Journal of Microbiology

Journal Articles

Repeated Exposure of Vancomycin to Vancomycin-Susceptible Staphylococcus aureus (VSSA) Parent Emerged VISA and VRSA Strains with Enhanced Virulence Potentials.: An Nguyen, J Jean Sophy Roy, Ji-Hoon Kim, Kyung-Hee Yun, Wonsik Lee, Kyeong Kyu Kim, Truc Kim, Akhilesh Kumar Chaurasia; J. Microbiol. 2024;62(7):535-553. Published online May 30, 2024; DOI: https://doi.org/10.1007/s12275-024-00139-8

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Abstract: The emergence of resistance against the last-resort antibiotic vancomycin in staphylococcal infections is a serious concern for human health. Although various drug-resistant pathogens of diverse genetic backgrounds show higher virulence potential, the underlying mechanism behind this is not yet clear due to variability in their genetic dispositions. In this study, we investigated the correlation between resistance and virulence in adaptively evolved isogenic strains. The vancomycin-susceptible Staphylococcus aureus USA300 was exposed to various concentrations of vancomycin repeatedly as a mimic of the clinical regimen to obtain mutation(s)-accrued-clonally-selected (MACS) strains. The phenotypic analyses followed by expression of the representative genes responsible for virulence and resistance of MACS strains were investigated. MACS strains obtained under 2 and 8 µg/ml vancomycin, named Van2 and Van8, respectively; showed enhanced vancomycin minimal inhibitory concentrations (MIC) to 4 and 16 µg/ml, respectively. The cell adhesion and invasion of MACS strains increased in proportion to their MICs. The correlation between resistance and virulence potential was partially explained by the differential expression of genes known to be involved in both virulence and resistance in MACS strains compared to parent S. aureus USA300. Repeated treatment of vancomycin against vancomycin-susceptible S. aureus (VSSA) leads to the emergence of vancomycin-resistant strains with variable levels of enhanced virulence potentials.

Ten Novel Species Belonging to the Genus Flavobacterium, Isolated from Freshwater Environments: F. praedii sp. nov., F. marginilacus sp. nov., F. aestivum sp. nov., F. flavigenum sp. nov., F. luteolum sp. nov., F. gelatinilyticum sp. nov., F. aquiphilum sp. nov., F. limnophilum sp. nov., F. lacustre: Hyunyoung Jo , Miri S. Park , Yeonjung Lim , Ilnam Kang , Jang-Cheon Cho; J. Microbiol. 2023;61(5):495-510. Published online May 23, 2023; DOI: https://doi.org/10.1007/s12275-023-00054-4

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4 Citations

Abstract: Eleven bacterial strains were isolated from freshwater environments and identified as Flavobacterium based on 16S rRNA gene sequence analyses. Complete genome sequences of the 11 strains ranged from 3.45 to 5.83 Mb with G + C contents of 33.41–37.31%. The average nucleotide identity (ANI) values showed that strains IMCC34515T and IMCC34518 belonged to the same species, while the other nine strains represented each separate species. The ANI values between the strains and their closest Flavobacterium species exhibited ≤ 91.76%, indicating they represent each novel species. All strains had similar characteristics such as being Gram-stain-negative, rod-shaped, and contained iso-C15:0 as the predominant fatty acid, menaquinone-6 as the respiratory quinone, and phosphatidylethanolamine and aminolipids as major polar lipids. Genomic, phylogenetic, and phenotypic characterization confirmed that the 11 strains were distinct from previously recognized Flavobacterium species. Therefore, Flavobacterium praedii sp. nov. (IMCC34515T = KACC 22282T = NBRC 114937T), Flavobacterium marginilacus sp. nov. (IMCC34673T = KACC 22284T = NBRC 114940T), Flavobacterium aestivum sp. nov. (IMCC34774T = KACC 22285T = NBRC 114941T), Flavobacterium flavigenum sp. nov. (IMCC34775T = KACC22286T = NBRC 114942T), Flavobacterium luteolum sp. nov. (IMCC34776T = KACC 22287T = NBRC 114943T), Flavobacterium gelatinilyticum sp. nov. (IMCC34777T = KACC 22288T = NBRC 114944T), Flavobacterium aquiphilum sp.nov. (IMCC34779T = KACC 22289T = NBRC 114945T), Flavobacterium limnophilum sp. nov. (IMCC36791T = KACC22290T = NBRC 114947T), Flavobacterium lacustre sp. nov. (IMCC36792T = KACC 22291T = NBRC 114948T), and Flavobacterium eburneipallidum sp. nov. (IMCC36793T = KACC 22292T = NBRC 114949T) are proposed as novel species.

