The exoskeleton of crabs serves functions in protection, support, and sensing. Among the microstructures that compose the exoskeleton, the Bouligand structure is known to contribute to its mechanical properties. Previous research on the influence of microstructures on the mechanical properties of the crustacean exoskeleton has primarily focused on stacking height (SH), yet it remained controversial whether SH is the dominant determining factor of the mechanical properties. In this study, we comprehensively analyzed the pitch angle, diameter of the chitin-protein fiber, and the interlamellar spacing in the Bouligand structure to compare their contribution to the mechanical properties. We found that in vent crabs, the carapace was harder than the claw, while the opposite was observed in ghost crabs. In vent crabs, SH was 1.95 times greater than in the claw, a difference likely attributable to the pitch angle-the only microstructural feature that varied. In contrast, no structural differences were detected between regions in ghost crabs, where SH was extremely small (< 1 μm) and thus mechanical properties appear to be governed by material characteristics rather than structure. These findings indicate that pitch angle influences the mechanical properties of the crab exoskeleton only when SH is sufficiently large.

Recent environmental changes have facilitated the poleward expansion of tropical ghost crabs (genus Ocypode ) into temperate zones, where closely related species increasingly co-occur on the same sandy beaches. Their strong morphological similarity, particularly immature individuals, has hindered the consistent application of diagnostic characters and let to potential misidentifications. In particular, the taxonomic distinction between Ocypode sinensis and O. cordimana has remained uncertain despite previous described diagnostic characters. Here, we demonstrate that previously described diagnostic morphological characters are applicable to these specimens, and that their taxonomic interpretation is supported by molecular evidence from mitochondrial ( mtCO1 and 16S rRNA ) and nuclear ( 28S rRNA ) loci. Phylogenetic analyses reveal that O. sinensis and O. cordiman a form distinct and well-supported lineages. Morphological comparisons further identified subtle but consistent differences previously reported between the two species. Our results confirm the taxonomic validity of O. sinensis and clarify its diagnostic features relative to O. cordimana , indicating that previous records of O. cordimana from Korea were likely based on misidentifications. We provide a clear identification key and taxonomic reassessment of East Asian Ocypode species based on integrative morphological and molecular analyses. More broadly, our results highlight the importance of integrative approaches for improving the accuracy of species identification and biodiversity assessments in coastal ecosystems.

PICES special research project “SEAturtle” launched in 2019 to understand the ecology of sea turtles around Jeju Island in relation to environmental stressors. Though COVID 19 had interrupted the project, we had quite a successful outcome over the last 5 years. Until now (June 15, 2023), a total of 16 iridium transmitters were deployed on sea turtles (14 on green sea turtles and 2 on loggerhead sea turtles). Among them, we received the signals successfully from 15 sea turtles. We found that quite a proportion of green sea turtles released in Jeju Island (N = 4 out of 12, approx. 40%) overwintered nearby even in the cold sea where the temperature dropped to 15 °C. The diving duration increased to approx. 6 hrs with decreasing temperature. Most of migrating green sea turtles (N = 4) traveled toward southern Japan which suggests a strong link to the population in Japan. Our population genetics result on green sea turtles stranded suggests that a subunit of Jeju population also have an affinity to Japan population. On the other hand, one of our loggerhead sea turtles moved westward but the other moved southward from Jeju Island, suggesting that they may also have connectivity to both Japan and China. Our populations genetics and stable isotope analysis on the commensal barnacles support this. We also have actively worked on the threat of plastics on Jeju populations and found that derelict recreational fishing gears might cause more serious problems than commercial derelict fishing gears. Microplastics are other threats to them too. To conserve the population of sea turtles in Jeju Island, we need further extensive research and should keep up international cooperation.

