Genome analysis of secondary metabolite‑biosynthetic gene clusters of Photorhabdus akhurstii subsp. akhurstii and its antibacterial activity against antibiotic-resistant bacteria

PLoS One. 2022 Sep 21;17(9):e0274956. doi: 10.1371/journal.pone.0274956. eCollection 2022.

Abstract

Xenorhabdus and Photorhabdus can produce a variety of secondary metabolites with broad spectrum bioactivity against microorganisms. We investigated the antibacterial activity of Xenorhabdus and Photorhabdus against 15 antibiotic-resistant bacteria strains. Photorhabdus extracts had strong inhibitory the growth of Methicillin-resistant Staphylococcus aureus (MRSA) by disk diffusion. The P. akhurstii s subsp. akhurstii (bNN168.5_TH) extract showed lower minimum inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC). The interaction between either P. akhurstii subsp. akhurstii (bNN141.3_TH) or P. akhurstii subsp. akhurstii (bNN168.5_TH) or P. hainanensis (bNN163.3_TH) extract in combination with oxacillin determined by checkerboard assay exhibited partially synergistic interaction with fractional inhibitory concentration index (FICI) of 0.53. Time-killing assay for P. akhurstii subsp. akhurstii (bNN168.5_TH) extract against S. aureus strain PB36 significantly decreased cell viability from 105 CFU/ml to 103 CFU/ml within 30 min (P < 0.001, t-test). Transmission electron microscopic investigation elucidated that the bNN168.5_TH extract caused treated S. aureus strain PB36 (MRSA) cell membrane damage. The biosynthetic gene clusters of the bNN168.5_TH contained non-ribosomal peptide synthetase cluster (NRPS), hybrid NRPS-type l polyketide synthase (PKS) and siderophore, which identified potentially interesting bioactive products: xenematide, luminmide, xenortide A-D, luminmycin A, putrebactin/avaroferrin and rhizomide A-C. This study demonstrates that bNN168.5_TH showed antibacterial activity by disrupting bacterial cytoplasmic membrane and the draft genome provided insights into the classes of bioactive products. This also provides a potential approach in developing a novel antibacterial agent.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / chemistry
  • Methicillin-Resistant Staphylococcus aureus* / genetics
  • Microbial Sensitivity Tests
  • Multigene Family
  • Oxacillin / pharmacology
  • Photorhabdus* / metabolism
  • Plant Extracts / pharmacology
  • Polyketide Synthases / genetics
  • Siderophores / metabolism
  • Staphylococcus aureus / genetics
  • Xenorhabdus* / genetics

Substances

  • Anti-Bacterial Agents
  • Plant Extracts
  • Siderophores
  • Polyketide Synthases
  • Oxacillin

Supplementary concepts

  • Photorhabdus akhurstii

Grants and funding

This work was supported by National Science, Research and Innovation Fund (Grant No. R2564B014). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.