Dong-Wook Hyun

Chronic Repression of mTOR Complex 2 Induces Changes in the Gut Microbiota of Diet-induced Obese Mice

Alterations in the gut microbiota play a crucial role in host physiology and metabolism; however, the molecular pathways underlying these changes in diet-induced obesity are unclear. Mechanistic target of rapamycin (mTOR) signaling pathway is associated with metabolic disorders such as obesity and type 2 diabetes (T2D). Therefore, we examined whether changes in the regulation of mTOR signaling induced by diet (a high-fat diet [HFD] or normal-chow diet) and/or therapeutics (resveratrol [a specific inhibitor of mTOR complex 1] or rapamycin [an inhibitor of both mTOR complex 1 and 2]) altered the composition of the gut microbiota in mice. Oral administration of resveratrol prevented glucose intolerance and fat accumulation in HFD-fed mice, whereas rapamycin significantly impaired glucose tolerance and exacerbated intestinal inflammation. The abundance of Lactococcus, Clostridium XI, Oscillibacter, and Hydrogenoanaerobacterium increased under the HFD condition; however, the abundance of these species declined after resveratrol treatment. Conversely, the abundance of unclassified Marinilabiliaceae and Turicibacter decreased in response to a HFD or rapamycin. Taken together, these results demonstrated that changes in the composition of intestinal microbiota induced by changes in mTOR activity correlate with obese and diabetic phenotypes.

Actinomyces haliotis sp. nov., a bacterium isolated from the gut of an abalone, Haliotis discus hannai.

A novel, Gram-staining-positive, facultatively anaerobic, non-motile and coccus-shaped bacterium, strain WL80(T), was isolated from the gut of an abalone, Haliotis discus hannai, collected from the northern coast of Jeju in Korea. Optimal growth occurred at 30 °C, pH 7-8 and with 1% (w/v) NaCl. Phylogenetic analyses based on the 16S rRNA gene sequence revealed that strain WL80(T) fell within the cluster of the genus Actinomyces, with highest sequence similarity to the type strains of Actinomyces radicidentis (98.8% similarity) and Actinomyces urogenitalis (97.0% similarity). The major cellular fatty acids were C18 : 1ω9c and C16 : 0. Menaquinone-10 (H4) was the major respiratory quinone. The genomic DNA G+C content of the isolate was 70.4 mol%. DNA-DNA hybridization values with closely related strains indicated less than 7.6% genomic relatedness. The results of physiological, biochemical, chemotaxonomic and genotypic analyses indicated that strain WL80(T) represents a novel species of the genus Actinomyces, for which the name Actinomyces haliotis sp. nov. is proposed. The type strain is WL80(T) ( = KACC 17211(T) = JCM 18848(T)).

Endozoicomonas atrinae sp. nov., isolated from the intestine of a comb pen shell Atrina pectinata

A novel bacterium, designated strain WP70(T), was isolated from the gut of a comb pen shell (Atrina pectinata) collected from the southern sea of Yeosu in Korea. The isolate was Gram-stain-negative, aerobic, non-motile and rod-shaped. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain WP70(T) belonged to the genus Endozoicomonas. The highest level of sequence similarity (98.4%) was shared with Endozoicomonas elysicola MKT110(T). Optimal growth occurred in 2% (w/v) NaCl at 30 °C and at pH 7. The major cellular fatty acids were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C16 : 0. The main respiratory quinone was Q-9. The polar lipids comprised phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, three unidentified phospholipids, an unidentified aminolipid, an unidentified aminophospholipid and an unidentified lipid. The genomic DNA G+C content was 50.5 mol% and DNA-DNA hybridization values indicated <11% genomic relatedness to the closest species. Physiological, biochemical, chemotaxonomic and genotypic analyses indicated that strain WP70(T) represents a novel species of the genus Endozoicomonas, for which the name Endozoicomonas atrinae sp. nov. is proposed. The type strain is WP70(T) ( = KACC 17474(T)  = JCM 19190(T)).

