Search Results (6)

Two novel strains, CB1-14^T and CB2-10, were isolated from the marine polychaetes Chaetopterus cautus from the Sea of Japan. Phylogenetic analysis based on the 16S rRNA sequences revealed that the two strains belong to the genus Vibrio, sharing 98.96% identity with Vibrio hangzhouensis CN 83^T. MLSA using five protein-coding genes (ftsZ, gyrA, gyrB, mreB, and rpoA) showed that CB1-14^T and CB2-10 are closely related to the members of the Mediterranei clade, namely Vibrio mediterranei CECT 621^T, Vibrio barjaei 3062^T, Vibrio thalassae CECT 8203^T, Vibrio hangzhouensis CGMCC 1.7062^T, Vibrio maritimus CAIM 1455^T, and Vibrio variabilis CAIM 1454^T. Based on both MLST neighbor-net phylogenetic network and phylogenomic tree results, they fell into the subclade formed by V. maritimus CAIM 1455^T and V. variabilis CAIM 1454^T. Both new strains CB1-14^T and CB2-10 showed the highest ANI/AAI values of 91.3%/92.7% with V. variabilis CAIM 1454^T and 90.3%/93.1% with V. maritimus CAIM 1455^T. The dDDH values between strain CB1-14^T and the members of the Mediterranei clade ranged from 20.9% to 45.7%. Major fatty acids were C_16:1ω9c, C_16:1ω7c, and C_18:1ω9c, followed by C_16:0 and C_18:1ω7c. The genome of CB1-14^T is 5,591,686 bp in size, with DNA G+C content of 46.1%. It consists of two circular chromosomes (3,497,892 and 1,804,652 bp) and one plasmid (241,015 bp) and comprises 4782 protein-coding genes and 10 rrn operons. The CB1-14^T and CB2-10 genomes were enriched in CAZyme-encoding genes of the following families: GH1, GH3, GH13, GH23, GH43, GH94, PL17, and CE4, indicating the potential to catabolize alginate, xylan, and chitin, common polysaccharides in marine ecosystems. Based on the combined phylogenomic analyses and phenotypic properties, a new species, Vibrio chaetopteri sp. nov., is proposed, with CB1-14^T = (KMM 8419^T = KCTC 92790^T) as the type strain. Full article

Vibrio mediterranei, a bacterial pathogen of bivalves, has exhibited strain-dependent virulence. The mechanisms behind the variations in bivalve pathogenicity between V. mediterranei strains have remained unclear. However, a preliminary analysis of the extracellular product (ECP) proteomes has revealed differences in protein compositions between low- and high-virulence strains; in addition to 1265 shared proteins, 127 proteins have been identified to be specific to one low-virulence strain and 95 proteins to be specific to two high-virulence strains. We further studied the ECP proteins of the three V. mediterranei strains from functional perspectives using integrated genomics and proteomics approaches. The results showed that lipid metabolism, transporter activity and membrane transporter pathways were more enriched in the ECPs of the two high-virulence strains than in those of the low-virulence strain. Additionally, 73 of the 95 high-virulence strain-specific proteins were found to have coding genes in the genome but were not expressed in the low-virulence strain. Moreover, comparisons with known virulence factors in the Virulence Factor Database (VFDB) and the Pathogen–Host Interactions Database (PHI-base) allowed us to predict more than 10 virulence factors in the categories of antimicrobial activity/competitive advantage, the effector delivery system and immune modulation, and the high-virulence strain-specific ECP proteins consisted of a greater percentage of known virulence factors than the low-virulence strain. Particularly, two virulence factors, MtrC and KatG, were identified in the ECPs of the two high-virulence strains but not in those of the low-virulence strain. Most coding genes of the ECP proteins including known virulence factors were identified on chromosome 1 of V. mediterranei. Our findings indicate that variations in virulence factor composition in the bacterial ECPs may partially account for the differences in the bivalve pathogenicity between V. mediterranei strains. Full article

