Aquimarina acroporae sp. nov., isolated from seawater surrounding scleractinian coral Acropora digitifera.

A Gram-stain-negative, aerobic, rod-shaped bacterium (D1M17T) was isolated from the seawater surrounding scleractinian coral Acropora digitifera in Daya Bay, Shenzhen, PR China. Strain D1M17T grew with 0-10 % (w/v) NaCl (optimum, 3-4 %), at 15-37 °C (optimum, 28 °C) and at pH 4.5-8.5 (optimum, pH 7.0-7.5). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain D1M17T formed a lineage within the genus Aquimarina, family Flavobacteriaceae, and it was distinct from the most closely related species Aquimarina salinaria LMG 25375T, Aquimarina gracilis JCM 17453T and Aquimarina spongiae KCTC 22663T with 16S rRNA gene sequence similarities of 97.2, 97.2 and 97.1 %, respectively. The major respiratory quinone was MK-6. The predominant fatty acids (more than 10 %) were iso-C15 : 0 (28.8 %), iso-C17 : 0 3-OH (21.5 %) and iso-C15 : 1 G (13.1 %). The DNA G+C content of D1M17T was 34.4 mol%. The polar lipids in D1M17T comprised one phospholipid and five unknown polar lipids. Phenotypic characteristics (physiological, biochemical and chemotaxonomic) also supported the taxonomic novelty of this isolate. Thus, strain D1M17T is considered to represent a novel species within the genus Aquimarina, for which the name Aquimarina acroporae sp. nov. is proposed. The type strain is D1M17T (=KCTC 92172T= MCCC 1K07224T).

Insights into the genomic repertoire of Aquimarina litoralis CCMR20, a symbiont of coral Mussismilia braziliensis.

Aquimarina litoralis CCMR20 originated from the coral Mussismilia braziliensis (Sebastião Gomes Reef, Brazil, summer 2010). To gain new insights into the genomic repertoire associated with symbioses, we obtained the genome sequence of this strains using Illumina sequencing. CCMR20 has a genome size of 6.3 Mb, 32.6%GC, and 5513 genes (37 tRNA and 4 rRNA). A more fine-grained examination of the gene repertoire of CCMR20 disclosed genes engaged with symbiosis (heterotrophic carbon metabolism, CAZymes, B-vitamins group, carotenoid pigment and antioxidant molecules production). Genomic evidence further expand the possible relevance of this symbiont in the health of Mussismilia holobiont.Whole Genome Shotgun project has been deposited at DDBJ/ENA/GeneBank under the accession number WEKL00000000.

Aquimarina algicola sp. nov., isolated from the surface of a marine red alga.

A bacterial strain, designated M625T, was isolated from the surface of a marine red alga. Phylogenetic trees were reconstructed based on the 16S rRNA gene and RpoB protein sequences, which indicated that the strain belongs to the genus Aquimarina within the family Flavobacteriaceae. Strain M625T showed high sequence similarities to A. aggregata RZW4-3-2 T (95.7%), A. seongsanensis CBA3208T (95.3%) and A. versatilis CBA3207T (95.0%). The AAI and POCP values between strain M625T and A. muelleri DSM 19832 T were 71.8% and 57.9% respectively. The dDDH and ANI values between strain M625T and A. aggregata were 19.5% and 74.6% respectively. The strain was Gram-stain negative, strictly aerobic, non-motile and long rod-shaped, and positive for hydrolysis of starch, cellulose, alginate, DNA and Tween 20. The dominant respiratory quinone was MK-6. The major fatty acids were iso-C15:0, iso-C17:0 3-OH, and iso-C15:1 G, and the polar lipids consisted of phosphatidylethanolamine, one unidentified phospholipid, two unidentified aminolipids, and seven unidentified lipids. Based on the polyphasic comparisons, strain M625T is proposed to represent a novel species within the genus Aquimarina, for which the name Aquimarina algicola sp. nov. (type strain M625T = MCCC 1H00399T = KCTC 72685 T) was proposed.

Inhibition of A549 Lung Cancer Cell Migration and Invasion by Ent-Caprolactin C via the Suppression of Transforming Growth Factor-ß-Induced Epithelial-Mesenchymal Transition.

