Abstract: A method for increasing the antibiotic-producing ability of an antibiotic-producing microbial host cell is disclosed. The method involves transforming an antibiotic-producing microorganism with a recombinant DNA cloning vector that codes for the expression of an antibiotic biosynthetic enzyme or other gene product. The gene preferably codes for a product that is rate-limiting in the antibiotic biosynthetic pathway in Streptomyces. Plasmids that are useful for increasing tylosin production in accordance with the present method include plasmids pHJL280, pHJL284, pHJL309, pHJL311, and pHJL315. The invention further comprises microorganisms transformed with plasmids pHJL280, pHJL284, pHJL309, pHJL311, and pHJL315 and also other microorganisms and vectors used in accordance with the present method.

Abstract: The present invention provides a method for transforming an actinomycete with an integrating vector which has the advantages of high transformation rates into a broad host range, site-specific integration, and stable maintenance without antibiotic selection. Also provided are methods for the increased production of antibiotics and for the production of hybrid antibiotics.

Abstract: The present invention, utilizing recombinant DNA technology, provides a novel method for obtaining 20-deoxotylosin from a tylosin producing microorganism. 20-deoxotylosin is useful as an antibiotic with a microbial inhibitory activity similar to tylosin.

Abstract: Provided are gene sequences encoding tylosin biosynthetic gene products. In particular, recombinant DNA vectors comprising DNA sequences encoding the tylA, tylB, tylI and tylG activities of Streptomyces fradiae are provided. Also provided are host cells transformed with the noted vectors and a method for increasing the tylosin-producing ability of a tylosin-producing organism.

Abstract: Spiramycin antibiotic biosynthetic genes of Streptomyces ambofaciens are provided by the present invention, in addition to a variety of recombinant DNA vectors. The genes also function in other macrolide producing organisms. The genes can be used to increase or otherwise alter the macrolide antibiotic-producing ability of an organism. The present invention also provides host strains comprising mutant spiramycin biosynthetic genes which can be used to generate novel antibiotics. Also provided is a method for preparing the mutant gene comprising mutating cloned spiramycin biosynthetic DNA by transposon mutagenesis with subsequent transformation into a macrolide-antibiotic producing host and homologous recombination into its genome, to generate stable mutant cell lines.

Abstract: The present invention discloses a method for producing a novel antibiotic, 2"'-O-demethyltylosin. The novel antibiotic, utilizing recombinant DNA technology, can be produced from a transformed mutant of a tylosin producing microorganism. By transforming for example Streptomyces fradiae GS 16 with plasmid pHJL284, the transformant can produce 2"'-O-demethyltylosin. Streytomyces fradiae GS16 is a tylosin producing species that contain a mutation in the tylE gene found in the tylosin biosynthetic pathway. The tylE gene codes for demethylmacrocin 2"'-O-methyltransferase enzyme (DMOMT), the enzyme that methylates the 2-hydroxyl position of the 6-deoxyallose moiety. Plasmid pHJL284 contains the cloned tylF gene which codes for the macrocin 3"'-O-methyltransferase enzxyme (MOMT), the enzyme that methylates the 3"'-hydroxyl position, but it does not contain the tylE gene. Transformation of S.

Abstract: The tlrC gene is a novel tylosin resistance-conferring gene isolated from Streptomyces fradiae and used to construct a number of cloning vectors for use in Streptomyces. One such cloning vector, plasmid pSKC10, can be obtained in S. fradiae JS87 under the accession number NRRL 18072. S. fradiae JS87 is the preferred host when the tlrC gene is used to select tylosin-resistant Streptomyces transformants.