Journal of Microbiology

Journal Articles

Synthesis of pinene in the industrial strain Candida glycerinogenes by modification of its mevalonate pathway: Tengfei Ma , Hong Zong , Xinyao Lu , Bin Zhuge; J. Microbiol. 2022;60(12):1191-1200. Published online October 24, 2022; DOI: https://doi.org/10.1007/s12275-022-2344-0

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Abstract: Terpenes have many applications and are widely found in nature, but recent progress in synthetic biology has enabled the use of microorganisms as chassis cells for the synthesis of these compounds. Candida glycerinogenes (C. glycerinogenes) is an industrial strain that may be developed as a chassis for the synthesis of terpenes since it has a tolerance to hyperosmolality and high sugar, and has a complete mevalonate (MVA) pathway. However, monoterpenes such as pinene are highly toxic, and the tolerance of C. glycerinogenes to pinene was investigated. We also measured the content of mevalonate and squalene to evaluate the strength of the MVA pathway. To determine terpene synthesis capacity, a pathway for the synthesis of pinene was constructed in C. glycerinogenes. Pinene production was improved by overexpression, gene knockdown and antisense RNA inhibition. Pinene production was mainly enhanced by strengthening the upstream MVA pathway and inhibiting the production of by-products from the downstream pathway. With these strategies, yield could be increased by almost 16 times, to 6.0 mg/L. Overall, we successfully constructed a pinene synthesis pathway in C. glycerinogenes and enhanced pinene production through metabolic modification.

Fus3 and Tpk2 protein kinases regulate the phosphorylation-dependent functions of RNA helicase Dhh1 in yeast mating and Ste12 protein expression: Jaehee Hwang , Daehee Jung , Jinmi Kim; J. Microbiol. 2022;60(8):843-848. Published online July 14, 2022; DOI: https://doi.org/10.1007/s12275-022-2213-x

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Abstract: Decapping of mRNA is a key regulatory step for mRNA decay and translation. The RNA helicase, Dhh1, is known as a decapping activator and translation repressor in yeast Saccharomyces cerevisiae. Dhh1 also functions as a gene-specific positive regulator in the expression of Ste12, a mating-specific transcription factor. A previous study showed that the Nerminal phosphorylation of Dhh1 regulates its association with the mRNA-binding protein, Puf6, to affect the protein translation of Ste12. Here, we investigated the roles of the phosphorylated residues of Dhh1 in yeast mating process and Ste12 expression. The phospho-deficient mutation, DHH1- T10A, was associated with decreased diploid formation during mating and decreased level of the Ste12 protein in response to α-mating pheromone. A kinase overexpression analysis revealed that Ste12 protein expression was affected by overexpression of Fus3 MAP kinase or Tpk2 kinase. Tpk2 was shown to be responsible for phosphorylation of Dhh1 at Thr10. Our study shows that overexpression of Fus3 or Tpk2 alters the Dhh1-Puf6 protein interaction and thereby affects Ste12 protein expression.

Down-regulation of microRNA-155 suppressed Candida albicans induced acute lung injury by activating SOCS1 and inhibiting inflammation response: Xiaohua Li , Yuanzhong Gong , Xin Lin , Qiong Lin , Jianxiong Luo , Tianxing Yu , Junping Xu , Lifang Chen , Liyu Xu , Ying Hu; J. Microbiol. 2022;60(4):402-410. Published online February 14, 2022; DOI: https://doi.org/10.1007/s12275-022-1663-5

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Abstract: Acute lung injury caused by Candida albicans could result in high mortality and morbidity. MicroRNA-155 (miR-155) and suppressor of cytokine signaling 1 (SOCS1) have been believed to play a key in the regulation of inflammatory response. Whether miR-155/SOCS1 axis could regulate the acute lung injury caused by C. albicans has not been reported. The acute lung injury animal model was established with acute infection of C. albicans. miR-155 inhibitor, miR-155 mimic, and sh-SOCS1 were constructed. The binding site between miR- 155 and SOCS1 was identified with dual luciferase reporter assay. Knockdown of miR-155 markedly inhibited the germ tube formation of C. albicans. Knockdown of miR-155 significantly up-regulated the expression of SOCS1, and the binding site between miR-155 and SOCS1 was identified. Knockdown of miR-155 improved the acute lung injury, suppressed inflammatory factors and fungus loading through SOCS1. Knockdown of SOCS1 greatly reversed the influence of miR- 155 inhibitor on the cell apoptosis in vitro. The improvement of acute lung injury caused by C. albicans, suppression of inflammatory response and C. albicans infection, and inhibitor of cell apoptosis were achieved by knocking down miR-155 through SOCS1. This research might provide a new thought for the prevention and treatment of acute lung injury caused by C. albicans through targeting miR-155/SOCS1 axis.

