Indiana poi is, I n diana 46285, USA Saccharopolyspora spinosa protoplasts were not transformable by several different streptomycete plasmids, and S. spinosa was not a host for plaque formation by the Saccharopolyspora bacteriophages 4SE6,4SE45, 4SE57, 4SE60, 4SE69 or HP10. Extracts of S. spinosa contained DNA-modifying activities that blocked cleavage of plasmid DNA by Nael and Sall, and partially blocked cleavage by Ncol. Plasmid pOJ434, a derivative of the 5. spinosa plasmid pSAS1, was modified in vitro by incubation with an extract of S. spinosa to circumvent restriction. Under optimal conditions, 5. spinosa protoplasts were transformed to apramycin resistance by modified pOJ434 at frequencies of about lo4 per pg of DNA. Transformants contained pOJ434 primarily integrated in the chromosome.