Dermal bacteria in urine take 2 weeks to raise pH to 9.2 by urea hydrolysis, why so long?

In our urine storage studies, it normally takes between 5 days and 3 week to see urea hydrolysis raise the pH to 9.2. Since we measure 10^6cfu/mL after only 2 days, why don't we see urea hydrolysis sooner? Are the bugs just eating organics without synthesizing urease? Our typical initial urea concentration is 7 g-ureaN/L and about 250 mg-TAN/L. I've also noted that we get urea hydrolysis quicker if the samples are subject to a cold temperature daily cycle. Our D.O. measures %26lt;0.1 mg/L after only one day of storage. Is urease synthesis a slow process? What is limiting the rate of urease production? Could it be nickel?

Dermal bacteria in urine take 2 weeks to raise pH to 9.2 by urea hydrolysis, why so long?
urease is a protein. Urease is found in bacteria, yeast and several higher plants.





Characteristics:





Active site metal: nickel(II)


Molecular weight: 480 kDa or 545 kDa for Jack Bean Urease (calculated mass from the amino acid sequence).


Optimum pH: 7.4


Optimum Temperature: 60 degrees Celsius


Enzymatic specificity: urea and hydroxyurea


Inhibitors: heavy metals