Journal of Microbiology

Volume 57(12); December 2019

Journal Articles

[Protocol]Construction of a multicopy genomic DNA library and its application for suppression analysis: Hongbaek Cho; J. Microbiol. 2019;57(12):1041-1047. Published online November 22, 2019; DOI: https://doi.org/10.1007/s12275-019-9417-8

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Abstract: Suppression analysis is used for the identification of new genes and genetic interactions when there is a notable phenotype available for genetic selection or screening. A random genomic DNA library constructed on a multi-copy plasmid is a useful tool for suppression analysis when one expects that an overdose of a few genes will suppress the phenotype. These libraries have been successfully used to determine the function of a gene by revealing genes whose functions are related to the gene of interest. They have also been used to identify the targets of chemical or biological agents by increasing the number of unaffected target gene products in a cell. In this article, I will discuss important considerations for constructing multicopy genomic DNA libraries. The protocol provided in this paper should be a useful guide for constructing genomic DNA libraries in many bacterial species for which multi-copy plasmids are available.

Hahyoungchilella caricis gen. nov., sp. nov., isolated from a rhizosphere mudflat of a halophyte (Carex scabrifolia), transfer of Thioclava arenosa Thongphrom et al. 2017 to Pseudothioclava as Pseudothioclava arenosa gen. nov., comb. nov. and proposal of Thioclava electrotropha Chang et al. 2018: Young-Ju Kim , Soon Dong Lee; J. Microbiol. 2019;57(12):1048-1055. Published online September 25, 2019; DOI: https://doi.org/10.1007/s12275-019-9260-y

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Abstract: A Gram-stain-negative, strictly aerobic, marine bacterium, designated GH2-2T, was isolated from a rhizosphere mudflat of a halophyte (Carex scabrifolia) in Gangwha Island, the Republic of Korea. The cells of the organism were oxidase- positive, catalase-positive, flagellated, short rods that grew at 10–40°C, pH 4–10, and 0–13% (w/v) NaCl. The predominant ubiquinone was Q-10. The major polar lipids were phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol. The major fatty acid is C18:1. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the novel isolate formed an independent lineage at the base of the radiation encompassing members of the genus Thioclava, except for Thioclava arenosa. The closest relatives were T. nitratireducens (96.03% sequence similarity) and T. dalianensis (95.97%). The genome size and DNA G+C content were 3.77 Mbp and 59.6 mol%, respectively. Phylogenomic analysis supported phylogenetic distinctness based on 16S rRNA gene sequences. Average nucleotide identity values were 73.6–74.0% between the novel strain and members of the genus Thioclava. On the basis of data obtained from a polyphasic approach, the strain GH2-2T (= KCTC 62124T = DSM 105743T) represents a novel species of a new genus for which the name Hahyoungchilella caricis gen. nov., sp. nov. is proposed. Moreover, the transfer of Thioclava arenosa Thongphrom et al. 2017 to Pseudothioclava gen. nov. as Pseudothioclava arenosa comb. nov. is also proposed. Finally, Thioclava electrotropha Chang et al. 2018 is proposed to be a later heterosynonym of Thioclava sediminum Liu et al. 2017.

Soft sweep development of resistance in Escherichia coli under fluoroquinolone stress: Xianxing Xie , Ruichen Lv , Chao Yang , Yajun Song , Yanfeng Yan , Yujun Cui , Ruifu Yang; J. Microbiol. 2019;57(12):1056-1064. Published online September 25, 2019; DOI: https://doi.org/10.1007/s12275-019-9177-5

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Abstract: We employed a stepwise selection model for investigating the dynamics of antibiotic-resistant variants in Escherichia coli K-12 treated with increasing concentrations of ciprofloxacin (CIP). Firstly, we used Sanger sequencing to screen the variations in the fluoquinolone target genes, then, employed Illumina NGS sequencing for amplicons targeted regions with variations. The results demonstrated that variations G81C in gyrA and K276N and K277L in parC are standing resistance variations (SRVs), while S83A and S83L in gyrA and G78C in parC were emerging resistance variations (ERVs). The variants containing SRVs and/or ERVs were selected successively based on their sensitivities to CIP. Variant strain 1, containing substitution G81C in gyrA, was immediately selected following ciprofloxacin exposure, with obvious increases in the parC SRV, and parC and gyrA ERV allele frequencies. Variant strain 2, containing the SRVs, then dominated the population following a 20× increase in ciprofloxacin concentration, with other associated allele frequencies also elevated. Variant strains 3 and 4, containing ERVs in gyrA and parC, respectively, were then selected at 40× and 160× antibiotic concentrations. Two variants, strains 5 and 6, generated in the selection procedure, were lost because of higher fitness costs or a lower level of resistance compared with variants 3 and 4. For the second induction, all variations/indels were already present as SRVs and selected out step by step at different passages. Whatever the first induction or second induction, our results confirmed the soft selective sweep hypothesis and provided critical information for guiding clinical treatment of pathogens containing SRVs.

