<p>This study reports the isolation and comprehensive characterization of two potent potassium-solubilizing bacterial (KSB) strains, KSB-1 and KSB-5, from the rhizospheric soil of <i>Iris kashmiriana</i> locally named as Mazarmond which is cultivated near graveyard. <i>Iris kashmiriana</i> has antimicrobial and anti-inflammatory activities, being also used to treat stomach disorders and respiratory ailments. Both strains exhibited efficient potassium solubilization on mica-amended Aleksandrov medium, with KSB-1 showing the highest solubilization index (3.00 ± 0.12) and a significant pH drop in broth cultures. Morphological, biochemical, and molecular identification revealed KSB-1 as <i>Priestia megaterium</i> and KSB-5 as <i>Bacillus paramycoides</i>. Peptide profiling via sodium dodecyl sulfate – polyacrylamide gel electrophoresis (SDS-PAGE) and ultra-performance liquid chromatography (UPLC) uncovered unique antimicrobial tetrapeptides rich in arginine, histidine, and proline. Two-dimensional correlation spectroscopy – Fourier transform nuclear magnetic resonance (2D COSY-FTNMR) spectroscopy further identified diverse polar and semi-polar metabolites such as amines, ether, alcohol, aldehydes, alkanes, and carboxylic acid contributing to bioactivity. KSB-5 exhibited superior plant growth promoting (PGPR) traits, including phosphate, silicate, and zinc solubilization, siderophore and IAA production, and strong antifungal activity against <i>Fusarium oxysporum</i>. Anti-biofilm assays showed a 57.03% inhibition by KSB-5 extracts. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS) analyses revealed hyphal deformation and deposition of biogenic putative nanoparticles—titanium, selenium, and aluminum—on fungal cells, absent in controls. High resolution transmission electron microscopy (HR-TEM) further confirmed intracellular damage including cytoplasmic disintegration and membrane detachment. This is the first report linking KSB strains from <i>Iris kashmiriana</i> with putative nanoparticle-mediated antifungal and anti-biofilm activities, emphasizing their dual role as biofertilizers and biocontrol agents. The findings highlight their potential application in sustainable agriculture and integrated disease management.</p> Graphical Abstract <p></p>

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Biological Peptides, Metabolites and Nanoparticles from Potassium-Solubilizing Bacteria: A Recent Horizon in Antimicrobial and Anti-biofilm Strategies

  • Zaffar Bashir,
  • Parvaze A. Wani,
  • Shagufta Majeed,
  • Bashir A. Ganai,
  • Tawzia Jan,
  • Burhan Hamid,
  • Fayaz A. Mohiddin

摘要

This study reports the isolation and comprehensive characterization of two potent potassium-solubilizing bacterial (KSB) strains, KSB-1 and KSB-5, from the rhizospheric soil of Iris kashmiriana locally named as Mazarmond which is cultivated near graveyard. Iris kashmiriana has antimicrobial and anti-inflammatory activities, being also used to treat stomach disorders and respiratory ailments. Both strains exhibited efficient potassium solubilization on mica-amended Aleksandrov medium, with KSB-1 showing the highest solubilization index (3.00 ± 0.12) and a significant pH drop in broth cultures. Morphological, biochemical, and molecular identification revealed KSB-1 as Priestia megaterium and KSB-5 as Bacillus paramycoides. Peptide profiling via sodium dodecyl sulfate – polyacrylamide gel electrophoresis (SDS-PAGE) and ultra-performance liquid chromatography (UPLC) uncovered unique antimicrobial tetrapeptides rich in arginine, histidine, and proline. Two-dimensional correlation spectroscopy – Fourier transform nuclear magnetic resonance (2D COSY-FTNMR) spectroscopy further identified diverse polar and semi-polar metabolites such as amines, ether, alcohol, aldehydes, alkanes, and carboxylic acid contributing to bioactivity. KSB-5 exhibited superior plant growth promoting (PGPR) traits, including phosphate, silicate, and zinc solubilization, siderophore and IAA production, and strong antifungal activity against Fusarium oxysporum. Anti-biofilm assays showed a 57.03% inhibition by KSB-5 extracts. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS) analyses revealed hyphal deformation and deposition of biogenic putative nanoparticles—titanium, selenium, and aluminum—on fungal cells, absent in controls. High resolution transmission electron microscopy (HR-TEM) further confirmed intracellular damage including cytoplasmic disintegration and membrane detachment. This is the first report linking KSB strains from Iris kashmiriana with putative nanoparticle-mediated antifungal and anti-biofilm activities, emphasizing their dual role as biofertilizers and biocontrol agents. The findings highlight their potential application in sustainable agriculture and integrated disease management.

Graphical Abstract