ADAPTIVE ACID TOLERANCE RESPONSE (ATR) IN AEROMONAS-HYDROPHILA

Aeromonas hydrophila, a gastrointestinal pathogen of humans. was strew n to exhibit a significant adaptive acid tolerance response (ATR) capa ble of protecting cells from severe acid at a ph of 3.5. The ATR was i nduced by exposure to a relatively mild ph level of 5.0 for 20 min. Ad aptation required protein synthesis since treatment with chloramphenic ol during adaptation to ph 5.0 prevented the development of acid toler ance. The adaptation to acid environment was found to be a non-transie nt phenomenon. Also, iron was not required for acid adaptation in A. h ydrophila. Two-dimensional protein analyses revealed an increased prod uction of 28 proteins and decreased synthesis of 10 following ph shift s from 7.2 to 5.0. The mild ph treatment must act as a signal to A. hy drophila to adapt and survive in acid environments by producing 'prote ctive' proteins. The adaptation and survival of this pathogen in low p h may provide valuable information about its ability to withstand acid environments in nature and in the human gastrointestinal tract.