Herbaspirillum sp. ZXN111 Colonization Characters to Different Tea Cultivars and the Effects on Tea Metabolites, Profiling on Zijuan ( Camellia sinensis var. assamica ).

Herbaspirillum sp. ZXN111 and its mutants (Δ acc , Δ tyrb , and Δ acc-tyrb ), which show PGP activity on Zijuan, were tested for tea plants' colonization characteristics and the strain-dependent response of tea metabolites. The results showed that strain ZXN111 could widely colonize in different tea cultivars of Zijuan, Yunkang-10, Longjin 43, and Shuchazao, but with significant colonization preference to Zijuan, which might be ascribed to anthocyanins' chemotaxis. After 9 weeks of co-cultivation, l-theanine and theobromine in Zijuan leaves that were inoculated with wild-type ZXN111 were decreased, while theobromine, caffeine, and l-theanine that were inoculated with mutant Δ acc were increased; especially l-theanine increased much significantly. Metabolomics analysis showed that tea metabolite profiling of inoculant groups was clearly separated from the control; therein, the flavanols were downregulated in ZXN111 and Δ acc groups, but the l-theanine of the Δ acc group was significantly upregulated compared to control and ZXN111 groups. These results indicated that strain ZXN111, especially of mutant Δ acc , improved Zijuan tea flavor.