Journal of Microbiology

Volume 54(9); September 2016

Review

MINIREVIEW] Multilayered regulations of RIG-I in the anti-viral signaling pathway: Nari Kim , Hesung Now , Nhung T.H. Nguyen , Joo-Yeon Yoo; J. Microbiol. 2016;54(9):583-587. Published online August 31, 2016; DOI: https://doi.org/10.1007/s12275-016-6322-2

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Abstract: RIG-I is a cytosolic receptor recognizing virus-specific RNA structures and initiates an antiviral signaling that induces the production of interferons and proinflammatory cytokines. Because inappropriate RIG-I signaling affects either viral clearance or immune toxicity, multiple regulations of RIG-I have been investigated since its discovery as the viral RNA detector. In this review, we describe the recent progress in research on the regulation of RIG-I activity or abundance. Specifically, we focus on the mechanism that modulates RIGI- dependent antiviral response through post-translational modifications of or protein-protein interactions with RIG-I.

Journal Articles

Gracilibacillus kimchii sp. nov., a halophilic bacterium isolated from kimchi§: Young Joon Oh , Hae-Won Lee , Seul Ki Lim , Min-Sung Kwon , Jieun Lee , Ja-Young Jang , Hae Woong Park , Young-Do Nam , Myung-Ji Seo , Hak-Jong Choi; J. Microbiol. 2016;54(9):588-593. Published online August 31, 2016; DOI: https://doi.org/10.1007/s12275-016-6349-4

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13 Citations

Abstract: A novel halophilic bacterium, strain K7T, was isolated from kimchi, a traditional Korean fermented food. The strain is Gram-positive, motile, and produces terminal endospores. The isolate is facultative aerobic and grows at salinities of 0.0–25.0% (w/v) NaCl (optimum 10–15% NaCl), pH 5.5–8.5 (optimum pH 7.0–7.5), and 15–42°C (optimum 37°C). The predominant isoprenoid quinone in the strain is menaquinone- 7 and the peptidoglycan of the strain is meso-diaminopimelic acid. The major fatty acids of the strain are anteisio- C15:0, iso-C15:0, and, C16:0 (other components were < 10.0%), while the major polar lipids are diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, and three unidentified lipids. A phylogenetic analysis of 16S rRNA gene sequence similarity showed that the isolated strain was a cluster of the genus Gracilibacillus. High levels of gene sequence similarity were observed between strain K7T and Gracilibacillus orientalis XH-63T (96.5%), and between the present strain and Gracilibacillus xinjiangensis (96.5%). The DNA G+C content of this strain is 37.7 mol%. Based on these findings, strain K7T is proposed as a novel species: Gracilibacillus kimchii sp. nov. The type strain is K7T (KACC 18669T; JCM 31344T).

Intestinal Lactobacillus community structure and its correlation with diet of Southern Chinese elderly subjects§: Yuanyuan Pan , Da-Wen Sun , Quanyang Li; J. Microbiol. 2016;54(9):594-601. Published online August 31, 2016; DOI: https://doi.org/10.1007/s12275-016-6131-7

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Abstract: This study aimed to investigate the relationship between the intestinal Lactobacillus species and diet of elderly subjects in a longevity area in Southern China. Healthy elderly subjects ranging from 80 to 99 years old were respectively selected from the regions of Bama and Nanning, Guangxi, China. The nested polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) technology was used to analyze the intestinal Lactobacillus community structure.
Results
showed that Weissella confusa, L. mucosae, L. crispatus, L. salivarius, and L. delbrueckii were the representative Lactobacillus of elderly subjects. Among them, L. crispatus and L. delbrueckii were the dominant Lactobacillus of all species. In comparison to Nanning elderly subjects, the detection frequencies of W. confusa and L. salivarius were significantly increased in Bama elderly subjects (P < 0.01), whereas L. mucosae was significantly decreased (P < 0.01). Interestingly, it was also found that there were 4 kinds of representative Lactobacillus, which were significantly correlated with dietary fiber. W. confusa (P < 0.01) and L. salivarius (P < 0.05) were significantly positively correlated with the intake of dietary fiber, while L. mucosae (P < 0.01) and L. crispatus (P < 0.05) were significantly negatively correlated with the intake of dietary fiber, respectively. Results confirmed that different diets had obvious effects on the intestinal Lactobacillus community structure of elderly subjects in Southern China, which may provide a certain theoretical basis for the elderly’s healthy food strategic design and probiotics product development.

