Journal of Microbiology

Volume 55(12); December 2017

Review

Minireview] Electron microscopic observations of prokaryotic surface appendages: Ki Woo Kim; J. Microbiol. 2017;55(12):919-926. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7369-4

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Abstract: Prokaryotic microbes possess a variety of appendages on their cell surfaces. The most commonly known surface appendages of bacteria include flagella, pili, curli, and spinae. Although archaea have archaella (archaeal flagella) and various types of pili that resemble those in bacteria, cannulae, and hami are unique to archaea. Typically involved in cell motility, flagella, the thickest appendages, are 20–26 nm and 10–14 nm wide in bacteria and archaea, respectively. Bacterial and archaeal pili are distinguished by their thin, short, hair-like structures. Curli appear as coiled and aggregative thin fibers, whereas spinae are tubular structures 50–70 nm in diameter in bacteria. Cannulae are characterized by ~25 nm-wide tubules that enter periplasmic spaces and connect neighboring archaeal cells. Hami are 1–3 μm in length and similar to barbed grappling hooks for attachment to bacteria. Recent advances in specimen preparation methods and image processing techniques have made cryo-transmission electron microscopy an essential tool for in situ structural analysis of microbes and their extracellular structures.

Journal Articles

Spirosoma migulaei sp. nov., isolated from soil: Joseph Okiria , Leonid N. Ten , Su-Jin Park , Seung-Yeol Lee , Dong Hoon Lee , In-Kyu Kang , Dae Sung Lee , Hee-Young Jung; J. Microbiol. 2017;55(12):927-932. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7377-4

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Abstract: A Gram-stain-negative, non-motile, non-spore-forming, rodshaped, aerobic bacterium, designated 15J9-8T, was isolated from soil on Jeju Island, Republic of Korea. The isolate was able to grow between 10 and 30°C, pH 6.5–8.5, and in presence of 0–1% (w/v) NaCl. The results of comparative 16S rRNA gene sequence analysis indicated that strain 15J9-8T represented a member of the family Cytophagaceae, phylum Bacteroidetes, and was most closely related to Spirosoma aerophilum 5516J-17T (96.1% similarity), Spirosoma pulveris JSH5-14T (95.6%), and Spirosoma linguale DSM 74T (95.2%). The G + C content of the genomic DNA of the isolate was 47.0 mol%. Strain 15J9-8T contained summed feature 3 (C16:1 ω7c/C16:1 ω6c), C16:1 ω5c, and iso-C15:0 as the major fatty acids, phosphatidylethanolamine and an unidentified aminophospholipid as the main polar lipids, and menaquinone MK-7 as the predominant respiratory quinone. On the basis of its phenotypic and genotypic properties, and phylogenetic distinctiveness, strain 15J9-8T should be classified as a representative of a novel species of the genus Spirosoma, for which the name Spirosoma migulaei sp. nov. is proposed. The type strain is 15J9-8T (=KCTC 52028T =JCM 31996T).

Virgibacillus kimchii sp. nov., a halophilic bacterium isolated from kimchi: Young Joon Oh , Ja-Young Jang , Seul Ki Lim , Min-Sung Kwon , Jieun Lee , NamHee Kim , Mi-Young Shin , Hyo Kyeong Park , Myung-Ji Seo , Hak-Jong Choi; J. Microbiol. 2017;55(12):933-938. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7386-3

