Geographic and position-based variations in phyllospheric bacterial communities present on flue-cured tobacco.

Although tobacco leaves (TLs) contain abundant bacteria, how the geography and leaf position of TLs affect these bacteria is unclear. Here, TLs at different positions from Henan (HN, strong flavor style) and Yunnan (YN, fresh flavor style) provinces were collected, and the bacteria were characterized by Illumina sequencing at harvest and 1 year of storage. Bacterial communities were very different between TLs originating from different geographical areas and positions, and beta diversity analysis showed that leaf position was the most important factor for phyllospheric bacterial communities, followed by geographical area and storage time. At the genus level, Subdoligranulum, Thermus, and Acinetobacter were obviously more abundant in HN than in YN, while Blautia and Ruminococcus were significantly more abundant in YN. These differences in bacterial communities decreased after 1 year of storage, indicating that the microbiota tends to become similar during tobacco processing. Storage time also affected the phyllospheric bacteria of TLs, as the bacterial communities shifted significantly on both HN and YN TLs after 1 year of storage. Significant differences in the predicted genes were also observed between the different geographic locations and leaf positions. Potential human pathogens, including Acinetobacter, Methylobacterium, and Escherichia-Shigella, were greatly different between TLs originating from different areas and positions. These data suggested that geographic variations and positions were associated with phyllospheric bacterial communities on TLs, which may be related to not only the flavor style and quality of TLs but also the potential health risks to humans. KEY POINTS: • Tobacco leaf position and tobacco growth location affected bacterial communities. • Microbial communities of TLs shifted significantly after one year of storage. • Potential human pathogens differed at different leaf positions and growth locations.