Cr(VI) removal from aqueous solution by thermophilic denitrifying bacterium Chelatococcus daeguensis TAD1 in the presence of single and multiple heavy metals: Han Li , Shaobin Huang , Yongqing Zhang; J. Microbiol. 2016;54(9):602-610. Published online August 31, 2016; DOI: https://doi.org/10.1007/s12275-016-5295-5

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Abstract: Cr(VI) pollution is increasing continuously as a result of ongoing industrialization. In this study, we investigated the thermophilic denitrifying bacterium Chelatococcus daeguensis TAD1, isolated from the biofilm of a biotrickling filter used in nitrogen oxides (NOX) removal, with respect to its ability to remove Cr(VI) from an aqueous solution. TAD1 was capable of reducing Cr(VI) from an initial concentration of 10 mg/L to non-detectable levels over a pH range of 7–9 and at a temperature range of 30–50°C. TAD1 simultaneously removed both Cr(VI) and NO3 −-N at 50°C, when the pH was 7 and the initial Cr(VI) concentration was 15 mg/L. The reduction of Cr(VI) to Cr(III) correlated with the growth metabolic activity of TAD1. The presence of other heavy metals (Cu, Zn, and Ni) inhibited the ability of TAD1 to remove Cr(VI). The metals each individually inhibited Cr(VI) removal, and the extent of inhibition increased in a cooperative manner in the presence of a combination of the metals. The addition of biodegradable cellulose acetate microspheres (an adsorption material) weakened the toxicity of the heavy metals; in their presence, the Cr(VI) removal efficiency returned to a high level. The feasibility and applicability of simultaneous nitrate removal and Cr(VI) reduction by strain TAD1 is promising, and may be an effective biological method for the clean-up of wastewater.

Long-term organic-inorganic fertilization ensures great soil productivity and bacterial diversity after natural-to-agricultural ecosystem conversion: Weibing Xun , Zhihui Xu , Wei Li , Yi Ren , Ting Huang , Wei Ran , Boren Wang , Qirong Shen , Ruifu Zhang; J. Microbiol. 2016;54(9):611-617. Published online August 31, 2016; DOI: https://doi.org/10.1007/s12275-016-6143-3

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22 Citations

Abstract: Natural ecosystems comprise the planet’s wild plant and animal resources, but large tracts of land have been converted to agroecosystems to support the demand for agricultural products. This conversion limits the number of plant species and decreases the soil biological diversity. Here we used highthroughput 16S rRNA gene sequencing to evaluate the responses of soil bacterial communities in long-term converted and fertilized red soils (a type of Ferralic Cambisol). We observed that soil bacterial diversity was strongly affected by different types of fertilization management. Oligotrophic bacterial taxa demonstrated large relative abundances in chemically fertilized soil, whereas copiotrophic bacterial taxa were found in large relative abundances in organically fertilized and fallow management soils. Only organic-inorganic fertilization exhibited the same local taxonomic and phylogenetic diversity as that of a natural ecosystem. However, the independent use of organic or inorganic fertilizer reduced local taxonomic and phylogenetic diversity and caused biotic homogenization. This study demonstrated that the homogenization of bacterial communities caused by natural-to-agricultural ecosystem conversion can be mitigated by employing rational organic-inorganic fertilization managemen

Application of high-resolution melting analysis for differentiation of spoilage yeasts: Mine Erdem , Zülal Kesmen , Esra Özbekar , Bülent Çetin , Hasan Yetim; J. Microbiol. 2016;54(9):618-625. Published online August 31, 2016; DOI: https://doi.org/10.1007/s12275-016-6017-8

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Abstract: A new method based on high resolution melting (HRM) analysis was developed for the differentiation and classification of the yeast species that cause food spoilage. A total 134 strains belonging to 21 different yeast species were examined to evaluate the discriminative power of HRM analysis. Two different highly variable DNA regions on the 26 rRNA gene were targeted to produce the HRM profiles of each strain. HRMbased grouping was compared and confirmed by (GTG)5 rep- PCR fingerprinting analysis. All of the yeast species belonging to the genera Pichia, Candida, Kazachstania, Kluyveromyces, Debaryomyces, Dekkera, Saccharomyces, Torulaspora, Ustilago, and Yarrowia, which were produced as species-specific HRM profiles, allowed discrimination at species and/or strain level. The HRM analysis of both target regions provided successful discrimination that correlated with rep-PCR fingerprinting analysis. Consequently, the HRM analysis has the potential for use in the rapid and accurate classification and typing of yeast species isolated from different foods to determine their sources and routes as well as to prevent contamination.