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6 Citations

Abstract: A Gram-stain-positive, halophilic, rod-shaped, non-motile, spore forming bacterium, strain NKC1-2T, was isolated from kimchi, a Korean fermented food. Comparative analysis based on 16S rRNA gene sequence demonstrated that the isolated strain was a species of the genus Virgibacillus. Strain NKC1- 2T exhibited high level of 16S rRNA gene sequence similarity with the type strains of Virgibacillus xinjiangensis SL6-1T (96.9%), V. sediminis YIM kkny3T (96.8%), and V. salarius SA-Vb1T (96.7%). The isolate grew at pH 6.5–10.0 (optimum, pH 8.5–9.0), 0.0–25.0% (w/v) NaCl (optimum, 10–15% NaCl), and 15–50°C (optimum, 37°C). The major menaquinone in the strain was menaquinone-7, and the main peptidoglycan of the strain was meso-diaminopimelic acid. The predominant fatty acids of the strain were iso-C14:0, anteisio-C15:0, iso- C15:0, and iso-C16:0 (other components were < 10.0%). The polar lipids consisted of diphosphatidylglycerol and phosphatidylglycerol. The genomic DNA G + C content of NKC1-2T was 42.5 mol%. On the basis of these findings, strain NKC1- 2T is proposed as a novel species in the genus Virgibacillus, for which the name Virgibacillus kimchii sp. nov. is proposed (=KACC 19404T =JCM 32284T). The type strain of Virgibacillus kimchii is NKC1-2T.

Cecal microbiome divergence of broiler chickens by sex and body weight: Kyu-Chan Lee , Dong Yong Kil , Woo Jun Sul; J. Microbiol. 2017;55(12):939-945. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7202-0

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75 Citations

Abstract: The divergence of gut bacterial community on broiler chickens has been reported as potentially possible keys to enhancing nutrient absorption, immune systems, and increasing poultry health and performance. Thus, we compared cecal bacterial communities and functional predictions by sex and body weight regarding the association between cecal microbiota and chicken growth performance. In this study, a total of 12 male and 12 female 1-day-old broiler chickens were raised for 35 days in 2 separate cages. Chickens were divided into 3 subgroups depending on body weight (low, medium, and high) by each sex. We compared chicken cecal microbiota compositions and its predictive functions by sex and body weight difference. We found that bacterial 16S rRNA genes were classified as 3 major phyla (Bacteroidetes, Firmicutes, and Proteobacteria), accounting for > 98% of the total bacterial community. The profiling of different bacterial taxa and predictive metagenome functions derived from 16S rRNA genes were performed over chicken sex and bodyweight. Male chickens were related to the enrichment of Bacteroides while female chickens were to the enrichment of Clostridium and Shigella. Male chickens with high body weight were associated with the enrichment of Faecalibacterium and Shuttleworthia. Carbohydrate and lipid metabolisms were suggested as candidate functions for weight gain in the males. This suggests that the variation of cecal bacterial communities and their functions by sex and body weight may be associated with the differences in the growth potentials of broiler chickens.

Effects of dietary poly-β-hydroxybutyrate (PHB) on microbiota composition and the mTOR signaling pathway in the intestines of Litopenaeus vannamei: Yafei Duan , Yue Zhang , Hongbiao Dong , Yun Wang , Jiasong Zhang; J. Microbiol. 2017;55(12):946-954. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7273-y

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47 Citations

Abstract: Poly-β-hydroxybutyrate (PHB) is a natural polymer of the short chain fatty acid β-hydroxybutyrate, which acts as a microbial control agent. The mammalian target of the rapamycin (mTOR) signaling pathway plays a crucial role in intestine inflammation and epithelial morphogenesis. In this study, we examined the composition of intestine microbiota, and mTOR signaling-related gene expression in Pacific white shrimp Litopenaeus vannamei fed diets containing different levels of PHB: 0% (Control), 1% (PHB1), 3% (PHB3), and 5% (PHB5) (w/w) for 35 days. High-throughput sequencing analysis revealed that dietary PHB altered the composition and diversity of intestine microbiota, and that the microbiota diversity decreased with the increasing doses of PHB. Specifically, dietary PHB increased the relative abundance of Proteobacteria and Tenericutes in the PHB1 and PHB5 groups, respectively, and increased that of Gammaproteobacteria in the three PHB groups. Alternatively, PHB decreased Alphaproteobacteria in the PHB3 and PHB5 groups. At the genus level, dietary PHB increased the abundance of beneficial bacteria, such as Bacillus, Lactobacillus, Lactococcus, Clostridium, and Bdellovibrio. The relative mRNA expression levels of the mTOR signaling-related genes TOR, 4E-BP, eIF4E1α, and eIF4E2 all increased in the three PHB treatment groups. These
results
revealed that dietary PHB supplementation had a beneficial effect on intestine health of L. vannamei by modulating the composition of intestine microbiota and activating mTOR signaling.

