A Linear Plasmid-Like Dna in Streptomyces Sp. Producing Lankacidin Group Antibiotics

Abstract

A linear plasmid-like DNA was isolated by Agarose gel electrophoresis from a lysate of Streptomyces sp. 7434-AN4 which produces lankacidin group antibiotics. The DNA (pSLA2) with a molecular weight of 11.2 x 106 was cleaved into five and three fragments, respectively, with XmaI and BamNI on the definite sites from the end, but not digested by EcoRI and HindIII. Upon treatment of the strain with ethidium bromide, variants were obtained which have lost the ability to produce the antibiotics. These variants were found to have lost pSLA2. These results suggest that the linear plasmid-like DNA is involved in the production of lankacidin group antibiotics.Since the first observation by OKANISHI et al.(1) that plasmids may be involved in the production of kasugamycin and aureothricin, lines of evidence have accumulated on plasmid involvement in antibiotic production (2, 3). These observations are based on genetic analysis (4, 5) or on the loss of antibiotic production by host cells upon treatment with curing agents (1, 6). In several antibiotic-producing Streptomyces species (3, 7, 8), extrachromosomal DNA elements have been found as covalently closed circular (ccc) DNA.We have extended these studies by screening 34 antibiotic-producing strains of Streptomyces for plasmid, in order to obtain further insight into possible involvement of plasmids in antibiotic production. During these processes, we found a linear plasmid-like DNA which may be involved in the production of lankacidin group antibiotics. Results obtained are described in this paper.

Genetic Stability of Differentiated Functions in Streptomyces hygroscopicus in Relation to Conditions of Continuous Culture

“…However, definite identification and physical characterization of this hypothetical plasmid DNA has not yet been possible due to insufficient reproducibility of banding in CsC1-ethidium bromide gradient centrifugation (Zippel, unpublished). Several authors have suggested the involvement of plasmids in genetic and metabolic processes in streptomycetes (see Hopwood, 1978;Akagawa et al, 1979), but evidence by physical characterization of plasmid DNA has been obtained in only a few cases (Kirby & Hopwood, 1977;Okanishi & Umezawa, 1978;Yagisawa et al, 1978;Akagawa et al, 1979;Hayakawa et al, 1979;Omura et al, 1979). Besides plasmid loss, the deletion of chromosomal DNA as a consequence of transposition of transposons or IS elements might also have caused the appearance of non-differentiating derivatives.…”

Giant linear plasmids in Streptomyces: a treasure trove of antibiotic biosynthetic clusters

“…Isolation and characterization of pSLA2-L Hayakawa et al 39 first isolated a linear plasmid pSLA2 from S. rochei 7434AN4, which produces two structurally unrelated polyketide antibiotics, lankacidin and lankamycin (Figure 1). Physical analysis revealed that pSLA2 is 17 kb in size and is structurally similar to adenovirus and bacteriophage f29 DNA; TIRs are present at both ends and a terminal protein is bound to the 5¢ ends.…”

Isolation and partial characterization of a new linear DNA plasmid isolated from Bacillus polymyxa SCE2

“…The linear form is shared with various transposons (Grindley & Reed, 1985), adenoviruses (Tamanoi & Stillman, 1983) and the bacteriophage 429 from Bacillus subtilis (Escarmis & Salas,198 1). Among eubacteria, Streptomyces (Hayakawa et al, 1979;Hirochika & Sakaguchi, 1982;Hirochika et al, 1984;Kinashi et al, 1987;Kinashi & Shimaji-Murayama, 1991), Nocardia (Kalkus et al, 1990) and Borrelia (Barbour & Garon, 1987) seem to be the only genera having strains that harbour linear plasmids, whereas the great majority of plasmids described in other genera are found as covalently closed circular DNA molecules. Many Bacillus strains carry endogenous plasmids, several of which do not express useful or identifiable genetic markers (Lovett & Bramucci, 1975;Tanaka & Koshikawa, 1977;Tanaka & Sakaguchi, 1978;Uozumi et al, 1980;Gryczan, 1982).…”