Flavobacterium zhairuonensis sp. nov., a gliding bacterium isolated from marine sediment of the East China Sea: Sanjit Chandra Debnath , Ahmed Mohammed Abdo Miyah , Can Chen , Huan Sheng , Xue-Wei Xu , Yue-Hong Wu , Dao-Qiong Zheng , Jin-Zhong Xu , Ya-Nan Di , Pin-Mei Wang , Li Shen; J. Microbiol. 2019;57(12):1065-1072. Published online September 27, 2019; DOI: https://doi.org/10.1007/s12275-019-9194-4

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Abstract: A yellow pigmented, Gram-stain-negative, aerobic bacterium designated A5.7T was studied to evaluate the taxonomic position following the modern polyphasic approach. The strain was isolated from sediments near Zhairuo Island, which is situated in the East China Sea. Cells were non-spore forming rods without flagella but showed motility by gliding. Growth was observed at 15–35°C (optimum 28°C), pH 6.0–9.0 (optimum pH 6.5) and 0–2% (w/v) NaCl (optimum 0–0.5%) in LB broth. The major respiratory quinone of A5.7T was menaquinone 6. The major polar lipid of A5.7T was phosphatidylethanolamine and the predominant fatty acids (> 5%) were iso-C15:0, iso-C17:0 3-OH, C15:1 ω6c, iso-C15:0 3-OH, iso-C15:1 G, summed feature 3 (C16:1 ω7c and/or C16:1 ω6c) and summed feature 9 (iso-C17:1 ω9c and/or C16:0 10-methyl). Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate belongs to the genus Flavobacterium and shares the highest sequence similarities with Flavobacterium sharifuzzamanii A7.6T (98.5%), Flavobacterium tistrianum GB 56.1T (98.3%), Flavobacterium nitrogenifigens NXU-44T (97.8%), Flavobacterium anhuiense D3T (97.6%), Flavobacterium ginsenosidimutans THG 01T (97.6%), and Flavobacterium foetidum CJ42T (97.6%). Digital DNA-DNA hybridization and average nucleotide identity values between the strain and its closest phylogenetic neighbors showed the ranges from 19.6 to 34.1% and 73.7 to 87.9%, respectively. Therefore, based on polyphasic characteristics, strain A5.7T represents a novel species of the genus Flavobacterium for which the name Flavobacterium zhairuonensis sp. nov. is proposed. The type strain is A5.7T (= KCTC 62406T = MCCC 1K03494T).

Anaerotignum faecicola sp. nov., isolated from human faeces: Seung-Hyeon Choi , Ji-Sun Kim , Jam-Eon Park , Keun Chul Lee , Mi Kyung Eom , Byeong Seob Oh , Seung Yeob Yu , Se Won Kang , Kook-Il Han , Min Kuk Suh , Dong Ho Lee , Hyuk Yoon , Byung-Yong Kim , Je Hee Lee , Ju Huck Lee , Jung-Sook Lee , Seung-Hwan Park; J. Microbiol. 2019;57(12):1073-1078. Published online November 4, 2019; DOI: https://doi.org/10.1007/s12275-019-9268-3