[PROTOCOL]Analyzing viral epitranscriptomes using nanopore direct RNA sequencing: Ari Hong , Dongwan Kim , V. Narry Kim , Hyeshik Chang; J. Microbiol. 2022;60(9):867-876. Published online August 24, 2022; DOI: https://doi.org/10.1007/s12275-022-2324-4

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6 Citations

Abstract: RNA modifications are a common occurrence across all domains of life. Several chemical modifications, including N6- methyladenosine, have also been found in viral transcripts and viral RNA genomes. Some of the modifications increase the viral replication efficiency while also helping the virus to evade the host immune system. Nonetheless, there are numerous examples in which the host's RNA modification enzymes function as antiviral factors. Although established methods like MeRIP-seq and miCLIP can provide a transcriptome- wide overview of how viral RNA is modified, it is difficult to distinguish between the complex overlapping viral transcript isoforms using the short read-based techniques. Nanopore direct RNA sequencing (DRS) provides both long reads and direct signal readings, which may carry information about the modifications. Here, we describe a refined protocol for analyzing the RNA modifications in viral transcriptomes using nanopore technology.

Analysis of phylogenetic markers for classification of a hydrogen peroxide producing Streptococcus oralis isolated from saliva by a newly devised differential medium: Ha Pham , Thi Dieu Thuy Tran , Youri Yang , Jae-Hyung Ahn , Hor-Gil Hur , Yong-Hak Kim; J. Microbiol. 2022;60(8):795-805. Published online July 14, 2022; DOI: https://doi.org/10.1007/s12275-022-2261-2

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Abstract: Hydrogen peroxide (H2O2) is produced by alpha-hemolytic streptococci in aerobic conditions. However, the suitable method for detection of H2O2-producing streptococci in oral microbiota has not been setup. Here we show that o-dianisidine dye and horseradish peroxidase were useful in tryptic soy agar medium to detect and isolate H2O2-producing bacteria with the detection limit of one target colony in > 106 colony-forming units. As a proof, we isolated the strain HP01 (KCTC 21190) from a saliva sample using the medium and analyzed its characteristics. Further tests showed that the strain HP01 belongs to Streptococcus oralis in the Mitis group and characteristically forms short-chain streptococcal cells with a high capacity of acid tolerance and biofilm formation. The genome analysis revealed divergence of the strain HP01 from the type strains of S. oralis. They showed distinctive phylogenetic distances in their ROS-scavenging proteins, including superoxide dismutase SodA, thioredoxin TrxA, thioredoxin reductase TrxB, thioredoxin-like protein YtpP, and glutaredoxin- like protein NrdH, as well as a large number of antimicrobial resistance genes and horizontally transferred genes. The concatenated ROS-scavenging protein sequence can be used to identify and evaluate Streptococcus species and subspecies based on phylogenetic analysis.

Yeast polyubiquitin unit regulates synaptonemal complex formation and recombination during meiosis: Min-Kyung Jo , Kiwon Rhee , Keun Pil Kim , Soogil Hong; J. Microbiol. 2022;60(7):705-714. Published online July 4, 2022; DOI: https://doi.org/10.1007/s12275-022-2204-y

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Abstract: Ubiquitin is highly conserved in most eukaryotes and involved in diverse physiological processes, including cell division, protein quality control, and protein degradation mediated by the ubiquitin-proteasome system after heat shock, glucose-starvation, and oxidative stress. However, the role of the ubiquitin gene UBI4, which contains five consecutive head-to-tail ubiquitin repeats, in meiosis has not been investigated. In this study, we show that the Saccharomyces cerevisiae polyubiquitin precursor gene, UBI4, is required to promote synaptonemal complex (SC) formation and suppress excess doublestrand break formation. Moreover, the proportion of Zip1 polycomplexes, which indicate abnormal SC formation, in cells with a mutation in UBI4 (i.e., ubi4Δ cells) is higher than that of wild-type cells, implying that the UBI4 plays an important role in the early meiotic prophase I. Interestingly, although ubi4Δ cells rarely form full-length SCs in the pachytene stage of prophase I, the Zip3 foci are still seen, as in wild-type cells. Moreover, ubi4Δ cells proficiently form crossover and noncrossover products with a slight delay compared to wild-type cells, suggesting that UBI4 is dispensable in SCcoupled recombination. Our findings demonstrate that UBI4 exhibits dual functions that are associated with both positive and negative roles in SC formation and recombination during meiosis.

