Waterman Scott R, Small P L C
Division of Human Immunology, Hanson Institute, Institute of Medical and Veterinary Science, Adelaide, South Australia, 5000, Australia.
J Bacteriol. 2003 Aug;185(15):4644-7. doi: 10.1128/JB.185.15.4644-4647.2003.
Resistance to being killed by acidic environments with pH values lower than 3 is an important feature of both pathogenic and nonpathogenic Escherichia coli. The most potent E. coli acid resistance system utilizes two isoforms of glutamate decarboxylase encoded by gadA and gadB and a putative glutamate:gamma-aminobutyric acid antiporter encoded by gadC. The gad system is controlled by two repressors (H-NS and CRP), one activator (GadX), one repressor-activator (GadW), and two sigma factors (sigma(S) and sigma(70)). In contrast to results of previous reports, we demonstrate that gad transcription can be detected in an hns rpoS mutant strain of E. coli K-12, indicating that gad promoters can be initiated by sigma(70) in the absence of H-NS.
对pH值低于3的酸性环境具有抗性是致病性和非致病性大肠杆菌的一个重要特征。最有效的大肠杆菌酸抗性系统利用由gadA和gadB编码的两种谷氨酸脱羧酶同工型，以及由gadC编码的一种假定的谷氨酸：γ-氨基丁酸反向转运体。gad系统由两个阻遏物（H-NS和CRP）、一个激活剂（GadX）、一个阻遏物-激活剂（GadW）和两个σ因子（σ(S)和σ(70)）控制。与之前报道的结果相反，我们证明在大肠杆菌K-12的hns rpoS突变株中可以检测到gad转录，这表明在没有H-NS的情况下，gad启动子可以由σ(70)启动。
