Rhizobacteria as agents to enhance high value natural products in plants
Beyond assessing the co-occurrence of specific metabolites associated with growth promotion in different plant-bacteria interactions, our result also revealed that the three different rhizobacterial genera can boost nutritionally and/or pharmaceutically important high value natural plant compounds (HVPC). The list of various putative HVPC are summarized in Supplementary Table S9 . Among these, flavonoid glycosides induced in the ineffective partnership between Pbg and Arabidopsis are considered vital phytochemicals in diets and are of great interest due to their diverse bioactivities (Xiao et al.2016). Similarly, glucosinolates in Brassica species (Traka 2016), hydroxycinnamic acid derivatives (Alam et al. 2016) and dihydroartemisinin in Artemisia (Tilley et al. 2016) are potential HPVC. In effective partnerships, the increase in these compounds is even more pronounced when we consider the increase in host biomass due to rhizobacteria inoculation. A typical example for this is the Pbg -Artemisia combination that resulted in five-fold increase in host biomass and up to three-fold increase in both artemisinic alcohol and dihydroartemisinin per unit fresh tissue biomass. Hence, the use of rhizobacteria may be considered as a simple and generic approach to boost economically or pharmaceutically interesting plant metabolites.