Aeromonas hydrophila

Department of Biology, University of Alabama a t Birmingham, Birmingham, AL 35294-1 170, USA Aeromonas hydrophila, a gastrointestinal pathogen of humans, was shown to exhibit a significant adaptive acid tolerance response (ATR) capable of protecting cells from severe acid at a pH of 3.5. The ATR was induced by exposure to a relatively mild pH level of 5-0 for 20 min. Adaptation required protein Synthesis since treatment with chloramphenicol during adaptation to pH 5-0 prevented the development of acid tolerance. The adaptation to acid environment was found to be a non-transient phenomenon. Also, iron was not required for acid adaptation in A. hydrophila. Two-dimensional protein analyses revealed an increased production of 28 proteins and decreased synthesis of 10 following pH shifts from 7.2 t o 5.0. The mild pH treatment must act as a signal t o A. hydrophila t o adapt and survive in acid environments by producing ‘protective proteins. The adaptation and survival of th is pathogen in low pH may provide valuable information about i t s ability t o withstand acid environments in nature and in the human gastrointestinal tract.