Streptococcus thermophilus is able to produce a beta-galactosidase active during its transit in the digestive tract of germ-free mice.

This work presents data on the application of a bacterial luciferase used to monitor gene expression of Streptococcus thermophilus in the digestive tract. The main result is that the bacterium was able to produce an active beta-galactosidase in the digestive tract, although it did not multiply during its transit. This production was enhanced when lactose (the inducer) was added to the diet.