Molecular characterization of SCO0765 as a cellotriose releasing endo-β-1,4-cellulase from Streptomyces coelicolor A(3): Joo-Bin Hong , Vijayalakshmi Dhakshnamoorthy , Chang-Ro Lee; J. Microbiol. 2016;54(9):626-631. Published online August 31, 2016; DOI: https://doi.org/10.1007/s12275-016-6271-9

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Abstract: The sco0765 gene was annotated as a glycosyl hydrolase family 5 endoglucanase from the genomic sequence of Streptomyces coelicolor A3(2) and consisted of 2,241 bp encoding a polypeptide of 747 amino acids (molecular weight of 80.5 kDa) with a 29-amino acid signal peptide for secretion. The SCO0765 recombinant protein was heterogeneously overexpressed in Streptomyces lividans TK24 under the control of a strong ermE* promoter. The purified SCO0765 protein showed the expected molecular weight of the mature form (718 aa, 77.6 kDa) on sodium dodecyl sulfate-polyacryl amide gel electrophoresis. SCO0765 showed high activity toward β-glucan and carboxymethyl cellulose (CMC) and negligible activity to Avicel, xylan, and xyloglucan. The SCO0765 cellulase had a maximum activity at pH 6.0 and 40°C toward CMC and at pH 9.0 and 50–60°C toward β-glucan. Thin layer chromatography of the hydrolyzed products of CMC and β-glucan by SCO0765 gave cellotriose as the major product and cellotetraose, cellopentaose, and longer oligosaccharides as the minor products. These results clearly demonstrate that SCO0765 is an endo-β-1,4-cellulase, hydrolyzing the β-1,4 glycosidic bond of cellulose into cellotriose.

D-Galactose as an autoinducer 2 inhibitor to control the biofilm formation of periodontopathogens: Eun-Ju Ryu , Jaehyun Sim , Jun Sim , Julian Lee , Bong-Kyu Choi; J. Microbiol. 2016;54(9):632-637. Published online August 31, 2016; DOI: https://doi.org/10.1007/s12275-016-6345-8

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Abstract: Autoinducer 2 (AI-2) is a quorum sensing molecule to which bacteria respond to regulate various phenotypes, including virulence and biofilm formation. AI-2 plays an important role in the formation of a subgingival biofilm composed mostly of Gram-negative anaerobes, by which periodontitis is initiated. The aim of this study was to evaluate D-galactose as an inhibitor of AI-2 activity and thus of the biofilm formation of periodontopathogens. In a search for an AI-2 receptor of Fusobacterium nucleatum, D-galactose binding protein (Gbp, Gene ID FN1165) showed high sequence similarity with the ribose binding protein (RbsB), a known AI-2 receptor of Aggregatibacter actinomycetemcomitans. D-Galactose was evaluated for its inhibitory effect on the AI-2 activity of Vibrio harveyi BB152 and F. nucleatum, the major coaggregation bridge organism, which connects early colonizing commensals and late pathogenic colonizers in dental biofilms. The inhibitory effect of D-galactose on the biofilm formation of periodontopathogens was assessed by crystal violet staining and confocal laser scanning microscopy in the absence or presence of AI-2 and secreted molecules of F. nucleatum. D-Galactose significantly inhibited the AI-2 activity of V. harveyi and F. nucleatum. In addition, D-galactose markedly inhibited the biofilm formation of F. nucleatum, Porphyromonas gingivalis, and Tannerella forsythia induced by the AI-2 of F. nucleatum without affecting bacterial growth. Our
results
demonstrate that the Gbp may function as an AI-2 receptor and that galactose may be used for prevention of the biofilm formation of periodontopathogens by targeting AI-2 activity.

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