CHARACTERIZATION OF POLYAMINE SYNTHESIS PATHWAY IN BACILLUS-SUBTILIS-168

The ubiquitous polyamines fulfil a variety of functions in all three k ingdoms of life. However, little is known about the biosynthesis of th ese compounds in Grampositive bacteria. We show that, in Bacillus subt ilis, there is a single pathway to polyamines, starting from arginine, with agmatine as an intermediate. We first identified the structural gene of arginine decarboxylase, speA (formerly cad), and then describe d the speE speB operon, directing synthesis of spermidine synthase and agmatinase. This operon is transcribed into two messenger RNAs, a maj or one for the speE gene and a minor one for both speE and speB, The p romoter of the operon was identified upstream from the speE gene by pr imer extension analysis. Transcription of this operon indicated that t he level of agmatinase synthesis is very low, thus allowing a stringen t control on the synthesis of putrescine and, therefore, of all polyam ines. This is consistent with the level of polyamines measured in the cell.