Organisms occupy diverse ecological niches worldwide, each with characteristics finely evolved for their environments. Crustaceans residing in deep-sea hydrothermal vents, recognized as one of Earth’s extreme environments, may have adapted to withstand severe conditions, including elevated temperatures and pressure. This study compares the exoskeletons of two vent crustaceans (bythograeid crab Austinograea sp. and squat lobster Munidopsis lauensis) with four coastal species (Asian paddle crabs, blue crab, hermit crab, and mantis shrimp) to identify traits influenced by vent environments. The goal was to identify distinctive exoskeletal characteristics commonly observed in vent crustaceans, resulting from their exposure to severe abiotic factors, including elevated temperatures and pressures, found in vent environments. Results show that the exoskeletons of vent crustaceans demonstrated significantly enhanced thermal stability compared to coastal species. These vent crustaceans consistently featured exoskeletons characterized by a reduced proportion of volatile components, such as water, and an increased proportion of CaCO3, compared with coastal crustaceans. Furthermore, vent crustaceans lacked carotenoid pigments that had low heat resistance. However, no apparent differences were observed in the mechanical properties. Our findings suggest that the similar composition of exoskeletons in vent crustaceans evolved convergently to withstand high temperatures.

This file include input files for molecular analyses used in Jang et al., 2023. Details for related methods were described in the Jang et al., 2023.

Limitations on energetic resources create evolutionary trade-offs, prompting us to investigate if investment in claw strength remains consistent across crustaceans living in diverse habitats. Decapod crustaceans living in deep-sea hydrothermal vents are ideal for this study due to their extreme environment. In this study, we investigated whether decapods (blind crab Austinograea sp. and the squat lobster Munidopsis lauensis) living in deep-sea hydrothermal vents prioritize investing in strong claws compared to the carapace, like coastal decapods. We analyzed exoskeleton morphology, mechanical properties, structures, and elemental composition in both the carapace and claws of four Decapoda species (two each from Brachyura and Anomura infraorders) in vent and coastal habitats. Coastal decapods had ∼4-9 times more teeth on their claw cutting edge than the vent species. Further, only the coastal species exhibited higher firmness in their claws than in their carapaces. Each infraorder controlled exoskeletal hardness differently: Brachyura changed the stacking height of the Bouligand structure, while Anomura regulated magnesium content in the exoskeleton. The vent decapods may prioritize strengthening their carapace over developing robust claws, allocating resources to adapt to the harsh conditions of deep-sea hydrothermal vents. This choice might enhance their survival in the extreme environment, where carapace strength is crucial for protecting internal organs from environmental factors, rather than relying on the powerful claws seen in coastal decapods for a competitive advantage.

The northwestern Pacific region is an important habitat for sea turtles, hosting five species out of seven. There is still limited information available about the sea turtle aggregations around the Korean Peninsula, which is the northern boundary for many sea turtle species in the western Pacific area. The present study aims to investigate the migratory route of sea turtles visiting Jeju Island. Five species of sea turtles were identified from by-catch and stranding data between 2013 and 2022 on Jeju Island in Korea: green (Chelonia mydas; 24 individuals), loggerhead (Caretta caretta; 9), hawksbill (Eretmochelys imbricata; 2), olive ridley (Lepidochelys olivacea; 2), and leatherback (Dermochelys coriacea; 1). Mixed stock analysis using mitochondrial DNA haplotypes revealed that Jeju green turtles primarily originate from the rookeries of the Japanese Archipelago. This connectivity between two regions was also supported by the similar genetic composition of loggerhead turtles. Similarly, satellite tracking data showed that several green turtles originating from Jeju Island migrated to waters near the Ryukyu Archipelago in Japan. Nevertheless, about 60% of the tracked green turtles stayed near Jeju Island, with most overwintering there, indicating the long residency in Jeju Island. This study also provides the genetic sequences of other three species including new orphan haplotypes of hawksbill and olive ridley turtles. Our findings suggest that Jeju Island serves as a stable foraging habitat and provide insight into understanding the habitat range of sea turtles in the western Pacific.

