Abstract: Novel microbial peptides called clavanins are of the formulaX'.sub.1 X.sub.2 B'.sub.3 X.sub.4 X.sub.5 U.sub.6 B.sub.7 X.sub.8 X.sub.9 B.sub.10 B.sub.11 X.sub.12 U.sub.13 Z.sub.14 X.sub.15 X.sub.16 B*.sub.17 U.sub.18 X.sub.19 U.sub.20 B.sub.21 X.sub.22 X.sub.23 ( 1)(SEQ ID NO: 1)including the salts, esters, amides and acylated forms thereofwherein X is a hydrophobic amino acid residue or modified form thereof;X' is a small or a hydrophobic amino acid residue or a modified form thereof;B is a basic amino acid residue or modified form thereof;B' is basic or a polar/large amino acid residue or modified form thereof; andB* is a basic or a hydrophobic amino acid residue or a modified form thereof;U is a small amino acid residue or modified form thereof;Z is a polar/large amino acid residue or modified form thereof.