Structural characterization and functional activity of an exopolysaccharide secreted by Rhodopseudomonas palustris GJ-22.

One water exopolysaccharide, designated G-EPS, was secreted by Rhodopseudomonas palustris GJ-22 culture media. The structure of G-EPS was characterized with HPGPC, GC-MS, methylation, 1D and 2D NMR, along with UV and FT-IR spectrum. The G-EPS molecular weight was 10.026 kilodalton, and is composed of D-mannose (92.8%) and d-glucose (7.2%). The purified G-EPS promoted plant growth and induced systemic resistance against TMV in Nicotiana benthamiana. These results suggested that G-EPS is an important active component of the bio-control capacity of GJ-22.