水稻内生联合固氮细菌阴沟肠杆菌生长条件及其在植株体内定殖的研究

Growth conditions of rice endophytic associative nitrogen-fixing bacterium Enterobacter cloace and its colonization in rice plants

阴沟肠杆菌(Enterobactercloacae)G161和J115是自水稻根和茎内分别分离获得的联合固氮细菌。其最适生长条件:培养时间为36 h左右,生长温度为27～30℃,培养液pH值为6～7,适当通气即振荡培养(120 r.min-1)。通过含药培养基梯度筛选,获得抗利福平350μg.mL-1标记菌株,以此测定2株菌在水稻植株体内的定殖动态。结果表明:该2株菌经喷雾和蘸根接种均能进入水稻根、茎、叶内,向下或向上移动,以及较好地定殖。以菌液(109cfu.mL-1)喷雾后,细菌在水稻叶和根内存在20 d以上,而在茎内存活时间较短(5～11 d);菌液(109cfu.mL-1)蘸根后,细菌能在水稻根、茎和叶内分别存在40 d以上、20～30 d和8～11 d。这表明2株菌在水稻不同器官内的定殖量与接种方法有关,也可能细菌在水稻根内的定殖能力要强于在茎、叶内。

Isolates G161 and J115 of Enterobacter cloace（Jordan） Hormaeche Edwards were two endophytic bacteria with associative nitrogen fixation from rice roots and stems respectively.The growth conditions of these bacteria were studied.The optimum culture time was about 36 hours.The optimum growth temperature ranged from 27 to 30 ℃.The optimum growth pH value in the media was from 6 to 7.Aeration or vibration culture（120 r·min-1） was beneficial to the bacterial growth.The resistant mutants to rifampicin of 350 μg·mL-1 from isolates J115 and G161 were induced by gradient screening on the media supplemented with the antibiotic and then used to study their colonization in rice plants.After leaf-spraying and root-dipping,these bacteria could enter rice plants,move upwards or downwards,and colonize well.After being sprayed with the culture of 109 cfu·mL-1,the bacteria could colonize in rice leaves and roots more than 20 days,but in the stems 5 to 11 days.After root-dipping（109 cfu·mL-1）,the bacteria could colonize in the roots,stems and leaves over 40 days,20 to 30 days and 8 to 11 days respectively.These results showed that the bacterial colonization ability in rice organs could be associated with inoculation methods,and the bacteria could colonize in rice roots better than in the stems or leaves.