Mutation of the toxR or mshA genes from Vibrio coralliilyticus strain OCN014 reduces infection of the coral Acropora cytherea

Abstract

Thermal stress increases the incidence of coral disease, which is predicted to become more common with climate change, even on pristine reefs such as those surrounding Palmyra Atoll in the Northern Line Islands that experience minimal anthropogenic stress. Here we describe a strain of Vibrio coralliilyticus, OCN014, which was isolated from Acropora cytherea during an outbreak of Acropora white syndrome (AWS), a tissue loss disease that infected 25% of the A. cytherea population at Palmyra Atoll in 2009. OCN014 recreated signs of disease in experimentally infected corals in a temperature-dependent manner. Genes in OCN014 with expression levels positively correlated with temperature were identified using a transposon-mediated genetic screen. Mutant strains harbouring transposon insertions in two such genes, toxR (a toxin regulator) and mshA (the 11th gene of the 16-gene mannose-sensitive hemagglutinin (MSHA) type IV pilus operon), had reduced infectivity of A. cytherea. Deletion of toxR and the MSHA operon in a second strain of V. coralliilyticus, OCN008, that induces acute Montipora white syndrome in a temperature-independent manner had similarly reduced virulence. This work provides a link between temperature-dependent expression of virulence factors in a pathogen and infection of its coral host.

Bacterial Communities Associated With Healthy and Diseased (Skeletal Growth Anomaly) Reef Coral Acropora cytherea From Palk Bay, India

“…The association of Vibrio spp. have been well documented with high abundance in various species of diseased reef corals (Cervino et al, 2004;Sussman et al, 2008;Luna et al, 2010;Ushijima et al, 2016;Hadaidi et al, 2018). Whereas, in our study Vibrio spp.…”

Disentangling causation: complex roles of coral‐associated microorganisms in disease

“…coralliilyticus is strongly temperature dependent; between 24°C and 26°C, the bacterium infects the Symbiodinium causing coral bleaching, and above 26°C, the bacterium produces proteases which results in coral tissue necrosis (Ben‐Haim et al ., ; Rosenberg and Falkovitz, ). Furthermore, yellow band disease in both Caribbean and the Indo‐Pacific (Cervino et al ., ), WSs in the Indo‐Pacific (Luna et al ., ; Sussman et al ., ), Montipora WS (Ushijima et al ., ), Acropora WS in the North Pacific (Ushijima et al ., ), WBD type II (Ritchie and Smith, ) and dark spots disease in the Caribbean (Gil‐Agudelo et al ., ) were all implied to be caused by either a single Vibrio spp. or the consortium of vibrios.…”

“…Such approaches have proved effective in many coral disease studies e.g. (Bruno et al, 2003;Gignoux-Wolfsohn et al, 2017;Patterson et al, 2002;Ushijima et al, 2016;Voss and Richardson, 2006;Welsh et al, 2017) and will continue to be a vital tool to underpin our understanding of the complex multifactorial processes involved in coral diseases. However, limitations also exist and need to be considered when designing and conducting such experiments.…”

Draft Genome Sequence of Vibrio sp. Strain OCN044, Isolated from Palmyra Atoll, Northern Line Islands

“…However, comparatively less is known about the mutualistic and commensal Vibrio strains associated with these host organisms. Strain OCN044 is a nonpathogenic constituent of the microflora associated with the reefbuilding coral Acropora cytherea (10), and sequencing its genome provides insight into the processes underlying such interspecies interactions.…”

“…Vibrio sp. strain OCN044 was isolated from a healthy A. cytherea colony off the western reef terrace of Palmyra Atoll in the Northern Line Islands as previously described (10). Briefly, a healthy A. cytherea fragment was crushed in artificial seawater, plated on glycerol seawater (GSW) medium solidified with 1.5% agar, and incubated at 29°C overnight.…”