The role of Bacillus megaterium PEF-1 in stimulating the growth of organic cotton under environmental stress conditions

Cotton (Gossypium spp.) is a key crop in Kazakhstan, yet its productivity is constrained by saline-alkaline soils, which affect approximately 41% of the nation's arable land. Conventional soil remediation methods are often unsustainable and economically impractical. This study investigates the potential of Bacillus megaterium PEF-1, a plant growth-promoting rhizobacterium (PGPR) isolated from cotton rhizospheres in the Turkestan region, as a biofertilizer for saline-alkaline conditions. The strain demonstrated high tolerance to salinity (up to 10% NaCl), alkalinity (pH 9.0), and heavy metals, and produced significant levels of indole-3-acetic acid (IAA; 895 mg/L in vitro). Field trials with seed inoculation (10⁹ CFU/mL) showed marked improvements in cotton growth, including increases in plant height (18%), boll number (22%), and yield (25%) relative to controls. Soil analyses revealed enhanced nutrient availability in treated plots: nitrogen (+ 4.3%), phosphorus (+ 15.1%), potassium (+ 26.8%), and humus content (+ 29.3%). Stress mitigation was achieved through ACC deaminase-mediated ethylene reduction and superoxide dismutase (SOD)-driven reactive oxygen species (ROS) scavenging. Acute toxicity tests, conducted in accordance with OECD guidelines, confirmed the strain's biosafety with no adverse effects in mammalian models. Bacillus megaterium PEF-1 exhibits strong potential as a sustainable biofertilizer for improving cotton yields and soil fertility under saline-alkaline stress. Its capacity for nutrient mobilization, phytohormone synthesis, and abiotic stress alleviation aligns with the United Nations Sustainable Development Goals (SDGs) 2 (Zero Hunger) and 15 (Life on Land), offering a scalable, eco-friendly alternative to chemical fertilizers for arid and degraded agroecosystems.