented dressing samples (garlic, pepper, and pepper paste). In salt samples, a significant high presence of Cytophagia, Sphingobacteria, Deltaproteobacteria and Halobacteria classes was observed. On the contrary, the presence of Bacilli class in fermented dressing samples was significantly higher compared to the other samples. Finally, the abundance of Gammaproteobacteria was statistically higher in the samples of herbs. At genus or family taxonomic level, Pseudomonas and diverse non-assigned genus of the Enterobacteriaceae family predominated in many samples of herbs. In fermented dressing samples, diverse genus belonging to the Enterobacteriaceae family appeared in a high relative abundance in pepper paste and garlic, and presence of Vibrio sp. was detected in pepper. However, Lactobacillus, Weisella, and Pediococcus were the predominant genera found in many of these fermented samples. Salinibacter was the most representative genus in both types of salt samples. Multivariate analysis (PCA) of the metataxonomic data sets discriminated well the samples belonging to the three different groups, showing a high proportion of sequences shared by samples-group. This survey reports for the first time the presence of new bacterial species not previously related with table olive processing, as well as the presence of others which could compromise the stability of olive packaging.

The research was funded by the Spanish Government (Project OliFilm AGL-2013-48300-R: www.olifilm.science.com.es) AB-C and JB-G thanks the Spanish Ministry of Economy and Competitiveness for their FPI grant and JDC-Incorp. contract, respectively. BC-D thanks the Andalusian Ministry of Economy, Science and Innovation by her pre-doctoral contract.

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Peer reviewed