Abstract
Various parts (root, rachis, petiole, leaflet, bark, and pith) of the sago palm were collected in the Phillipine islands of Leyte, Cebu, and Aklan, and their nitrogen-fixing ability was measured with an acetylene reduction assay (ARA). Almost all the samples, except for the leaflets, showed positive ARA activity ranging from 1.1 to 961 nmol g-1day-1. Among the samples, roots collected during July, 2003 showed the highest activity, followed by the pith. ARA activity in the petiole, rachis, and pith samples was quite variable. Some parts showed high activity, while others showed very low activity, suggesting a heterogeneous distribution of the nitrogen-fixing potential. Nitrogen-fixing bacteria (NFB) were then isolated by aerobic cultures using a N-free Rennie semi-solid medium from the samples showing high ARA activity. A homology search of 16S rDNA sequences revealed that the nitrogen fixers belonged to various genera, such as Klebsiella pnuemoniae, Pantoea agglomerans, Enterobacter cloacae, Burkholderia sp., and Bacillus megaterium. Some of the Gram-negative strains were confirmed by physiological tests using API20E and API20NE, while the physiological identification and 16S rDNA sequence did not match in a few strains. The relationship between the ARA of the isolates and their carbon sources showed that all the isolates preferred simple sugar compounds, such as glucose, sucrose, and mannitol, but showed very low activity in pectin, starch, and hemi-cellulose media. This study demonstrated the extensive colonization of sago palms by various types of nitrogen-fixing bacteria for the first time.
https://ror.org/00qg0kr10 