Background: Antibacterial peptides have a broad antibacterial spectrum and are not affected by classical resistance mechanisms; therefore, they can be used in combination with classic antibiotics to treat multidrug-resistant Acinetobacter baumannii infections, making them an alternative for the development of new therapeutic strategies. Objectives: This study aimed to assess the effectiveness of combining amphiphilic peptides, specifically C12-prp and mastoparan, with antibiotics in combating A. baumannii clinical isolates. Methods: We investigated combinations that inhibited the growth of A. baumannii clinical isolates, consisting of 24 extensively drug-resistant (XDR) and 11 pan-drug-resistant (PDR) strains collected between January 2004 and December 2014 at Chosun University Hospital using a multiple combination bactericidal test (MCBT). A time-kill study was used to confirm the bactericidal activity and synergism of the four combinations selected via MCBT. Results: Four combinations (C12-prp-colistin, C12-prp-rifampicin, mastoparan-colistin, and mastoparan-rifampicin) showed 100% (24/24) synergy with XDR A. baumannii strains. However, in the case of the PDR strains, only two combinations, C12-prp-colistin and mastoparan-colistin, showed a 9.1% (1/11) synergy. Moreover, the mastoparan-colistin and mastoparan-rifampicin combinations showed 100% (24/24) bactericidal activity against the XDR A. baumannii strains, whereas the C12-prp-colistin and C12-prp-rifampicin combinations showed 91.7% (22/24) bactericidal activity. None of the combinations showed bactericidal activity against PDR strains. Conclusions: Our study highlighted the substantial synergistic antibacterial efficacy of C12-prp and mastoparan peptides when combined with colistin or rifampicin. Furthermore, this approach could be a promising alternative for developing new treatment strategies for XDR A. baumannii infections.

Ghost crabs, as a species of the Ocypode within the subfamily Ocypodinae, are distributed in the upper intertidal zone worldwide and are ecologically remarkable. They play an important role in the energy circulation in the intertidal zone and are used as an ecological indicator to predict the impacts of environmental change or anthropogenic activities on the marine ecosystem. In this study, we provide the first evidence for the distribution of O. sinensis in Jeju Island and the southern coastal area on the Korean Peninsula. We generated a high-fidelity mitochondrial genome (mitogenome) for the species. The mitogenome was assembled into a circular chromosome of 15,589 bp, including 13 protein-coding genes, two ribosomal RNA genes, and twenty-two transfer RNA genes. High genetic variation compared with closely related species enabled the precise reconstruction of phylogenetic relationships and an estimation of the divergence times among the Ocypode species. The phylogenetic inference indicated that O. sinensis forms a monophyletic clade with O. cordimanus and diverged from ancestral species approximately 20.41 million years ago.

BACKGROUND:Ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) is a reliable and accurate method for measuring steroid hormone levels. There is an increasing need for sensitive and precise methods to measure estradiol in pediatric patients. Here, we established reference intervals for estradiol in healthy children using a UHPLC-MS/MS-based method for the first time in South Korea. METHODS:Serum estradiol was measured using a Sciex Triple QuadTM 6500 + UHPLC-MS/MS (Sciex, Framingham, MA, USA). Reference intervals for estradiol were established according to the CLSI document EP28-A3c:2008. The reference intervals were validated using serum samples from 634 pediatric patients, including neonates, children, and adolescents. Among them, 389 specimens were used in analysis of the specimen acceptance time. Statistical analysis was performed using MedCalc (MedCalc, Ostend, Belgium) and Analyse-it (Analyse-it Software Ltd., Leeds, United Kingdom) software. RESULTS:Reference intervals for boys (n = 297) were <16.6, <7.3, <19.0, <30.5, 7.6-96.5, and 10.6-134.4 pmol/L among those aged <1, 1-5, 6-9, 10-11, 12-14, and 15-17 years, respectively. Reference intervals for girls (n = 337) were <114.7, <24.2, <34.8, 8.0-177.0, 10.4-480.5, and 9.1-486.7 pmol/L among those aged <1, 1-5, 6-9, 10-11, 12-14, and 15-17 years, respectively. Overall, there was no effect of specimen acceptance time on estradiol measurements in boys or girls, except for that in the group aged 10-11 years. CONCLUSIONS:The reference intervals for healthy children were validated using a UHPLC-MS/MS-based method. The highly analytical sensitive UHPLC-MS/MS method may be useful for estradiol determination in pediatric patients.

