普通田菁根瘤菌及其类菌体的碳源研究

Studies on carbon sources by rhizobia and bacteroids isolated from nodules of Sesbania cannabina.Acta Agriculturae Universitatis Zhejiangensis,

普通田菁(Sesbania cannabina)根瘤菌属快生型,24小时形成菌落,杆状,大小为0.28～0.47μm×1.3～2.5 μm,运动,具两根侧生鞭毛,类菌体形态与其培养基上形态相似。能广泛利用碳源。产能基质试验结果表明,类菌体不能利用蔗糖,丙酮酸是最有效的能源,其次是葡萄糖、α-酮戊二酸、延胡索酸、琥珀酸、草酰乙酸、乳酸和苹果酸,果糖利用较差。类菌体的固氮酶活性从 10 m mol·L^(-1)始随基质浓度递增而增加,琥珀酸和丙酮酸分别在 200和300mmol·L^(-1)时达最高活性,而葡萄糖达 500 mmol·L^(-1)时乙炔还原活性还在上升,未出现抑制现象。葡萄糖为产能基质要求低氧浓度,当氧浓度为反应瓶气体体积的2％时,类菌体乙炔还原活性最高,6％时活性很低,而丙酮酸,琥珀酸为基质,类菌体适应氧浓度范围比较宽,在6％时固氮酶活性最强。

Sesbania cannabina rhizobium was one of rhizobia of fast-growing type. It could form colony within 24h, and was rod, 0.28-0.47 μm by 1.3-2.5μm in size, motile by means of two lateral flagella. Bacteroids were similar to rhzobia in morphology and able to utilize a wider range of carbon sources. When supplied with different carbon compounds to the bacleroid suspension as energy sources, it was shown that sucrose was nonutilizable, pyruvate was the most effective substrate, glucose, αa-oxyglutarate, fumarate, succinate,oxaloacetate, lactate, malate were the next, and fructose was very poorly used. C2H2-reducing activity of bacteroids initially increased with increasing substrate concentration. It reached an optimum activity with succinate at 200 mmol. L-1, pyruvate at 300 mmol. L-1. Whereas, no inhibition was seen for the glucose at 500 mmol. L-1. When oxygen concentrations were 2%, 4%, 6% and 8% by volume respectively in N2 gas phase, it was optimal at low O2 concentration ( 2% ) with glucose as respiratory substrate. In contrast, pyruvate, succinate stimulated C2H2 reduction activity of bacteroid over a wider range of O2 values ( 2-8% ), with an optimum activity at 6%, at which glucose was ineffective.