CONSTRUCTION OF A BIOTIN-OVERPRODUCING STRAIN OF SERRATIA-MARCESCENS

We have isolated mutants resistant to acidomycin, a biotin analog, fro m Serratia marcescens Sr41. Strain SB304, resistant to 0.5 mg of acido mycin (frequently called actithiazic acid) per ml, produced 5 mg of D- biotin per liter of a medium containing sucrose and urea. Strain SB412 , which was isolated from SB304 on a minimal agar plate containing 2 m g of acidomycin per ml and 0.1 mg of 5-(2-thienyl)-valeric acid per ml , produced 20 mg of D-biotin per ml. The two enzymes related to biotin synthesis were found to be released from biotin-mediated feedback rep ression in these mutants. Transductional analysis revealed that SB412 had acquired at least two mutations, one in the biotin operon locus an d the other in an unknown locus distant from the biotin operon locus.