Nitrogen Fixation in Extracts of Azotobacter vinelandii

Abstract

IT is well established that soil micro-organisms, including species of Azotobacter and Clostridia, fix atmospheric nitrogen. Although several attempts have been made to demonstrate the incorporation of nitrogen-15 into extracts of these micro-organisms the results at best have been variable and of doubtful significance¹. Protoplasts, prepared from Azotobacter by careful lysis of the cells with lysozyme, incorporated only small amounts of nitrogen-15, namely, an enrichment of 0.04 atom per cent excess². We have recently succeeded in preparing cell-free extracts from Azotobacter vinelandii, either by treating the cells with lysozyme or with the ultrasonic probe, which will incorporate nitrogen-15 at a measurable rate. The cells must, however, be disrupted in the culture medium in which they were grown.