Among such candidates, rluD gene for pseudouridine synthase of
B. bifidum YIT 4007 was found to have an 8 bp deletion within the
ORF leading to truncation of pseudouridine synthase peptide. All nine
neomycin resistant mutants newly isolated had mutations of rluD
gene, of which six mutants had nonsense mutations or deletions
leading to truncation of the peptide and three had single base changes
leading to alteration of an amino acid. Furthermore, nine mutations
distributed widely along the rluD gene (Table 3). These findings
evidently suggest that neomycin resistance of B. bifidum YIT 4007 is
associated with the loss of the function of rluD gene.