Two bacterial strains (DY05(T) and 47666-1) were isolated in Queensland, Australia, from diseased cultured crustaceans Panulirus ornatus and Penaeus monodon, respectively. On the basis of 16S rRNA gene sequence identity, the strains were shown to belong to the Harveyi clade of the genus Vibrio. Multilocus sequence analysis using five housekeeping genes (rpoA, pyrH, topA, ftsZ and mreB) showed that the strains form a monophyletic group with 94.4% concatenated sequence identity to the closest species. DNA-DNA hybridization experiments showed that strains DY05(T) and 47666-1 had 76% DNA similarity to each other, but <70% to their closest neighbours Vibrio harveyi LMG 4044(T) (< or =55%), Vibrio campbellii LMG 11216(T) (< or =52%) and Vibrio rotiferianus LMG 21460(T) (< or =46%). Strains DY05(T) and 47666-1 could be differentiated from their relatives on the basis of several phenotypic characteristics. The major fatty acids were C(15:0) iso 2-OH and/or C(16:1)omega7, C(16:0), C(18:1)omega7 and C(14:0). Based on the polyphasic evidence presented here, it can be concluded that strains DY05(T) and 47666-1 belong to the same novel species of the genus Vibrio, for which the name Vibrio owensii sp. nov. is proposed. The type strain is DY05(T) (=JCM 16517(T)=ACM 5300(T)).

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This is the first report of the successful induction of a transmissible disease in the coral-eating crown-of-thorns starfish Acanthaster planci (COTS). Injection of thiosulfate-citratebile-sucrose agar (TCBS) culture medium into COTS induced a disease characterized by discoloured and necrotic skin, ulcerations, loss of body turgor, accumulation of colourless mucus on many spines especially at their tip, and loss of spines. Blisters on the dorsal integument broke through the skin surface and resulted in large, open sores that exposed the internal organs. Oedema and reddened digestive tissues and destruction of connective fibers were common. Moreover, healthy COTS in contact with these infected animals also displayed signs of disease and died within 24 h. TCBS induced 100% mortality in injected starfish. There was no intro duction of new pathogens into the marine environment. TCBS promoted the growth of COTS' naturally occurring Vibrionales to high densities with subsequent symbiont imbalance followed by disease and death.

We used a polyphasic approach for precise identification of bacterial flora (Vibrionaceae) isolated from crown-of-thorns starfish (COTS) from Lizard Island (Great Barrier Reef, Australia) and Guam (USA, Western Pacific Ocean). Previous 16S rRNA gene phylogenetic analysis was useful to allocate and identify isolates within the Photobacterium, Splendidus and Harveyi clades but failed in the identification of Vibrio harveyi-like isolates. Species of the V. harveyi group have almost indistinguishable phenotypes and genotypes, and thus, identification by standard biochemical tests and 16S rRNA gene analysis is commonly inaccurate. Biochemical profiling and sequence analysis of additional topA and mreB housekeeping genes were carried out for definitive identification of 19 bacterial isolates recovered from sick and wild COTS. For 8 isolates, biochemical profiles and topA and mreB gene sequence alignments with the closest relatives (GenBank) confirmed previous 16S rRNA-based identification: V. fortis and Photobacterium eurosenbergii species (from wild COTS), and V. natriegens (from diseased COTS). Further phylogenetic analysis based on topA and mreB concatenated sequences served to identify the remaining 11 V. harveyi-like isolates: V. owensii and V. rotiferianus (from wild COTS), and V. owensii, V. rotiferianus, and V. harveyi (from diseased COTS). This study further confirms the reliability of topA−mreB gene sequence analysis for identification of these close species, and it reveals a wider distribution range of the potentially pathogenic V. harveyi group.

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