Abstract
Drought stress is one of the most severe abiotic constraints limiting crop productivity worldwide, a challenge that is intensifying under ongoing climate change. In recent years, beneficial microorganisms have emerged as sustainable, nature-based tools to enhance plant drought tolerance and stabilize agricultural production under water-limited conditions. This review synthesizes current knowledge on the major groups of beneficial bacteria involved in drought stress mitigation, including plant growth-promoting rhizobacteria (PGPR), a functional subgroup of rhizosphere-associated microbes, endophytic bacteria, rhizosphere-associated microbes, and cyanobacteria, highlighting their primary physiological, biochemical, and soil-mediated mechanisms. These microorganisms enhance drought resilience through multiple complementary pathways, such as modulation of abscisic acid (ABA) and auxin (IAA) signaling, ACC deaminase activity, osmotic adjustment, antioxidant defense, improved nutrient acquisition, and enhancement of soil structure and water retention. The review further discusses practical application strategies, including seed inoculation, soil and root application, foliar spraying, the use of single strains versus microbial consortia, and advances in bioformulations and carrier materials that improve microbial survival and field efficacy. Emphasis is placed on recent experimental and field studies demonstrating the effectiveness of microbial inoculants under drought conditions. Collectively, the evidence highlights the potential of beneficial bacteria as key components of climate-resilient agriculture and underscores the need for integrated, formulation-driven approaches to translate laboratory success into consistent field performance.