The complete mitochondrial genome of Trematomus hansoni Boulenger, 1902 (Perciformes, Nototheniidae).

The striped notothen Trematomus hansoni is an Antarctic fish species belonging to the family Nototheniidae (cod icefishes) that is distributed throughout the Southern Ocean. In this study, the complete mitochondrial genome of T. hansoni was sequenced using an Illumina MiSeq platform. The circular mitochondrial genome is 19,218 bp long and contains 13 protein-coding genes, 23 tRNA genes, two rRNA genes, and one control region. Notably, there are two trnG-UCC genes and the second gene, located between trnE-UUC and trnI-GAU, has no D-arm structure. The base composition is 56.18% of A + T and 43.82% of G + C. The phylogenetic analysis supports that T. hansoni is grouped into a single clade with T. bernacchii. This study will be a valuable resource for further research on the phylogeny and evolution of the genus Trematomus.

The complete mitochondrial genome of Gobionotothen gibberifrons (Perciformes, Nototheniidae).

The humped rockcod, Gobionotothen gibberifrons, is an Antarctic fish of the genus Gobionotothen in the family Nototheniidae and order Perciformes. To date, little biological information has been recorded about the genus Gobionotothen. Here, we report the first complete mitogenome of the genus Gobionotothen. The mitochondrial genome of G. gibberifrons is 18,631 bp in length, comprising 13 protein-coding genes, 24 tRNA genes (trnP-UGG and trnT-UGU were duplicated), 2 rRNA genes, and non-coding control regions. The base composition was 53.74% for A + T and 46.26% for G + C. This new mitochondrial genome of G. gibberifrons provides basic information for further phylogenetic analysis, suggesting the necessity to exploit a variety of newly discovered mitogenome sequences to infer inconclusive evolutionary relationships in Antarctic fishes.

Effects of dopamine and melatonin treatment on the expression of the genes associated with artificially induced sexual maturation in Japanese eel, Anguilla japonica.

Japanese eel (Anguilla japonica) is a commercially important fish species in Asia. Understanding factors like photoperiod, temperature, and lunar cycles is crucial for successful aquaculture and managing its reproduction. Melatonin and dopamine (DA) are essential for regulating reproduction in vertebrates, including fish. This study investigated the effects of melatonin and DA on the reproductive system of mature male Japanese eels to better understand reproductive regulation in fish. To clarify the effects of these hormones on sexual maturation in eels, a critical stage in the reproductive process, sexual maturation was induced by injecting human chorionic gonadotropin, which stimulates the production of sex hormones. To check the effect of melatonin and DA on sexual maturation, DA, melatonin, and DA + domperidone were intraperitoneally injected into fish from each group (six per treatment) at a dose of 1 mg/kg body weight. The fish were then examined using quantitative RT-PCR by comparing the messenger RNA level of reproduction-related genes (gonadotropin releasing hormone 1; gnrh1, gonadotropin releasing hormone 2; gnrh2, follicle stimulating hormone; fshß, luteinizing hormone; lhß and DA receptor 2b; d2b), involved in the gonadotropic axis in eels, to those that received a control injection. The results indicate significant differences in the expression levels of gnrh1, gnrh2 and d2b in the brain and d2b, fshß, lhß in the pituitary at different stages of sexual maturation. Melatonin appears to enhance the production of sex gonadotropins, whereas DA inhibits them. These findings suggest an interaction between melatonin and DA in regulating reproduction in Japanese eels.

DNA barcoding and morphological identification of spiny lobsters in South Korean waters: a new record of Panulirus longipes and Panulirus homarus homarus.

To date, 19 species of spiny lobsters from the genus Panulirus have been discovered, of which only P. japonicus, P. penicilatus, P. stimpsoni, and P. versicolor have been documented in South Korean waters. In this study, we aimed to identify and update the current list of spiny lobster species that inhabit South Korean waters based on the morphological features and the phylogenetic profile of cytochrome oxidase I (COI) of mitochondrial DNA (mtDNA). Spiny lobsters were collected from the southern and eastern coasts of Jeju Island, South Korea. Phylogenetic analyses were performed using neighbor-joining (NJ), maximum likelihood (ML), and Bayesian inference (BI) methods. The ML tree was used to determine the spiny lobster lineages, thereby clustering the 17 specimens collected in this study into clades A, B, C, and D, which were reciprocally monophyletic with P. japonicus, P. homarus homarus, P. longipes, and P. stimpsoni, respectively. These clades were also supported by morphological examinations. Interestingly, morphological variations, including the connected pleural and transverse groove at the third abdominal somite, were observed in four specimens that were genetically confirmed as P. japonicus. This finding is novel within the P. japonicus taxonomical reports. Additionally, this study updates the documentation of spiny lobsters inhabiting South Korean waters as P. longipes and P. homarus homarus were recorded for the first time in this region.

