Indigenous rhizobacteria drive stepwise detoxification of mancozeb via strain-specific metabolic pathways

Mancozeb-tolerant rhizobacteria isolated from apple orchard soils of Kashmir were evaluated for biodegradation, metabolite production, plant growth-promoting traits, and genomic stability. Two isolates, K-6 and K-8, showed high tolerance (1200-1400 μg/mL) and were identified as Pantoea agglomerans and Pseudomonas oleovorans, respectively. FTIR analysis revealed strain-specific extracellular metabolite production in mancozeb-amended cultures. Strain K-6 synthesized glucans, polysaccharides, fatty acids, proteins, and biosurfactants, while strain K-8 produced diverse exopolysaccharides, glycolipids, peptide-linked biosurfactants, lipid derivatives, and phosphoester-containing compounds, enhancing biofilm formation and interaction with hydrophobic substrates. Comparative FTIR profiling also demonstrated strain specific progressive disruption of the dithiocarbamate functional group like CN and CS vibrations, with partial cleavage by K-6 and advanced oxidative transformation by K-8, indicated by dominant hydroxyl and carbonyl-associated bands. GC-MS analysis further confirmed strain-dependent degradation pathways. Strain K-6 mediated partial degradation, producing fatty acid esters, sulfur-oxidized intermediates, and smaller aliphatic compounds, reflecting enzymatic cleavage of sulfur-rich moieties. In contrast, strain K-8 exhibited advanced biotransformation, generating saturated and unsaturated fatty acid methyl esters, amide derivatives, and triterpenoid compounds such as α-amyrin, indicating deeper metabolic assimilation. These strain specific degradation of mancozeb might be due to the synthesis of strain specific biosurfactants and polymers. Both strains displayed multiple plant growth-promoting traits; however, K-6 showed superior mineral solubilization and antifungal activity against Fusarium oxysporum. Fluorescence microscopy-based comet analysis confirmed genomic stability of both strains under high mancozeb exposure. These findings highlight the strain-specific and multifunctional potential of indigenous rhizobacteria for mancozeb detoxification and sustainable agricultural applications.