Aspergillus fumigatusis an important human fungal pathogen. The Asper-gillus fumigatus genome contains 14 nonribosomal peptide synthetase genes, potentially responsible for generating metabolites that contribute to organismal virulence. Differential expression of the nonribosomal peptide synthetase gene,pes1, in four strains of Aspergillus fumigatuswas observed.