Compartment niche and bamboo variety influence the diversity, composition, network and potential keystone taxa functions of rhizobacterial communities

Soil bacterial communities play a key role in regulating biogeochemical cycles and plant development. However, variations in soil bacterial communities in rhizosphere soil (RS) and bulk soil (BS) under different varieties of Phyllostachys edulis (bamboo) have not yet been investigated. In this study, we used 16S rRNA gene sequences to investigate the bacterial diversity, composition, network and potential keystone taxa functions in both RS and BS under Phyllostachys edulis and its four variants. We found that RS differed significantly from BS in terms of bacterial community diversity, composition and potential keystone taxa among the bamboo varieties. RS had a lower bacterial richness (931-1325) and Shannon index (4.9-6.3) than BS (1401-1508 and 6.5-6.8, respec-tively), indicating that the bacterial communities were affected by the compartment niches (i.e. RS vs. BS). The bacterial richness and Shannon index did not differ among bamboo varieties in BS but they decreased in RS following an order of P. edulis f. pachyloen (HB) > P. edulis f. luteosulcata (HC) > P. edulis (M) > P. edulis f. tao kiang (H) > P. edulis f. gracilis (JS). The co-occurrence network analysis revealed that the RS and BS bacteria showed a highly modular topology, and that the complexity of the RS bacterial network was greater (average degrees 11.9) than that of the BS network (6.4). The bacterial communities were predominantly positive, with a number of edges of 98% for RS and 87% for BS, indicating extensive reciprocal symbiosis within the bacterial communities for both RS and BS. The soil bacterial communities under JS and HC were more complex and closely connected than those under the other three varieties (M, H, HB). The co-occurrence network analysis selected 16 potential keystone taxa of soil bacteria, which are mainly involved in the biochemical carbon and nitrogen cycles. These results expand the current understanding of P. edulis soil bacterial communities at the intraspecific level, and they support further functional explorations and experimental validations of the soil bacterial strains in bamboo plants.