title: Structural and regulatory mutations in Vibrio parahaemolyticus type III secretion systems display variable effects on virulence.
abstract: The Gram-negative bacterium, Vibrio parahaemolyticus, is a major cause of seafood-derived food poisoning throughout the world. The pathogenicity of V. parahaemolyticus is attributed to several virulence factors, including two type III secretion systems (T3SS), T3SS1 and T3SS2. Herein, we compare the virulence of V. parahaemolyticus POR strains, which harbor a mutation in the T3SS needle apparatus of either system, to V. parahaemolyticus CAB strains, which harbor mutations in positive transcriptional regulators of either system. These strains are derived from the clinical RIMD 2210633 strain. We demonstrate that each mutation affects the virulence of the bacterium in a different manner. POR and CAB strains exhibited similar levels of swarming motility and T3SS effector production and secretion, but the CAB3 and CAB4 strains, which harbor a mutation in the T3SS2 master regulator gene, formed reduced biofilm growth under T3SS2 inducing conditions. Additionally, while the cytotoxicity of the POR and CAB strains was similar, the CAB2 (T3SS1 regulatory mutant) strain was strikingly more invasive than the comparable POR2 (T3SS1 structural mutant) strain. In summary, creating structural or regulatory mutations in either T3SS1 or T3SS2 causes differential downstream effects on other virulence systems. Understanding the biological differences of strains created from a clinical isolate is critical for interpreting and understanding the pathogenic nature of V. parahaemolyticus.
authors.affiliation: Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Calder
authors.forename: Marcela
authors.initials: M
authors.lastname: de Souza Santos
authors.forename: Victoria
authors.initials: V
authors.lastname: Attah
authors.forename: John
authors.initials: J
authors.lastname: Klimko
authors.forename: Jessie
authors.initials: J
authors.lastname: Fernandez
authors.forename: Dor
authors.initials: D
authors.lastname: Salomon
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Krachler
authors.forename: Kim
authors.initials: K
authors.lastname: Orth
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D015964:Gene Expression Regulation, Bacterial; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D014735:Vibrio Infections / Q000382:microbiology*; D014736:Vibrio parahaemolyticus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems
keywords: T3SS; Vibrio parahaemolyticus; bacterial virulence; biofilm; invasion