The effect of growth and urea concentration on ammonia production by a urea-hydrolysing mycoplasma (Ureaplasma urealyticum).

The rate of accumulation of ammonium ion in cultures of Ureaplasma urealyticum was independent of the growth rate and of the initial urea concentration above 0-025% in the medium, although the quantity of ammonium ion accumulating did depend on the initial urea concentration. Ammonium ions accumulated at a similar rate in U. urealyticum cultures of both rapidly and slowly growing organisms. Viable but non-growing ureaplasmas also produced ammonia in complete medium at a lower temperature than usual (25 degrees C) or in an inadequate growth medium at 37 degrees C. The rate of ammonium ion accumulation in a dying culture depended on the number of viable organisms present; this is relevant to diagnostic methods for ureaplasms which depend on detecting ammonia colorimetrically.