Mi-Ja Jung

Insect gut bacterial diversity determined by environmental habitat, diet, developmental stage, and phylogeny of host.

ABSTRACT Insects are the most abundant animals on Earth, and the microbiota within their guts play important roles by engaging in beneficial and pathological interactions with these hosts. In this study, we comprehensively characterized insect-associated gut bacteria of 305 individuals belonging to 218 species in 21 taxonomic orders, using 454 pyrosequencing of 16S rRNA genes. In total, 174,374 sequence reads were obtained, identifying 9,301 bacterial operational taxonomic units (OTUs) at the 3% distance level from all samples, with an average of 84.3 (±97.7) OTUs per sample. The insect gut microbiota were dominated by Proteobacteria (62.1% of the total reads, including 14.1% Wolbachia sequences) and Firmicutes (20.7%). Significant differences were found in the relative abundances of anaerobes in insects and were classified according to the criteria of host environmental habitat, diet, developmental stage, and phylogeny. Gut bacterial diversity was significantly higher in omnivorous insects than in stenophagous (carnivorous and herbivorous) insects. This insect-order-spanning investigation of the gut microbiota provides insights into the relationships between insects and their gut bacterial communities.

Bacterial, archaeal, and eukaryal diversity in the intestines of Korean people

The bacterial, archaeal, and eukaryal diversity in fecal samples from ten Koreans were analyzed and compared by using the PCR-fingerprinting method, denaturing gradient gel electrophoresis (DGGE). The bacteria all belonged to the Firmicutes and Bacteroidetes phyla, which were known to be the dominant bacterial species in the human intestine. Most of the archaeal sequences belonged to the methane-producing archaea but several halophilic archarea-related sequences were also detected unexpectedly. While a small number of eukaryal sequences were also detected upon DGGE analysis, these sequences were related to fungi and stramenopiles (Blastocystis hominis). With regard to the bacterial and archaeal DGGE analysis, all ten samples had one and two prominent bands, respectively, but many individual-specific bands were also observed. However, only five of the ten samples had small eukaryal DGGE bands and none of these bands was observed in all five samples. Unweighted pair group method and arithmetic averages clustering algorithm (UPGMA) clustering analysis revealed that the archaeal and bacterial communities in the ten samples had relatively higher relatedness (the average Dice coefficient values were 68.9 and 59.2% for archaea and bacteria, respectively) but the eukaryal community showed low relatedness (39.6%).

Unexpected convergence of fungal and bacterial communities during fermentation of traditional Korean alcoholic beverages inoculated with various natural starters.

Makgeolli is a traditional Korean alcoholic beverage manufactured with a natural starter, called nuruk, and grains. Nuruk is a starchy disk or tablet formed from wheat or grist containing various fungal and bacterial strains from the surrounding environment that are allowed to incorporate naturally into the starter, each of which simultaneously participates in the makgeolli fermentation process. In the current study, changes in microbial dynamics during laboratory-scale fermentation of makgeolli inoculated with six different kinds of nuruk were evaluated by barcoded pyrosequencing using fungal- and bacterial-specific primers targeting the internal transcribed spacer 2 region and hypervariable regions V1 to V3 of the 16S rRNA gene, respectively. A total of 61,571 fungal and 68,513 bacterial sequences were used for the analysis of microbial diversity in ferment samples. During fermentation, the proportion of fungal microorganisms belonging to the family Saccharomycetaceae increased significantly, and the major bacterial phylum of the samples shifted from γ-Proteobacteria to Firmicutes. The results of quantitative PCR indicated that the bacterial content in the final ferments was higher than in commercial rice beers, while total fungi appeared similar. This is the first report of a comparative analysis of bacterial and fungal dynamics in parallel during the fermentation of Korean traditional alcoholic beverage using barcoded pyrosequencing.

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.

