Identification Of Nitrogen Fixing Microsymbionts From Mucuna Bracteata Nodules
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Date
2011-04
Authors
Shaffie, Salwani
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Publisher
Universiti Sains Malaysia
Abstract
Mucuna bracteata is a new leguminous cover plant which forms nodules and establises a nitrogen-fixing symbiosis. However, there is little information available on the N2-fixer of M. bracteata. Rhizobia are used to be recognized for all the bacteria that are able to produce nodule and fix N2 in legume’s root and collectively a member of the Rhizobiaceae in α-class of proteobacteria. There have been an increasing number of bacteria that can nodulate and fix N2 in legume which are not belong to the original genus Rhizobium in Rhizobiaceae family and traditional rhizobial phylogenetic lineages. Thus, isolation and characterization of microsymbiont from nodules of M. bracteata was carried based on biochemical tests. Furthermore, clearer identification of the isolates was performed based on 16S rDNA sequence analysis. Thirteen microsymbionts could nodulate and promote N2 fixation activity in association with M. bracteata. For evaluation of N2-fixing bacteria, analysis of nifH, the gene encoding nitrogenase enzyme, has been used with various PCR primers. Amplified nifH and 16S rRNA gene were successfully obtained from PCR technique. The sequence analysis revealed that root nodules of M. bracteata consisted of Burkholderia sp., Brevundimonas sp., Achromobacter sp., Stenotrophomonas sp. and Bacillus sp. The results presented here suggested that bacteria which were able to form N2-fixing symbioses with root known as rhizobia is not only from the α-class of proteobacteria but also from β-class of proteobacteria (Burkholderia sp. and Achromobacter sp., 99-100% of similarity) and gamma(γ)-class of proteobacteria (Stenotrophomonas sp., 99% of similarity).
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Keywords
Mucuna bracteata new leguminous cover plant , forms nodules and establises a nitrogen-fixing symbiosis