Kulakov Y K, Guigue-Talet P G, Ramuz M R, O'Callaghan D
Institut National de la Santé et de la Recherche Médicale, Unité 431, Faculté de Médecine, Nîmes, France.
Res Microbiol. 1997 Feb;148(2):145-51. doi: 10.1016/S0923-2508(97)87645-0.
Acid pH is an environmental stress often encountered by Brucella during both the "environmental" and the "pathogenic" stages of its life. We have investigated the behaviour of B. suis biovar 1 and B. canis in acid conditions. Growth at suboptimal pH was characterized by a dramatic reduction in growth yield due to an early onset of stationary phase. B. suis was more resistant to low pH than B. canis, which lysed at pH 4.6. Viable counts measured after a 4-h acid shock at pH 3.2 showed that the relative survival of B. suis was 1,000-fold greater than that of B. canis. An adaptive acid tolerance response (ATR) was induced in both species by culture at pH 5.8; however, while the acid-sensitive B. canis had more than a 2,000-fold increase in survival following acid shock at pH 3.2, the increase in survival of B. suis was only around 50-fold. The kinetics of the induction of ATR were followed: for B. suis, 1-2 h (1 generation) at pH 5.8 were required to induce acid tolerance (50-fold protection), and these levels remained constant over 24 h. B. canis became relatively acid-resistant after only 30-min exposure to pH 5.8. Levels of acid tolerance continued to increase and were maximal at 24 h. Stationary phase pH 7.2 cultures of either species did not exhibit acid resistance, suggesting that, like Salmonella, Brucella does not have an rpoS-controlled stationary phase acid resistance.
酸性pH值是布鲁氏菌在其生活的“环境”和“致病”阶段经常遇到的一种环境压力。我们研究了猪布鲁氏菌生物变种1和犬布鲁氏菌在酸性条件下的行为。在次优pH值下生长的特征是由于稳定期提前开始，生长产量急剧下降。猪布鲁氏菌比犬布鲁氏菌对低pH值更具抗性，犬布鲁氏菌在pH 4.6时会裂解。在pH 3.2下进行4小时酸冲击后测得的活菌数表明，猪布鲁氏菌的相对存活率比犬布鲁氏菌高1000倍。通过在pH 5.8下培养，两种菌都诱导出了适应性耐酸反应（ATR）；然而，虽然对酸敏感的犬布鲁氏菌在pH 3.2酸冲击后的存活率增加了2000倍以上，但猪布鲁氏菌的存活率仅增加了约50倍。跟踪了ATR诱导的动力学：对于猪布鲁氏菌，在pH 5.8下需要1-2小时（1代）来诱导耐酸性（50倍保护），并且这些水平在24小时内保持恒定。犬布鲁氏菌仅在暴露于pH 5.8 30分钟后就变得相对耐酸。耐酸水平持续增加，并在24小时时达到最大值。两种菌在稳定期pH 7.2培养时均未表现出耐酸性，这表明，与沙门氏菌一样，布鲁氏菌没有受rpoS控制的稳定期耐酸性。
