Endophytic bacterial communities in peels and pulp of five root vegetables

Plants contain endophytic bacteria, whose communities both influence plant growth and can be an important source of probiotics. Here we used deep sequencing of a 16S rRNA gene fragment and bacterial cultivation to independently characterize the microbiomes of five plant species from divergent taxonomic orders—potato (Solanum tuberosum), carrot (Daucus sativus), beet (Beta vulgaris), neep (Brassica napus spp. napobrassica), and topinambur (Helianthus tuberosus). We found that both species richness and diversity tend to be higher in the peel, where Alphaproteobacteria and Actinobacteria dominate, while Gammaproteobacteria and Firmicutes dominate in the pulp. A statistical analysis revealed that the main characteristic features of the microbiomes of plant species originate from the peel microbiomes. Topinambur pulp displayed an interesting characteristic feature: it contained up to 108 CFUs of lactic acid bacteria, suggesting its use as a source of probiotic bacteria. We also detected Listeria sp., in topinambur pulps, however, the 16S rRNA gene fragment is unable to distinguish between pathogenic versus non-pathogenic species, so the evaluation of this potential health risk is left to a future study.