Rhizobia are bacteria that can fixate atmospheric nitrogen in association within the root or the stem nodules of legume plants and transform atmospheric nitrogen to ammonia. Soil environmental conditions are critical factors for the persistence and survival of rhizobia in the soil. The changes in the rhizosphere environment can affect both growth and saprophytic competence, which will influence competitiveness and persistence. Environmental stress imposes a major threat to symbiotic nitrogen fixation and agriculture that can be limited by soil and climatic factors such as salinity, drought, temperature, acidity/alkalinity and heavy metals. In this review we present several different mechanisms in rhizobia adaptation under stress factors.