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Genome-Wide In Silico Analysis of the Type VI Secretion System (T6SS) Within the Morganella Genus

Mathilde Duque1,2,3, Aymeric Jacquemin1,3, Delphine Girlich1,3

  • 1INSERM, CEA, Center for Immunology of Viral, Auto-Immune, Hematological and Bacterial Diseases » (IMVA-HB/IDMIT/UMRS1184), Paris-Saclay University, Fontenay-aux-Roses & Le Kremlin-Bicêtre, France.

Microbiologyopen
|April 30, 2026
PubMed

Insights

Morganella sibonii possesses diverse type VI secretion systems (T6SS), unlike most Morganella morganii. This T6SS variation may influence their roles as opportunistic pathogens and interactions within the gut microbiota.

Area of Science:

  • Microbiology
  • Genomics
  • Bacterial Pathogenesis

Background:

  • Morganella spp. are opportunistic pathogens in the human gut microbiota, known for adaptability and difficult-to-treat infections.
  • Morganella spp. are listed on the WHO Bacterial Pathogen Priority List (BPPL) due to their clinical significance.
  • Recent genomic studies highlight species-specific differences, particularly the presence of a unique type VI secretion system (T6SS) operon in M. sibonii.

Purpose of the Study:

  • To investigate the distribution and diversity of type VI secretion systems (T6SS) across different Morganella species.
  • To compare T6SS content, including effectors and immunity proteins, between clinically relevant species like M. sibonii and M. morganii.
  • To explore the potential role of T6SS in bacterial competition and host-pathogen interactions within the Morganella genus.

Main Methods:

  • Retrospective analysis of 293 Morganella genomes collected between 1966 and 2023.
  • Annotation of T6SS clusters and subtypes using SecReT6 and RAST platforms.
  • Phylogenetic analysis of tssB genes and in silico identification of putative effectors and immunity proteins using BlastP and Alphafold.

Main Results:

  • M. sibonii isolates were found to possess four distinct T6SS clusters (subtypes i1, i3 v.1, i3 v.2, and i5).
  • In contrast, the majority of M. morganii isolates lacked T6SS, with only one-third harboring a subtype i1 T6SS.
  • M. morganii frequently carried a T6SS-predicted TseV effector (95%), while M. sibonii displayed a broader range of effectors.

Conclusions:

  • Significant species-specific patterns in T6SS distribution exist within the Morganella genus.
  • The presence and diversity of T6SS, particularly in M. sibonii, may contribute to their pathogenicity and ecological niche.
  • T6SS likely plays a role in bacterial lifestyle competition and host-pathogen interactions, warranting further investigation into Morganella pathogenicity.
Keywords:
Morganella spp.host–pathogen interactionin silico characterizationtype VI secretion system (T6SS)

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