Abstract

Termites play an important role in promoting agricultural ecosystem balance and the degradation of lignocelluloses, but also have caused considerable damage to agriculture, forestry and buildings. Previous studies showed that there were a lot of nitrogen-fixing bacteria in the termite gut, and up to 60% of the nitrogen in termite organs came from the nitrogen fixation of symbiotic microorganisms which lived in the hindgut of termites. We obtained a endophytic bacterium from Odontotermes formosanus, and the morphology, physiochemical characteristics, 16S rDNA sequence, fatty acid dyeing and SDS-PAGE analysis of strain HUB-IV-005 were very similar to those of Klebsiella variicola. Strain HUB-IV-005 had nitrogen fixation activities because it could grow on nitrogen deficient medium under anaerobic condition with nitrogen gas in the headspace. In addition, the nitrogenase gene from HUB-IV-005 was cloned and transformed into E. coli, and we identified that the expressed protein was a nitrogenase (iron protein) by mass spectrometry. Strain HUB-IV-005 had nitrogen fixation activities and belonged to the species K. variicola. The results provided the basis for studying the nitrogen-fixing mechanism in the termite gut, and nitrogen fixation also provided useful information for further explaining the mechanism of the termite’s biological nitrogen fixation.

Key words: Odontotermes formosanus, Klebsiella variicola, endophytic bacteria, nitrogen fixation, protein separation and purification.