The epithelial-mesenchymal transition (EMT) of cancer cells is a crucial process in cancer cell metastasis. An Aquimarina sp. MC085 extract was found to inhibit A549 human lung cancer cell invasion, and caprolactin C (1), a new natural product, α-amino-ε-caprolactam linked to 3-methyl butanoic acid, was purified through bioactivity-guided isolation of the extract. Furthermore, its enantiomeric compound, ent-caprolactin C (2), was synthesized. Both 1 and 2 inhibited the invasion and γ-irradiation-induced migration of A549 cells. In transforming growth factor-ß (TGF-ß)-treated A549 cells, 2 inhibited the phosphorylation of Smad2/3 and suppressed the EMT cell marker proteins (N-cadherin, ß-catenin, and vimentin), as well as the related messenger ribonucleic acid expression (N-cadherin, matrix metalloproteinase-9, Snail, and vimentin), while compound 1 did not suppress Smad2/3 phosphorylation and the expression of EMT cell markers. Therefore, compound 2 could be a potential candidate for antimetastatic agent development, because it suppresses TGF-ß-induced EMT.

Characterization of Aquimarina hainanensis isolated from diseased mud crab Scylla serrata larvae in a hatchery.

Mass mortality due to necrosis signs occurred in hatchery-reared zoea stage larvae of the mud crab Scylla serrata in Okinawa, Japan, and a causative bacterium was isolated. In this study, we identified and characterized the bacterium by genome analysis, biochemical properties and pathogenicity. The bacterium was a Gram-negative, non-motile, long rod, forming yellow colonies on a marine agar plate. It grew at 20-33°C (not at 37°C) and degraded chitin and gelatin. Phylogenetic analysis of the 16S rRNA gene sequence identified the bacterium as Aquimarina hainanensis. Genome sequence data obtained from Illumina MiSeq generated 29 contigs with 3.56 Mbp in total length and a G + C content of 32.5%. The predicted 16 chitinase genes, as putative virulence factors, had certain homologies with those of genus Aquimarina. Experimental infection with the bacterium conducted on larvae of four crustacean species, brine shrimp Artemia franciscana, freshwater shrimp Caridina multidentata, swimming crab Portunus trituberculatus and mud crab S. serrata, revealed that this bacterium was highly virulent to these species. The present study suggests that the bacterium caused mass mortality in mud crab seed production was A. hainanensis and can be widely pathogenic to crustaceans.

Aquimarina celericrescens sp. nov., isolated from seawater.

An orange-coloured, slender rod-shaped, gliding bacterium, designated NS08T, was isolated from coastal water of Xiaoshi Island, Weihai, China (37° 31' 36'' N 122° 00' 58'' E). Cells were Gram-stain-negative, non-spore-forming, non-flagellated, aerobic, catalase-positive and oxidase-negative. Growth occurred at 10-37 °C (optimum 30 °C), in the presence of 1.0-5.0 % (w/v) NaCl (optimum 2.0-3.0 %) and at pH 6.5-9.0 (optimum pH 7.0-7.5). Carotenoid pigments were produced but flexirubin-type pigments were not. The major fatty acids (>10 %) were iso-C15 : 0 and iso-C17 : 0 3-OH. The sole isoprenoid quinone of strain NS08T was menaquinone MK-6 and the DNA G+C content was 39.4 mol%. The polar lipid compositions of strain NS08T and the type strain of the type species of the genus Aquimarina, Aquimarina muelleri KCTC 12285T, were very similar with phosphatidylethanolamine, an unidentified aminolipid and two unknown polar lipids as the major components. A phylogenetic tree based on 16S rRNA gene sequences showed that strain NS08T formed an evolutionary lineage within the genus Aquimarina and shared the highest level of similarity to A. versatilis JCM 19528T (96.0 %) while level to A. muelleri KCTC 12285T was 95.0 %. Phenotypic characteristics distinguished strain NS08T from described members of the genus Aquimarina. On the basis of the evidence presented in this study, strain NS08T represents a novel species of the genus Aquimarina, for which the name Aquimarina celericrescens sp. nov. is proposed. The type strain is NS08T (=KCTC 52897T=MCCC 1H00191T).