Lactobacillus plantarum-derived metabolites sensitize the tumorsuppressive effects of butyrate by regulating the functional expression of SMCT1 in 5-FU-resistant colorectal cancer cells: Hye-Ju Kim , JaeJin An , Eun-Mi Ha; J. Microbiol. 2022;60(1):100-117. Published online December 29, 2021; DOI: https://doi.org/10.1007/s12275-022-1533-1

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26 Citations

Abstract: A critical obstacle to the successful treatment of colorectal cancer (CRC) is chemoresistance. Chemoresistant CRC cells contribute to treatment failure by providing a mechanism of drug lethargy and modifying chemoresistance-associated molecules. The gut microbiota provide prophylactic and therapeutic effects by targeting CRC through anticancer mechanisms. Among them, Lactobacillus plantarum contributes to the health of the host and is clinically effective in treating CRC. This study confirmed that 5-fluorouracil (5-FU)-resistant CRC HCT116 (HCT116/5FUR) cells acquired butyrateinsensitive properties. To date, the relationship between 5- FU-resistant CRC and butyrate resistance has not been elucidated. Here, we demonstrated that the acquisition of butyrate resistance in HCT116/5FUR cells was strongly correlated with the inhibition of the expression and function of SMCT1, a major transporter of butyrate in colonocytes. L. plantarum-cultured cell-free supernatant (LP) restored the functional expression of SMCT1 in HCT116/5FUR cells, leading to butyrate-induced antiproliferative effect and apoptosis. These results suggest that LP has a synergistic effect on the SMCT1/butyrate-mediated tumor suppressor function and is a potential chemosensitizer to overcome dual 5-FU and butyrate resistance in HCT116 cells.

Constantimarinum furrinae gen. nov., sp. nov., a marine bacterium isolated from saline volcanic rock aquifer (lava seawater) at Jeju Island, Republic of Korea: Sung-Hyun Yang , Hyun-Myung Oh , Mi-Jeong Park , Dongil Jang , Kae Kyoung Kwon; J. Microbiol. 2022;60(1):11-17. Published online December 29, 2021; DOI: https://doi.org/10.1007/s12275-022-1468-6

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Abstract: A Gram-stain-negative, aerobic, rod-shaped (0.3–0.5 × 1.0– 1.9 μm), non-motile marine bacterium designated as ALE3EIT was isolated from a saline volcanic rock aquifer (lava seawater) on Jeju Island, Republic of Korea. The 16S rRNA gene sequence analysis revealed that strain ALE3EIT showed high similarity to ‘Altibacter lentus’ JLT2010T (97.2%), followed by Marixanthomonas ophiurae KMM 3046T (94.5%). Growth was observed at 10–41°C (optimum, 30°C), at pH 6.0–8.5 (optimum, pH 7.5) and at 0.5–8% (optimum, 4.0%) NaCl. The predominant cellular fatty acids were iso-C15:0 (23.5%), iso-C16:0 (10.2%), iso-C16:0 3OH (10.5%), and iso-C17:0 3OH (16.8%). The DNA G + C contents was 40.4 mol%. The major respiratory quinone was MK-6. The major polar lipids were determined to be phosphatidylethanolamine, two unidentified glycolipids, and two unidentified aminolipids. Several phenotypic characteristics such as production of acetoin, activities of arginine dihydrolase and acid phosphatase, and utilization pattern of carbon sources differentiate strain ALE3EIT from ‘A. lentus’ JLT2010T. Activities of the lipase, trypsin, α- chymotrypsin and gelatinase and utilization pattern of carbon sources differentiate strain ALE3EIT from M. ophiurae KMM 3046T. The genome of strain ALE3EIT is 3.0 Mbp long and its ANI and AAI values against ‘A. lentus’ JLT2010T were 76.58 and 72.76, respectively, however, AAI values against members in other genera were lower than 72%. The phylogenomic tree inferred by PhyloPhlAn clearly differentiated the strain ALE3EIT together with strain JLT2010T from other genera in the Falvobacteriaceae. This polyphasic taxonomic data indicates that strain ALE3EIT should be identified as a novel species in the genus ‘Altibacter’, however, the name has not been validated. Therefore, the strain is classified as a novel genus and is proposed as Constantimarinum furrinae gen. nov., sp. nov. The type strain is ALE3EIT (= KCCM 43303T = JCM 33022T).

A study of P release from Fe-P and Ca-P via the organic acids secreted by Aspergillus niger: Da Tian , Liyan Wang , Jun Hu , Liangliang Zhang , Ningning Zhou , Jingjing Xia , Meiyue Xu , Kianpoor Kalkhajeh Yusef , Shimei Wang , Zhen Li , Hongjian Gao; J. Microbiol. 2021;59(9):819-826. Published online August 12, 2021; DOI: https://doi.org/10.1007/s12275-021-1178-5