Oceanobacillus kimchii sp. nov. Isolated from a Traditional Korean Fermented Food

A moderate halophile, strain X50T, was isolated from mustard kimchi, a traditional Korean fermented food. The organism grew under conditions ranging from 0–15.0% (w/v) NaCl (optimum: 3.0%), pH 7.0–10.0 (optimum: pH 9.0) and 15–45°C (optimum: 37°C). The morphological, physiological, and biochemical features and the 16S rRNA gene sequences of strain X50T were characterized. Colonies of the isolate were creamcolored and the cells were rod-shaped. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain X50T belongs to the genus Oceanobacillus and is closely related phylogenetically to the type strain O. iheyensis HTE831T (98.9%) and O. oncorhynchi subsp. oncorhynchi R-2T (97.0%). The cellular fatty acid profiles predominately included anteiso-C15:0 and iso-C15:0. The G+C content of the genomic DNA of the isolate was 37.9 mol% and the major isoprenoid quinone was MK-7. Analysis of the 16S rRNA gene sequences, DNA-DNA relatedness and physiological and biochemical tests indicated genotypic and phenotypic differences among strain X50T and reference species in the genus Oceanobacillus. Therefore, strain X50T was proposed as a novel species and named Oceanobacillus kimchii. The type strain of the new species is X50T (=JCM 16803T =KACC 14914T =DSM 23341T).

Kocuria atrinae sp. nov., isolated from traditional Korean fermented seafood

A novel actinobacterium, strain P30(T), was isolated from jeotgal, a traditional Korean fermented seafood. Cells were aerobic, Gram-positive, non-motile and coccoid. Optimal growth occurred at 30-37 degrees C, at pH 8-9 and in the presence of 0-2 % (w/v) NaCl. Based on 16S rRNA gene sequence analysis, strain P30(T) was phylogenetically closely related to Kocuria carniphila, Kocuria gwangalliensis, Kocuria rhizophila, Kocuria marina, Kocuria rosea and K. varians with levels of similarity of 98.6, 98.2, 98.1, 97.4, 97.3 and 97.3 %, respectively, to the type strains of these species. Levels of DNA-DNA relatedness between strain P30(T) and the type strains of K. carniphila, K. rhizophila, K. marina, K. rosea and K. varians were 37, 43, 37, 25 and 17 %, respectively. The predominant menaquinone of strain P30(T) was MK-7. Major cellular fatty acids were anteiso-C(15 : 0), iso-C(15 : 0) and iso-C(16 : 0). The genomic DNA G+C content of strain P30(T) was 70.2 mol%. Based on these data, strain P30(T) is considered to represent a novel species of the genus Kocuria, for which the name Kocuria atrinae sp. nov. is proposed. The type strain is P30(T) (=KCTC 19594(T)=JCM 15914(T)).

Leucobacter celer sp. nov., isolated from Korean fermented seafood

A novel, Gram-reaction-positive, aerobic, rod-shaped, non-motile bacterial strain, designated NAL101(T), was isolated from gajami-sikhae, a traditional Korean fermented seafood made of flatfish. Growth occurred at 4-45 °C, at pH 5-10 and in 0-12 % (w/v) NaCl. Optimum growth occurred at 30-37 °C, at pH 8 and in 0-1 % (w/v) NaCl. The cell-wall amino acids were 2,4-diaminobutyric acid, alanine, glycine, threonine and glutamic acid and the major fatty acids were anteiso-C(15 : 0), iso-C(16 : 0) and anteiso-C(17 : 0). The predominant menaquinone was MK-11. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and an unknown glycolipid. The 16S rRNA gene sequence of strain NAL101(T) showed 97.7 % similarity to that of Leucobacter chironomi MM2LB(T), its closest relative. The DNA G+C content was 68.8 mol% and DNA-DNA hybridization values with closely related strains were <22 %. Phylogenetic analyses based on 16S rRNA gene sequences as well as differences in its physiological and biochemical characteristics indicated that strain NAL101(T) represents a novel species of the genus Leucobacter in the family Microbacteriaceae, for which the name Leucobacter celer sp. nov. is proposed. The type strain is NAL101(T) ( = KACC 14220(T)  = JCM 16465(T)).

