Characterization of pathogenic vibrios isolated from bivalve hatcheries in Galicia, NW Atlantic coast of Spain. Description of Vibrio tubiashii subsp. europaeus [corrected] subsp. nov

The taxonomic position of the bivalve pathogen PP-638 was studied together with five similar isolates. The strains were isolated from flat oyster (Ostrea edulis) and Manila clam (Venerupis philippinarum) cultures during outbreaks of disease in two shellfish hatcheries (Galicia, NW Spain). The pathogenicity, previously established for PP-638, was demonstrated with all isolates and for several bivalve species, including the original hosts. On the basis of phenotypic characterization and 16S rRNA gene sequences, a tight group was defined within the genus Vibrio. Multilocus sequence analysis (MLSA) based on concatenated sequences of the 16S rRNA gene and the five housekeeping genes recA, rpoA, pyrH, gyrB and ftsZ revealed that these strains form a cluster within the Orientalis clade, close to the species Vibrio tubiashii. The results of MLSA, the DDH rate and the phenotypic differences with the type strain of V. tubiashii supported the differentiation of the Galician isolates as a new subspecies within V. tubiashii, for which the name V. tubiashii subsp. europaeus [corrected] subsp. nov. is proposed (type strain PP-638(T)=CECT 8136(T)=DSM 7349(T)) The emended description of V. tubiashii is included. The pathogenicity assays widen the host range of V. tubiashii to add two unreported species, Venerupis decussata and Donax trunculus, and the described as relatively resistant species V. philippinarum.

Vibrio bivalvicida sp. nov., a novel larval pathogen for bivalve molluscs reared in a hatchery

Three isolates were obtained from cultures of carpet shell clam (Ruditapes decussatus) reared in a bivalve hatchery (Galicia, NW Spain) from different sources: healthy broodstock, moribund larvae and the seawater corresponding to the larval tank. All isolates were studied by a polyphasic approach, including a phylogenetic analysis based on concatenated sequences of the five housekeeping genes ftsZ, gyrB, pyrH, recA and rpoA. The analysis supported their inclusion in the Orientalis clade of the genus Vibrio, and they formed a tight group separated from the closest relatives: Vibrio tubiashii subsp. europaensis, Vibrio tubiashii subsp. tubiashii and Vibrio orientalis. The percentages of genomic resemblance, including average nucleotide identity, DNA-DNA hybridization and in silico genome-to-genome comparison, between the type strain and the closest relatives were below values for species delineation and confirmed the taxonomic position of the new species, which could be differentiated from the related taxa on the basis of several phenotypic and chemotaxonomic features, including FAME and MALDI-TOF-MS. The pathogenicity of the new species was demonstrated in larvae of R. decussatus, Ruditapes philippinarum, Ostrea edulis and Donax trunculus. The results demonstrated that the strains analyzed represented a novel species in the Orientalis clade of the genus Vibrio, for which the name Vibrio bivalvicida sp. nov. is proposed, with 605(T) (= CECT 8855(T)=CAIM 1904(T)) designated as the type strain.

The threat of pesticide and disease co-exposure to managed and wild bee larvae

Brood diseases and pesticides can reduce the survival of bee larvae, reduce bee populations, and negatively influence ecosystem biodiversity. However, major gaps persist in our knowledge regarding the routes and implications of co-exposure to these stressors in managed and wild bee brood. In this review, we evaluate the likelihood for co-exposure to brood pathogen and pesticide stressors by examining the routes of potential co-exposure and the possibility for pollen and nectar contaminated with pathogens and pesticides to become integrated into brood food. Furthermore, we highlight ways in which pesticides may increase brood disease morbidity directly, through manipulating host immunity, and indirectly through disrupting microbial communities in the guts of larvae, or compromising brood care provided by adult bees. Lastly, we quantify the brood research bias towards Apis species and discuss the implications the bias has on brood disease and pesticide risk assessment in wild bee communities. We advise that future studies should place a higher emphasis on evaluating bee brood afflictions and their interactions with commonly encountered stressors, especially in wild bee species.

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Brood exposure to pathogens and pesticides may occur frequently and in combination during the consumption of pollen and nectar.

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Brood pathogen virulence can be directly increased due to pesticide-mediated manipulation of larvae immune responses.

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Pesticides may indirectly increase brood disease morbidity by affecting larval gut microbial compositionand adult bee health.

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Research bias towards Apis species skews our understanding and management of brood disease and pesticide risks in wild bees.

First draft genome sequence of Vibrio rotiferianus isolated from diseased larvae of the spiny rock-scallop Spondylus limbatus during hatchery outbreaks

Scallop aquaculture is of economic importance along the east coast of the tropical Pacific. However, scallop diseases have been observed and there is limited knowledge about bacterial pathogens, especially in hatcheries. The objective of this study was to identify and characterize one of the predominant bacteria in outbreaks of vibriosis that occurred in a scallop hatchery in south-central Ecuador. The strain SA-10GR was isolated from moribund veliger larvae of the scallop Spondylus limbatus. SA-10GR was identified as Vibrio rotiferianus by phenotypic characterization and whole genome sequence analysis. SA-10GR is a strain with lytic activity, susceptible to many antibiotics except amoxicillin (25 μg), capable of producing siderophores and extracellular products with alkaline phosphatase, esterase, lipase esterase, leucine arylamidase, acid phosphatase, among others. The genome of V. rotiferianus consists of 5,579,217 bp; 5160 genes; 5086 protein-coding sequences (CDSs); 74 RNA genes (57 tRNA, 13 rRNA, and 4 ncRNA), and 40 pseudogenes. A total of six resistance genes vanT, adeF, E. coli parE, txR, CRP, and PBP3 were identified, and 110 virulence factors were detected. Functional characterization of SA-10GR shows extracellular products that cause damage to the fish model cell line (Epithelioma Papulosum Cyprini) and pathogenicity against larvae of the scallop Spondylus crassisquama and the oyster Magallana gigas (≥86 % mortality at a concentration of 104 CFU mL-1 at 24 h post-challenge). Both species of larvae infected with the SA-10GR strain showed clinical signs of vibriosis. This study represents the first documentation of a Vibrio rotiferianus strain as a potential pathogen of two important cultured bivalve species along the Pacific coast, expanding the susceptible host range and geographic distribution for this Vibrio species.