Phosphate-solubilizing bacteria associated with proteoid roots of seedlings of waratah [Telopea speciosissima (Sm.) R.Br.].

Bacteria isolated from proteoid roots and non-proteoid lateral roots of Telopea speciosissima (Sm.) R.Br. seedlings were able to acidify the medium and solubilize calcium phosphates when grown in culture in the presence of ammonium salts and an appropriate carbon source. In general this activity was not detected when NO was substituted for NH , and it is proposed that protons were secreted in exchange for ammonium ions. Cation exchange between these protons and calcium in the medium is a possible cause of the calcium phosphate solubilizing activity. The relevance of these data to phosphate-solubilizing activity in natural environments is discussed.