Effects of elevated ozone on bacterial communities inhabiting the phyllo- and endo-spheres of rice plants.

To explore the effects of elevated ozone (O) on microbial communities inhabiting phyllo- and endo-spheres of Japonica rice leaves, cultivars Nangeng 5055 (NG5055) and Wuyujing 27 (WYJ27) were grown in either charcoal-filtered air (CF) or elevated O (ambient O + 40 ppb, E-O) in field open-top chambers (OTCs) during a growing season. E-O increased the values of the Shannon (43-80%) and Simpson (34-51%) indexes of the phyllo-and endo-spheric bacterial communities in NG5055. E-O also increased the values of the phyllosphere Simpson index by 58% and the endosphere Shannon index by 54% in WYJ27. Both diversity indexes positively correlated with the contents of nitrogen, phosphorus, magnesium, and soluble sugar, and negatively correlated with the contents of starch and condensed tannins. The leaf-associated bacterial community composition significantly changed in both rice cultivars under E-O. Moreover, the leaf-associated bacterial communities in NG5055 were more sensitive to E-O than those in WYJ27. The chemical properties explained 70% and 98% of variations in the phyllosphere and endosphere bacterial communities, respectively, suggesting a predominant role of chemical status for the endospheric bacterial community. Most variation (57.3%) in the endosphere bacterial community assembly was explained by phosphorus. Gammaproteobacteria and Pantoea were found to be the most abundant class (63-76%) and genus (38-48%) in the phyllosphere and endosphere, respectively. E-O significantly increased the relative abundance of Bacteroidetes in the phyllosphere bacterial community and decreased the relative abundance of Gammaproteobacteria in the endophytic community. In conclusion, elevated O increased the diversity of bacterial communities of leaf phyllosphere and endosphere, and leaf chemical properties had a more pronounced effect on the endosphere bacterial community.