Nutrition and physiology of denitrifying bacteria

Summary The size of both the denitrifying and the total bacterial population was found to be positively correlated with soil pH, but the denitrifying bacteria were more sensitive to acid environments than the bacterial microflora as a whole. The ecological evidence for a pH effect was supported by studies with individual pure cultures. The estimate of abundance of denitrifying micro-organisms was also affected markedly by the composition of the medium, and an improved medium has been proposed.Marked differences were noted in the nutrition of the bacteria capable of N₂ production. In the absence of oxygen, certain strains developed readily using nitrate as the terminal electron acceptor for growth in media with no preformed growth factors, but others required ammonium or growth factors for denitrification to occur.The investigation was supported in part by funds provided by the Sun Oil Company and Cooperative Regional Research Project NE-39. Present address of senior author: Department of Soils, College of Agriculture, University of Phillippines. A gronomy Paper No. 528.