Survival and potential denitrifying activity of Azospirillum lipoferum and Bradyrhizobium japonicum inoculated into sterilized soil

Summary Potential denitrifying activity and population dynamics of Azospirillum lipoferum (137C) and Bradyrhizobium japonicum (G2sp) inoculated into a -sterilized soil were studied for a period of 3 weeks. The denitrifying enzyme potential of soil inoculated independently with each bacterial species was strongly stimulated by the presence of a plant (Zea mays L.). Simultaneous inoculation of both bacteria also produced a higher denitrifying enzyme potential than simple inoculation. Even with double inoculation, the presence of a plant did not modify the evolution of the activity. The response of the population dynamics to these treatments followed a different pattern. The population dynamics of A. lipoferum was not affected by the presence of the plant or by the presence of B. japonicum. In contrast, the presence of both a plant and of A. lipoferum seemed to promote the growth of B. japonicum.