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Inhibition of quorum sensing-mediated virulence in Serratia marcescens by Bacillus subtilis R-18

Kannan Rama Devi1, Subramaniyan Srinivasan1, Arumugam Veera Ravi1

  • 1Department of Biotechnology, Science Campus, Alagappa University, Karaikudi, 630 003, Tamil Nadu, India.

Microbial Pathogenesis
|April 17, 2018
PubMed

Insights

Bacillus subtilis strain R-18 supernatant inhibits quorum sensing (QS) in the nosocomial pathogen Serratia marcescens. Its petroleum ether extract reduces virulence factors and downregulates key genes, offering a potential anti-virulence strategy.

Area of Science:

  • Microbiology
  • Bacteriology
  • Molecular Biology

Background:

  • Serratia marcescens is a significant opportunistic pathogen responsible for nosocomial infections, particularly urinary tract infections (UTIs).
  • This bacterium displays increasing resistance to conventional antibiotics, necessitating alternative therapeutic strategies.
  • Virulence factor production in S. marcescens is often regulated by quorum sensing (QS), a cell-to-cell communication mechanism.

Purpose of the Study:

  • To investigate the anti-virulence potential of Bacillus subtilis strain R-18 against the uropathogen S. marcescens.
  • To evaluate the quorum sensing inhibitory (QSI) activity of B. subtilis R-18 culture supernatant.
  • To characterize the effects of B. subtilis R-18 extracts on S. marcescens virulence factors and gene expression.

Main Methods:

  • Bacterial cell-free culture supernatant (CFCS) of B. subtilis R-18 was tested for QSI activity against Chromobacterium violaceum and S. marcescens.
  • CFCS was extracted using different solvents, and the petroleum ether (PE) extract was further analyzed for its impact on biofilm formation, protease, lipase, and hemolysin production.
  • Fourier transform infrared spectroscopy (FT-IR), differential gene expression analysis, and gas chromatography-mass spectrometry (GC-MS) were employed to assess cellular changes, gene regulation, and active compounds.

Main Results:

  • B. subtilis R-18 CFCS significantly inhibited QS-mediated pigment production in both C. violaceum and S. marcescens.
  • The PE extract of B. subtilis R-18 demonstrated notable inhibition of biofilm formation and key virulence factors (protease, lipase, hemolysin) in S. marcescens.
  • FT-IR and gene expression studies confirmed alterations in cellular components and downregulation of virulence-associated genes in treated S. marcescens.
  • GC-MS analysis of the PE extract identified multiple compounds with potential therapeutic value for reducing QS-dependent phenotypes.

Conclusions:

  • Bacillus subtilis strain R-18 possesses significant anti-virulence properties against Serratia marcescens.
  • The quorum sensing inhibitory activity and the presence of bioactive compounds in its extracts suggest a promising alternative approach to combat S. marcescens infections.
  • This study highlights the potential of B. subtilis R-18 as a source for novel anti-virulence agents targeting QS-dependent mechanisms.
Keywords:
Anti-virulenceQuorum sensingRhizosphere soil bacteriumSerratia marcescensUrinary tract infections

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