Bioprospecting a mountain-derived phosphorus-solubilizing bacterium: Bacillus thuringiensis B3 as a plant-growth promoter in lettuce and tomato horticultural crops.

• A Bacillus thuringiensis , isolated and bioprospected from Cuba's mountain region demonstrated a high phosphate solubilization potential, releasing up to 16.39 mg/mL of PO 4 3-. • This study revealed the bacterium's agrobiogtechnological potential, showcasing its ability to enhance plant nutrition and health, extending its use beyond pest control to broader agricultural applications. • The bacterium improved lettuce and tomato germination and root architecture, suggesting a possible 50 % reduction in synthetic fertilizer use during their early growth stages opening the possibility of directing Cuba horticulture towards sustainability. The biogeographic and climatic conditions of islands like Cuba generate distinctive ecosystems as reservoirs of microbial biodiversity. This study explores the potential of the B3 strain, isolated from the Guamuhaya Mountain in Cuba, in Cuban urban horticulture, where the soil phosphorus availability poses a significant challenge to crop productivity. The B3 strain demonstrates remarkable phosphorus solubilization capabilities, along with nitrogen fixation and nutrient mobilization, production of growth regulators, siderophores, lipases, and both volatile and diffusible antimicrobial compounds. The strain's multifaceted functionalities indicate its potential to limit phytopathogen proliferation, contributing to plant health. The strain showed Bacilli morphological characteristics, confirmed through MALDI-ToF MS and MLSA, classify it as Bacillus thuringiensis. The strain's safety profile, demonstrated by negative results in hemolysis and DNA degradation tests, underscores its suitability for agricultural applications. The Bacillus thuringiensis B3 significantly enhanced germination of lettuce and tomato seeds, root structure and early plant growth, confirming its value in horticultural production. The integration of this strain into Cuban urban horticulture represents a step forward in sustainable agriculture with low environmental impact. [ABSTRACT FROM AUTHOR]