Bacterias cultivables promotoras del crecimiento vegetal de un ecosistema de suelo de páramo como posibles fuentes de biofertilizantes

Introduction: High-altitude páramo ecosystems, characterized by harsh and fluctuating environmental conditions that significantly influence soil ecological and biological processes, harbor diverse and potentially beneficial microbial communities. Objective: This study aimed to isolate and characterize culturable plant growth-promoting bacteria from rhizosphere and bulk soils associated with Espeletia conglomerata in a high-altitude páramo ecosystem to screen for potential microbial biofertilizers. Methodology: The study site was the Santurbán Páramo Regional Natural Park, Colombia. Soil samples were collected from different altitudes for the isolation and identification of potential plant growth-promoting bacteria and evaluated by phenotypic (nitrogen fixation and phosphate solubilization) and genotypic (presence of three marker genes) approaches. The efficacy of the isolates as plant growth promoters was validated using assays conducted on tomato seedlings in controlled environments. Results: Twenty bacterial isolates were recovered and taxonomically classified, with the majority belonging to the genera Pseudomonas, Serratia, and Paraburkholderia. Functional and molecular screening revealed that 80% of the isolates could fix atmospheric nitrogen, 75% could solubilize phosphate, and 60% possessed genes associated with auxin production. Six of the isolates exhibited all the tested plant growth-promoting traits and were further evaluated in tomato seedling growth assays. Compared with the control plants, the inoculated plants presented significant increases in height, hypocotyl length, and biomass, particularly when treated with isolates of Pseudomonas yamanorum, Pseudomonas fluorescens, Serratia proteamaculans, and Rhodococcus qingshengii. Conclusion: These results highlight the biotechnological potential of cold-adapted bacteria from páramo ecosystems for promoting plant growth and as biofertilizer candidates. The multifunctional traits and ecological resilience of these bacteria support their application in sustainable agriculture and ecological restoration efforts in high-altitude or stressful soil environments