Isolation and characterization of endophytic bacteria from wild and traditionally cultivated rice varieties

Endophytic bacteria were isolated from surface-sterilized stems, seeds, and leaf sheaths of wild and traditionally cultivated rice varieties. Phylogenetic analyses based on 16S rDNA revealed a wide divergence among the isolates, However, the most frequently isolated groups were Methylobacterium sp. in the alpha-subdivision of Proteobacteria, and Curtobacterium sp. in the high G+C Gram-positive group. Various phenotypic traits that are expected to be involved in the persistence and functions of the bacteria were analyzed: Most of the isolates from rice excreted pectinase, were motile, and showed an osmotic resistance to 0.6 M sucrose, These traits may be involved in endophytic characteristics in rice, About 50% of the isolates showed a cellulase activity, A few isolates fixed nitrogen, produced indole-3-acetic acid, and formed capsules. These activities were partially correlated with the phylogenetic group.