Asociaciones de las leguminosas con bacterias

Abstract

Legumes form a large group of plants that constitute the third largest family of angiosperms, including near 20000 species a nd 750 genera included in the subfamilies Faboideae (or Papilionoideae), Caesalpinioideae and Mimosoideae within the family Fabaceae. They are the second largest source of vegetable foods for human nutrition and in combination with cereals can contain all the amino acids necessary for a healthy diet. The benefits of using legumes are derived from their ability to establish symbiotic associations with some bacteria, best know n by the generic name of rhizobia, which form characteristic organs in the roots, sometimes on stems and leaves, called nodules. Inside the nodule, rhizobia transform into specialized cells called the bacteroids, which have the property of synthesizing the nitrogenase enzyme, which reduces the atmospheric nitrogen (N2) to ammonium (NH4+). Subsequently, the ammonia formed is incorporated into the hydrocarbon products from the photosynthesis of the plant to form amino acids, proteins and other nitrogenous compounds to be used for plant growth and development. This group of bacteria that for many years was thought to be formed by a scarce number of genera and species with in the Alphaproteobacteria class shows nowadays an important genetic diversity in cluding species phyloge netically divergent both in core and symbiotic genes sequences . In addition to rhizobia, other endophytic bacteria are found within the legume nodules that are known toda y to coexist with rhizobial strains and have a likely effect in plant health, plant growth or even in the rhizobia-legume symbiosis. Here we present an overview of the associations of bacteria with legumes and the current available knowle dge on the phylogenetic diversity of both rhizobia and endophytic bacteria inhabiting root nodules