Isolation, Characterization, and GC–MS Profiling of Bacillus zhangzhouensis NB1 with Plant Growth-Promoting and Antibacterial Activity Against Xanthomonas sp.

Abstract

Plant growth-promoting rhizobacteria (PGPR) have emerged as promising alternatives to chemical inputs for sustainable crop protection. A total of 21 rhizospheric bacterial isolates were systematically evaluated for key plant growth-promoting (PGP) attributes, including indole-3-acetic acid (IAA) production, hydrogen cyanide (HCN) synthesis, phosphate solubilization (PS), siderophore production (SP), ammonia (NH 3 ) generation, and hydrolytic enzyme activities (amylase, protease, and cellulase). Among these, isolate NB1 exhibited a broad spectrum of PGP traits, demonstrating consistent positive responses across all tested parameters. Quantitatively, NB1 produced 36.4 ± 1.2 µg mL -1 of IAA and showed a high phosphate solubilization index of 4.2. Molecular characterization based on partial 16S rRNA gene sequencing indicated that isolate NB1 shared 99.78% sequence similarity with Bacillus zhangzhouensis . The antimicrobial efficacy of its extracellular crude extract was confirmed against Xanthomonas sp., producing inhibition zones of up to 16 mm. The chemical profiling of extracellular metabolites using gas chromatography–mass spectrometry (GC–MS) revealed presence of bioactive compounds such as N-acetyltyramine, pyrrolo [1,2-a] pyrazine derivatives, and fatty acid esters, which are known for their antimicrobial properties.The application of B. zhangzhouensis (NB1) demonstrated enhanced antagonistic activity against phytopathogenic bacteria. This formulation highlight its potential as an effective biocontrol strategy under in vitro conditions.