Effects of low-pH stress on the morphology and activity of bacteria from lakes receiving acid precipitation

Field and laboratory studies on the effects of low-pH stress are reported here for lacustrine bacteria. Two biochemical parameters, respiration and substrate utilization, reveal a marked decrease under severe low-pH stress. Bacterial ultrastructure and cell diversity can be correlated with a given level of pH. Structural changes in the cell envelope as a function of pH are highlighted. The biochemical, physiological and morphological observations are united into a hypothesis which seeks to relate cell adaptation to environmental stress.