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Abstract: A strictly anaerobic bacterium, designated as strain KGMB- 03357T, was isolated from the faeces of a healthy Korean selected by Bundang Seoul National University based on health status. Cells of strain KGMB03357T are Gram-stain-positive, non-motile, non-spore-forming, and observed as straight or curved rods. The isolate grew at 10–45°C (optimum temperature of 40°C) and a pH range of 5.1–10.5 (optimum pH of 6.8). Analysis of phylogenetic trees based on the 16S rRNA gene sequences revealed that strain KGMB03357T forms a lineage within the genus Anaerotignum, and is most closely related to Anaerotignum lactatifermentans G17T (= KCTC 15066T, 96.1%), Anaerotignum propionicum DSM 1682T (= KCTC 5582T, 94.9%), Anaerotignum neopropionicum DSM 03847T (= KCTC 15564T, 94.9%), and Anaerotignum aminivorans SH021T (= KCTC 15705T, 94.8%). The ANI values between strain KGMB 03357T and members of the genus Anaerotignum were 73.3–71.0%, which are below the ANI criterion for interspecies identity. The DNA G + C content based on the whole-genome sequence is 47.3 mol%. The major cellular fatty acids of strain KGMB03357T are C16:0, C18:0, C18:1 cis 9, and anteiso-C15:0. Strain KGMB03357T contains meso-diaminopimelic acid as the diagnostic amino acid in the cell wall peptidoglycan. Based on the phenotypic, phylogenetic, and genomic properties, strain KGMB 03357T represents a novel species of the genus Anaerotignum, for which the name Anaerotignum faecicola sp. nov. is proposed. The type strain is KGMB03357T (= KCTC 15736T = DSM 107953T).

Flavobacterium humi sp. nov., a flexirubin-type pigment producing bacterium, isolated from soil: Inhyup Kim , Jiyoun Kim , Geeta Chhetri , Taegun Seo; J. Microbiol. 2019;57(12):1079-1085. Published online November 22, 2019; DOI: https://doi.org/10.1007/s12275-019-9350-x

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28 Citations

Abstract: A yellow pigmented, Gram-stain-negative, strictly aerobic, rod-shaped, motile by means of gliding, catalase and oxidase positive bacterium, designated strain DS2-AT, was isolated from soil. Growth was observed at 4–32°C (optimum, 28°C), pH 6–9 (optimum, 7.0), and with 0–0.25% (w/v) NaCl (optimum, 0%). Phylogenetic analysis of 16S rRNA gene sequence revealed that strain DS2-AT belonged to the genus Flavobacterium and was most closely related to Flavobacterium aquatile LMG 4008T (96.4%), Flavobacterium terrae DSM 18829T (95.6%), Flavobacterium vireti THG-SM1T (95.5%), Flavobacterium inkyongense IMCC27201T (95.4%), Flavobacterium brevivitae TTM-43T (95.2%), and Flavobacterium cucumis DSM 18830T (95.2%). Strain DS2-AT produces flexirubin- type pigments. The major fatty acids were iso-C15:0, iso-C17:0 3-OH, and iso-C15:0 3-OH. The major respiratory quinone was identified as menaquinone-6. The major polar lipid was found to be phosphatidylethanolamine. The average nucleotide identity values between strain DS2-AT and selected taxa, F. aquatile LMG 4008T, F. terrae DSM 18829T, and F. cucumis DSM 18830T, were 72, 72.7, and 71.6%, respectively. The draft genome of strain DS2-AT has a number of 14 contigs, scaffold N50 of 476,310 bp and a total size of 3,563,867 bp. Additionally, strain DS2-AT contains 3,127 of gene, 41 of tRNA, 6 of rRNA, and 3 of ncRNA. The DNA G + C content of stain DS2-AT was 40.7 mol%. Based on phylogenetic and phenotypic analyses, strain DS2-AT is considered as a novel species of the genus Flavobacterium, for which the name Flavobacterium humi sp. nov., (type strain DS2-AT = KACC 19715T = JCM 32786T) has been proposed.

Partial characteristics of hemolytic factors secreted from airborne Aspergillus and Penicillium, and an enhancement of hemolysis by Aspergillus micronesiensis CAMP-like factor via Staphylococcus aureus-sphingomyelinase: Sumonrat Kaveemongkonrat , Kwanjit Duangsonk , Jos Houbraken , Phimchat Suwannaphong , Nongnuch Vanittanakom Vanittanakom , Malee Mekaprateep; J. Microbiol. 2019;57(12):1086-1094. Published online November 4, 2019; DOI: https://doi.org/10.1007/s12275-019-9133-4

