Modern agriculture faces critical challenges due to increasing soil degradation resulting from overcultivation and excessive chemical use. These factors have led to declining agricultural productivity, reduced soil fertility, and a significant loss of microbial biodiversity. This review examines the role of plant growth-promoting bacteria (PGPB) as symbiotic microorganisms in restoring degraded soils. Key molecular and physiological mechanisms that enhance soil structure, improve water retention, and increase the bioavailability of essential nutrients for plants are explored. Additionally, the capacity of halotolerant bacteria to mitigate salt stress—an urgent issue in soils affected by salinization due to organic matter decomposition and irrigation practices—is analyzed. The role of plant growth regulators (PGRs) in both plant adaptation to adverse conditions and the stimulation of plant growth and development is also highlighted. Finally, current limitations in understanding biotic and abiotic stress resistance mechanisms in plants treated with growth-promoting strains are discussed, emphasizing the need for further research to optimize soil restoration strategies. This work provides a comprehensive overview of microorganism-based approaches for fostering more sustainable and resilient agriculture.