Vibrio vulnificus Type 6 Secretion System 1 Contains Anti-Bacterial Properties

Abstract

Vibrio vulnificus is a bacterium responsible for severe gastroenteritis, sepsis and wound infections. Gastroenteritis and sepsis are commonly associated with the consumption of raw oysters, whereas wound infection is often associated with the handling of contaminated fish. Although classical virulence factors of this emerging pathogen are well characterised, there remains a paucity of knowledge regarding the general biology of this species. To investigate the presence of previously unreported virulence factors, we applied whole genome sequencing to a panel of ten V. vulnificus strains with varying virulence potentials. This identified two novel type 6 secretion systems (T6SSs), systems that are known to have a role in bacterial virulence and population dynamics. By utilising a range of molecular techniques and assays we have demonstrated the functionality of one of these T6SSs. Furthermore, we have shown that this system is subject to thermoregulation and is negatively regulated by increasing salinity concentrations. This secretion system was also shown to be involved in the killing of V. vulnificus strains that did not possess this system and a model is proposed as to how this interaction may contribute to population dynamics within V. vulnificus strains. In addition to this intra-species killing, this system also contributes to the killing of inter bacterial species and may have a role in the general composition of Vibrio species in the environment.

Complete Genome Sequence of Vibrio campbellii LMB 29 Isolated from Red Drum with Four Native Megaplasmids

“…Importantly, the recently identified T6SS (Coulthurst, 2013 ; Ho et al, 2014 ) was predicted in strain LMB 29 with T6SS1 (1,649,571–1,672,337 region) on chromosome I, T6SS2 (850,171–881,172 region) and T6SS3 (936,359–959,932 region) on chromosome II (Table 1 ). T6SSs have been implicated in eukaryotic cell targeting and virulence (Coulthurst, 2013 ; Ho et al, 2014 ), and is also believed to have anti-bacterial properties in Vibrio (Church et al, 2016 ). In addition, the tlh gene encoding a thermolabile hemolysin (TLH) of V. parahaemolyticus was found on chromosome II in strain LMB29.…”

Ecological implications of gene regulation by TfoX and TfoY among diverse Vibrio species

“…cholerae O1 El Tor strains, which are responsible for the current seventh pandemic of cholera (further referred to as pandemic strains), harbour a single T6SS. In contrast, many non-cholera Vibrio species encode several T6SSs, such as clinical isolates of V. parahaemolyticus and environmental isolates of V. vulnificus, both of which carry two T6SSs (Yu et al, 2012;Church et al, 2016). The genome of the squid symbiont V. fischeri, on the other hand, codes for one T6SS even though a recent study by Speare et al identified a secondary T6SS in several V. fischeri isolates that fostered niche domination within the squid's light organ (Speare et al, 2018).…”

The Antibacterial and Anti-Eukaryotic Type VI Secretion System MIX-Effector Repertoire in Vibrionaceae

“…The role of T6SSs in antibacterial competition and virulence has been characterized in several Vibrionaceae species, among them V. cholerae [ 12 , 19 ], V. parahaemolyticus [ 20 ], V. alginolyticus [ 21 ], V. proteolyticus [ 16 ], V. fluvialis [ 22 ], V. anguillarum [ 23 ], Aliivibrio fischeri [ 24 ], and V. vulnificus [ 25 ]. All Vibrionaceae T6SSs that have been studied to date exhibit antibacterial activities by delivering effectors carrying various catalytic domains, such as nucleases [ 26 ], peptidoglycan hydrolyses [ 27 , 28 ], phospholipases [ 21 ], and pore-forming toxin domains [ 29 ].…”