The hairy snails of the genus Alviniconcha are representative deep-sea hydrothermal vent animals distributed across the Western Pacific and Indian Ocean. Out of six known species in the genus Alviniconcha, only one nominal species of A. marisindica was found in the Indian Ocean from the Carlsberg Ridge (CR), Central Indian Ridge (CIR) to the northern part of Southwest Indian Ridge (SWIR) and Southeast Indian Ridge (SEIR). Recently, the Alviniconcha snails were found at three new vent fields, named Onnare, Onbada, and Onnuri, in the northern CIR, which promotes a more comprehensive phylogeographic study of this species. Here, we examined the phylogeography and connectivity of the Alviniconcha snails among seven vent fields representing the CR and CIR based on DNA sequence data of a mitochondrial COI gene and two protein-coding nuclear genes. Phylogenetic inferences revealed that the Alviniconcha snails of the newly found in the northern CIR and two vent fields of Wocan and Tianxiu in the CR were divergent with the previously identified A. marisindica in the southern CIR and mitochondrial COI data supported the divergence with at least greater than 3% sequence divergence. Population structure analyses based on the three genetic markers detected a phylogeographic boundary between Onnuri and Solitaire that divides the whole snail populations into northern and southern groups with a low migration rate. The high degree of genetic disconnection around the ‘Onnuri’ boundary suggests that the Alviniconcha snails in the Indian Ocean may undergo allopatric speciation. The border may similarly act as a dispersal barrier to many other vent species co-distributed in the CIR. This study would expand understanding the speciation and connectivity of vent species in the Indian Ocean.

The mytilid mussel Bathymodiolus thermophilus lives in the deep-sea hydrothermal vent regions due to its relationship with chemosynthetic symbiotic bacteria. It is well established that symbionts reside in the gill bacteriocytes of the mussel and can utilize hydrogen sulfide, methane, and hydrogen from the surrounding environment. However, it is observed that some mussel symbionts either possess or lack genes for hydrogen metabolism within the single-ribotype population and host mussel species level. Here, we found a hydrogenase cluster consisting of additional H2-sensing hydrogenase subunits in a complete genome of B. thermophilus symbiont sampled from an individual mussel from the East Pacific Rise (EPR9N). Also, we found methylated regions sparsely distributed throughout the EPR9N genome, mainly in the transposase regions and densely present in the rRNA gene regions. CRISPR diversity analysis confirmed that this genome originated from a single symbiont strain. Furthermore, from the comparative analysis, we observed variation in genome size, gene content, and genome re-arrangements across individual hosts suggesting multiple symbiont strains can associate with B. thermophilus. The ability to acquire locally adaptive various symbiotic strains may serve as an effective mechanism for successfully colonizing different chemosynthetic environments across the global oceans by host mussels.

This study compared the accuracy of a new MALDI-TOF mass spectrometry system, ASTA MicroIDSys system, with that of MALDI Biotyper system for the identification of reference and clinical bacterial and yeast strains. The identification accuracy of the 2 systems was compared using a total of 406 strains comprising 142 aerobic and 180 anaerobic bacterial strains and 84 yeast strains. The genus and species identification rates were 98.0% and 89.4% using MicroIDSys and 96.1% and 89.4% using Biotyper, respectively. The species identification rates of MicroIDSys and Biotyper for aerobic bacteria were 93.0% and 97.2%, respectively, and those for anaerobic bacteria were 85.6% and 81.7%, respectively. The accuracy of yeast identification at the species level was 91.7% using MicroIDSys and 92.9% using Biotyper. These findings indicate that MicroIDSys could be useful for the accurate identification of bacteria and yeast in clinical microbiology laboratories.

Wooshin Kim, M.D., Ho Jong Lee, M.D., Seulbi Lee, M.Sc., Choon-Mee Kim, Ph.D., Jong Hee Shin, M.D., Soo Hyun Kim, M.D., Young Jin Ko, M.D., Seong-Ho Kang, M.D., Geon Park, M.D., Sook Jin Jang, M.D.. Lab Med Online 2022;12:183-90. https://doi.org/10.47429/lmo.2022.12.3.183

