chicken-embryo-as-an-vivo-model-to-revive-viable-but-non-culturable

Chicken Embryo as an <em>In Vivo</em> Model to Revive Viable but Non-Culturable Pathogens

The chicken embryo has emerged as a popular in vivo model with increasing application in biomedical research due to its simplicity, affordability, and ...

INRAE, Université Paris-Saclay, AgroParisTech, Micalis Institute

L. monocytogenes causes listeriosis, a foodborne disease that is particularly dangerous for immunocompromised individuals and fetuses. Several virulence factors of this bacterial pathogen belong to a family of leucine-rich repeat (LRR)-containing proteins called internalins. Among these, InlP is known for its role in placental infection. We report here a function of InlP in mammalian cell nucleus organization. We demonstrate that bacteria do not produce InlP under in vitro culture conditions. When ectopically expressed in human cells, InlP translocates into the nucleus and changes the morphology of nuclear speckles, which are membrane-less organelles storing splicing factors. Using yeast two-hybrid screen, immunoprecipitation and pull-down experiments, we identify the tumor suppressor and splicing factor RBM5 as a major nuclear target of InlP. InlP inhibits RBM5-induced cell death and stimulate the formation of RBM5-induced nuclear granules, where the SC35 speckle protein redistributes. Taken together, these results suggest that InlP acts as a nucleomodulin controlling compartmentalization and function of RBM5 in the nucleus and that L. monocytogenes has developed a mechanism to target the host cell splicing machinery.

A bacterial virulence factor interacts with the splicing factor RBM5 and stimulates formation of nuclear RBM5 granules.

Stressed bacteria can enter a dormant viable but non-culturable (VBNC) state. VBNC pathogens pose an increased health risk as they are undetectable by growth-based techniques and can wake up back into a virulent state. Although widespread in bacteria, the mechanisms governing this phenotypic switch remain elusive. Here, we investigate the VBNC state transition in the human pathogen Listeria monocytogenes. We show that bacteria starved in mineral water become VBNC by converting into osmotically stable cell wall-deficient coccoid forms, a phenomenon that occurs in other Listeria species. We reveal the bacterial stress response regulator SigB and the autolysin NamA as major actors of VBNC state transition. We lastly show that VBNC Listeria revert to a walled and virulent state after passage in chicken embryos. Our study provides more detail on the VBNC state transition mechanisms, revealing wall-free bacteria naturally arising in aquatic environments as a potential survival strategy in hypoosmotic and oligotrophic conditions.

Article	Year
A bacterial virulence factor interacts with the splicing factor RBM5 and stimulates formation of nuclear RBM5 granules. Scientific reports\| PubMed ID: 36535993	2022
Aquatic environment drives the emergence of cell wall-deficient dormant forms in Listeria. Nature communications\| PubMed ID: 39358320	2024

Alessandro Pagliuso

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