Plant growth-promoting Arthrobacter sp. MD55 alleviates heavy metal toxicity in barley (Hordeum vulgare L.) by enhancing germination and seedling growth

Crop productivity and food security are severely threatened worldwide by heavy metal contamination of agricultural soils. The ability of MD55 to reduce heavy metal stress in barley ( Hordeum vulgare L.) was assessed in this study after it was isolated from the rhizosphere of Diplachne fusca growing close to a sewage-impacted site. Strain MD55, identified as Arthrobacter sp., exhibited several plant growth-promoting traits, including phosphate solubilization, nitrogen fixation, and indole-3-acetic acid production, and improved barley germination and seedling growth under heavy metal stress. Barley grains under heavy metal stress showed an 86% germination rate when inoculated with strain MD55 was added, in comparison to 0% for non-inoculated grains. MD55 substantially improved barley growth under different heavy metals. At the highest concentration, MD55 treatment significantly increased plant growth, increasing shoot length by up to 120% and root length by more than 300% in comparison to non-inoculated plants. These findings demonstrate Arthrobacter sp. MD55 potent potential to reduce metal phytotoxicity, probably via improving nutrient uptake, phytohormone production, and metal sequestration. The isolated strain showed great promise as a bioinoculant for enhancing barley establishment and growth in metal-polluted soils and may support microbe-assisted phytoremediation techniques. Future research should concentrate on clarifying the precise mechanisms underlying MD55-mediated stress reduction.