Identification of linear plasmid pAM1 in the flavonoid degrading strain Actinoplanes missouriensisT (DSM 43046)

By pulsed-field gel electrophoresis, a linear DNA element of about 100 kb was identified in Actinoplanes missouriensisT DSM 43046, which grows on the flavonoids hesperidin, rutin and quercetin, and which contains a CO forming quercetinase. Among six Actinoplanes species and strains tested, including A. globisporusT DSM 43857, A. philippinensisT DSM 43019, A. brasiliensisT DSM 43805, A. auranticolorT DSM 43031, and A. utahensisT DSM 43147, only the A. missouriensis strain exhibited such a genetic element. The linear plasmid, named pAM1, has proteins covalently attached to its 5′-ends like other linear replicons of actinomycetes. Attempts to cure pAM1 failed, however a mutant with reduced plasmid content was obtained, which showed reduced ability to degrade the flavonoid rutinosides rutin and hesperidin. Plasmid pAM1 is the first extrachromosomal genetic element identified in an Actinoplanes species and may be useful to develop genetic tools for biotechnologically important Actinoplanes strains.