Background: To solve the difficulty in determining the appropriate treatment regimen for patients infected with extensively drug-resistant Acinetobacter baumannii (XDRAB), it is necessary to develop various strategies to increase the therapeutic effect of antimicrobial agents. The purpose of this study was to select the treatment combination showing the greatest antimicrobial effect among seven candidate antimicrobial substances. Methods: Seven strains of XDRAB were used in this study. The composition of the treatment consisted of colistin as the base and one of the seven antimicrobial substances, doripenem, minocycline, tigecycline, linezolid, fusidic acid, vancomycin, or alyteserin E4K peptide. The interaction between the drugs in each combination was evaluated by measuring the synergy rates using time-kill analysis. Results: The synergy rates of the seven combinations tested in the time-kill assay in this study were as follows, in descending order from the combination with the highest synergy rate: colistin + minocycline (57.1%), colistin + alyteserin E4K (50.0%), colistin + tigecycline (42.9%), colistin + vancomycin (28.6%), colistin + doripenem (14.3%), colistin + fusidic acid (14.3%), and colistin + linzolid (0%). None of the combinations showed antagonism. The three combinations showing bactericidal activity and the rates of their bactericidal activity were colistin + alyteserin E4K combination (33.3%), colistin + minocycline (14.3%), and colistin + vancomycin (14.3%). Conclusion: The colistin + minocycline and colistin + alyteserin E4K treatment combinations, which showed high synergy rates, can be considered as promising candidates for future in vivo experiments evaluating combination therapies.

Adjuvant use of geraniol, a plant essential oil component, is known to increase the efficacy of antibiotics by acting as a potent inhibitor of efflux mechanisms. In this study, we assessed the effect of a geraniol-antibiotic combination in 21 Acinetobacter baumannii clinical isolates consisting of high efflux (HE) and low efflux (LE) activity groups. We determined the MIC for geraniol and the four antibiotics and evaluated the adjuvant antimicrobial activity and resensitization efficacy of adjuvant geraniol. Geraniol-antibiotic combinations significantly reduced the MIC of all four antibiotics (P < 0.0001), and the fold change in MIC decreased by 4 to >256-fold for tigecycline, >16 to >4,096-fold for ceftazidime, 1 to >4,096-fold for cefepime, and >2 to >4096-fold for ciprofloxacin. Importantly, geraniol showed adjuvant antimicrobial activity and resensitization efficacy when used in combination with antibiotics in 21 A. baumannii clinical isolates. However, there was no statistically significant difference between the HE and LE groups. Low concentrations (0.125% and 0.0625%) of geraniol showed no cytotoxic or hemolytic activity. Our study shows that geraniol, acting as an antibiotic adjuvant, is a good candidate for in vivo studies of combination therapy for the treatment of MDR/XDR A. baumannii infections.

Mytilid mussel Bathymodiolus thermophilus lives in the deep-sea hydrothermal vent regions through a symbiotic relationship with chemosynthetic Gammaproteobacteria species. The mussel depends on the nutrient provided by the symbiont residing inside specialized gill cells. The symbionts in the gill bacteriocytes oxidize the reduced sulfur amply available in the vent environment. Here we sequenced and assembled the complete gill symbiont genome of an individual mussel from the East Pacific Rise (EPR9N), using PacBio sequencing technology. The final symbiont assembly consists of a single contig size of 2.83 Mb, with a GC content of 38.6% and encodes for 2,133 protein-coding genes. CRISPR diversity analysis confirmed that we sequenced a single symbiont strain. Comparative analysis revealed 2,554 core gene clusters were shared with other B. thermophilus thiotrophic gill symbiont genomes whereas 125 were unique to this EPR9N strain. These unique gene clusters included genes such as Ni,Fe-hydrogenases I subunits, rubredoxins, and hydrogenase maturation factors but were mainly comprised of various repeats, transposases and uncharacterized proteins. Variation in genome size, gene content and genome re-arrangement across individual hosts suggests multiple symbiont strains can associate with B. thermophilus. This complete mussel symbiont genome will be invaluable for further comparative genomic analyses studying structural genome evolution, symbiont population diversity, and symbiont ecology.

