Diversity, Environmental Adaptability, and Functional Potential of Salt-Tolerant Phosphate- Solubilizing Bacteria from Coastal and Mangrove Soils of Diu, India

Abstract

Coastal and mangrove ecosystems represent unique ecological niches that support diverse and stress-adapted microbial communities. The
present investigation aimed to isolate and characterize phosphate-solubilizing bacteria (PSB) from coastal and mangrove soils of Diu, India, and
evaluate their adaptability under varying environmental conditions. Soil samples collected from four ecologically distinct coastal sites yielded
twenty-one morphologically diverse bacterial isolates using selective media. All isolates demonstrated phosphate-solubilizing
capability on Pikovskaya’s agar and were Gram-positive, indicating their resilience in saline environments. Environmental factors significantly
influenced phosphate solubilization efficiency. Acidic conditions (pH 5) enhanced solubilization, whereas alkaline conditions reduced activity,
although some isolates exhibited tolerance. Moderate salinity (1–2.5%) supported optimal activity, confirming halotolerance, while higher
salinity reduced efficiency without completely inhibiting bacterial function. Temperature also played a critical role, with maximum solubilization
observed at 37 °C, indicating mesophilic adaptation. Biochemical characterization revealed metabolic versatility, including enzyme production and
oxidative stress tolerance. These findings highlight the ecological importance of PSB in phosphorus cycling and their potential role in improving
nutrient availability in salt-affected soils. The study demonstrates that coastal and mangrove soils serve as valuable reservoirs of agriculturally
beneficial microorganisms, offering promising candidates for eco-friendly biofertilizer development and sustainable crop production in saline
and coastal agro ecosystems.