The type III secretion system of Vibrio alginolyticus induces rapid apoptosis, cell rounding and osmotic lysis of fish cells

Abstract

Vibrio alginolyticus is a Gram-negative bacterium and has been recognized as an opportunistic pathogen in humans as well as marine animals. However, the virulence mechanisms for this species of Vibrio have not been elucidated. This study characterized multiple mechanisms that induce cell death in fish cells upon infection with a V. alginolyticus strain, ZJO. The bacterium required its type III secretion system (T3SS) to cause rapid death of infected fish cells. Dying cells exhibited some features of apoptotic cells, such as membrane blebbing, nuclear condensation and DNA fragmentation. Further studies showed that caspase-3 was activated by the T3SS of the ZJO strain, confirming that infection with V. alginolyticus rapidly induces T3SS-dependent apoptosis in fish cells. Infection with the ZJO strain also led to membrane pore formation and release of cellular contents from infected fish cells, as evidenced by lactate dehydrogenase release and the uptake of a membrane-impermeable dye. Importantly, inhibition of apoptosis did not prevent ZJO-infected cells from releasing cellular contents and did not block cell rounding. Taken together, these data demonstrate that infection with V. alginolyticus may promote at least three different T3SS-dependent events, which lead to the death of fish cells. This study provides an important insight into the mechanism used by Vibrio species to cause host-cell death.

ExsE Is a Negative Regulator for T3SS Gene Expression in Vibrio alginolyticus

“…VscC is a structural protein that is required for a functional T3SS in V. alginolyticus (Zhao et al, 2010). When vscC was knocked out and exsE was expressed in trans (Δ vscC :p exsE ), ExsE was not detected in the supernatant (Figure 5, lane 6).…”

“…V. alginolyticus is prevalent in coastal waters of southern China and it is commonly associated with costly disease of aquatic animals (Austin, 2010). Previous studies demonstrated that V. alginolyticus induces apoptosis, cell rounding and osmotic lysis in fish cells and autophagy in mammalian cell lines in a T3SS-dependent manner (Zhao et al, 2010, 2011). Although the T3SS of V. alginolyticus is similar to T3SS1 of V. parahaemolyticus with respect to gene synteny (Zhao et al, 2010), it is unclear if the same regulatory mechanism is employed by V. alginolyticus .…”

“…Vibrio alginolyticus is widely distributed as the part of the normal microbial flora in marine environments (Zhao et al, 2010). It is also an opportunistic pathogen to people and causes otitis, conjunctivitis, superficial pyodermatitis, gastroenteritis, and life-threating infections in immunocompromised patients (Chien et al, 2002; Campanelli et al, 2008).…”

Expression and functional characterization of a gene associated with retinoid-interferon-induced mortality 19 (GRIM-19) from orange-spotted grouper (Epinephelus coioides)

“…The pNA light emission was quantified on a TECAN Infinite 200 plate reader at 405 nm. The assay was performed as described previously [20].…”

An Overview of Virulence-Associated Factors of Gram-Negative Fish Pathogenic Bacteria

“…Infection experiments in fish showed that the eseD mutant exhibited slower proliferation and a 10-fold decrease in virulence in fish (Wang et al, 2010a). Finally, in V. alginolyticus, a type III secretion system (T3SS) is required to cause rapid death of infected carp fish cells (Zhao et al, 2010).…”