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Abstract: One of the advantages for initial survival of inhaled fungal spores in the respiratory tract is the ability for iron acquisition via hemolytic factor-production. To examine the ability of indoor Aspergillus and Penicillium affecting hemolysis, the secreted factors during the growth of thirteen strains from eight species were characterized in vitro for their hemolytic activity (HA) and CAMP-like reaction. The hemolytic index of HA on human blood agar of Aspergillus micronesiensis, Aspergillus wentii, Aspergillus westerdijkiae, Penicillium citrinum, Penicillium copticola, Penicillium paxilli, Penicillium steckii, and Penicillium sumatrense were 1.72 ± 0.34, 1.61 ± 0.41, 1.69 ± 0.16, 1.58 ± 0.46, 3.10 ± 0.51, 1.22 ± 0.19, 2.55 ± 0.22, and 1.90 ± 0.14, respectively. The secreted factors of an Aspergillus wentii showed high HA when grown in undernourished broth at 25°C at an exponential phase and were heat sensitive. Its secreted proteins have an estimated relative molecular weight over 50 kDa. Whereas, the factors of Penicillium steckii were secreted in a similar condition at a late exponential phase but showed low HA and heat tolerance. In a CAMP-like test with sheep blood, the synergistic hemolytic reactions between most tested mold strains and Staphylococcus aureus were identified. Moreover, the enhancement of α-hemolysis of Staphylococcus aureus could occur through the interaction of Staphylococcus aureus-sphingomyelinase and CAMP-like factors secreted from Aspergillus micronesiensis. Further studies on the characterization of purified hemolytic- and CAMP-like-factors secreted from Aspergillus wentii and Aspergillus micronesiensis may lead to more understanding of their involvement of hemolysis

H2 Metabolism revealed by metagenomic analysis of subglacial sediment from East Antarctica: Zhifeng Yang , Yu Zhang , Yongxin Lv , Wenkai Yan , Xiang Xiao , Bo Sun , Hongmei Ma; J. Microbiol. 2019;57(12):1095-1104. Published online November 22, 2019; DOI: https://doi.org/10.1007/s12275-019-9366-2

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Abstract: Subglacial ecosystems harbor diverse chemoautotrophic microbial communities in areas with limited organic carbon, and lithological H2 produced during glacial erosion has been considered an important energy source in these ecosystems. To verify the H2-utilizing potential there and to identify the related energy-converting metabolic mechanisms of these communities, we performed metagenomic analysis on subglacial sediment samples from East Antarctica with and without H2 supplementation. Genes coding for several [NiFe]- hydrogenases were identified in raw sediment and were enriched after H2 incubation. All genes in the dissimilatory nitrate reduction and denitrification pathways were detected in the subglacial community, and the genes coding for these pathways became enriched after H2 was supplied. Similarly, genes transcribing key enzymes in the Calvin cycle were detected in raw sediment and were also enriched. Moreover, key genes involved in H2 oxidization, nitrate reduction, oxidative phosphorylation, and the Calvin cycle were identified within one metagenome-assembled genome belonging to a Polaromonas sp. As suggested by our results, the microbial community in the subglacial environment we investigated consisted of chemoautotrophic populations supported by H2 oxidation. These results further confirm the importance of H2 in the cryosphere.

Vibrio parahaemolyticus cqsA controls production of quorum sensing signal molecule 3-hydroxyundecan-4-one and regulatessensing signal molecule 3-hydroxyundecan-4-one and regulates colony morphology: Kui Wu , Yangyun Zheng , Qingping Wu , Haiying Chen , Songzhe Fu , Biao Kan , Yongyan Long , Xiansheng Ni , Junling Tu; J. Microbiol. 2019;57(12):1105-1114. Published online November 4, 2019; DOI: https://doi.org/10.1007/s12275-019-9379-x

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Abstract: In order to adapt to different environments, Vibrio parahaemolyticus employed a complicated quorum sensing system to orchestrate gene expression and diverse colony morphology patterns. In this study, the function of the putative quorum sensing signal synthase gene cqsA (VPA0711 in V. parahaemolyticus strain RIMD2210633 genome) was investigated. The cloning and expression of V. parahaemolyticus cqsA in Escherichia coli system induced the production of a new quorum sensing signal that was found in its culture supernatant. The signal was purified by high performance liquid chromatography
methods
and determined to be 3-hydroxyundecan- 4-one by indirect and direct mass spectra assays. The deletion of cqsA in RIMD2210633 changed V. parahaemolyticus colony morphology from the classical ‘fried-egg’ shape (thick and opaque in the center, while thin and translucent in the edge) of the wild-type colony to a ‘pancake’ shape (no significant difference between the centre and the edge) of the cqsAdeleted colony. This morphological change could be restored by complementary experiment with cqsA gene or the signal extract. In addition, the expression of opaR, a well-known quorum sensing regulatory gene, could be up-regulated by cqsA deletion. Our results suggested that V. parahaemolyticus used cqsA to produce 3-hydroxyundecan-4-one signal and thereby regulated colony morphology and other quorum sensing-associated behaviors.

