Adenylation domains (AD) of nonribosomal peptide synthetases (NRPS) are responsible for substrate selection and activation in biosynthesis of many bioactive natural products. In this study we designed an alternative oligonucleotide primer set, which enables to extend the coverage of AD sequence abundance in analyzed samples in addition to the widely used A3F/A7R primers. In contast to A3F/A7R pair the new primers were designed according to amino acid sequence alignment. The amino acid sequences of 28 selected actinomycetal ADs from 20 various biosynthetic gene clusters were employed. The newly designed primers, as well as known A3F/A7R pair, were compared in 454 pyrosequencing analysis of AD sequences in two sets of actinomycete strains from highly dissimilar environments: marine subseafloor sediments, collected during the Integrated Ocean Drilling Program, and a forest soil. Annotation and statistical analysis of obtained sequences revealed that the total number and diversity of identified ADs were noticeably extended using newly designed primers.