IDENTIFICATION OF NITROGEN FIXING MICROSYMBIONTS FROM Mucuna bracteata NODULES
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Date
2011-04
Authors
SHAFFIE, SALWANI
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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 a-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 rhizobia! 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., Brevundirnonas sp., Achrornobacter sp., Stenotrophornonas sp. and
Bacillus sp. The results presented here suggested that bacteria which were able to form Nzfixing
symbioses with root known as rhizobia is not only from the a-class of proteobacteria
but also from /3-class of proteobacteria (Burkholderia sp. and Achrornobacter sp., 99-100%
of similarity) and gamma(y)-class of proteobacteria (Stenotrophomonas sp., 99% of
similarity).
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IDENTIFICATION OF NITROGEN FIXING MICROSYMBIONTS