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从水稻根内分离到的菌株2208S2,具有固氮酶活性,革兰氏阴性,细胞杆状,单生,以单端丛生鞭毛运动,细胞两端有聚β-羟基丁酸盐颗粒,不形成孢囊和芽孢.改良培养基上形成乳白色菌落,分泌大量粘稠的粘液.接触酶阳性,马铃薯薯块上生长差,薯块不变色,不还原硝酸盐.15～40.5℃中生长,最适25～30℃;pH 5.16～11.15生长,最适pH 6.98～9.20,DNA中G+C 物质的量百分数为60.1%.经鉴定初步认为菌株2208S2是德氏拜叶林克氏菌(Beijerinckia derxii.)的菌株.“,”Strain 2208S2, a strain isolated from the root of rice with positive nitrogenase activity and negative Gram activity, is straight rod-shaped with lophotrichaete and produces granules of poly-β-hydroxybutyric acid in both cell ends. It produces no xyst or spore. It forms a white colony of bacteria and produces a lot of sticky liquid. It does not grow well on the potato slent thus the colour of the medium remains unchanged. Nitrate is not reduced. The catalase is positive. Strain 2208S2 grows at the temperature range of 15℃ to 40.5℃ but the optimum temperature is 25～30℃. The range of pH values is 5.16 to 11.15 with the optimum being 6.98 to 9.20. The G+C content of DNA is 60.1 moles percent (Tm). On the basis of morphological, physiological and biochemical charaterization, it is identified as Beijerinckia derxii.