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)).

bThe type strain of Vibrio owensii (DY05) was isolated during an epizootic of aquaculture-reared larvae (phyllosomas) of the ornate spiny lobster (Panulirus ornatus). V. owensii DY05 was formally demonstrated to be the etiological agent of a disease causing rapid and reproducible larval mortality with pathologies similar to those seen during disease epizootics. Vectored challenge via the aquaculture live feed organism Artemia (brine shrimp) caused consistent cumulative mortality rates of 84 to 89% after 72 h, in contrast to variable mortality rates seen after immersion challenge. Histopathological examination of vector-challenged phyllosomas revealed bacterial proliferation in the midgut gland (hepatopancreas) concomitant with epithelial cell necrosis. A fluorescent-protein-labeled V. owensii DY05 transconjugant showed dispersal of single cells in the foregut and hepatopancreas 6 h postexposure, leading to colonization of the entire hepatopancreas within 18 h and eventually systemic infection. V. owensii DY05 is a marine enteropathogen highly virulent to P. ornatus phyllosoma that uses vector-mediated transmission and release from host association to a planktonic existence to perpetuate transfer. This understanding of the infection process will improve targeted biocontrol strategies and enhance the prospects of commercially viable larviculture for this valuable spiny lobster species. Major steps toward the commercialization of closed life cycle aquaculture production of the ornate spiny lobster (Panulirus ornatus) have been reported recently (36), yet nutritional deficits (41) and mortality caused by bacterial disease (5) remain major constraints to hatchery productivity. Mass mortalities of larvae (phyllosomas) are often associated with enteric vibriosis, an infection of the midgut gland (hepatopancreas) caused by Vibrio species (6, 52).Members of the genus Vibrio are natural marine inhabitants, playing important roles in nutrient cycling and forming associations with zooplankton (49). Microhabitat preferences and ecological selection may be key factors in the speciation of vibrios (20), and intensive aquaculture systems are thought to select for bacterial virulence, including traits that enhance infectivity and transmission (29,33). Accordingly, many Vibrio species are pathogenic to cultured crustacean zooplanktonic larval forms, including the three closely related species Vibrio harveyi (32, 35), V. campbellii (17, 44), and the recently described V. owensii (8).It is of paramount importance to the development of efficient disease management strategies that pathogens be identified by using experimental infection models that provide information on infection routes and infection dynamics (38). Recently, microorganisms engineered to express fluorescent proteins (FP) have significantly increased the understanding of invasive pathways and infection dynamics of pathogens, including V. anguillarum, Aeromonas hydrophila, and Edwardsiella tarda in fish models (10, 24, 30) and V. harveyi in abalone (50). Panulirus sp. p...

With recent technologies making it possible for commercial scale closed life-cycle aquaculture production of spiny lobster (Panulirus ornatus) comes a strong impetus to further understand aspects of lobster health. The gut microbiome plays a crucial role in host health, affecting growth, digestion, immune responses and pathogen resistance. Herein we characterise and compare gut microbiomes across different developmental stages (6-7 days post-emergence [dpe], 52 dpe and 13 months post-emergence [mpe]) and gut regions (foregut, midgut and hindgut) of cultured P. ornatus juveniles. Gut samples were analysed using 16S rRNA next-generation sequencing. Core gut microbiomes of P. ornatus comprised the phyla Tenericutes and Proteobacteria. Within class Gammaproteobacteria, families Pseudoalteromonadaceae and Vibrionaceae were dominant members across the majority of the gut microbiomes. Characterisation of bacterial communities from 13 mpe lobsters indicated that the hindgut microbiome was more diverse and compositionally dissimilar to the foregut and midgut. The bacterial composition of the hindgut was more similar among younger juveniles (6-7 dpe and 52 dpe) compared to 13 mpe lobsters. This is the first study to explore gut microbiomes of spiny lobster juveniles. We demonstrate that the composition of the gut microbiome was shaped by gut region, whereas the structure of the hindgut microbiome was influenced by developmental stage.