Characterization of glycoside hydrolase family 11 xylanase from Streptomyces sp. strain J103; its synergetic effect with acetyl xylan esterase and enhancement of enzymatic hydrolysis of lignocellulosic biomass.

BACKGROUND: Xylanase-containing enzyme cocktails are used on an industrial scale to convert xylan into value-added products, as they hydrolyse the ß-1,4-glycosidic linkages between xylopyranosyl residues. In the present study, we focused on xynS1, the glycoside hydrolase (GH) 11 xylanase gene derived from the Streptomyces sp. strain J103, which can mediate XynS1 protein synthesis and lignocellulosic material hydrolysis. RESULTS: xynS1 has an open reading frame with 693 base pairs that encodes a protein with 230 amino acids. The predicted molecular weight and isoelectric point of the protein were 24.47 kDa and 7.92, respectively. The gene was cloned into the pET-11a expression vector and expressed in Escherichia coli BL21(DE3). Recombinant XynS1 (rXynS1) was purified via His-tag affinity column chromatography. rXynS1 exhibited optimal activity at a pH of 5.0 and temperature of 55 °C. Thermal stability was in the temperature range of 50-55 °C. The estimated Km and Vmax values were 51.4 mg/mL and 898.2 U/mg, respectively. One millimolar of Mn2+ and Na+ ions stimulated the activity of rXynS1 by up to 209% and 122.4%, respectively, and 1 mM Co2+ and Ni2+ acted as inhibitors of the enzyme. The mixture of rXynS1, originates from Streptomyces sp. strain J103 and acetyl xylan esterase (AXE), originating from the marine bacterium Ochrovirga pacifica, enhanced the xylan degradation by 2.27-fold, compared to the activity of rXynS1 alone when Mn2+ was used in the reaction mixture; this reflected the ability of both enzymes to hydrolyse the xylan structure. The use of an enzyme cocktail of rXynS1, AXE, and commercial cellulase (Celluclast® 1.5 L) for the hydrolysis of lignocellulosic biomass was more effective than that of commercial cellulase alone, thereby increasing the relative activity 2.3 fold. CONCLUSION: The supplementation of rXynS1 with AXE enhanced the xylan degradation process via the de-esterification of acetyl groups in the xylan structure. Synergetic action of rXynS1 with commercial cellulase improved the hydrolysis of pre-treated lignocellulosic biomass; thus, rXynS1 could potentially be used in several industrial applications.

A Novel Agarase, Gaa16B, Isolated from the Marine Bacterium Gilvimarinus agarilyticus JEA5, and the Moisturizing Effect of Its Partial Hydrolysis Products.

We recently identified a ß-agarase, Gaa16B, in the marine bacterium Gilvimarinus agarilyticus JEA5. Gaa16B, belonging to the glycoside hydrolase 16 family of ß-agarases, shows less than 70.9% amino acid similarity with previously characterized agarases. Recombinant Gaa16B lacking the carbohydrate-binding region (rGaa16Bc) was overexpressed in Escherichia coli and purified. Activity assays revealed the optimal temperature and pH of rGaa16Bc to be 55 ∘C and pH 6-7, respectively, and the protein was highly stable at 55 ∘C for 90 min. Additionally, rGaa16Bc activity was strongly enhanced (2.3-fold) in the presence of 2.5 mM MnCl2. The Km and Vmax of rGaa16Bc for agarose were 6.4 mg/mL and 953 U/mg, respectively. Thin-layer chromatography analysis revealed that rGaa16Bc can hydrolyze agarose into neoagarotetraose and neoagarobiose. Partial hydrolysis products (PHPs) of rGaa16Bc had an average molecular weight of 88-102 kDa and exhibited > 60% hyaluronidase inhibition activity at a concentration of 1 mg/mL, whereas the completely hydrolyzed product (CHP) showed no hyaluronidase at the same concentration. The biochemical properties of Gaa16B suggest that it could be useful for producing functional neoagaro-oligosaccharides. Additionally, the PHP of rGaa16Bc may be useful in promoting its utilization, which is limited due to the gel strength of agar.

Characterization of an acetyl xylan esterase from the marine bacterium Ochrovirga pacifica and its synergism with xylanase on beechwood xylan.

