Researchers have conducted studies that reveal that reveal that small animals are emerging as the largest source of producing complex peptides. These complex peptides, which are cyclized, methylated, or contain D-amino acids and organic groups, such as dihydroxyl benzoate, can keep synthetic chemists in making efforts at developing artificial peptides. It has also been observed that microbes make these peptides, using nonribosomal peptide synthetase (NRPS) enzymes. Most of the peptides produced through NRPS are potential antibiotics, such as penicillin and vancomycin, which microbes use against each other in biological warfare. Researchers have also found that microbes use NRPS enzymes to make these complex peptides. The largest NRPS comes from a fungus that produces the antibiotic cyclosporin, using 11 catalytic modules.