Flagellimonas aquimarina sp. nov., and transfer of Spongiibacterium flavum Yoon and Oh 2012 and S. pacificum Gao et al. 2015 to the genus Flagellimonas Bae et al. 2007 as Flagellimonas flava comb. nov. and F. pacifica comb. nov., respectively.

A Gram-stain-negative, non-spore-forming, rod-shaped, aerobic and diffusible yellow-coloured bacterial strain, designated strain ECD12T was isolated from a seaweed, Ecklonia cava. The isolate required sea salts for growth. Catalase-positive and oxidase-negative. A phylogenetic tree based on 16S rRNA gene sequences showed that strain ECD12T formed an evolutionary lineage within the radiation enclosing the members of genera Spongiibacterium and Flagellimonas sharing the highest similarity to Flagellimonas eckloniae DOKDO007T (96.8 % 16S rRNA gene sequence similarity) followed by Spongiibacterium pacificum SW169T (96.4 %) and Spongiibacterium flavum DSM 22638T (96.1 %). The major fatty acids were iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 1 G. The new isolate contained MK-6 as the only isoprenoid quinone and phosphatidylethanolamine, two unidentified amino lipids and two unidentified lipids as the major polar lipids. The genomic DNA G+C content is 39 mol%. A number of phenotypic characteristics such as the production of diffusible pigment distinguished strain ECD12T from the related species. On the basis of the evidence presented in this study, a novel species, Flagellimonas aquimarina sp. nov., is proposed for strain ECD12T (=KCTC 52351T=JCM 32292T). Based on the sequence similarity, phylogenetic relationship and common morphological, physiological and chemical characters among the members of the genera Spongiibacterium and Flagellimonas, it is recommended that the two genera are combined into a single genus. Thus, transfer of S. flavumYoon and Oh 2012 and S. pacificum Gao et al. 2015 to the genus FlagellimonasBae et al. 2007 as Flagellimonas flava comb. nov. and Flagellimonas pacifica comb. nov., respectively, is also proposed.

Aquimarina spongiicola sp. nov., isolated from spongin.

A Gram-reaction-negative, aerobic, motile by gliding, non-spore-forming, rod-shaped bacterial strain, designated 122CH820-2T, was isolated from spongin. This bacterium was characterized to determine its taxonomic position by using a polyphasic approach. Strain 122CH820-2T grew well at 25-30 °C on marine agar. On the basis of 16S rRNA gene sequence similarity, strain 122CH820-2T belonged to the family Flavobacteriaceae and was closely related to Aquimarina mytili PSC33T (96.8 % sequence similarity) and A. penaei P3-1T (96.7 %). Lower sequence similarities (<96.5 %) were found with all of the other recognized members of the genus Aquimarina. The G+C content of the genomic DNA was 35.2 mol%. The major respiratory quinone was menaquinone MK-6 and the major fatty acids were C15 : 0, iso-C17 : 0 3-OH, iso-C15 : 1 G and iso-C15 : 0 3-OH. The polar lipids were phosphatidylethanolamine, one aminophospholipid and five unidentified polar lipids. Strain 122CH820-2T could be differentiated genotypically and phenotypically from recognized species of the genus Aquimarina. The isolate therefore represents a novel species, for which the name Aquimarina spongiicola sp. nov. is proposed, with the type strain 122CH820-2T (=KACC 19274T=LMG 30078T).

Aquimarina algiphila sp. nov., a chitin degrading bacterium isolated from the red alga Tichocarpus crinitus.

A strictly aerobic, Gram-stain-negative, rod-shaped, motile by gliding and yellow-orange pigmented flavobacterium, designated strain 9Alg 151T, was isolated from the Pacific red alga Tichocarpus crinitus. Phylogenetic analysis based on 16S rRNA gene sequences showed that the novel strain fell into the genus Aquimarina of the family Flavobacteriaceae with a 16S rRNA gene sequence similarity range of 94.2-98.2 % to the recognized species of the genus. Strain 9Alg 151T grew in the presence of 0.5-5 % NaCl and at 5-34 °C, and hydrolysed aesculin, agar, gelatin, starch, Tween 40, DNA and chitin. The predominant fatty acids were iso-C17 : 0 3-OH, iso-C15 : 0, iso-C15 : 1 G, iso-C15 : 0 3-OH, iso-C16 : 0, iso-C17 : 1ω8c and summed feature 3. The polar lipid profile comprised phosphatidylethanolamine, three unidentified aminolipids and three unidentified lipids. The major respiratory quinone was MK-6. The genomic DNA G+C content was 32.6 mol%. On the basis of 16S rRNA gene sequence data, and chemotaxonomic and phenotypic characteristics, strain 9Alg 151T represents a novel species of the genus Aquimarina, for which the name Aquimarina algiphila sp. nov. is proposed. The type strain is 9Alg 151T (=KCTC 23622T=KMM 6462T).

