Identification of a bacterial pathogen associated with Porites white patch syndrome in the Western Indian Ocean MATHIEU G. S  ER  E,* †‡ PABLO TORTOSA, § PASCALE CHABANET, ‡ JEAN-PASCAL QUOD,* MICHAEL J. SWEET ¶ and MICHAEL H. SCHLEYER † *Agence pour la Recherche et la Valorisation Marines (ARVAM), Ste Clotilde, Reunion Island, France, †Oceanographic Research Institute (ORI), Durban, KwaZulu-Natal, South Africa, ‡IRD – UMR ENTROPIE, Labex CORAIL, CS 41095, 97495 Sainte Clotilde Cedex, La R eunion, §Unit  e Mixte de Recherche “Processus Infectieux en Milieu Insulaire Tropical” (UMR PIMIT), Universit  e de La R eunion, Inserm1187, CNRS9192, IRD249, Plateforme de Recherche CYROI, 2 rue Maxime Rivi  ere, 97490 Ste Clotilde, Saint Denis, France, ¶Molecular Health and Disease Laboratory College of Life and Natural Sciences, University of Derby, Kedleston Road, Derby, UK Abstract Porites white patch syndrome (PWPS) is a coral disease recently described in the Western Indian Ocean. This study aimed to isolate and identify potential pathogens associated with PWPS utilizing both culture and nonculture screening techniques and inoculation trials. A total of 14 bacterial strains (those dominant in disease lesions, absent or rare in healthy tissues and considered potential pathogens in a previous study) were cultured and used to experimentally inoculate otherwise healthy individu- als in an attempt to fulfil Henle–Koch’s postulates. However, only one (P180R), identi- fied as closely related (99–100% sequence identity based on 1.4 kb 16S RNA sequence) to Vibrio tubiashii, elicited signs of disease in tank experiments. Following experimen- tal infection (which resulted in a 90% infection rate), the pathogen was also success- fully re-isolated from the diseased tissues and re-inoculated in healthy corals colonies, therefore fulfilling the final stages of Henle–Koch’s postulates. Finally, we report that PWPS appears to be a temperature-dependent disease, with significantly higher tissue loss (ANOVA: d.f. = 2, F = 39.77, P < 0.01) occurring at 30 °C [1.45  0.85 cm 2 per day (mean  SE)] compared to ambient temperatures of 28 and 26 °C (0.73  0.80 cm 2 per day (mean  SE) and 0.51  0.50 cm 2 per day (mean  SE), respectively). Keywords: coral disease, inoculation trials, Porites lutea, Vibrio tubiashii, Western Indian Ocean Received 2 May 2015; revision received 15 July 2015; accepted 16 July 2015 Introduction Coral diseases are increasingly recognized as a signifi- cant threat to coral reefs (Bruno & Selig 2007; Harvell et al. 2007) with over 30 different syndromes being reported worldwide (Weil et al. 2006; Godwin et al. 2012). These include 12 distinct white syndromes (WS), grossly characterized by advancing acute tissue loss (Willis et al. 2004; Sussman et al. 2008; Bourne et al. 2015). Although lacking definitive proof, many studies have proposed that bacteria are the main causative agents of these syndromes (Patterson et al. 2002; Sussman et al. 2008; Arboleda & Reichardt 2010; Luna et al. 2010; Sutherland et al. 2011; Godwin et al. 2012; Sweet & Bythell 2012; Ushijima et al. 2012). For example, Thalassomonas loyana has been proposed as the causal agent for white plaguelike diseases on Eilat coral reefs (Thompson et al. 2006) and Aurantimonas coralicida as the aetiological agent of white plague (WP) type II (Denner et al. 2003). More common, however, is the reference to the known marine pathogenic genus Vibrio. Several members of this genus, for example V. coralliilyticus (Ben-Haim & Rosenberg 2002; Sussman et al. 2008; Ushijima et al. 2014), V. harveyi (Luna et al. 2010; Godwin et al. 2012) and V. shiloi (Kushmaro et al. 1996, 2001; Israely et al. 2001), have been reported to be putative pathogens in many instances of WS over a large Correspondence: Mathieu G. S er e, Fax: 262 (0)2 62 48 33 53; E-mail: mathieu.sere@gmail.com © 2015 John Wiley & Sons Ltd Molecular Ecology (2015) 24, 4570–4581 doi: 10.1111/mec.13326