Polaribacter atrinae sp. nov., isolated from the intestine of a comb pen shell, Atrina pectinata

A novel Gram-staining-negative, aerobic, non-motile, yellow-to-orange carotenoid-type-pigmented and rod-shaped bacterium, designated strain WP25T, was isolated from the intestine of a comb pen shell, Atrina pectinata, which was collected from the South Sea near Yeosu in Korea. The isolate grew optimally at 20 °C, at pH 7 and with 2% (w/v) NaCl. 16S rRNA gene sequence analysis showed that strain WP25T belonged to the genus Polaribacter in the family Flavobacteriaceae and the highest sequence similarity was shared with the type strain of Polaribacter sejongensis (98.5%). The major cellular fatty acids were iso-C15:0, anteiso-C15:0, C15:1ω6c and iso-C15:0 3-OH. The main respiratory quinone was menaquinone MK-6. The polar lipids of strain WP25T were phosphatidylethanolamine, two unidentified aminolipids, an unidentified phospholipid and four unidentified lipids. The genomic DNA G+C content was 31.2 mol%. DNA-DNA hybridization experiments indicated <12.6% genomic relatedness with closely related strains. Based on phylogenetic, phenotypic and genotypic analyses, strain WP25T represents a novel species in the genus Polaribacter, for which the name Polaribacter atrinae sp. nov. is proposed, with the type strain WP25T (=KACC 17473T=JCM 19202T).

Blastopirellula cremea sp. nov., isolated from a dead ark clam.

Strain LHWP2(T), a novel, aerobic, budding, motile and ovoid bacterium belonging to the phylum Planctomycetes, was isolated from a dead ark clam (Scapharca broughtonii) from the south coast of Korea. Strain LHWP2(T) grew optimally at 30 °C, in the presence of 4% (w/v) NaCl, and at pH 7. The predominant cellular fatty acids were C16:0, C18:1ω7c and/or C18:1ω6c (summed feature 8) and C18:1ω9c. The major isoprenoid quinone was menaquinone-6 (MK-6). The dominant polar lipid was identified as phosphatidylglycerol. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the novel strain was most closely related to Blastopirellula marina DSM 3645(T), with a 16S rRNA gene sequence similarity of 94.1%. The genomic DNA G+C content of strain LHWP2(T) was 49.5 mol%. Strain LHWP2(T) was distinguished from B. marina DSM 3645(T) based on its optimum salinity, acid production from substrates, assimilation of substrates and DNA G+C content. Overall, these phenotypic, genotypic and phylogenetic data suggest that strain LHWP2(T) should be classified as a novel species belonging to the genus Blastopirellula, for which the name Blastopirellula cremea sp. nov. is proposed. The type strain is LHWP2(T) (=KACC 15559(T)=JCM 17758(T)).

Acinetobacter apis sp. nov., isolated from the intestinal tract of a honey bee, Apis mellifera

A novel Gram-negative, obligate aerobic, non-motile, and both coccobacillus- and bacillus-shaped bacterium, designated strain HYN18T, was isolated from the intestinal tract of a honey bee (Apis mellifera). The isolate was oxidasenegative and catalase-positive. Strain HYN18T showed optimum growth at 25°C, pH 6–7, and in the presence of 1% (w/v) NaCl in trypticase soy broth medium. The isolate was negative for hydrolyses of starch, casein, gelatin and urea, indole production from tryptone and hemolysis on sheep blood agar. A phylogenetic analysis based on the 16S rRNA gene and rpoB gene sequence showed that strain HYN18T was most closely related to Acinetobacter nectaris SAP 763.2T and A. boissieri SAP 284.1T with 98.3% and 98.1% similarity (16S rRNA gene), respectively, and 84.4% similarity with Acinetobacter nectaris SAP 763.2T (rpoB gene). The major cellular fatty acids were summed features 3 (comprising C16:1ω7c/C16:1ω6c), C12:0 and C16:0. The main isoprenoid quinone was ubiquinone-9 (Q-9). The polar lipids of strain HYN18T were phosphatidylethanolamine, three unidentified lipids, an unidentified phospholipid and an unidentified glycolipid. The DNA G+C content was 40.6 mol%. DNADNA hybridization experiments indicated less than 33 ± 10% relatedness to the closest phylogenetic species, Acinetobacter nectaris SAP 763.2T. Thus, the phenotypic, phylogenetic and genotypic analyses indicate that strain HYN18T is a novel species within the genus Acinetobacter, for which the name Acinetobacter apis is proposed. The type strain is HYN18T (=KACC 16906T =JCM 18575T).

