Cold Shock Domain Family Proteins Contribute to Virulence, Cellular Aggregation, and Flagella-based Motility in Listeria monocytogenes

Introduction: The gram-positive bacterium Listeria monocytogenes is an important foodborne pathogen that causes listeriosis and high rates of mortality amongst those with weakened immunity. Cold shock domain family proteins (Csps) are small global gene expression regulating proteins implicated in stress protection and virulence responses in bacteria. Listeria monocytogenes harbors three Csps; CspA, CspB and CspD.

Purpose: This study examined Csps roles in L. monocytogenes virulence, cell aggregation, and motility phenotypes.

Methods: A wild type strain and a series of csp gene (ΔcspABD, ΔcspBD, ΔcspAD, and ΔcspAB) deletion mutants of L. monocytogenes EGDe were compared with respect to virulence, aggregation, and flagella-based motility.

Results: Without Csps, the capability of L. monocytogenes to survive inside human macrophages and induce virulence, in zebra fish, was severely diminished. Moreover, cellular aggregation, surface flagellation, and swarming motility was attenuated upon loss of Csps. Protein and mRNA based comparison of gene expression showed that the optimal expression of important virulence (prfA, hly, mpl, actA, and plcB) and flagella (flaA) associated genes in L. monocytogenes, also, depends on intact Csp functions.

Significance: Our studies shows that Csp-dependent regulation of the expression of key virulence and flagella genes plays an important role in enabling the optimal expression of host virulence, cellular aggregation, and flagella-based motility in L. monocytogenes.