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Gorgonian octocorals are threatened by global and local stressors that can act synergistically to affect their health. In recent years, mass mortality events triggered by marine heatwaves have caused demographic declines in Mediterranean gorgonian populations that may lead to their collapse. Potential changes in microbiome composition under stressful conditions may further increase the susceptibility of the gorgonian holobiont to disease. Given the low recovery capacity of gorgonians, restoration approaches using transplantation are becoming an increasingly attractive option to counteract their decline. Here, we compared the survival and microbiome diversity of Paramuricea clavata colonies transplanted to sites differing in depth and local environmental conditions. Gorgonians sampled at a greater depth than the transplantation site were more likely to suffer necrosis after 1 year of monitoring. Gorgonian transplantation into environments disturbed by an anthropogenic source of pollution resulted in an imbalance of the microbiome with potential consequences on the success of restoration initiatives. • Necrosis and survival rates vary by site of origin and site of transplantation. • Transplantation can affect the composition and variability of the microbiome. • Dysbiosis of transplants is associated with colonisation by pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Two Gram-stain-negative, facultative anaerobic, motile, rod-shaped strains, S-B4-1U T and JOB-63a, forming small whitish transparent colonies on marine agar, were isolated from a sponge of the genus Haliclona . The strains shared 99.7% 16S rRNA gene sequence identity and a DNA-DNA hybridization value of 100%, but were differentiated by genomic fingerprinting using rep-PCRs. 16S rRNA gene sequence phylogeny placed the strains as a sister branch to the monophyletic genus Endozoicomonas ( Oceanospirillales ; Gammaproteobacteria) with 92.3–94.3% 16S rRNA gene sequence similarity to Endozoicomonas spp., 91.9 and 92.1% to Candidatus Endonucleobacter bathymodiolin, and 91.9 to 92.1% to the type strains of Kistimonas spp. Core genome based phylogeny of strain S-B4-1U T confirmed the phylogenetic placement. Major fatty acids were summed feature 3 (C 16:1 ω7c/C 16:1 ω6c) and 8 (C 18:1 ω7c/C 18:1 ω6c) followed by C 10:0 3-OH, C 16:0 , and C 18:0 . The G + C content was 50.1–51.4 mol%. The peptidoglycan diamino acid of strain S-B4-1U T was meso- diaminopimelic acid, the predominant polyamine spermidine, the major respiratory quinone ubiquinone Q-9; phosphatidylethanolamine, phosphatidylglycerol and phosphatidylserine were major polar lipids. Based on the clear phylogenetic distinction, the genus Parendozoicomonas gen. nov. is proposed, with Parendozoicomonas haliclonae sp. nov. as type species and strain S-B4-1U T (= CCM 8713 T = DSM 103671 T = LMG 29769 T ) as type strain and JOB-63a as a second strain of the species. Based on the 16S rRNA gene sequence phylogeny of the Oceanospirillales within the Gammaproteobacteria, the Endozoicomonaceae fam. nov. is proposed including the genera Endozoicomonas, Parendozoicomonas, and Kistimonas as well as the Candidatus genus Endonucleobacter. [ABSTRACT FROM AUTHOR]

Two gram-negative, facultative anaerobic, chemoorganoheterotrophic, motile and rod-shaped bacteria, strains AVMART05 T and KASP37, were isolated from ascidians (Tunicata, Ascidiaceae) of the genus Ascidiella collected at Gullmarsfjord, Sweden. The strains are the first cultured representatives of an ascidian-specific lineage within the genus Endozoicomonas (Gammaproteobacteria, Oceanospirillales, Hahellaceae). Both strains feature three distinct 16S rRNA gene paralogs, with identities of 98.9–99.1% (AVMART05 T ) and 97.7–98.8% (KASP37) between paralogs. The strains are closely related to Endozoicomonas atrinae and Endozoicomonas elysicola , with which they share 97.3–98.0% 16S rRNA gene sequence identity. Digital DNA–DNA hybridization, average nucleotide identity, and tetra-nucleotide correlation analysis indicate that both strains belong to a single species distinct from their closest relatives. Both strains feature similar DNA G + C contents of 46.70 mol% (AVMART05 T ) and 44.64 mol% (KASP37). The fatty acid patterns of AVMART05 T and KASP37 are most similar to those of Endozoicomonas euniceicola and Endozoicomonas gorgoniicola . Based on the polyphasic approach, we propose the species Endozoicomonas ascidiicola sp. nov. to accommodate the newly isolated strains. E. ascidiicola sp. nov. is represented by the type strain AVMART05 T (=DSM 100913 T = LMG 29095 T ) and strain KASP37 (=DSM 100914 = LMG 29096). [ABSTRACT FROM AUTHOR]