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[The type IX secretion system and the type V pilus in the phylum Bacteroidetes]

Koji Nakayama1

  • 1Department of Microbiology and Oral Infection, Nagasaki University Graduate School of Biomedical Sciences.

Nihon Saikingaku Zasshi. Japanese Journal of Bacteriology
|November 8, 2017
PubMed

Insights

Researchers discovered a novel secretion system (type IX secretion system) in Bacteroidetes bacteria, linked to gliding motility. They also identified a new pilus formation mechanism (type V pili) in Porphyromonas gingivalis.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Bacteroidetes phylum bacteria, including Porphyromonas gingivalis, are significant human symbionts and pathogens.
  • Porphyromonas gingivalis causes periodontitis, with gingipain protease and pili being key virulence factors.
  • Previous understanding of bacterial secretion systems and pilus formation in Bacteroidetes was limited.

Purpose of the Study:

  • To investigate the secretion mechanism of gingipain in Porphyromonas gingivalis.
  • To characterize the biogenesis and function of P. gingivalis pili.
  • To identify novel secretion systems and pilus formation mechanisms within the Bacteroidetes phylum.

Main Methods:

  • Analysis of Porphyromonas gingivalis secretion pathways.
  • Proteolytic degradation studies involving gingipain.
  • Comparative genomic analysis across Bacteroidetes species.
  • Microscopy and biochemical assays to study pilus formation.

Main Results:

  • A novel secretion system, termed the Por secretion system (renamed type IX secretion system), was identified for gingipain secretion.
  • This type IX secretion system is conserved across Bacteroidetes and associated with gliding motility.
  • Pilus formation in P. gingivalis involves lipoprotein transport and arginine-gingipain-mediated processing.
  • This unique pilus assembly mechanism (type V pili) is prevalent in the class Bacteroidia.

Conclusions:

  • The type IX secretion system represents a significant discovery in bacterial protein transport within Bacteroidetes.
  • The novel type V pili formation mechanism highlights unique adaptations in P. gingivalis and related bacteria.
  • These findings advance our understanding of bacterial virulence, motility, and evolution in the Bacteroidetes phylum.

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