Salinisphaera aquimarina sp. nov., isolated from seawater.

A Gram-stain-negative, aerobic, rod-shaped, motile bacterium with a subpolar flagellum, designated strain CCMM005T, was isolated from offshore seawater at Qingdao, China. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain CCMM005T belonged to the genus Salinisphaera and exhibited highest 16S rRNA gene sequence similarity to Salinisphaera dokdonensis CL-ES53T (96.9 %). It showed lower sequence similarities (94.9-96.4 %) with all other representatives of the genus Salinisphaera. Optimal growth occurred in the presence of 4 % (w/v) NaCl, at 30 °C and at pH 7.0. The polar lipids of strain CCMM005T consisted of phosphatidylethanolamine, phosphatidylcholine, phosphatidylglycerol, one unidentified phosphoglycolipid and one unidentified phospholipid. The predominant isoprenoid quinone was Q-8. The major fatty acids were C19 : 0cyclo ω8c, C18 : 0 and C18 : 1ω7c. The DNA G+C content of strain CCMM005T was 65.3 mol%. On the basis of data from this polyphasic study, strain CCMM005T is considered to represent a novel species of the genus Salinisphaera, for which the name Salinisphaera aquimarina sp. nov. is proposed. The type strain is CCMM005T (=MCCC 1K03246T=KCTC 52640T).

Aquimarina sediminis sp. nov., isolated from coastal sediment.

A strictly aerobic, Gram-stain negative, long rod-shaped, motile by gliding and yellow pigmented bacterium, designated strain w01T, was isolated from marine sediment. The strain was characterised to determine its taxonomic position by using a polyphasic approach. Strain w01T was observed to grow optimally in the presence of 3.0% (w/v) NaCl, at 30 °C and to hydrolyse Tweens 20, 40 and 80, starch, casein and alginate. Carotenoid pigments were found to be produced but not flexirubin-type pigments. On the basis of 16S rRNA gene sequence similarities, strain w01T is phylogenetically affiliated with the genus Aquimarina and is closely related to Aquimarina macrocephali JCM 15542T (97.4% sequence similarity) and Aquimarina muelleri KCTC 12285T (97.0%). Lower sequence similarities (< 97.0%) were found with the other currently recognised members of the genus Aquimarina. The predominant fatty acids were identified as iso-C15:0 (33.7%), C18:0 3-OH (16.8%) and C17:1ω7c (10.6%). The polar lipid profile was found to contain phosphatidylethanolamine, an unidentified aminolipid and two unidentified polar lipids. MK-6 was identified as the sole respiratory quinone. The G + C content of the genomic DNA was determined to be 33.3 mol%. Strain w01T can be differentiated genotypically and phenotypically from recognised species of the genus Aquimarina. The isolate is therefore concluded to represent a novel species, for which the name Aquimarina sediminis sp. nov. is proposed, with the type strain w01T (= KCTC 62350T = MCCC 1H00287T).

Aquimarina seongsanensis sp. nov., isolated from sea water.

An orange, rod-shaped, gliding bacterium, designated strain CBA3208T, was isolated from sea water of Jeju Island, Republic of Korea. Cells were observed to be Gram-stain negative, strictly aerobic, catalase positive and oxidase negative and to hydrolyse starch, gelatin, and Tweens 40 and 80. The major fatty acids were identified as iso-C15:0, iso-C17:0 3-OH, and iso-C15:1 G. The only isoprenoid quinone was found to be menaquinone-6 (MK-6) and the major polar lipids were identified as phosphatidylethanolamine, two aminolipids and four unidentified polar lipids. The DNA G+C content of strain CBA3208T was determined to be 34.9 mol%. Strain CBA3208T is considered to represent a novel species of the genus Aquimarina, for which the name Aquimarina seongsanensis sp. nov. is proposed based on this polyphasic taxonomic analysis. The type strain is CBA3208T (=KACC 17667T =JCM 19529T).

