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Agave lechuguilla is a widely distributed plant in arid ecosystems. It has been suggested that its microbiome is partially responsible for its great adaptability to the oligotrophic environments of the Chihuahuan Desert. To lead the recruitment of beneficial rhizobacteria, the root exudates are essential; however, the amino acids contained within these compounds had been largely overlooked. Thus, we investigated how the variations of amino acids in the rhizosphere at different growth stages of A. lechuguilla affect the rhizobacterial community composition, its functions, and activity of the beneficial bacteria. In this regard, it was found that arginine and tyrosine were related to the composition of the rhizobacterial community associated to A. lechuguilla, where the most abundant genera were from the phylum Proteobacteria and Bacteroidetes. Moreover, Firmicutes was largely represented by Bacillus in the phosphorus-mineralizing bacteria community, which may indicate its great distribution and versatility in the harsh environments of the Chihuahuan Desert. In contrast, we found a high proportion of Unknown taxa of nitrogen-fixing bacteria, reflecting the enormous diversity in the rhizosphere of these types of plants that remains to be explored. This work also reports the influence of micronutrients and the amino acids methionine and arginine over the increased activity of the nitrogen-fixing and phosphorus-mineralizing bacteria in the rhizosphere of lechuguillas. In addition, the results highlight the multiple beneficial functions present in the microbiome that could help the host to tolerate arid conditions and improve nutrient availability.

Agave lechuguilla has one of the widest distributions among other agave species in the Chihuahuan Desert. Their capacity to grow in poorly developed soils and harsh conditions has been related to their association with plant growth-promoting rhizobacteria. In this work, we explored how soil properties and plant growth stage influence the composition of the rhizobacterial communities, their interactions, and the enzymatic activity and abundance of nitrogen-fixing bacteria and organic phosphorus-mineralizing bacteria in two subregions of the Chihuahuan Desert. We found that mature plants of lechuguilla stimulated the activity and abundance of nutrient-improvement rhizobacteria, and these soil samples had a higher content of total organic carbon, ammonium (NH4) and nitrite + nitrate (NO2+NO3). Nutrient availability seems to be an essential driver of the bacterial community's structure since the genera with more connections (hubs) were those with known mechanisms related to the availability of nutrients, such as env. OPS17 (Bacteroidetes), Gemmatimonadaceae uncultured, S0134terrestrial group, BD211terrestrial group (Gemmatimonadetes), Chthoniobacteracea and Candidatus Udaeobacter (Verrucomicrobia). This work shows that the late growth stages of lechuguilla recruit beneficial bacteria that favor its establishment and tolerance to harsh conditions of the arid lands.

Zea mays L. ssp. mexicana (teosinte) is a naturally occurring grass related to maize. The two plants have developed foliar fungal diseases that can be controlled with beneficial bacterial antagonists. While the beneficial effects on stem and root development of the application of bacteria of the genus Azospirillum is widely known, the effects of the bacteria on the control of the phytopathogenic fungi associated with teosinte leaves and seeds are unknown. Bacterium of the species A. brasilense that present acetylene reducing activity, siderophore production and the ability to antagonise pathogenic fungi in vitro and in vivo in teosinte plants were selected for this study, in which the incidence of fungal diseases caused by Alternaria, Bipolaris and Fusarium were reduced in plants. Furthermore, biomass (root and stem) production increased, improving teosinte plant health in greenhouse and field conditions.

The chitinase enzyme was identified in isolated bacteria of maize rhizosphere as well as its potential for the biological control of fungi associated at seeds of the same plant. The production of c...

El suelo rizosférico se encuentra interactuando con compuestos de bajo peso molecular como los ácidos carboxílicos, entre otras sustancias, cuya dinámica de sorción a la superficie de las partículas minerales se desconoce. Se determinó por el método cromatográfico, la adsorción de agua y ácidos carboxílicos volátiles de origen vegetal y bacteriano (metanoico, etanoico, propanoico y butanoico) en un suelo agrícola de San Juan Atenco, Puebla, México. El suelo de estudio, se caracterizó en sus propiedades físicas, químicas, biológicas y de superficie. Se determinó la porosidad por el método de adsorción de N2 a su temperatura de ebullición (76 K). Los valores de la superficie específica fueron determinados utilizando el método de Brunauer- Emmett-Teller (BET), el volumen de poro fue obtenido aplicando el método de Gursvitch y la distribución de tamaño de poros fue estudiada por la aproximación de Barrett-Joyner-Halenda (BJH). La adsorción de los adsorbatos ha sido determinada en el intervalo de temperaturas de 423-523 K, usando cromatografía de gases con detector de conductividad térmica y usando helio como gas portador. Los principios de las ecuaciones de Freundlich y Langmuir fueron aplicadas a todos los casos. Los resultados demuestran que la adsorción de agua y ácidos carboxílicos volátiles, derivados del metabolismo biológico en el suelo, está en función de la estructura diferencial de las moléculas, repercutiendo en el grado de interacción al sistema poroso del suelo.