Most bacteria of medical interest grow and develop at pH values around neutrality (pH 7). However, many of these bacteria are also capable of maintaining themselves for long periods of time in acidic environments. The same goes for bacteria that thrive in the environment. Such is the case of some rhizobial bacteria associated with plants, where the acidic pH of the soil could represent a limiting aspect of their growth, however this is not the case because these bacteria can grow at low pH. These bacteria have different mechanisms to survive in acidic environments, which are presented in a general way in this work.