Carapace microbiota in American lobsters (Homarus americanus) associated with epizootic shell disease and the green gland.

Epizootic Shell Disease (ESD) has posed a great threat, both ecologically and economically, to the American lobster population of Long Island Sound since its emergence in the late 1990s. Because of the polymicrobial nature of carapace infections, causative agents for ESD remain unclear. In this study, we aimed to identify carapace microbiota associated with ESD and its potential impact on the microbiota of internal organs (green gland, hepatopancreas, intestine, and testis) using high-throughput 16S rRNA gene sequencing. We found that lobsters with ESD harbored specific carapace microbiota characterized by high abundance of Aquimarina, which was significantly different from healthy lobsters. PICRUSt analysis showed that metabolic pathways such as amino acid metabolism were enriched in the carapace microbiota of lobsters with ESD. Aquimarina, Halocynthiibacter, and Tenacibaculum were identified as core carapace bacteria associated with ESD. Particularly, Aquimarina and Halocynthiibacter were detected in the green gland, hepatopancreas, and testis of lobsters with ESD, but were absent from all internal organs tested in healthy lobsters. Hierarchical clustering analysis revealed that the carapace microbiota of lobsters with ESD was closely related to the green gland microbiota, whereas the carapace microbiota of healthy lobsters was more similar to the testis microbiota. Taken together, our findings suggest that ESD is associated with alterations in the structure and function of carapace microbiota, which may facilitate the invasion of bacteria into the green gland.

Agarolytic Pathway in the Newly Isolated Aquimarina sp. Bacterial Strain ERC-38 and Characterization of a Putative ß-agarase.

Marine microbes, particularly Bacteroidetes, are a rich source of enzymes that can degrade diverse marine polysaccharides. Aquimarina sp. ERC-38, which belongs to the Bacteroidetes phylum, was isolated from seawater in South Korea. It showed agar-degrading activity and required an additional carbon source for growth on marine broth 2216. Here, the genome of the strain was sequenced to understand its agar degradation mechanism, and 3615 protein-coding sequences were predicted, which were assigned putative functions according to their annotated functional feature categories. In silico genome analysis revealed that the ERC-38 strain has several carrageenan-degrading enzymes but could not degrade carrageenan because it lacked genes encoding κ-carrageenanase and S1_19A type sulfatase. Moreover, the strain possesses multiple genes predicted to encode enzymes involved in agarose degradation, which are located in a polysaccharide utilization locus. Among the enzymes, Aq1840, which is closest to ZgAgaC within the glycoside hydrolase 16 family, was characterized using a recombinant enzyme expressed in Escherichia coli BL21 (DE3) cells. An enzyme assay revealed that recombinant Aq1840 mainly converts agarose to NA4. Moreover, recombinant Aq1840 could weakly hydrolyze A5 into A3 and NA2. These results showed that Aq1840 is involved in at least the initial agar degradation step prior to the metabolic pathway that uses agarose as a carbon source for growth of the strain. Thus, this enzyme can be applied to development and manufacturing industry for prebiotic and antioxidant food additive. Furthermore, our genome sequence analysis revealed that the strain is a potential resource for research on marine polysaccharide degradation mechanisms and carbon cycling.

Long-read sequencing reveals the shell microbiome of apparently healthy American lobsters Homarus americanus from Atlantic Canada.

The shell microbial community of lobsters-a key factor in the development of epizootic shell disease (ESD)-is still insufficiently researched in Atlantic Canada and many knowledge gaps remain. This study aimed to establish a baseline description and analysis of the shell microbiome of apparently healthy lobsters from four locations in the region. More than 180 lobster shell swab samples were collected from New Brunswick, Nova Scotia and Prince Edward Island (PEI). PacBio long-read 16S rDNA sequencing and bioinformatic analyses in QIIME2 identified the shell-associated bacteria. The shell microbiome of healthy lobsters consisted mainly of the bacterial classes Gammaproteobacteria, Saprospiria, Verrucomicrobiae, Alphaproteobacteria, Flavobacteriia, Acidimicrobiia and Planctomycetia. The microbial composition differed regionally and seasonally, with some classes showing decreased or increased relative abundances in the PEI samples as well as in the winter and spring samples in Nova Scotia. The core shell microbiome included potentially pathogenic as well as beneficial bacterial taxa, of which some were present only in certain regions. Bacterial taxa that have previously been associated with ESD were present on healthy lobsters in Atlantic Canada, but their frequency differed by location, sampling time, and moult stage. This study indicated that geographical and seasonal factors influenced the shell microbiome of apparently healthy lobsters more than host factors such as sex, size, and moult stage. Our results provide valuable reference microbial data from lobsters in a disease-free state.