The quorum sensing regulator OpaR is a repressor of polar flagellum genes in Vibrio parahaemolyticus: Renfei Lu , Junfang Sun , Yue Qiu , Miaomiao Zhang , Xingfan Xue , Xue Li , Wenhui Yang , Dongsheng Zhou , Lingfei Hu , Yiquan Zhang; J. Microbiol. 2021;59(7):651-657. Published online June 1, 2021; DOI: https://doi.org/10.1007/s12275-021-0629-3

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21 Citations

Abstract: Vibrio parahaemolyticus possesses two types of flagella: a single polar flagellum (Pof) for swimming and the peritrichous lateral flagella (Laf) for swarming. Expression of Laf genes has previously been reported to be regulated by the quorum sensing (QS) regulators AphA and OpaR. In the present study, we showed that OpaR, the QS regulator at high cell density (HCD), acted as a negative regulator of swimming motility and the transcription of Pof genes in V. parahaemolyticus. OpaR bound to the promoter-proximal DNA regions of flgAMN, flgMN, and flgBCDEFGHIJ within the Pof gene loci to repress their transcription, whereas it negatively regulates the transcription of flgKL-flaC in an indirect manner. Thus, this work investigated how QS regulated the swimming motility via direct action of its master regulator OpaR on the transcription of Pof genes in V. parahaemolyticus.

Full-repertoire comparison of the microscopic objects composing the human gut microbiome with sequenced and cultured communities: Edmond Kuete Yimagou , Jean-Pierre Baudoin , Rita Abou Abdallah , Fabrizio Di Pinto , Jacques Yaacoub Bou Khalil , Didier Raoult; J. Microbiol. 2020;58(5):377-386. Published online April 11, 2020; DOI: https://doi.org/10.1007/s12275-020-9365-3

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Abstract: The study of the human gut microbiome is essential in microbiology and infectious diseases as specific alterations in the gut microbiome might be associated with various pathologies, such as chronic inflammatory disease, intestinal infection and colorectal cancer. To identify such dysregulations, several strategies are being used to create a repertoire of the microorganisms composing the human gut microbiome. In this study, we used the “microscomics” approach, which consists of creating an ultrastructural repertoire of all the cell-like objects composing stool samples from healthy donors using transmission electron microscopy (TEM). We used TEM to screen ultrathin sections of 8 resin-embedded stool samples. After exploring hundreds of micrographs, we managed to elaborate ultrastructural categories based on morphological criteria or features. This approach explained many inconsistencies observed with other techniques, such as metagenomics and culturomics. We highlighted the value of our cultureindependent approach by comparing our microscopic images to those of cultured bacteria and those reported in the literature. This study helped to detect “minimicrobes” Candidate Phyla Radiation (CPR) for the first time in human stool samples. This “microscomics” approach is non-exhaustive but complements already existing approaches and adds important data to the puzzle of the microbiota.

Improved tolerance of Escherichia coli to oxidative stress by expressing putative response regulator homologs from Antarctic bacteria: Seo-jeong Park , Sangyong Lim , Jong-il Choi; J. Microbiol. 2020;58(2):131-141. Published online December 23, 2019; DOI: https://doi.org/10.1007/s12275-020-9290-5

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Abstract: Response regulator (RR) is known a protein that mediates cell’s response to environmental changes. The effect of RR from extremophiles was still under investigation. In this study, response regulator homologs were mined from NGS data of Antarctic bacteria and overexpressed in Escherichia coli. Sixteen amino acid sequences were annotated corresponding to response regulators related to the two-component regulatory systems; of these, 3 amino acid sequences (DRH632, DRH1601 and DRH577) with high homology were selected. These genes were cloned in pRadGro and expressed in E. coli. The transformant strains were subjected to various abiotic stresses including oxidative, osmotic, thermal stress, and acidic stress. There was found that the robustness of E. coli to abiotic stress was increased in the presence of these response regulator homologs. Especially, recombinant E. coli overexpressing drh632 had the highest survival rate in oxidative, hypothermic, osmotic, and acidic conditions. Recombinant E. coli overexpressing drh1601 showed the highest tolerance level to osmotic stress. These results will be applicable for development of recombinant strains with high tolerance to abiotic stress.

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.

