Abstract
To investigate the structural and functional similarities of microbial communities in burnt-sweetness alcoholized tobacco as a function of distance from the equator and their effects on tobacco quality, we sampled alcoholized tobacco from Chenzhou, Hunan Province, China and from Brazil and Zimbabwe, which are also burnt-sweetness-type tobacco producing regions, and performed high-throughput sequencing of tobacco bacterial and fungal communities along with an analysis of the main chemical constituents of the tobacco to analyze differences in the quality of the tobacco and similarities in the structure of the microbial communities. The total nitrogen, nicotine and starch contents of Chenzhou tobacco were greater than those of Brazilian and Zimbabwean tobacco, and the total sugar and reducing sugar contents of the Brazilian and Zimbabwean tobacco were greater than those of the Chenzhou tobacco (P < 0.05). The alpha diversity indices of the bacterial communities in Chenzhou tobacco were lower than those in the Brazilian and Zimbabwean tobacco, and the alpha diversity indices of the fungal communities in Chenzhou tobacco were greater than those in the Brazilian and Zimbabwean tobacco (P < 0.05). In the ecological networks, bacterial-fungal interactions in the Brazilian and Zimbabwean tobacco were more complex than those in the Chenzhou tobacco, and the microbial ecological networks of the burnt-sweetness-type tobacco from three different regions were dominated by competitive relationships. The microbial community composition of Chenzhou tobacco was similar to that of Brazilian tobacco at the bacterial genus and fungal phylum level, with Sphingomonas being a significantly enriched genus in Brazilian tobacco and a key genus in the Chenzhou network that is able to participate in the degradation of polyphenols and aromatic compounds. Functional microbes related to aromatic compounds and cellulose degradation were significantly more abundant in the Brazilian and Zimbabwean tobacco than in Chenzhou tobacco, and the related degradation of tobacco substances was responsible for the better quality of the Brazilian and Zimbabwean tobacco. In conclusion, there are similarities in the structure, composition and functional flora of microbial communities in tobacco from Chenzhou and Brazil because these regions have similar latitudinal distributions. This study provides theoretical support for selecting cultivation regions for the burnt-sweetness-type alcoholized tobacco and for the alcoholization of tobacco leaves.