Shell Disease Syndrome Is Associated with Reduced and Shifted Epibacterial Diversity on the Carapace of the Crustacean Cancer pagurus.

Cancer pagurus is highly susceptible to shell disease syndrome. However, little is known about concomitant changes in the epibacterial community. We compared the bacterial communities of black spot affected and nonaffected areas of the carapace by amplicon sequencing of 16S rRNA genes and 16S rRNA. Within each spot, bacterial communities of affected areas were less diverse compared to communities from nonaffected areas. Communities of different affected spots were, however, more divergent from each other, compared to those of different nonaffected areas. This indicates a reduced and shifted microbial community composition caused by the black spot disease. Different communities found in black spots likely indicate different stages of the disease. In affected areas, Flavobacteriaceae rose to one of the most abundant and active families due to the increase of Aquimarina spp., suggesting a significant role in shell disease syndrome. We isolated 75 bacterial strains from diseased and healthy areas, which are primarily affiliated with Proteobacteria and Bacteroidetes, reflecting the dominant phyla detected by amplicon sequencing. The ability to degrade chitin was mainly found for Gammaproteobacteria and Aquimarina spp. within the Flavobacteriia, while the ability to use N-acetylglucosamine, the monomer of the polysaccharide chitin, was observed for most isolates, including many Alphaproteobacteria. One-third of the isolates, including most Aquimarina spp., showed antagonistic properties, indicating a high potential for interactions between the bacterial populations. The combination of bacterial community analysis and the physiological properties of the isolates provided insights into a functional complex epibacterial community on the carapace of C. pagurus. IMPORTANCE In recent years, shell disease syndrome has been detected for several ecologically and economically important crustacean species. Large proportions of populations are affected, e.g., >60% of the widely distributed species Cancer pagurus in different North Sea areas. Bacteria play a significant role in the development of different forms of shell disease, all characterized by microbial chitinolytic degradation of the outer shell. By comparing the bacterial communities of healthy and diseased areas of the shell of C. pagurus, we demonstrated that the disease causes a reduced bacterial diversity within affected areas, a phenomenon co-occurring also with many other diseases. Furthermore, the community composition dramatically changed with some taxa rising to high relative abundances and showing increased activity, indicating strong participation in shell disease. Characterization of bacterial isolates obtained from affected and nonaffected spots provided deeper insights into their physiological properties and thus the possible role within the microbiome.

Engineering of salt-tolerant Shewanella aquimarina XMS-1 for enhanced pollutants transformation and electricity generation.

Saline wastewater poses a challenge during bio-treatment process due to salinity affecting the physiological activity of microorganisms and inhibiting their growth and metabolism. Thus, screening and engineering the salt-tolerant strains with stronger performances are urgent. Shewanella aquimarina XMS-1, a salt-tolerant dissimilated metal reducing bacteria (DMRB), was isolated from seawater environment. Its ability for reducing pollutants and generating electricity was enhanced by overexpression of riboflavin synthesis pathway encoding genes from S. oneidensis MR-1 under salt stress. Furthermore, upon contact with graphene oxide (GO), the engineered strain XMS-1/pYYDT-rib with enhanced flavins synthesis could reduce GO and self-assemble to form a three-dimensional (3D) biohybrid system named XMS-1/flavins/rGO. This 3D biohybrid system significantly enhanced the EET efficiency of S. aquimarina XMS-1. Our findings provide a feasible strategy for treatment of salt-containing industrial wastewater contaminated by metal and organic pollutants.

Aquimarina sp. Associated With a Cuticular Disease of Cultured Larval Palinurid and Scyllarid Lobsters.

