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<p>The ethyl acetate fraction of <i>Lacticaseibacillus</i>&#xa0;sp. KJK14S1 exhibited antibacterial activity against Gram-negative pathogens under the experimental conditions employed. Microbroth dilution assays showed that <i>Klebsiella pneumoniae</i> ATCC 700603 had a mean MIC of 75 ± 27.95&#xa0;µg/mL, whereas <i>Pseudomonas aeruginosa</i> ATCC 27853 displayed a higher mean MIC of 104.17 ± 36.09&#xa0;µg/mL. Mechanistic analyses indicated that the extract compromised bacterial membrane integrity. Treatment resulted a dose-dependent increase in outer membrane permeability, as reflected by enhanced crystal violet uptake, reaching 54.34 ± 4.39% in <i>K. pneumoniae</i>&#xa0;and 69.10 ± 2.64% in <i>P. aeruginosa</i>&#xa0;at 2 MIC. Inner membrane disruption was further confirmed by the&#xa0;<i>β</i>-galactosidase release, which increased with both exposure time and extract concentration, with the greatest enzyme leakage recorded at 2 × MIC. Treatment also reduced the negative surface charge of bacterial cells, as evidenced by shifts in zeta potential toward neutrality, while higher polydispersity index values suggested membrane destabilization and increased cell aggregation. The extract suppressed biofilm formation in both bacteria, with&#xa0;<i>K. pneumoniae</i>&#xa0;showing greater susceptibility. Reductions in crystal violet stained biofilm biomass were supported by decreased extracellular polymeric substance production, indicating disruption of the biofilm matrix. Agarose gel electrophoresis further revealed concentration-dependent genomic DNA degradation. In ciprofloxacin-enriched persister assays, the extract significantly reduced viable persister-like cells, particularly at concentrations of 10 × MIC or higher after 24&#xa0;h. Preliminary safety evaluation demonstrated low toxicity in&#xa0;<i>Artemia salina</i>&#xa0;and gamma hemolysis of the producing strain, supporting a favourable initial safety alongside its membrane-targeted antibacterial and antibiofilm activities.</p>

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Evaluation of antibacterial and antibiofilm activity of Lacticaseibacillus sp. KJK14S1 strain isolated from unexplored region of Indian Sundarbans against Gram-negative bacteria

  • 期刊论文

  • 发表日期：

    2026年8月2日

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  • Ruchita Santra,
  • Pankaj Paul,
  • Sandip Dolui,
  • Somnath Roy,
  • Sk Sohel,
  • Subhankar Patra,
  • Poulomi Biswas,
  • Sanmoy Karmakar,
  • Kaushik Biswas

摘要

The ethyl acetate fraction of Lacticaseibacillus sp. KJK14S1 exhibited antibacterial activity against Gram-negative pathogens under the experimental conditions employed. Microbroth dilution assays showed that Klebsiella pneumoniae ATCC 700603 had a mean MIC of 75 ± 27.95 µg/mL, whereas Pseudomonas aeruginosa ATCC 27853 displayed a higher mean MIC of 104.17 ± 36.09 µg/mL. Mechanistic analyses indicated that the extract compromised bacterial membrane integrity. Treatment resulted a dose-dependent increase in outer membrane permeability, as reflected by enhanced crystal violet uptake, reaching 54.34 ± 4.39% in K. pneumoniae and 69.10 ± 2.64% in P. aeruginosa at 2 MIC. Inner membrane disruption was further confirmed by the β-galactosidase release, which increased with both exposure time and extract concentration, with the greatest enzyme leakage recorded at 2 × MIC. Treatment also reduced the negative surface charge of bacterial cells, as evidenced by shifts in zeta potential toward neutrality, while higher polydispersity index values suggested membrane destabilization and increased cell aggregation. The extract suppressed biofilm formation in both bacteria, with K. pneumoniae showing greater susceptibility. Reductions in crystal violet stained biofilm biomass were supported by decreased extracellular polymeric substance production, indicating disruption of the biofilm matrix. Agarose gel electrophoresis further revealed concentration-dependent genomic DNA degradation. In ciprofloxacin-enriched persister assays, the extract significantly reduced viable persister-like cells, particularly at concentrations of 10 × MIC or higher after 24 h. Preliminary safety evaluation demonstrated low toxicity in Artemia salina and gamma hemolysis of the producing strain, supporting a favourable initial safety alongside its membrane-targeted antibacterial and antibiofilm activities.