Abstract

Endophytic bacteria with combined plant growth-promoting (PGP) and pesticide biodegradation capacities offer sustainable agroecosystem management. This study reports the isolation, biochemical characterization, whole-genome sequencing, and in silico functional analysis of an endophytic bacterium, Acinetobacter sp. strain HSTU-Asm16, isolated from rice (Oryza sativa L.). Biochemical assays show catalase, oxidase, and citrate utilization; carbohydrate fermentation; and a suite of extracellular hydrolases consistent with plant-associated metabolism. The draft genome (~3.94 Mb) was annotated using the NCBI PGAP pipeline and analyzed for phylogenetic placement, including phylogenomics, average nucleotide identity (ANI), digital DNA–DNA hybridization (dDDH), pangenome assessment, and synteny analysis. Genome taxonomy placed HSTU-Asm16 within the Acinetobacter soli clade, confirming its status as a genomically distinct strain rather than a novel species. The identified genes are used in plant growth promotion (IAA, siderophore biosynthesis, ACC deaminase, and phosphate metabolism), stress tolerance (heat-/cold-shock proteins and heavy-metal resistance), and a complement of putative organophosphate-degrading enzymes (carboxylesterases, phosphotriesterases, amidohydrolases, and opd-like sequences). The genome encodes nif-associated and isc-related iron-sulfur cluster assembly genes, including nifS, nifU, iscU, and iscA, are involved in Fe–S protein maturation rather than canonical nitrogen fixation. Molecular docking with representative organophosphate ligands showed plausible substrate active site interactions for several hydrolases. The biochemical, genomic, and in silico evidence indicates Acinetobacter sp. HSTU-Asm16 is a promising plant-associated bacterium with dual potential for plant growth promotion and organophosphate pesticide bioremediation in rice farming.

Key words: Acinetobacter sp., Endophytic bacteria, plant growth–promoting traits, genomic analysis, organophosphorus hydrolase, Catalytic triads, pesticide biodegradation