Shell (cuticular) disease manifests in various forms and affects many crustaceans, including lobsters. Outbreaks of white leg disease (WLD) with distinct signs of pereiopod tissue whitening and death have been observed in cultured larvae (phyllosomas) of ornate spiny lobster Panulirus ornatus, eastern rock lobster Sagmariasus verreauxi, and slipper lobster Thenus australiensis. This study aimed to characterise and identify the causative agent of WLD through morphological and molecular (16S rRNA gene and whole genome sequencing) analysis, experimental infection of damaged/undamaged P. ornatus and T. australiensis phyllosomas, and bacterial community analysis (16S rRNA gene amplicon sequencing) of P. ornatus phyllosomas presenting with WLD during an outbreak. Bacterial communities of WLD-affected pereiopods showed low bacterial diversity and dominant abundance of Aquimarina spp. compared to healthy pereiopods, which were more diverse and enriched with Sulfitobacter spp. 16S rRNA gene Sanger sequencing of cultures from disease outbreaks identified the dominant bacterial isolate (TRL1) as a Gram-negative, long non-flagellated rod with 100% sequence identity to Aquimarina hainanensis. Aquimarina sp. TRL1 was demonstrated through comparative genome analysis (99.99% OrthoANIu) as the bacterium reisolated from experimentally infected phyllosomas presenting with typical signs of WLD. Pereiopod damage was a major predisposing factor to WLD. Histopathological examination of WLD-affected pereiopods showed masses of internalised bacteria and loss of structural integrity, suggesting that Aquimarina sp. TRL1 could enter the circulatory system and cause death by septicaemia. Aquimarina sp. TRL1 appears to have important genomic traits (e.g., tissue-degrading enzymes, gliding motility, and aggregate-promoting factors) implicated in the pathogenicity of this bacterium. We have shown that Aquimarina sp. TRL1 is the aetiological agent of WLD in cultured Palinurid and Scyllarid phyllosomas and that damaged pereiopods are a predisposing factor to WLD.

An agarase of glycoside hydrolase family 16 from marine bacterium Aquimarina agarilytica ZC1.

A novel ß-agarase gene aga672 was cloned from strain ZC1, the typical strain of agar-degrading Aquimarina agarilytica. Gene aga672 is composed of 2130 bp, and the encoded protein Aga672 showed an amino acid sequence identity of only 42% with reported agarases. Aga672 should belong to glycoside hydrolase family 16 according to the protein sequence similarity. The molecular mass of the recombinant Aga672 was estimated to be 98 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Aga672 decomposed agarose to produce neoagarotetraose, neoagarohexaose and neoagarooctaose as the main products. That is the main difference between Aga672 and other reported agarases of family GH16. The Km and Vmax for agarose degradation were 59.8 mg mL-1 and 154.3 U mg-1, respectively. The activity of Aga672 was stable at temperatures below 40°C and at pH 7.0-11.0 with the maximal agarase activity at 25°C and pH 7.0. The results showed that agarase Aga672 could be suitable to hydrolyze the gelated agarose. Thus, it has potential applications in the production of neoagarooligosaccharides directly from red alga.

Cuticles of European and American lobsters harbor diverse bacterial species and differ in disease susceptibility.

Diseases of lobster shells have a significant impact on fishing industries but the risk of disease transmission between different lobster species has yet to be properly investigated. This study compared bacterial biofilm communities from American (Homarus americanus) and European lobsters (H. gammarus), to assess both healthy cuticle and diseased cuticle during lesion formation. Culture-independent molecular techniques revealed diversity in the bacterial communities of cuticle biofilms both within and between the two lobster species, and identified three bacterial genera associated with shell lesions plus two putative beneficial bacterial species (detected exclusively in healthy cuticle or healing damaged cuticle). In an experimental aquarium shared between American and European lobsters, heterospecific transmission of potentially pathogenic bacteria appeared to be very limited; however, the claws of European lobsters were more likely to develop lesions when reared in the presence of American lobsters. Aquarium biofilms were also examined but revealed no candidate pathogens for environmental transmission. Aquimarina sp. 'homaria' (a potential pathogen associated with a severe epizootic form of shell disease) was detected at a much higher prevalence among American than European lobsters, but its presence correlated more with exacerbation of existing lesions rather than with lesion initiation.