Do Root Exudates Exert More Influence on Rhizosphere Bacterial Community Structure Than Other Rhizodeposits?

Root exudates are credited with having a major influence on the structure of rhizosphere bacterial communities. However, evidence indicates that direct influence of root exudates on bacterial communities is limited to small spatiotemporal windows surrounding root apices. Furthermore, root exudates are modified upon assimilation by microorganisms, prior to rerelease into the rhizosphere. Also, many of the compounds that dominate root exudates are ubiquitous in the rhizosphere and arise from microbial metabolites and rhizodeposits other than exudates. Consequently, rhizosphere carbon pools associated with regions of roots other than apices are unlikely to be dominated by root exudates. Thus, it is important to consider all carbon pools in the rhizosphere as potential drivers of microbial community structure. This has implications for the distribution of rhizosphere bacteria and should factor as an important consideration in the development of effective strategies for managing beneficial plant–microbe interactions.