Antarctic tundra soil metagenome as useful natural resources of cold-active lignocelluolytic enzymes: Han Na Oh , Doyoung Park , Hoon Je Seong , Dockyu Kim , Woo Jun Sul; J. Microbiol. 2019;57(10):865-873. Published online September 30, 2019; DOI: https://doi.org/10.1007/s12275-019-9217-1

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19 Citations

Abstract: Lignocellulose composed of complex carbohydrates and aromatic heteropolymers is one of the principal materials for the production of renewable biofuels. Lignocellulose-degrading genes from cold-adapted bacteria have a potential to increase the productivity of biological treatment of lignocellulose biomass by providing a broad range of treatment temperatures. Antarctic soil metagenomes allow to access novel genes encoding for the cold-active lignocellulose-degrading enzymes, for biotechnological and industrial applications. Here, we investigated the metagenome targeting cold-adapted microbes in Antarctic organic matter-rich soil (KS 2-1) to mine lignolytic and celluloytic enzymes by performing single molecule, real-time metagenomic (SMRT) sequencing. In the assembled Antarctic metagenomic contigs with relative long reads, we found that 162 (1.42%) of total 11,436 genes were annotated as carbohydrate-active enzymes (CAZy). Actinobacteria, the dominant phylum in this soil’s metagenome, possessed most of candidates of lignocellulose catabolic genes like glycoside hydrolase families (GH13, GH26, and GH5) and auxiliary activity families (AA7 and AA3). The predicted lignocellulose degradation pathways in Antarctic soil metagenome showed synergistic role of various CAZyme harboring bacterial genera including Streptomyces, Streptosporangium, and Amycolatopsis. From phylogenetic relationships with cellular and environmental enzymes, several genes having potential for participating in overall lignocellulose degradation were also found. The results indicated the presence of lignocellulose-degrading bacteria in Antarctic tundra soil and the potential benefits of the lignocelluolytic enzymes as candidates for cold-active enzymes which will be used for the future biofuel-production industry.

Paenibacillus psychroresistens sp. nov., isolated from the soil of an Arctic glacial retreat: In-Tae Cha , Eui-Sang Cho , Yoo Kyung Lee , Seong Woon Roh , Myung-Ji Seo; J. Microbiol. 2019;57(7):569-574. Published online June 27, 2019; DOI: https://doi.org/10.1007/s12275-019-8666-x

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Abstract: Strain ML311-T8T was isolated from a glacial retreat area in Svalbard, Norway, and was taxonomically characterized by a polyphasic approach. Upon phylogenetic analysis, strain ML311-T8T was clustered with Paenibacillus arcticus MME2_ R6T and P. contaminans CKOBP-6T with 98.3–98.6 and 93.5– 93.9% 16S rRNA gene sequence similarities, respectively. DNA-DNA hybridization values between strain ML311-T8T and P. arcticus MME2_R6T was 19.9%. The genomic DNA G+C content was 41.1 mol%. The isolated strain was Gramstain- positive, strictly aerobic and rod-shaped, and grew in 0–0.5% (w/v) NaCl, at 4–23°C and pH 6.0–10.0, with optimal growth in 0% (w/v) NaCl, at 20°C and pH 7.0–8.0. The predominant respiratory quinone of strain ML311-T8T was MK- 7 and the major fatty acids were anteiso-C15:0 and C16:0. The polar lipids of strain ML311-T8T were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, three unidentified amino lipids, and three unidentified lipids. On the basis of polyphasic taxonomic analysis, the strain ML311-T8T is proposed to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus psychroresistens sp. nov. is proposed. The type strain is ML311-T8T (= KCCM 43190T = JCM 31243T).

Review

MINIREVIEW] Dynamics of microbial communities and CO2 and CH4 fluxes in the tundra ecosystems of the changing Arctic: Min Jung Kwon , Ji Young Jung , Binu M. Tripathi , Mathias Göckede , Yoo Kyung Lee , Mincheol Kim; J. Microbiol. 2019;57(5):325-336. Published online January 16, 2019; DOI: https://doi.org/10.1007/s12275-019-8661-2

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Abstract: Arctic tundra ecosystems are rapidly changing due to the amplified effects of global warming within the northern high latitudes. Warming has the potential to increase the thawing of the permafrost and to change the landscape and its geochemical characteristics, as well as terrestrial biota. It is important to investigate microbial processes and community structures, since soil microorganisms play a significant role in decomposing soil organic carbon in the Arctic tundra. In addition, the feedback from tundra ecosystems to climate change, including the emission of greenhouse gases into the atmosphere, is substantially dependent on the compositional and functional changes in the soil microbiome. This article reviews the current state of knowledge of the soil microbiome and the two most abundant greenhouse gas (CO2 and CH4) emissions, and summarizes permafrost thaw-induced changes in the Arctic tundra. Furthermore, we discuss future directions in microbial ecological research coupled with its link to CO2 and CH4 emissions.

