However, the microbial diversity associated with vegetables, fruits and herbs is less studied, especially in this context. Recently it was shown that plant-associated microbiota including bacteria, fungi and viruses transiently colonized the gut ( David et al., 2014) thus, forming our transient microbiome ( Derrien and van Hylckama Vlieg, 2015).
The plant-gut microbiome axis could be of special importance for human health, and raw-eaten plants seem an important source for microbes ( Leff and Fierer, 2013 Berg et al., 2014 Wassermann et al., 2017). However, this connection and the exchange between microbiomes are less understood, despite their importance to health reflected now also in the one health concept ( Flandroy et al., 2018). Despite being specifically composed and partly deeply embedded within the host, microbial communities are essentially open and interconnected ecosystems ( Berg, 2015). The host-associated microbiota is involved in health issues of the host this was shown for humans and plants as well ( Derrien and van Hylckama Vlieg, 2015 Berg et al., 2017). Although this amount was the same, the bacterial composition was significantly different in conventionally and organically produced apples. Our results suggest that we consume about 100 million bacterial cells with one apple. Among them, especially bacterial signatures known for health-affecting potential were found to be enhanced in conventionally managed apples. In addition, despite the similar structure in general dominated by Proteobacteria (80%), Bacteroidetes (9%), Actinobacteria (5%), and Firmicutes (3%), significant shifts of almost 40% of bacterial genera and orders were monitored. Abundances were not influenced by the management practice but we found a strong reduction in bacterial diversity and evenness in conventionally managed apples. In all, approximately 10 8 16S rRNA bacterial gene copy numbers were determined in each g apple. Interestingly, fruit pulp and seeds were bacterial hot spots, while the peel was less colonized. Each apple fruit harbors different tissues (stem, peel, fruit pulp, seeds, and calyx), which were colonized by distinct bacterial communities. We analyzed the apple microbiome to detect differences between tissues and the impact of organic and conventional management by a combined approach of 16S rRNA gene amplicon analysis and qPCR, and visualization using fluorescence in situ hybridization and confocal laser scanning microscopy (FISH-CLSM).
They represent a source of direct human exposure to bacterial communities, which is less studied. Institute of Environmental Biotechnology, Graz University of Technology, Graz, AustriaĪpples are among the most consumed fruits world-wide.Birgit Wassermann, Henry Müller and Gabriele Berg *