High frequency transformation of Streptomyces niveus protoplasts by plasmid DNA

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Abstract
H.A. HUSSAIN AND D.A. RITCHIE. 1991. A procedure has been developed for transforming protoplasts of the novobiocin producing strain Streptomyces niveus at high frequency. This required the isolation of strains LH13 and LH20 defective in DNA restriction from the wild type (ATCC 19793) which is transformed at very low frequencies. The LH13 and LH20 derivatives were obtained by curing pIJ702 DNA from the few S. niveus transformed protoplasts obtained by transformation of the wild type with high concentrations of pIJ702 DNA. Protoplasts of S. niveus strains LH13 and LH20 produced about 106 transformants/μg DNA with modified pIJ702 DNA derived by replication in S. niveus. Unmodified DNA (derived from replication in S. lividans) from a series of pIJ101, SCP2 and pSN2‐based derivatives, gave transformation frequencies in the range of 102‐103 transformants/μg DNA. Optimal conditions for the formation and transformation of S. niveus protoplasts are described.