Nitrogen Fixation by Soil Yeasts

Abstract

SINCE the discovery by Starkey and De¹ of the soil bacterium Azotobacter indicum, which is capable of fixing atmospheric nitrogen under acid conditions, many unsuccessful attempts have been made to isolate this species from acid soils in western Europe. In one such attempt, preliminary experiments had suggested that the soil of a Betula–Calluna heath in Kent contained organisms able to fix atmospheric nitrogen, but attempts to isolate these organisms by the ‘still culture’ enrichment method failed. This method is not suited to the isolation of organisms present in acid soil in very small numbers: for such organisms continuous perfusion of a large volume of soil with selective media is a far superior method.