An isolated polynucleotide containing a polynucleotide sequence selected from the group a) polynucleotide which is at least 70% identical to a polynucleotide which codes for a polypeptide containing the amino acid sequence of SEQ ID no. 2, b) polynucleotide which codes for a polypeptide which contains an amino acid sequence which is at least 70% identical to the amino acid sequence of SEQ ID no. 2, c) polynucleotide which is complementary to the polynucleotides of a) or b) and d) polynucleotide containing at least 15 successive bases of the polynucleotide sequence of a), b) or c), and a process for the fermentative production of L-amino acids by attenuation of the poxB gene.