Bacterial and fungal communities associated with the surface of hemp seeds and poppy seeds

Microbial contamination of oil seeds can cause their deterioration leading to reduction of the quality of the produced oil. Knowledge of the levels and composition of microbial communities may be therefore helpful to set up the effective control measures. Seeds of hemp and poppy (blue and white cultivars) from two farms in Slovakia were analysed by culture-based microbiological methods and by metagenomic high-throughput sequencing of 16S rDNA and 28S rDNA to provide information on surface bacterial and fungal communities. The results of culture-based analysis showed a comparatively high level of contamination by bacteria and by fungi of hemp seeds. High-throughput sequencing revealed that the bacterial community of hemp seeds consisted mainly of families Enterobacteriaceae and Pseudomonadaceae. The fungal community was composed mainly of Pleosporaceae, Davidiellaceae and Tremellaceae. In poppy seeds, the bacterial community was found to be composed mainly of Enterobacteriaceae (genus Klebsiella), Pseudomonadaceae and Xanthomonadaceae or Streptomycetaceae. The fungal community was composed mainly of Pleosporaceae and Davidiellaceae (genus Cladosporium), while some samples were characterized by increased levels of Trichocomaceae (genus Aspergillus). The determined presence of pseudomonads and aspergilli in certain seeds may indicate that more effective cleaning and sanitation will be required as they could affect the produced oil.