The lipidic extract of Undaria pinnatifida, one of the worst invasive species, was investigated for its potential exploitation in biotechnological applications. The antimicrobial activity of the lipidic extract in three different portions (blade, sporophyll, and holdfast) was assessed by using the Kirby–Bauer method, while the antioxidant activity was evaluated by the TEAC, ORAC, and Folin–Ciocalteu assays. NMR spectroscopy and thin-layer chromatography were employed for the chemical characterization. The extracts showed antibacterial activity against several of the tested Vibrio species: V. aestuarinus, V. fischeri, V. furnisii, V. inusitatus, V. litoralis, and V. mediterranei, including some pathogens for farmed fish. Intriguing antioxidant activity was recorded, with the highest value in the blade (126.907 ± 28.993 mmol Trolox equivalent/g TEAC). Free, saturated, unsaturated, and polyunsaturated fatty acids were highlighted by 1D and 2D NMR spectroscopy. The presence of ω-3 and ω-6 PUFAs indicates the importance of this algal species in the food industry. We suggest the employment of U. pinnatifida as source of new and safer therapeutic agents to control fish and shellfish diseases due to vibriosis, as well as a source of natural antioxidants that are useful for human health, considering the growing interest in the development of strategies for invasive seaweed control. Full article

Due to the emergence of multidrug-resistant bacteria, commonly known as “superbugs”, phage therapy for the control of bacterial diseases rose in popularity. In this context, the use of phages for the management of many important bacterial diseases in the aquaculture environment is auspicious. Vibrio harveyi, a well-known and serious bacterial pathogen, is responsible for many disease outbreaks in aquaculture, resulting in huge economic and production losses. We isolated and fully characterized a novel bacteriophage, Vibrio phage Virtus, infecting V. harveyi strain VH2. Vibrio phage Virtus can infect a wide spectrum of Vibrio spp., including strains of V. harveyi, V. owensii, V. campbellii, V. parahaemolyticus, and V. mediterranei. It has a latent period of 40 min with an unusually high burst size of 3200 PFU/cell. Vibrio phage Virtus has a double-stranded DNA of 82,960 base pairs with 127 predicted open reading frames (ORFs). No virulence, antibiotic resistance, or integrase-encoding genes were detected. In vivo phage therapy trials in gilthead seabream, Sparus aurata, larvae demonstrated that Vibrio phage Virtus was able to significantly improve the survival of larvae for five days at a multiplicity of infection (MOI) of 10, which suggests that it can be an excellent candidate for phage therapy. Full article

Pinna nobilis populations, constituting the largest bivalve mollusk endemic to the Mediterranean, is characterized as critically endangered, threatened by extinction. Among the various factors proposed as etiological agents are the Haplosporidium pinnae and Mycobacterium sp. parasites. Nevertheless, devastation of the fan mussel populations is still far from clear. The current work is undertaken under a broader study aiming to evaluate the health status of Pinna nobilis population in Aegean Sea, after the mass mortalities that occurred in 2019. A significant objective was also (a) the investigation of the etiological agents of small-scale winter mortalities in the remaining populations after the devastating results of Haplosporidium pinnae and Mycobacterium sp. infections, as well as (b) the examination of the susceptibility of the identified bacterial strains in antibiotics for future laboratory experiments. Microbiological assays were used in order to detect the presence of potential bacterial pathogens in moribund animals in combination with molecular tools for their identification. Our results provide evidence that Vibrio bacterial species are directly implicated in the winter mortalities, particularly in cases where the haplosporidian parasite was absent. Additionally, this is the first report of Vibrio mediterranei and V. splendidus hosted by any bivalve on the Greek coastline. Full article

Vibrio mediterranei 117-T6 is extensively pathogenic to several Pyropia species, leading to the death of conchocelis. In this study, the first V. mediterranei phage (named Vibrio phage Yong-XC31, abbreviated as Yong-XC31) was isolated. Yong-XC31 is a giant phage containing an icosahedral head about 113 nm in diameter and a contractible tail about 219 nm in length. The latent period of Yong-XC31 is 30 min, and burst size is 64,227. Adsorption rate of Yong-XC31 to V. mediterranei 117-T6 can reach 93.8% in 2 min. The phage genome consisted of a linear, double-stranded 290,532 bp DNA molecule with a G + C content of 45.87%. Bioinformatic analyses predicted 318 open reading frames (ORFs), 80 of which had no similarity to protein sequences in current (26 January 2021) public databases. Yong-XC31 shared the highest pair-wise average nucleotide identity (ANI) value of 58.65% (below the ≥95% boundary to define a species) and the highest nucleotide sequence similarity of 11.71% (below the >50% boundary to define a genus) with the closest related phage. In the proteomic tree based on genome-wide sequence similarities, Yong-XC31 and three unclassified giant phages clustered in a monophyletic clade independently between the family Drexlerviridae and Herelleviridae. Results demonstrated Yong-XC31 as a new evolutionary lineage of phage. We propose a new phage family in Caudovirales order. This study provides new insights and fundamental data for the study and application of giant phages. Full article