Endophytic bacteria community of ryegrass under Cd stress

The study investigated the endophytic bacteria community of ryegrass under Cd stress (at both low and high levels). Results showed that ryegrass could tolerant relative high concentration of Cd, the fresh weight and height were not significantly affected by Cd even at 50 mg/kg, while some other physiochemical parameters (including TN, TP, SP, Mg, Ca) were altered by Cd exposure. The ryegrass has a distinctive bacteria community, Rhodococcus, Candidatus_Portiera, Rickettsia, Candidatus_Hamiltonella, Salinicola were the dominant members, account for 23.4%, 23.3%, 6.2%, 6.0%, 3.9%, respectively. Cd exposure disturbed the composition of endophyte on both phylum and genus levels, including bacteria belongs to Streptomyces, Exiguobacterium, Saccharothrix and Pandoraea, etc.. Pseudomonas that well-known for plant-growth-promoting and Cd tolerant characterizes was account for relatively high proportion in ryegrass, and was increased under Cd stress. In addition, correlation analysis identified that physicochemical parameters (such as TP, TN, Ca, Mg, etc.) significantly affect the abundance and composition of endophytic bacteria genera, suggested the potential roles of these parameters in regulating endophytic microbe communities. In summary, our study investigated the endophytic bacteria community of ryegrass, and further characterized their response to Cd stress. These results could help to better understand the Cd-tolerant mechanisms of ryegrass, and may shed light on the process to improve Cd remediation efficiency by modulating endophyte community.