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23 Citations

Abstract: Phosphate solubilizing fungi (PSF) have been widely applied to dissolve insoluble phosphates (IPs). However, the PSF usually demonstrates a different phosphate solubilizing capacity for various IPs. This study explored the mechanisms of Aspergillus niger for the dissolution of ferric phosphate (FePO4, Fe-P), and tricalcium phosphate (Ca3[PO4]2, Ca-P) regarding the tricarboxylic acid (TCA) cycle. Aspergillus niger has higher phosphorus (P) content released from Ca-P, reached the maximum value of 861 mg/L after seven days of incubation, compared with the 169 mg/L from Fe-P. Oxalic acid promoted the release of P from Ca-P through the formation of calcium oxalate. The presence of Fe-P can stimulate A. niger to secrete large amounts of citric acid, confirmed by the enhancement of citrate synthase (CS) activity. However, citric acid only promotes 0.5% of P released from Fe-P. Meanwhile, although oxalic acid still dominates the release of P from Fe-P, its abundance was significantly declined. In contrast, oxalic acid also shows a higher P release ratio in Ca-P than citric acid, i.e., 36% vs. 22%. This study points to the future usage of A. niger to dissolve IPs in soil required to enhance oxalic acid secretion.

Review

Dissection of plant microbiota and plant-microbiome interactions: Kihyuck Choi , Raees Khan , Seon-Woo Lee; J. Microbiol. 2021;59(3):281-291. Published online February 23, 2021; DOI: https://doi.org/10.1007/s12275-021-0619-5

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36 Citations

Abstract: Plants rooted in soil have intimate associations with a diverse array of soil microorganisms. While the microbial diversity of soil is enormous, the predominant bacterial phyla associated with plants include Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, and Verrucomicrobia. Plants supply nutrient niches for microbes, and microbes support plant functions such as plant growth, development, and stress tolerance. The interdependent interaction between the host plant and its microbes sculpts the plant microbiota. Plant and microbiome interactions are a good model system for understanding the traits in eukaryotic organisms from a holobiont perspective. The holobiont concept of plants, as a consequence of co-evolution of plant host and microbiota, treats plants as a discrete ecological unit assembled with their microbiota. Dissection of plant-microbiome interactions is highly complicated; however, some reductionist approaches are useful, such as the synthetic community method in a gnotobiotic system. Deciphering the interactions between plant and microbiome by this reductionist approach could lead to better elucidation of the functions of microbiota in plants. In addition, analysis of microbial communities’ interactions would further enhance our understanding of coordinated plant microbiota functions. Ultimately, better understanding of plantmicrobiome interactions could be translated to improvements in plant productivity.

Journal Article

Leucobacter coleopterorum sp. nov., Leucobacter insecticola sp. nov., and Leucobacter viscericola sp. nov., isolated from the intestine of the diving beetles, Cybister brevis and Cybister lewisianus, and emended description of the genus Leucobacter: Dong-Wook Hyun , Hojun Sung , Pil Soo Kim , Ji-Hyun Yun , Jin-Woo Bae; J. Microbiol. 2021;59(4):360-368. Published online January 26, 2021; DOI: https://doi.org/10.1007/s12275-021-0472-6

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9 Citations

Abstract: Three novel bacterial strains, HDW9AT, HDW9BT, and HDW9CT, isolated from the intestine of the diving beetles Cybister lewisianus and Cybister brevis, were characterized as three novel species using a polyphasic approach. The isolates were Gram-staining-positive, strictly aerobic, non-motile, and rod-shaped. They grew optimally at 30°C (pH 7) in the presence of 0.5% (wt/vol) NaCl. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that they belong to the genus Leucobacter and are closely related to L. denitrificans M1T8B10T (98.4–98.7% sequence similarity). Average nucleotide identity (ANI) values among the isolates were 76.4–84.1%. ANI values for the isolates and the closest taxonomic species, L. denitrificans KACC 14055T, were 72.3–73.1%. The isolates showed ANI values of < 76.5% with all analyzable Leucobacter strains in the EzBioCloud database. The genomic DNA G + C content of the isolates was 60.3–62.5%. The polar lipid components were phosphatidylglycerol, diphosphatidylglycerol, and other unidentified glycolipids, phospholipids, and lipids. The major cellular fatty acids were anteiso- C15:0, iso-C16:0, and anteiso-C17:0. MK-10 was the major respiratory quinone, and MK-7 and MK-11 were the minor respiratory quinones. The whole-cell sugar components of the isolates were ribose, glucose, galactose, and mannose. The isolates harbored L-2,4-diaminobutyric acid, L-serine, L-lysine, L-aspartic acid, glycine, and D-glutamic acid within the cell wall peptidoglycan. Based on phylogenetic, phenotypic, chemotaxonomic, and genotypic analyses, strains HDW9AT, HDW9BT, and HDW9CT represent three novel species within the genus Leucobacter. We propose the name Leucobacter coleopterorum sp. nov. for strain HDW9AT (= KACC 21331T = KCTC 49317T = JCM 33667T), the name Leucobacter insecticola sp. nov. for strain HDW9BT (= KACC 21332T = KCTC 49318T = JCM 33668T), and the name Leucobacter viscericola sp. nov. for strain HDW9CT (= KACC 21333T = KCTC 49319T = JCM 33669T).

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