The mytilid mussel Bathymodiolus thermophilus lives in the deep-sea hydrothermal vent regions due to its symbiotic relationship with chemosynthetic Gammaproteobacteria species which reside inside specialized gill cells. The symbionts in the gill bacteriocytes oxidize the reduced sulfur amply available in the vent environment. Here we sequenced and assembled the complete genome of a gill symbiont sampled from an individual mussel from the East Pacific Rise (EPR9N), using PacBio sequencing technology. The final symbiont assembly consists of a single contig size of 2.83 Mb, with a GC content of 38.6% and encodes for 2,133 protein-coding genes. CRISPR diversity analysis confirmed this genome originated from a single symbiont strain. Comparative analysis revealed 2,554 core gene clusters were shared with other B. thermophilus thiotrophic gill symbiont genomes, whereas 125 were unique to this EPR9N strain. In addition, we found that EPR9N strain has a unique hydrogenase operon among Bathymodiolus mussels consisting of additional H2-sensing hydrogenase subunits and a histidine kinase gene. Also, we found methylated regions sparsely distributed throughout the EPR9N genome, mainly in the transposases regions and densely present in the rRNA gene regions. Variation in genome size, gene content and genome re-arrangements across individual hosts suggest multiple symbiont strains can associate with B. thermophilus. This complete mussel symbiont genome will be invaluable for further comparative genomic analyses studying structural genome evolution, symbiont population diversity, and symbiont ecology in deep-sea chemosynthetic environments.

The population divergence process of deep-sea vent invertebrates is driven by both biotic (e.g., dispersal during the larval stage) and abiotic factors such as deep-ocean currents, depth, and the geological setting of vents. However, little is known regarding the divergence of hydrothermal vent microorganisms. Therefore, our study sought to investigate the influence of geological and geographic factors on the divergence of symbiotic bacteria of Bathymodiolus vent mussels. The genetic differentiation patterns of symbionts were examined using next-generation sequencing DNA data in two ocean basins with distinct geological features: the slow-spreading Central Indian Ridge (CIR) and the fast- or superfast-spreading eastern Pacific Ridges. Our findings showed that the degree of differentiation of symbiont populations was geographically hierarchical: the highest between ocean basins, followed by inter-ridge sites between the East Pacific Rise and the Pacific Antarctic Ridge. The Easter Microplate intervening these two ridges acted as a biogeographic physical barrier for both symbionts and their host mussels. On a scale of intra-ridge, symbionts showed isolation by distance in the CIR but not in the eastern Pacific ridges. These contrasting genetic patterns relate to different ridge spreading rates determining most of the geological characteristics of mid-ocean ridges that affect the connectivity of vent habitats in space and time. At the intra-ridge geographic scale of the CIR, population divergence processes of both symbionts and hosts from separate three ridge segments were analyzed in detail using a genetic model of isolation with migration (IM). The phylogenetic topology of symbiont populations was congruent with the host populations, indicating the influence of common historical and physical constraints for habitats and dispersal between vents in the Central Indian Ridge. Collectively, our findings provide key insights into the dynamics of microbial population divergence in deep-sea vents.

Various mechanisms underlying antimicrobial resistance in Acinetobacter baumannii have been reported. However, the relationships between efflux pump activity, biofilm formation, and antimicrobial resistance in A. baumannii is controversial. In this study, we investigated the relative expression of RND efflux pump genes, H33342 efflux activity, and biofilm-forming activity in 120 A. baumannii clinical isolates, examined their potential relationships with each other, and statistically analyzed their effects on antibiotic resistance. High adeB expression and high H33342 efflux activity were correlated with low biofilm-forming activity. High adeB expression was significantly correlated with resistance to tigecycline and cefotaxime, but not with the multidrug resistance (MDR) phenotype. Importantly, only high adeJ expression was significantly correlated with the MDR phenotype and was correlated with resistance to various antibiotics. However, we found no significant correlation between adeJ expression and biofilm-forming activity. Furthermore, adeG expression was not correlated with antibiotic resistance and biofilm-forming activity. The results of multivariate analysis showed that adeB overexpression and high H33342 efflux activity were related to biofilm-forming activity, and only adeJ overexpression was significantly associated with the MDR phenotype, highlighting the importance of adeJ overexpression.