PSM production in MSA3407 wild-type, psm-mec deletion and psm-mec and fudoh start codon deletion mutants. Culture filtrates from 16-h cultures grown in TSB were analyzed for PSM production by HPLC/MS. Parts of bars with cross stripes represent N-deformylated portions. wt, wild-type strain; Δpsm-mec, psm-mec gene deletion strain; psm-mec*, strain harboring a psm-mec start codon mutation abolishing translation; fudoh*, fudoh (hypothetical) start codon mutation abolishing translation of hypothetical Fudoh protein.