The symbiotic interaction between Rhizobia and leguminous plants allows that atmospheric nitrogen, an essential element in vegetal nutrition, can be assimilated by plants, avoiding the use of nitrogen fertilizers. Thus, this interaction has encouraged the genomic and proteomic studies of these microorganisms.
In this way, the proteome of Bradyrhizobium elkanii (SEMIA 587) was analysed, in this work, by multi-dimensional liquid chromatography (MudPIT) and mass spectrometry (MS/MS).
Microorganisms living symbiotically with soy plants were lysated and the proteins present on total cell lysate were proteolyzed with trypsin. The complex peptides mixture was fractionated by ion exchange chromatography off line, followed by reverse phase. The identification and characterization of peptides were made on line, by MS/MS.
The acquired spectra of unidentified ion fragments were compared with MSDB database using MASCOT tools.
The results of MASCOT search engine revealed the existence of chaperones, heat shock protein, dinitrogen reductase, nitrogenase molybednum-iron protein beta-chain and nitrogenase iron protein. The presence of such proteins could be confirmed when compared to B. elkanii partial genome database (http://lbmp.fcav.unesp.br/be587 – sequences data not published).
From data confirmation, we hope to obtain informations about proteins expressed in microorganism, while associated to leguminous, that can be potentially related to biological nitrogen fixation and definitely, explain their metabolic route. This progress in the molecular and biological understanding of the symbiotic interaction could establish the expected economic and ecologic agriculture.