Abstract: Two strains 549 258,which belong to Klebsiella pneumoniae have the ability of producing acids and releasing phosphate.In culture process,549 can produce many kinds of organic acids and improve the effectiveness of mineral phosphate.549 can also use organic phosphate as nutrient.The amount of produced acids in culture medium is limited to a certain level.549,258 can increease the phosphate supply for crops,so some nitrogen-fixing bacteria that can also produce acids have double characters:fixing nitrogen and releasing phosphate.

Key words: Producing acid, Releasing phosphate, Klebsiella pueumouiae