Journal Article

Bacillus piscis sp. nov., a novel bacterium isolated from the muscle of the antarctic fish Dissostichus mawsoni: Jae-Bong Lee , Seon Hwa Jeon , Seok-Gwan Choi , Hee-Young Jung , Myung Kyum Kim , Sathiyaraj Srinivasan; J. Microbiol. 2016;54(12):809-813. Published online November 26, 2016; DOI: https://doi.org/10.1007/s12275-016-6473-1

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Abstract: In this paper, a new bacterial strain designated as 16MFT21T is isolated from the muscle of a fish caught in the Antarctic Ocean. Strain 16MFT21T is a Gram-staining-positive, catalase- oxidase-positive, rod-shaped facultative-aerobic bacterium. The phylogenetic analysis that is based on the 16S-rRNA gene sequence of strain 16MFT21T revealed that it belongs to the genus Bacillus in the family Bacillaceae in the class Bacilli. The highest degrees of the sequence similarity of the strain 16MFT21T is with Bacillus licheniformis ATCC 14580T (96.6%) and Bacillus sonorensis NBRC 101234T (96.6%). The isolate formed a pale-yellow pigment, and it grew in the presence of 0% to 10% (w/v) NaCl (optimum at 2% NaCl), a pH of 6.0 to 10.0 (optimum pH􍾘from 7.0 to 8.0), and from 4°C to 30°C (optimum at 30°C). The major polar lipids consist of diphosphatidylglycerol (DPG) and phosphatidylglycerol (PG). The predominant fatty acids are iso-C15:0, anteiso-C15:0, iso-C17:0, and anteiso-C17:0. The main respiratory quinone is menaquinone- 7 (MK-7), and based on the use of the meso-diaminopimelic acid as the diagnostic diamino acid, the peptidoglycan cell-wall type is A1γ. Based on the phylogenetic, phenotypic, and chemotaxonomic data, strain 16MFT21T (=KCTC 18866T =JCM 31664T) for which the name Bacillus piscis sp. nov. is proposed should be classified as a new species.

Research Support, Non-U.S. Gov'ts

Identification of Proteolytic Bacteria from the Arctic Chukchi Sea Expedition Cruise and Characterization of Cold-active Proteases: Ha Ju Park , Yung Mi Lee , Sunghui Kim , Ah Ram Wi , Se Jong Han , Han-Woo Kim , Il-Chan Kim , Joung Han Yim , Dockyu Kim; J. Microbiol. 2014;52(10):825-833. Published online August 27, 2014; DOI: https://doi.org/10.1007/s12275-014-4226-6

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Abstract: Following collection of seawater samples during an Arctic Chukchi Sea expedition cruise of the Korean icebreaker Araon in 2012, a total of 15,696 bacteria were randomly isolated from Marine Broth 2216 agar plates. Of these, 2,526 (16%) showed proteolytic activity and were identified as mainly Alteromonas (31%), Staphylococcus (27%), and Pseudoalteromonas (14%). Among the proteolytic strains, seven were selected based on their significant ability to grow and produce a halo on skim milk plates at low temperatures (<5°C) owing to cold-active proteases. These strains were affiliated with the genus Pseudoalteromonas and were divided into three groups based on phylogenetic analysis of the 16S rRNA genes. Profiling cell membrane fatty acids confirmed the 16S rRNA-based differentiation and revealed the accordance between the two analyses. Seven genes for serine protease precursors were amplified from the corresponding strains, and based on sequence similarities, these genes were divided into three groups that were identical to those identified by the 16S rRNA phylogenetic analysis. Three protease genes from the representative strains of each group were composed of 2,127–2,130 bp, encoding 708–709 amino acids, and these genes yielded products with calculated molecular weights of approximately 72.3–72.8 kDa. Amino acid sequence analysis suggested that the precursors are members of the subtilase serine endo- and exo-peptidase clan and contain four domains (signal peptide, N-terminal prosequence, catalytic domain, and two pre-peptidase C-terminal domains). Upon expression in E. coli, each recombinant protease exhibited proteolytic activity on zymogram gels.

