RESUMO
Based on the physiological properties of ammonium-resistant N2-fixingbacterium ( Klebsiella oxytoca NG13/pMC73A), the fermentation technology of it was studied. The basic medium of high-density culture was established, with glucose as carbon source coupled with appropriate nitrogen source and inorganic salts. At the middle and late phase of culture, glucose and ammonia were added to supply carbon source and nitrogen source, stabilizing the pHat 6.5 ~ 6.8. Optimal level of dissolved oxygen was kept by controlling aeration and stirring rate. Bacterium number of Klebsiella oxytoca NG13/pMC73A reached 600 ~ 700 x 10s cfu/mL at the end of culture. Compared with previous technology, bacterium number was increased by more than ten-fold with a comparable culture period.
RESUMO
The ability to induce hypersensity on leaves of tomato and the stability of double-plasmid of an harpin-producing, nitrogen-fixing engineered strain E4 were tested. Hypelsensitivity-inducing experiment indicated that the time and density of hypersensitivity-induction of E4 was similar to those of DH5, the positive control of pCPP430. Although E4 took the same time to induce hypersensitivity as 308R, another positive control of pCPP430, it induced weaker hypersen- sitivity on tobacco leaves. On tomato leaves, there was no difference in time and density of hypersensitivity between E4 and 308R (pCPP430). Results revealed that the two plasmids, pCPP430 and pMC73A, were unstable in host bacteria, with the losing rate of 100% at the 48th generation. The emergence probability of bacteria with either pCPP430 or pMC73A was almost the same.
RESUMO
By using cup culture, influence of different strains (ammonium-resistant N2-fixing type, wild type, none N2-fixing type) of Klebsiella oxytoca on the growth of rice seedling was compared. It was discovered that ammonium-resistant N2 -fixing bacteria could excrete some plant growth promoting substance, which could be adsorbed by cation resin. It' s activity wouldn't be affected at 80℃. At optimal concentration, the weight of rice root and seedling were increased by