BACKGROUND: Acetyl xylan esterase plays an important role in the complete enzymatic hydrolysis of lignocellulosic materials. It hydrolyzes the ester linkages of acetic acid in xylan and supports and enhances the activity of xylanase. This study was conducted to identify and overexpress the acetyl xylan esterase (AXE) gene revealed by the genomic sequencing of the marine bacterium Ochrovirga pacifica. RESULTS: The AXE gene has an 864-bp open reading frame that encodes 287 aa and consists of an AXE domain from aa 60 to 274. Gene was cloned to pET-16b vector and expressed the recombinant AXE (rAXE) in Escherichia coli BL21 (DE3). The predicted molecular mass was 31.75 kDa. The maximum specific activity (40.08 U/mg) was recorded at the optimal temperature and pH which were 50 °C and pH 8.0, respectively. The thermal stability assay showed that AXE maintains its residual activity almost constantly throughout and after incubation at 45 °C for 120 min. The synergism of AXE with xylanase on beechwood xylan, increased the relative activity 1.41-fold. CONCLUSION: Resulted higher relative activity of rAXE with commercially available xylanase on beechwood xylan showed its potential for the use of rAXE in industrial purposes as a de-esterification enzyme to hydrolyze xylan and hemicellulose-like complex substrates.

A Novel Glycosyl Hydrolase Family 16 ß-Agarase from the Agar-Utilizing Marine Bacterium Gilvimarinus agarilyticus JEA5: the First Molecular and Biochemical Characterization of Agarase in Genus Gilvimarinus.

The agarase gene gaa16a was identified from a draft genome sequence of Gilvimarinus agarilyticus JEA5, an agar-utilizing marine bacterium. Recently, three agarase-producing bacteria, G. chinensis, G. polysaccharolyticus, and G. agarilyticus, in the genus Gilvimarinus were reported. However, there have been no reports of the molecular characteristics and biochemical properties of these agarases. In this study, we analyzed the molecular characteristics and biochemical properties of agarases in Gilvimarinus. Gaa16A comprised a 1,323-bp open reading frame encoding 441 amino acids. The predicted molecular mass and isoelectric point were 49 kDa and 4.9, respectively. The amino acid sequence of Gaa16A showed features typical of glycosyl hydrolase family 16 (GH16) ß-agarases, including a GH16 domain, carbohydrate-binding region (RICIN domain), and signal peptide. Recombinant Gaa16A (excluding the signal peptide and carbohydrate-binding region, rGaa16A) was expressed as a fused protein with maltose-binding protein at its N-terminus in Escherichia coli. rGaa16A had maximum activity at 55°C and pH 7.0 and 103 U/mg of specific activity in the presence of 2.5 mM CaCl2. The enzyme hydrolyzed agarose to yield neoagarotetraose as the main product. This enzyme may be useful for industrial production of functional neoagaro-oligosaccharides.

Corallibacterium pacifica gen. nov., sp. nov., a Novel Bacterium of the Family Vibrionaceae Isolated from Hard Coral.

A gram-negative, rod-shaped, motile, oxidase- and catalase-positive, non-pigmented marine bacterium, designated strain OS-11M-2T, was isolated from a coral sample collected from the Osakura coastal area in Micronesia. Phylogenetic analysis based on 16S ribosomal RNA (rRNA) gene sequences indicated that strain OS-11M-2T is a member of the family Vibrionaceae, its closest neighbors being Photobacterium damselae subsp. piscicida NCIMB 2058T (94.9%), Photobacterium damselae subsp. damselae CIP 102761T (94.75%), Grimontia marina IMCC5001T (94.5%), Enterovibrio coralii LMG 22228T (94.5%), and Grimontia celer 96-237T (94.5%). The major cellular fatty acids were summed feature 3 (21.4%), summed feature 8 (18.5%), iso-C16:0 (13.8%), and C16:0 (11.9%). The major respiratory quinone of the bacterium was ubiquinone-8 (Q-8) and its major polar lipid phosphatidylethanolamine. Six amino lipids, two phospholipids, and one polar lipid, all unidentified, were detected. The DNA G+C content was 49.7 mol%. The 16S rRNA gene sequence of OS-11M-2T was registered in GenBank under accession number MF359550. On the basis of phenotypic, genotypic, and phylogenetic analyses, strain OS-11M-2T represents a novel genus of the family Vibrionaceae, for which we propose the name Corallibacterium pacifica gen. nov., sp. nov., with the type strain of the type species being OS-11M-2T (= KCCM 43265T). The digital protologue database (DPD) taxon number for strain OS-11M-2T is GA00041.