Metabolism-mediated induction of zinc tolerance in Brassica rapa by Burkholderia cepacia CS2-1: Sang-Mo Kang , Raheem Shahzad , Saqib Bilal , Abdul Latif Khan , Young-Hyun You , Won-Hee Lee , Hee-La Ryu , Ko-Eun Lee , In-Jung Lee; J. Microbiol. 2017;55(12):955-965. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7305-7

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12 Citations

Abstract: Brassica rapa (Chinese cabbage) is an essential component of traditional Korean food. However, the crop is often subject to zinc (Zn+) toxicity from contaminated irrigation water, which, as a result, compromises plant growth and production, as well as the health of human consumers. The present study investigated the bioaccumulation of Zn+ by Burkholderia cepacia CS2-1 and its effect on the heavy metal tolerance of Chinese cabbage. Strain CS2-1 was identified and characterized on the basis of 16S rRNA sequences and phylogenetic analysis. The strain actively produced indole-3-acetic acid (3.08 ± 0.21 μg/ml) and was also able to produce siderophore, solubilize minerals, and tolerate various concentrations of Zn+. The heavy metal tolerance of B. rapa plants was enhanced by CS2-1 inoculation, as indicated by growth attributes, Zn+ uptake, amino acid synthesis, antioxidant levels, and endogenous hormone (ABA and SA) synthesis. Without inoculation, the application of Zn+ negatively affected the growth and physiology of B. rapa plants. However, CS2-1 inoculation improved plant growth, lowered Zn+ uptake, altered both amino acid regulation and levels of flavonoids and phenolics, and significantly decreased levels of superoxide dismutase, endogenous abscisic acid, and salicylic acid. These findings indicate that B. cepacia CS2-1 is suitable for bioremediation against Zn+-induced oxidative stress.

Direct interaction between the transcription factors CadC and OmpR involved in the acid stress response of Salmonella enterica: Yong Heon Lee , Ji Hye Kim; J. Microbiol. 2017;55(12):966-972. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7410-7

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8 Citations

Abstract: In Salmonella enterica serovar Typhimurium, the acid-sensing regulator CadC activates transcription of the cadBA operon which contributes to the acid tolerance response. The DNA-binding response regulator OmpR in two-component regulatory system with EnvZ binds to its own promoter for autoinduction. We previously reported that CadC exerts a negative influence on ompR transcription during acid adaptation. However, its underlying mechanisms remain to be elucidated. Here we show that the level of OmpR protein is gradually reduced by a gradual increase in the CadC level using an arabinose-inducible expression system, indicating there exists a negative correlation between the expression levels of two transcription factors. To explore the molecular basis for OmpR repression by CadC, we performed in vitro binding assays and determined that CadC directly interacts with OmpR. We further show that inactivation of cadC inhibits transcription of the fliC gene, which encodes the major flagellar subunit,
result
ing in impaired flagellar motility under acid-adaptation conditions. Together, our findings suggest that CadC may repress autoinduction of the OmpR response regulator through their direct interaction.

Guinea pig complement potently measures vibriocidal activity of human antibodies in response to cholera vaccines: Kyoung Whun Kim , Soyoung Jeong , Ki Bum Ahn , Jae Seung Yang , Cheol-Heui Yun , Seung Hyun Han; J. Microbiol. 2017;55(12):973-978. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7478-0

