固氮球形芽孢杆菌与巨大芽孢杆菌的混合增效作用

球形芽孢杆菌Bs7与巨大芽孢杆菌Bm1 0 1混合培养时具有固氮增效作用。稀释 40 0倍的巨大芽孢杆菌的无菌上清液与球形芽孢杆菌共培养 ,同样能增强后者的固氮活性。Bs7(pAB5 76 )在纯培养时的nifA表达活性为 6 849 5Miller单位 ,与巨大芽孢杆菌上清培养液进行混合培养时的表达活性为 75 0 0 4Miller单位。上述结果表明 :某些微量非碳源的活性分泌物和某些固氮调节基因可能在固氮增效作用中起重要作用。在与水稻联合培养条件下 ,混合接种球形芽孢杆菌与巨大芽孢杆菌可以提高固氮菌在水稻根表的定殖能力

THE ENHANCED EFFECT OF CO|CULTURE ON NITROGEN|FIXING ACTIVITY OF B.sphaerium AND B.megaterium

The enhanced effect of B.sphaerium Bs7 co-cultured with B.megaterium Bm101 on nitrogen-fixing activity was observed.The cell-free supernatant from pure cuture of Bm101,which was diluted 400 times,could enhance the nitrogen-fixing activity of Bs7.The expressional activities of nifA-lacZ transcriptional gene in Bs7 was increased obviously during co-culture of Bs7 and Bm101.The enhanced effect on nitrogen-fixing activity is not only associated with metabolism,but also with some bioactive materials or some regulatory genes,which may play important roles in enhancing nitrogen-fixing activity of co-culture.Co-inoculation of Bs7 and Bm101 could stimulate colonization of both bacteria to rice roots.