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The two-component system RstAB regulates production of a polysaccharide capsule with a role in virulence in the

Xosé M Matanza1, Laura López-Suárez1, Ana do Vale2,3

  • 1Departamento de Microbioloxía e Parasitoloxía, Instituto de Acuicultura, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.

Environmental Microbiology
|August 23, 2021
PubMed

Insights

The RstAB system in Photobacterium damselae subsp. damselae regulates key virulence factors, including a polysaccharide capsule crucial for pathogen survival and fish disease. This study elucidates RstAB

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Marine Biology

Background:

  • Photobacterium damselae subsp. damselae (Pdd) is a significant marine pathogen affecting aquatic animals and humans.
  • The two-component system RstAB is known to influence Pdd virulence, but its regulatory network remains incompletely understood.

Purpose of the Study:

  • To elucidate the RstAB regulon in Pdd.
  • To investigate the role of RstAB in regulating virulence factors, particularly a polysaccharide capsule.

Main Methods:

  • Comparative transcriptome analysis using RNA-sequencing of wild-type Pdd RM-71 and its ΔrstA and ΔrstB mutants.
  • Transmission electron microscopy to visualize capsular structures.
  • Phenotypic analysis of capsule synthesis mutants (wza, wzc) regarding serum/mucus resistance and fish virulence.

Main Results:

  • RstAB positively regulates known cytotoxins (Dly, PhlyP, PhlyC) and outer membrane proteins.
  • RstAB controls the synthesis of a polysaccharide capsule, essential for Pdd virulence.
  • Capsule synthesis mutants showed reduced resistance to host innate immunity (fish serum and mucus) and significantly impaired virulence in fish.

Conclusions:

  • RstAB is a critical positive regulator of Pdd virulence factors.
  • The polysaccharide capsule regulated by RstAB is essential for Pdd's full virulence, mediating resistance to host defenses.

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