Urease activity in the genus Bifidobacterium.

The urease activity of 414 strains representing 21 species of the genus Bifidobacterium was surveyed. The strongest ureolytic strains belong mostly to the species B. suis and only a few to B. breve, B. magnum and "subtile" homology group. The study of some strongly ureolytic strains showed that urea and organic nitrogen concentration did not influence urease production. The high urease activity found also in the absence of urea suggested that this enzyme is not inducible. An ammonia concentration of 14 mM did not repress urease activity.