Characterisation of different polyclonal antisera to quantify Herbaspirillum spp. in elephant grass (Pennisetum purpureum Schun.)

Immunological techniques can be applied to detect micro-organisms in differ ent ecosystems. To follow the fate of Herbaspirillum seropedicae strain Z67 and H. rubrisubalbicans strain M4 in the rhizosphere of elephant grass, Pe nnisetum purpureum Schun, var. Capim Coma D'Africa, polyclonal antisera wer e raised against both strains. Both antisera were purified with protein-A, followed by a primary characterisation for cross-reactivity. To reduce cros s-reactivity for both sera, affinity purification was used for improvement. After that, both sera could be considered as species specific. The detecti on limit was 10(5) cells ml(-1) for the anti H. rubrisubalbicans serum and 10(6) cells ml(-1) for the anti H, seropedicae serum. It was shown that two months after inoculation, both strains could be detected in the rhizoplane of elephant grass in high densities. The estimated numbers by ELISA were 1 0(7) cells g(-1) fresh weight.