On the role of cell chaining in the attenuation of a Listeria monocytogenes divIVA mutant

10/08/2026

AI Summary

DivIVA promotes SecA2-dependent autolysin secretion and daughter cell separation; its loss causes cell chaining and attenuated virulence.
Coccoid mreB and filamentous ezrA morphologies do not impair invasion or intracellular replication, unlike ΔdivIVA cell chaining.
PrfA hyperactivation restores ΔdivIVA invasion but not intracellular replication; secA2 suppressors recover autolysin secretion, separation, invasion and partial replication.

Virulence. 2026 Dec;17(1):2707789. doi: 10.1080/21505594.2026.2707789. Epub 2026 Aug 9.

ABSTRACT

Listeria monocytogenes is a human pathogen invading nonphagocytic host cells, replicating within their cytosol, and spreading directly from cell to cell. These processes are mediated by specialized virulence factors but also depend on the DivIVA protein. DivIVA aids in the secretion of peptidoglycan-degrading autolysins in a process that requires the accessory secretion ATPase SecA2, thereby promoting daughter cell separation following cytokinesis. Consequently, a ΔdivIVA mutant forms elongated chains of unseparated daughter cells, which may explain its attenuated virulence. To further explore the role of cell chaining for attenuation, we here investigated how different morphological aberrations affect the virulence of L. monocytogenes. We generated coccoid mreB and filamentous ezrA mutants and compared them to the ΔdivIVA mutant in different in-vitro infection assays. Coccoid or filamentous morphologies did not impair host-cell invasion or intracellular replication, unlike the cell chaining of the ΔdivIVA mutant. Introduction of a hyperactive allele of the PrfA virulence regulator, resulting in constitutive overexpression of virulence genes, was sufficient to restore the invasion defect of the ΔdivIVA mutant, despite its pronounced cell-chaining phenotype but did not recover intracellular replication. We isolated suppressors of the ΔdivIVA mutant carrying mutations in secA2, which likely enhance the SecA2 ATPase activity. In these suppressors, autolysin secretion, daughter cell separation, and invasion were fully restored, and intracellular replication was partially recovered. Thus, maintaining normal rod-shaped morphology plays a minor role in L. monocytogenes pathogenesis. Instead, virulence attenuation in the ΔdivIVA mutant is better explained by distortions in PrfA- and SecA2-dependent processes.