Taurine dioxygenase (tauD)-independent taurine assimilation in Escherichia coli

On the basis of previous studies on taurine assimilation in Escherichia coli, TauD, an iron- and α-ketoglutarate-dependent taurine dioxygenase, has been regarded as an indispensable factor for assimilation. However, we found that tauD-deficient strains did not lose their taurine assimilation ability when there was no deletion of ssuD, which encodes a reduced flavin mononucleotide [FMNH(2)]-dependent alkanesulfonate monooxygenase, which is responsible for the desulfonation of alkanesulfonates. There were no significant differences in lag phase time, growth rate and final growth yield between the tauD-deficient strain and the tauD wild-type strain. Iron increased the growth rate and final growth yield of the ssuD mutant, but not those of the tauD mutant. The double deletion of tauD and ssuD resulted in the loss of the ability to assimilate taurine. When ssuD was artificially expressed in the double-deletion mutant, the mutant recovered its taurine assimilation ability. These findings indicate that there is another taurine assimilation pathway that is dependent on ssuD but independent of tauD.