A polynucleotide comprising any one of the following nucleotide sequences: (i) a nucleotide sequence encoding a polylysine synthetase consisting of the amino acid sequence of SEQ ID NO: 2; (ii) a nucleotide sequence encoding a polylysine synthetase consisting of an amino acid sequence having at least 70% identity to the amino acid sequence of SEQ ID NO: 2; (iii) the nucleotide sequence of SEQ ID NO: 1; (iv) a nucleotide sequence encoding a polylysine synthetase, which can hybridize to a nucleotide sequence complementary to the nucleotide sequence of SEQ ID NO: 1 under highly stringent hybridization conditions (5 × SSC; 5 × Denhart solution; 0.5% (w/v) SDS; 50% (w/v) formamide; and 50°C); (v) a nucleotide sequence encoding a polylysine synthetase, which has at least 65% identity to the nucleotide sequence of SEQ ID NO: 1; (vi) a nucleotide sequence encoding a condensation reaction catalytic domain or a subdomain thereof of a polylysine synthetase, wherein said condensation reaction catalytic domain consists of the amino acid sequence of SEQ ID NO: 13, 15, 17 or 19; (vii) a nucleotide sequence encoding a condensation reaction catalytic domain or a subdomain thereof of a polylysine synthetase, wherein said condensation reaction catalytic domain consists of an amino acid sequence having at least 65%, 70%, 80%, or 75% identity, respectively, to the amino acid sequence of SEQ ID NO: 13, 15, 17 or 19; (viii) the nucleotide sequence of SEQ ID NO: 12, 14, 16 or 18; (ix) a nucleotide sequence encoding a condensation reaction catalytic domain or a subdomain thereof of a polylysine synthetase, wherein said nucleotide sequence can hybridize to a nucleotide sequence complementary to the nucleotide sequence of SEQ ID NO: 12, 14, 16 or 18 under highly stringent hybridization conditions (5 × SSC; 5 × Denhart solution; 0.5% (w/v) SDS; 50% (w/v) formamide; and 50 °C); and (x) a nucleotide sequence encoding a condensation reaction catalytic domain or a subdomain thereof of a polylysine synthetase, wherein said nucleotide sequence has at least 65%, 75%, 80%, or 80% identity, respectively, to the nucleotide sequence of SEQ ID NO: 12, 14, 16 or 18. (i) a nucleotide sequence encoding a polylysine synthetase consisting of the amino acid sequence of SEQ ID NO: 2; (ii) a nucleotide sequence encoding a polylysine synthetase consisting of an amino acid sequence having at least 70% identity to the amino acid sequence of SEQ ID NO: 2; (iii) the nucleotide sequence of SEQ ID NO: 1; (iv) a nucleotide sequence encoding a polylysine synthetase, which can hybridize to a nucleotide sequence complementary to the nucleotide sequence of SEQ ID NO: 1 under highly stringent hybridization conditions (5 × SSC; 5 × Denhart solution; 0.5% (w/v) SDS; 50% (w/v) formamide; and 50°C); (v) a nucleotide sequence encoding a polylysine synthetase, which has at least 65% identity to the nucleotide sequence of SEQ ID NO: 1; (vi) a nucleotide sequence encoding a condensation reaction catalytic domain or a subdomain thereof of a polylysine synthetase, wherein said condensation reaction catalytic domain consists of the amino acid sequence of SEQ ID NO: 13, 15, 17 or 19; (vii) a nucleotide sequence encoding a condensation reaction catalytic domain or a subdomain thereof of a polylysine synthetase, wherein said condensation reaction catalytic domain consists of an amino acid sequence having at least 65%, 70%, 80%, or 75% identity, respectively, to the amino acid sequence of SEQ ID NO: 13, 15, 17 or 19; (viii) the nucleotide sequence of SEQ ID NO: 12, 14, 16 or 18; (ix) a nucleotide sequence encoding a condensation reaction catalytic domain or a subdomain thereof of a polylysine synthetase, wherein said nucleotide sequence can hybridize to a nucleotide sequence complementary to the nucleotide sequence of SEQ ID NO: 12, 14, 16 or 18 under highly stringent hybridization conditions (5 × SSC; 5 × Denhart solution; 0.5% (w/v) SDS; 50% (w/v) formamide; and 50 °C); and (x) a nucleotide sequence encoding a condensation reaction catalytic domain or a subdomain thereof of a polylysine synthetase, wherein said nucleotide sequence has at least 65%, 75%, 80%, or 80% identity, respectively, to the nucleotide sequence of SEQ ID NO: 12, 14, 16 or 18.