Kocuria koreensis sp. nov., isolated from fermented seafood

A Gram-positive, aerobic, non-motile and coccoid actinobacterium, designated P31(T), was isolated from a traditional, fermented seafood. The strain was catalase-positive and oxidase-negative. Cells grew in the presence of 0-15.0 % (w/v) NaCl, and at pH 5-10 and 15-37 degrees C. Major cellular fatty acids were anteiso-C(15 : 0), anteiso-C(17 : 0) and iso-C(16 : 0). Strain P31(T) contained MK-7 as the predominant menaquinone. The DNA G+C content of the genomic DNA of strain P31(T) was 65.2 mol%. A phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain P31(T) was most closely related to Kocuria kristinae DSM 20032(T), with 96.9 % similarity, and these two strains clustered together in constructed phylogenetic trees. The DNA-DNA hybridization value between strain P31(T) and K. kristinae DSM 20032(T) was 21.1 %. On the basis of the phenotypic, chemotaxonomic and phylogenetic data, it is suggested that strain P31(T) represents a novel species of the genus Kocuria, for which the name Kocuria koreensis sp. nov. is proposed. The type strain is P31(T) (=KCTC 19595(T)=JCM 15915(T)).

Alishewanella jeotgali sp. nov., isolated from traditional fermented food, and emended description of the genus Alishewanella

A novel Gram-negative and facultative anaerobic strain, designated MS1T, was isolated from gajami sikhae, a traditional fermented food in Korea made from flatfish. Strain MS1T was motile, rod-shaped and oxidase- and catalase-positive, and required 1-2% (w/v) NaCl for growth. Growth occurred at temperatures ranging from 4 to 40 degrees C and the pH range for optimal growth was pH 6.5-9.0. Strain MS1T was capable of reducing trimethylamine oxide, nitrate and thiosulfate. Phylogenetic analysis placed strain MS1T within the genus Alishewanella. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain MS1T was related closely to Alishewanella aestuarii B11T (98.67% similarity) and Alishewanella fetalis CCUG 30811T (98.04% similarity). However, DNA-DNA reassociation experiments between strain MS1T and reference strains showed relatedness values<70% (42.6 and 14.8% with A. aestuarii B11T and A. fetalis CCUG 30811T, respectively). Genotypic, physiological and biochemical analyses allowed the differentiation of strain MS1T from type strains of species belonging to the genus Alishewanella. Therefore, we propose that strain MS1T (=KCTC 22429T=JCM 15561T) is assigned to a novel species, Alishewanella jeotgali sp. nov.

Kocuria salsicia sp. nov., isolated from salt-fermented seafood

Strain 104(T) was isolated from a traditional salt-fermented seafood in Korea. It was a Gram-positive, non-motile, coccus-shaped bacterium. It formed lemon-yellow, opaque colonies that were circular with entire margins. Optimal growth occurred at 30-37 °C, pH 7-8 and in the presence of 0-2 % (w/v) NaCl. Phylogenetic analysis of 16S rRNA gene sequences from strain 104(T) and reference species of the genus Kocuria indicated that strain 104(T) formed an independent line. The G+C content of the chromosomal DNA was 60.6 mol%. MK-7 was the major menaquinone and the predominant fatty acids were anteiso-C(15 : 0) (76.7 %), anteiso-C(17 : 0) (10.9 %) and iso-C(16 : 0) (4.5 %). Strain 104(T) was most closely related to Kocuria rhizophila TA68(T) (98.9 % 16S rRNA gene sequence similarity). The DNA-DNA hybridization value between strain 104(T) and K. rhizophila TA68(T) was 14.1±3.4 %. On the basis of this polyphasic taxonomic analysis, strain 104(T) appears to represent a novel species in the genus Kocuria. The name Kocuria salsicia sp. nov. is proposed. The type strain is 104(T) (=KACC 21128(T)=JCM 16361(T)).