Booth J L, Vishniac H S
Can J Microbiol. 1987 May;33(5):396-404. doi: 10.1139/m87-069.
When urease production was assayed by the hydrolysis of [14C]urea, all basidiomycetous yeasts tested, including the Cryptococcus vishniacii complex (previously reported urease negative), produced significant amounts of 14CO2. The Schizosaccharomycetaceae were the only urease-positive ascomycetous yeasts tested. Yarrowia lipolytica was urease negative. The stoichiometry of [14C]urea hydrolysis paralleled by Roberts' rapid urea hydrolysis (RUH) test indicated that causes of anomalous results in conventional urease testing include acidification and alkalinization of the test medium by products of endogenous metabolism and autolysis rather than urease activity. Anomalous results also occurred when cells were grown on media containing the chelating agent ethylenediaminetetraacetic acid (EDTA) prior to RUH. The addition of EDTA to a complex natural medium inhibited urease production in all yeasts reportedly growing at 35 degrees C (and all other yeasts tested), except Filobasidiella (Cr.) neoformans var. neoformans (NIH 12). The RUH test could differentiate at the varietal level: Fil. (Cr.) neoformans var. neoformans was about 10 times more resistant to EDTA in media used for the growth of cells prior to RUH testing than was Fil. neoformans var. bacillispora (Cr. neoformans var. gattii) (NIH 191). Urease production by Fil. neoformans var. bacillispora was specifically restored to half maximal activity by the addition of 22 microM Ni+2 (as NiCl2) to a growth medium containing 0.100 mM EDTA.
当通过[¹⁴C]尿素水解来测定脲酶产生时，所有测试的担子菌酵母，包括新型隐球菌复合体（先前报道为脲酶阴性），都产生了大量的¹⁴CO₂。裂殖酵母科是唯一测试的脲酶阳性子囊菌酵母。解脂耶氏酵母脲酶阴性。[¹⁴C]尿素水解的化学计量与罗伯茨快速尿素水解（RUH）试验平行，表明传统脲酶测试中异常结果的原因包括内源性代谢和自溶产物对测试培养基的酸化和碱化，而非脲酶活性。当细胞在RUH试验前在含有螯合剂乙二胺四乙酸（EDTA）的培养基上生长时，也会出现异常结果。向复杂天然培养基中添加EDTA可抑制据报道在35℃生长的所有酵母（以及所有其他测试酵母）中的脲酶产生，但新型隐球菌新生变种（NIH 12）除外。RUH试验可在变种水平上进行区分：在用于RUH试验前细胞生长培养基中，新型隐球菌新生变种对EDTA的抗性比新型隐球菌芽孢变种（新型隐球菌加蒂变种）（NIH 191）高约10倍。向含有0.100 mM EDTA的生长培养基中添加22 μM Ni⁺²（以NiCl₂形式）可使新型隐球菌芽孢变种的脲酶产生特异性恢复至最大活性的一半。