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Abstract: The vibriocidal assay using guinea pig complement is widely used for the evaluation of immune responses to cholera vaccines in human clinical trials. However, it is unclear why guinea pig complement has been used over human complement in the measurement of vibriocidal activity of human sera and there have not been comparison studies for the use of guinea pig complement over those from other species. Therefore, we comparatively investigated the effects of complements derived from human, guinea pig, rabbit, and sheep on vibriocidal activity. Complements from guinea pig, rabbit, and human showed concentration-dependent vibriocidal activity in the presence of quality control serum antibodies. Of these complements, guinea pig complement was the most sensitive and effective over a wide concentration range. When the vibriocidal activity of complements was measured in the absence of serum antibodies, human, sheep, and guinea pig complements showed vibriocidal activity up to 40-fold, 20- fold, and 1-fold dilution, respectively. For human pre- and post-vaccination sera, the most potent vibriocidal activity was observed when guinea pig complement was used. In addition, the highest fold-increases between pre- and post- vaccinated sera were obtained with guinea pig complement. Furthermore, human complement contained a higher amount of V. cholerae- and its lipopolysaccharide-specific antibodies than guinea pig complement. Collectively, these results suggest that guinea pig complements are suitable for vibriocidal assays due to their high sensitivity and effectiveness to human sera.

Comparison of anti-influenza virus activity and pharmacokinetics of oseltamivir free base and oseltamivir phosphate: Jin Soo Shin , Keun Bon Ku , Yejin Jang , Yi-Seul Yoon , Daeho Shin , Oh Seung Kwon , Yun Young Go , Seong Soon Kim , Myoung Ae Bae , Meehyein Kim; J. Microbiol. 2017;55(12):979-983. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7371-x

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14 Citations

Abstract: Influenza viruses are major human respiratory pathogens that cause high morbidity and mortality worldwide. Currently, prophylactic vaccines and therapeutic antiviral agents are used to prevent and control influenza virus infection. Oseltamivir free base (OSV-FB), a modified generic antiviral drug of Tamiflu (oseltamivir phosphate, OSV-P), was launched in the Republic of Korea last year. Here, we examine the bioequivalence of these two compounds by assessing their antiviral efficacy in infected cells and in a mouse model. It was observed that both antivirals showed comparable efficacy against 11 different influenza A and B viruses in vitro. Moreover, in mice infected with influenza A virus (mouse-adapted A/Puerto Rico/8/34), they showed a dose-dependent therapeutic activity and alleviated infection-mediated reductions in body weight, leading to significantly better survival. There was histopathological disappearance of virus-induced inflammatory cell infiltration of the lung after oral treatment with either antiviral agent (at 10 mg/kg). Pharmacokinetic analysis also exhibited similar plasma concentrations of the active drug, oseltamivir carboxylate, metabolised from both OSVB and OSV-P. This is the first report showing bioequivalence of OSV-FB to its phosphate salt form in the mouse system. The free base drug has some beneficial points including simple drug formulation process and reduced risk of undesirable cation-phosphate precipitation within solution. The long term stability of OSV-FB requires further monitoring when it is provided as a national stock in readiness for an influenza pandemic.

An ethanol extract of Lysimachia mauritiana exhibits inhibitory activity against hepatitis E virus genotype 3 replication: Seong Eun Jin , Jung-Eun Kim , Sun Yeou Kim , Bang Ju Park , Yoon-Jae Song; J. Microbiol. 2017;55(12):984-988. Published online December 7, 2017; DOI: https://doi.org/10.1007/s12275-017-7477-1

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Abstract: Hepatitis E virus (HEV) is an etiological agent of acute hepatitis E, a self-limiting disease prevalent in developing countries. HEV can cause fulminant hepatic failure with high mortality rates in pregnant women, and genotype 3 is reported to trigger chronic hepatitis in immunocompromised individuals worldwide. Screening of plant extracts for compounds with potential anti-HEV effects led to the identification of a 70% ethanol extract of Lysimachia mauritiana (LME) that interferes with replication of the swine HEV genotype 3 replicon. Furthermore, LME significantly inhibited replication of HEV genotype 3 and expression of HEV ORF2 in infected cells without exerting cytotoxic effects. Collectively, our findings demonstrate the potential utility of LME in the development of novel antiviral drugs against HEV infection.

Published Erratum

Corrigendum] Application of high-resolution melting analysis for differentiation of spoilage yeasts: Mine Erdem , Zülal Kesmen , Esra Özbekar , Bülent Çetin , Hasan Yetim; J. Microbiol. 2017;55(12):989-989.; DOI: https://doi.org/10.1007/s12275-017-0671-3

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