Abstract
Plant-microbe interactions play a critical role in maintaining plant health, enhancing soil fertility, and sustaining ecosystem functionality. Agave americana (Asparagales, Asparagaceae, L.), a crassulacean acid metabolism (CAM) species known for its remarkable drought tolerance and diverse industrial uses, represents a valuable model for exploring the ecological and functional dynamics of these associations. This study explores the diversity and functional potential of bacterial communities associated with A. americana and their role in promoting plant growth. A combination of culture-dependent techniques and metagenomic sequencing was employed to isolate and characterize rhizospheric and endophytic bacteria. Prominent bacterial genera identified included Acinetobacter, Bacillus, Rhizobium/Mesorhizobium, and Microbacterium. Metagenomic analyses revealed a high abundance of Actinobacteria, Proteobacteria, and Chloroflexi, highlighting their roles in nutrient cycling and organic matter decomposition. Plant growth-promoting assays demonstrated that Rhizobium sp. 34 A produced significant levels of indole-3-acetic acid (IAA), enhancing nutrient availability and plant growth. Mesorhizobium sp. 28 A had the greatest overall impact, significantly increasing total fresh weight, chlorophyll content, and sugar profiles, surpassing the effects of chemical fertilizers. Furthermore, Bacillus sp. T12C12, in combination with other plant growth-promoting bacteria (PGPB), exhibited the highest nitrogenase activity, as measured through acetylene reduction assays (ARA). These findings suggest that bacterial inoculants can enhance the nutritional and agronomic value of Agave species, which are of significant agro-industrial and food importance, providing a sustainable alternative to chemical fertilizers. This study offers valuable insights into sustainable agricultural practices by leveraging microbial communities to enhance crop productivity and resilience.