CHARACTERIZATION OF NATIVE FRANKIA STRAINS ISOLATED FROM CHILEAN SHRUBS (RHAMNACEAE)

Nine native Frankia strains were isolated from root nodules of four ch ilean actinorhizal plants (Rhamnaceae). The strains were designated as ChI1, ChI2, ChI3 and ChI4 from Colletia hystrix; ReI4 and ReI6 from R etanilla ephedra; TqI12 and TqI15 from Talguenea quinquinervis and TtI 42 from Trevoa trinervis. By scanning electron microscopy, all the str ains exhibited similar actinomycetal structures: hyphae, sporangia and vesicles. The growth patterns of the isolates in BAP medium were simi lar. All showed a lag phase of approximately 6-7 days, then exhibited a logarithmic phase, except the ReI4 strain which seems to follow a li near growth pattern. A common feature of all the strains was a rapid l oss of biomass at the end of the growth phase. All native strains grew on BAP medium supplemented with glucose. In six out of nine strains, the glucose was the best of the carbon sources tested. However, the st rains differed in their ability to use other carbon sources such as ar abinose, mannitol, maltose, succinate, sucrose, pyruvate, propionate a nd galactose. The isolates were sensitive to six antibiotics assayed ( ampicillin, penicillin G, rifampicin, chloramphenicol, erythromycin an d kanamycin). Using the acetylene reduction assay, the nitrogenase act ivity of the strains was determined. All strains grown in BAP medium l acking a combined nitrogen source were able to reduce acetylene 'in vi tro'.