Possible involvement of plasmids in biosynthesis of neomycin.

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been possible due to insufficient reproducibility of banding in CsC1-ethidium bromide gradient centrifugation (Zippel, unpublished).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.…”

Mutants blocked in streptomycin production in Streptomyces griseus - the role of A-factor.

“…8,[12][13][14][15][16][17][18][19][20] Treatment of streptomycetes with acridine dyes or at high temperature frequently causes loss of various phenotypic characters with coincidental disappearance of plasmids. In S. coelicolor A3(2), the direct involvement of plasmids in the production of methylenomycin A (SCP1 plasmid) 21,22) and streptocin A, B and amrumycin (SCP2 plasmid)23) has been confirmed.…”

Accumulation of Diphosphorylated Butirosin A Derivatives by Phosphatase-negative Mutants ofBacillus vitellinus

“…Alternatively, it seems possible that phosphatase-negative mutation may accelerate the segregation into idiotrophs by some unknown mechanisms. A presumed mflchanism is that the biosynthesis of 2-DS is mediated by a plasmid(s) in B. vitellin us as discussed for other aminoglycoside antibiotic producers, [32][33][34][35] and the maintenance may become unstable with the phosphatase-negative mutation.…”