Antioxidant Capacity of Novel Pigments from an Antarctic Bacterium: Daniela N. Correa-Llantén , Maximiliano J. Amenábar , Jenny M. Blamey; J. Microbiol. 2012;50(3):374-379. Published online June 30, 2012; DOI: https://doi.org/10.1007/s12275-012-2029-1

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51 Citations

Abstract: In Antarctica microorganisms are exposed to several conditions that trigger the generation of reactive oxygen species, such as high UV radiation. Under these conditions they must have an important antioxidant defense system in order to prevent oxidative damage. One of these defenses are pigments which are part of the non-enzymatic antioxidant mechanisms. In this work we focused on the antioxidant capacity of pigments from an Antarctic microorganism belonging to Pedobacter genus. This microorganism produces different types of pigments which belong to the carotenoids group. The antioxidant capacity of a mix of pigments was analyzed by three different methods: 1,1-diphenyl-2-picrylhydrazyl, ROS detection and oxygen electrode. The results obtained from these approaches indicate that the mix of pigments has a strong antioxidant capacity. The oxidative damage induced by UVB exposure to liposomes was also analyzed. Intercalated pigments within the liposomes improved its resistance to lipid peroxidation. Based on the analysis carried out along this research we conclude that the antioxidant properties of the mix of pigments protect this bacterium against oxidative damage. These properties make this mix of pigments a powerful antioxidant mixture with potential biotechnological applications.

Rescue of a Cold-Sensitive Mutant at Low Temperatures by Cold Shock Proteins from Polaribacter irgensii KOPRI 22228: Ji-hyun Uh , Youn Hong Jung , Yoo Kyung Lee , Hong Kum Lee , Hana Im; J. Microbiol. 2010;48(6):798-802. Published online January 9, 2011; DOI: https://doi.org/10.1007/s12275-010-0402-5

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Abstract: Exposure to low temperatures induces the biosynthesis of specific sets of proteins, including cold shock proteins (Csps). Since many of the specific functions of pychrophilic Csps are unknown, the roles of Csps from an Arctic bacterium, Polaribacter irgensii KOPRI 22228, were examined. The genes encoding CspA and CspC of P. irgensii were cloned in this study. Sequence analysis showed that these proteins have cold shock domains containing two RNA-binding motifs, RNP1 and RNP2. Both proteins bound oligo(dT)-cellulose resins, suggesting single-stranded nucleic acid-binding activity. When the P. irgensii Csps were overexpressed in Escherichia coli, the cold-resistance of the host was increased by more than five-fold. The P. irgensii Csps also rescued a cold-sensitive E. coli csp-quadruple deletion strain, BX04, at low temperatures. These results suggest that Csps from P. irgensii play a role in survival in polar environments.

Diversity of Cold-Active Protease-Producing Bacteria from Arctic Terrestrial and Marine Environments Revealed by Enrichment Culture: Eun Hye Kim , Kyeung Hee Cho , Yung Mi Lee , Joung Han Yim , Hong Kum Lee , Jang-Cheon Cho , Soon Gyu Hong; J. Microbiol. 2010;48(4):426-432. Published online August 20, 2010; DOI: https://doi.org/10.1007/s12275-010-0015-z

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25 Citations

Abstract: A new approach for enrichment culture was applied to obtain cold-active protease-producing bacteria for marine and terrestrial samples from Svalbard, Norway. The method was developed for the enrichment of bacteria by long-term incubation at low temperatures in semi-solid agar medium containing meat pieces as the main source of carbon and energy. ZoBell and 0.1× nutrient broth were added for marine and terrestrial microorganisms, respectively, to supply basal elements for growth. One to three types of colonies were observed from each enrichment culture, indicating that specific bacterial species were enriched during the experimental conditions. Among 89 bacterial isolates, protease activity was observed from 48 isolates in the screening media containing skim milk. Good growth was observed at 4°C and 10°C while none of the isolates could grow at 37°C. At low temperatures, enzyme activity was equal to or higher than activity at higher temperatures. Bacterial isolates were included in the genera Pseudoalteromonas (33 isolates), Arthrobacter (24 isolates), Pseudomonas (16 isolates), Psychrobacter (6 isolates), Sphingobacterium (6 isolates), Flavobacterium (2 isolates), Sporosarcina (1 isolate), and Stenotrophomonas (1 isolate). Protease activity was observed from Pseudoalteromonas (33 isolates), Pseudomonas (10 isolates), Arthrobacter (4 isolates), and Flavobacterium (1 isolate).

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