A histone deacetylase, MoHOS2 regulates asexual development and virulence in the rice blast fungus: Jongjune Lee , Jae-Joon Lee , Junhyun Jeon; J. Microbiol. 2019;57(12):1115-1125. Published online November 22, 2019; DOI: https://doi.org/10.1007/s12275-019-9363-5

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Abstract: Histone acetylation/deacetylation represent a general and efficient epigenetic mechanism through which fungal cells control gene expression. Here we report developmental requirement of MoHOS2-mediated histone deacetylation (HDAC) for the rice blast fungus, Magnaporthe oryzae. Structural similarity and nuclear localization indicated that MoHOS2 is an ortholog of Saccharomyces cerevisiae Hos2, which is a member of class I histone deacetylases and subunit of Set3 complex. Deletion of MoHOS2 led to 25% reduction in HDAC activity, compared to the wild-type, confirming that it is a bona-fide HDAC. Lack of MoHOS2 caused decrease in radial growth and impinged dramatically on asexual sporulation. Such reduction in HDAC activity and phenotypic defects of ΔMohos2 were recapitulated by a single amino acid change in conserved motif that is known to be important for HDAC activity. Expression analysis revealed up-regulation of MoHOS2 and concomitant down-regulation of some of the key genes involved in asexual reproduction under sporulation-promoting condition. In addition, the deletion mutant exhibited defect in appressorium formation from both germ tube tip and hyphae. As a result, ΔMohos2 was not able to cause disease symptoms. Wound-inoculation showed that the mutant is compromised in its ability to grow inside host plants as well. We found that some of ROS detoxifying genes and known effector genes are de-regulated in the mutant. Taken together, our data suggest that MoHOS2-dependent histone deacetylation is pivotal for proper timing and induction of transcription of the genes that coordinate developmental changes and host infection in M. oryzae.

Methyltransferase of a cell culture-adapted hepatitis E inhibits the MDA5 receptor signaling pathway: Jinjong Myoung , Jeong Yoon Lee , Kang Sang Min; J. Microbiol. 2019;57(12):1126-1131. Published online November 22, 2019; DOI: https://doi.org/10.1007/s12275-019-9478-8

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Abstract: Hepatitis E virus (HEV) is a causative agent of acute hepatitis and jaundice. The number of human infections is approximated to be over 20 million cases per year. The transmission is mainly via the fecal-oral route and contaminated water and food are considered to be a major source of infection. As a mouse model is not available, a recent development of a cell culture-adapted HEV strain (47832c) is considered as a very important tools for molecular analysis of HEV pathogenesis in cells. Previously, we demonstrated that HEV-encoded methyltransferase (MeT) encoded by the 47832c strain inhibits MDA5- and RIG-I-mediated activation of interferon β (IFN-β) promoter. Here, we report that MeT impairs the phosphorylation and activation of interferon regulatory factor 3 and the p65 subunit of NF-κB in a dose-dependent manner. In addition, the MeT encoded by the 47832c, but not that of HEV clinical or field isolates (SAR-55, Mex-14, KC-1, and ZJ-1), displays the inhibitory effect. A deeper understanding of MeTmediated suppression of IFN-β expression would provide basis of the cell culture adaptation of HEV.

Published Erratum

Erratum]Flavobacterium parvum sp. nov., isolated from soil polluted by sewer water: Hyun Seo Lee , Woon Mo Hwang , Keunsoo Kang , Tae-Young Ahn; J. Microbiol. 2019;57(12):1132-1132.; DOI: https://doi.org/10.1007/s12275-019-0720-1

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Abstract: In the article by Lee et al. published in Journal of Microbiology 2018; 56, 542–548, The KACC 19447T on 26th line of 4th paragraph in the section of ‘Description of Flavobacterium parvum sp. nov.’ on page 546 should be corrected in KACC 19448T. The sentence should have read: The type strain, HS916T (= KACC 19448T, = JCM 32368T), was isolated from soil polluted by sewer water in Cheonan, South Korea. We apologize for any inconvenience that this may have caused.

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