HELICOBACTER-PYLORI REQUIRES AN ACIDIC ENVIRONMENT TO SURVIVE IN THE PRESENCE OF UREA
HELICOBACTER-PYLORI REQUIRES AN ACIDIC ENVIRONMENT TO SURVIVE IN THE PRESENCE OF UREA
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DOI：
10.1128/iai.63.5.1669-1673.1995
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发表时间：
1995-05-01
影响因子：
3.1
通讯作者：
DRUMM, B
中科院分区：
文献类型：
--
作者：
CLYNE, M;LABIGNE, A;DRUMM, B
本研究的目的是研究脲酶在不同环境下促进幽门螺杆菌存活的意义，将一株脲酶阳性的幽门螺杆菌分离株N6和一株等基因脲酶阴性的菌株N6（ureB::TnKm）在pH为2.2至7.2的磷酸盐缓冲盐水中，在37℃下，在存在和不存在10 mM尿素的情况下培养60分钟。测量了每种溶液中每毫升CFU的数量、细菌上清液的pH值和溶液中氨的含量。幽门螺杆菌N6在无尿素条件下pH值为4.5 ~ 7.0的溶液中存活良好，但在有尿素条件下pH值低于3.5的溶液中存活。当存在野生型菌株和尿素时，酸性溶液（即3.5）的pH值迅速上升到8.45。无论尿素是否存在，尿素阴性突变体在pH值为4.5至7.2的溶液中都能存活。当幽门螺杆菌N6在尿素存在下孵育时，氨的含量显著增加。菌株N6暴露于浓度高达80毫米的氨中存活。胃中的酸性环境可能对幽门螺杆菌在尿素存在下的存活至关重要。幽门螺杆菌在尿素存在的正常环境中不能存活，因为随后的pH值升高而不是氨毒性。
The aim of this work was to study the significance of the urease enzyme in promoting Helicobacter pylori survival in various environments, A urease-positive H, pylori isolate, strain N6, and an isogenic urease-negative strain, strain N6(ureB::TnKm), were incubated in phosphate-buffered saline at a pH ranging from 2.2 to 7.2 for 60 min at 37 degrees C in both the presence and the absence of 10 mM urea. Tbe number of CFU per milliliter in each solution, the pH of the bacterial supernatant, and the amounts of ammonia present in the solutions were measured. H. pylori N6 survived well in solutions with pH values ranging from 4.5 to 7.0 in the absence of urea but survived in solutions only with an initial pH below 3.5 in the presence of urea, Neither strain grew after incubation in an alkaline environment. The pH of an acidic solution (i.e., 3.5) rose rapidly to 8.45 in the presence of the wild-type strain and urea. The urease-negative mutant survived in solutions with pH values ranging from 4.5 to 7.2 irrespective of the presence of urea, Ammonia was present in significant amounts when H. pylori N6 was incubated in the presence of urea. Strain N6 survived exposure to concentrations of ammonia as high as 80 mM. The acid environment of the stomach may be crucial for H. pylori survival in the presence of urea. H. pylori does not survive in the normal environment in the presence of urea because of the subsequent rise in pH rather than ammonia toxicity.