SELECTIVE RECOVERY OF STREPTOSPORANGIUM FRAGILE FROM SOIL BY INDIRECTIMMUNOMAGNETIC CAPTURE

A polyclonal antibody raised to Streptosporangium fragile spores react ed strongly and specifically with the immunizing strain and to a numbe r of related species of Streptosporangium, as determined by dot immuno blotting. An indirect immunomagnetic capture method was developed for the recovery of the target organism from sterile and non-sterile soil, using sheep anti-rabbit M-280 Dynabeads. The effects of different soi l blocking agents, antibody labelling concentrations and spore/Dynabea d capture times on the recovery of S. fragile spores were investigated . Pre-blocking of antibody binding sites within the soil, with either 2% partially hydrolysed gelatin or 10% skimmed milk, was essential pri or to immunomagnetic capture, Increasing the capture time from 15 to 6 0 min did not affect spore recovery; however, a 10-fold decline in the magnetic bead concentration did result in a significantly lower recov ery of spores from soil. S, fragile was selectively enriched (1:190-fo ld) when present as a mixed population with Arthrobacter oxydans in st erile soil. The indirect immunomagnetic capture method was used to sel ectively recover S. fragile spores seeded into non-sterile soil, altho ugh some background binding of non-target bacteria was noted. The targ et was successfully recovered from a sterile soil microcosm after 14 d incubation and the capture rate was increased by the inclusion of an initial soil dispersion and biomass concentration procedure, using the ion-exchange resin Chelex 100.