NOVEL ANTIBACTERIAL PEPTIDES ISOLATED FROM A EUROPEAN BUMBLEBEE, BOMBUS-PASCUORUM (HYMENOPTERA, APOIDEA)

We present here the isolation and characterization of four antimicrobi al peptides produced by a European bumblebee Bombus pascuorum. A 51-re sidue insect defensin was characterized which, like the Apis mellifera defensins, had a highly conserved 12-residue extension to its C-termi nal compared to defensins from other insects, Monoisotopic mass analys is of the C-terminal of B. pascuorum defensin confirmed that this mole cule was C-terminally amidated, This defensin showed strong anti-Gram- positive activity and some anti-fungal activity; also, in contrast to other insect defensins, it showed anti-Gram-negative activity, A 17-re sidue apidaecin was characterized, showing anti-Gram-negative activity , and differing by a single amino acid substitution from the A, mellif era apidaecin, A 39-residue abaecin was isolated, the largest proline- rich antimicrobial peptide characterized to date, which showed activit y against both Gram-negative and Gram-positive bacteria, Finally, we i solated an N-terminally blocked molecule, with a molecular mass of 10, 122 Da, which showed activity against Gramnegative bacteria only, Thes e characteristics are reminiscent of hymenoptaecin from the honeybee A , mellifera, but a definitive characterization of this molecule awaits further work, No evidence of lysozyme activity was found in the haemo lymph of challenged or naive B. pascuorum. (C) 1997 Elsevier Science L td.