Composition variation of agarwood-associated microbial communities from Aquilaria sinensis

Abstract

Agarwood, derived from Aquilaria sinensis and Aquilaria malaccensis, is of medicinal and ecological value and religious importance as incense. The existing imbalance between short supply and increasing demand of this product remains to be solved. Thus, the biologically artificial agarwood-inducing methods commonly called whole-tree agarwood-inducing techniques (agar-wit) have been established to dramatically improve agarwood yield within a short period. However, several studies reported a lower content of ethanol-soluble extractive in the agar-wit agarwood than in the natural agarwood. To further understand the role of microorganisms in agarwood formation, we investigated and contrasted the endophytic bacteria and fungi between different types of agarwood from A. sinensis through high-throughput sequencing. Results showed that the same dominant phyla of bacteria consisting of Proteobacteria, Actinobacteria, and Acidobacteria were shared by the natural agarwood and agar-wit agarwood. Meanwhile, Ascomycota and Basidiomycota constituted the similar dominant fungal phyla of these two kinds of agarwood. However, the principal microbial communities at the genus or order level evidently varied from natural agarwood to agar-wit agarwood. Moreover, the bacterial communities are closely connected with terpenoid and carbohydrate metabolism, which indicated that the bacterial communities also play a vital role in agarwood formation. In conclusion, the higher concentrated abundance of the dominant microbial communities in agar-wit agarwood than in natural agarwood may promote agarwood formation, however, the low evenness of microbial communities also lowers the content of ethanol-soluble extractive.\n\nIMPORTANCEAgarwood has become an indispensable product in modern life because of medicinal value, ecological and religious importance as incense. Nevertheless, the enormous demand for agarwood markedly exceeds the supply because of the dramatically declining population of genus Aquilaria. Agarwood formation occurring slowly and infrequently in a natural environment, so various artificial techniques were developed to promote the formation of agarwood, such as the physical methods and chemical methods. However, these techniques still are insufficient to compensate for the agarwood shortage. In this case, a novel biological method called the whole-tree agarwood-inducing technique (Agar-wit) induces agarwood production. However, several studies have shown that agarwood harvested from biological technology contains lower content of ethanol-soluble extractive compared with natural agarwood. So to further expose and understand the endophytic bacteria and fungi in agarwood formation is important for the improvement of biological method.