Orbus sasakiae sp. nov., a bacterium isolated from the gut of the butterfly Sasakia charonda, and emended description of the genus Orbus

A novel Gram-stain-negative, facultatively anaerobic, non-motile and coccus-shaped bacterium, strain C7(T), was isolated from the gut of the butterfly Sasakia charonda. Strain C7(T) grew optimally at 20-25 °C, at pH 7-8 and with 1 % (w/v) NaCl. The strain was negative for oxidase activity but positive for catalase activity. The 16S rRNA gene sequences of strain C7(T) and Orbus hercynius CN3(T) shared 96.8 % similarity. The major fatty acids identified were C14 : 0, C16 : 0, C18 : 1ω7c and summed feature 2 (comprising C14 : 0 3-OH/iso-C16 : 1). The major respiratory quinone was ubiquinone-8 (Q-8). The polar lipids of strain C7(T) were phosphatidylethanolamine, phosphatidylglycerol, an unidentified phospholipid and two unidentified aminophospholipids. The G+C content of the genomic DNA extracted from strain C7(T) was 32.1 mol%. Taken together, the phenotypic, genotypic and phylogenetic analyses indicate that strain C7(T) represents a novel species of the genus Orbus, for which the name Orbus sasakiae sp. nov. is proposed. The type strain is C7(T) ( = KACC 16544(T) = JCM 18050(T)). An emended description of the genus Orbus is provided.

Actibacter haliotis sp. nov., isolated from the gut of an abalone, Haliotis discus hannai, and emended description of the genus Actibacter.

A novel strain, designated strain W113(T), was isolated from the gut of an abalone, Haliotis discus hannai, which was collected from the northern coast of Jeju in Korea. The isolate was a Gram-staining-negative, facultatively anaerobic, non-motile, rod-shaped bacterium producing yellow-to-orange carotenoid-type pigments. 16S rRNA gene sequence analysis showed that the isolate belonged to the genus Actibacter in the family Flavobacteriaceae and it shared the highest sequence similarity with the type strain of Actibacter sediminis (98.8 % similarity). Optimal growth occurred at 25 °C, at pH 7 and with 2 % (w/v) NaCl. The major cellular fatty acids were iso-C15:0, anteiso-C15:0 and iso-C15:1 G. Menaquinone-6 was the main respiratory quinone. The polar lipids of the isolate were phosphatidylethanolamine, three unidentified amino lipids, and three unidentified lipids. The genomic DNA G+C content was 42.6 mol% and DNA-DNA hybridization values indicated that the strain shared <18 % genomic relatedness with the most closely related species. The results of the phylogenetic, phenotypic and genotypic analyses indicated that strain W113(T) represents a novel species in the genus Actibacter, for which the name Actibacter haliotis sp. nov. is proposed. The type strain is W113(T) ( = KACC 17209(T) = JCM 18868(T)).

Dyella jejuensis sp. nov., isolated from soil of Hallasan Mountain in Jeju Island

A novel bacterium, designated JP1T, was isolated from soil of Hallasan Mountain in Jeju Island. The isolate was a Gramnegative, aerobic, motile and rod-shaped (0.2–0.4 × 1.2–2.0 μm) bacterium. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain JP1T was closely related to Dyella koreensis with 97.6% similarity. Growth of strain JP1T occurred at 10–37°C, pH 5–7 and 0–1% (w/v) NaCl. The genomic DNA G+C content of strain JP1T was 62.1 mol%. The major fatty acids were iso-C16:0, iso-C17:1 ω9c, and iso-C15:0. The predominant quinone was ubiquinone-8. The major polar lipids of strain JP1T were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, unidentified aminolipids and unidentified aminophospholipids. The DNA-DNA relatedness values between strain JP1T and previously reported Dyella species were <10%. Based on phenotypic, genotypic, and phylogenetic distinctness, strain JP1T represents a novel species in the genus Dyella, for which the name Dyella jejuensis sp. nov. is proposed. The type strain is JP1T (=KACC 17701T =JCM 19615T).

Weissella diestrammenae sp. nov., isolated from the gut of a camel cricket (Diestrammena coreana)

A novel, Gram-stain-positive, non-motile, facultatively anaerobic, rod- or coccoid-shaped bacterium, designated strain ORY33(T), was isolated from the gut of a camel cricket (Diestrammena coreana). The 16S rRNA gene sequence analysis showed that strain ORY33(T) belonged to the genus Weissella, with highest sequence similarity to Weissella koreensis S-5623(T) (97.7 %). The strain grew optimally at 30 °C and pH 7 in the presence of 0 % (w/v) NaCl. Catalase and oxidase activities were negative. The genomic DNA G+C content of strain ORY33(T) was 45.1 mol%. DNA-DNA hybridization values between strain ORY33(T) and closely related members of the genus Weissella were less than 27 %. The major fatty acids of strain ORY33(T) were C18 : 1ω9c, C16 : 0 and C14 : 0. Based on these phenotypic, phylogenetic and genotypic analyses, strain ORY33(T) represents a novel species belonging to the genus Weissella, for which the name Weissella diestrammenae sp. nov. is proposed. The type strain is ORY33(T) (= KACC 16890(T) = JCM 18559(T)).