水稻根系分离菌泌氨菌株的筛选试验

本试验采用Burris推荐的氨微量扩散法,从309个水稻根系分离菌株中筛选具有泌氨特性的固氮菌自然突变菌株。初步试验结果表明,培养基以含氮较低的每升加0.1克酵母膏的慢型快长培养基较为适宜。供试菌株中大部分没有泌氨作用,并能消耗培养基中的氮源。发现维涅兰德固氮菌230(Azotobacter uinelandii)菌株的泌氨作用较强,其泌氨量为固氮量的2.05％。该菌在以前的长期试验中尚未注意到有泌氨特性。属于德氏固氮菌属(Derxia)的“卷4”菌株也具有泌氨作用,但固氨量较低,只有固氮量的1.18％。

A SCREENING EXPERIMENT ON STRAINS OF AMMONIA EXCRETING NITROGEN-FIXING BACTERIA ISOLATED FROM RICE ROOTS

Our experiment showed that ammonium microdiffusion apparatus as recommended by Burris in screening the strains of natural mutant among nitrogen-fixing organisms was feasible. The culture media employed with lower nitrogen contents of Ol gram yeast extract per liter seemed preferable Most of the trial 309 strains did not exude ammonia and in contrast consumed the nitrogen source present in the culture media. Azotobacter vinelandii 230 strain functioning as freeliving nitrogen fixation bacteria was found to exude ammonia in larger amounts than any other strains. the quantity of ammonia recorded is 2.05％ of the nitrogen fixed. This was so far not yet found in the reported previous experiments although long search for the problem had been done. In addition, "Juan 4" strain of the Derxia genera possessed the ability of ammonia excreting but with less quantity. The amount of ammonia excreted was only 1.18％ of the total amount of nitrogen-fixed.