Journal of Microbiology

Journal Articles

Cultivation of Diverse Novel Marine Bacteria from Deep Ocean Sediment Using Spent Culture Supernatant of Ca. Bathyarchaeia Enrichment.: Sidra Erum Ishaq, Tariq Ahmad, Lewen Liang, Ruize Xie, Tiantian Yu, Yinzhao Wang, Fengping Wang; J. Microbiol. 2024;62(8):611-625. Published online July 10, 2024; DOI: https://doi.org/10.1007/s12275-024-00145-w

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Abstract: Most microorganisms resist pure cultivation under conventional laboratory conditions. One of the primary issues for this un-culturability is the absence of biologically produced growth-promoting factors in traditionally defined growth media. However, whether cultivating microbes by providing spent culture supernatant of pivotal microbes in the growth medium can be an effective approach to overcome this limitation is still an under-explored area of research. Here, we used the spent culture medium (SCM) method to isolate previously uncultivated marine bacteria and compared the efficiency of this method with the traditional cultivation (TC) method. In the SCM method, Ca. Bathyarchaeia-enriched supernatant (10%) was used along with recalcitrant organic substrates such as lignin, humic acid, and organic carbon mixture. Ca. Bathyarchaeia, a ubiquitous class of archaea, have the capacity to produce metabolites, making their spent culture supernatant a key source to recover new bacterial stains. Both cultivation methods resulted in the recovery of bacterial species from the phyla Pseudomonadota, Bacteroidota, Actinomycetota, and Bacillota. However, our SCM approach also led to the recovery of species from rarely cultivated groups, such as Planctomycetota, Deinococcota, and Balneolota. In terms of the isolation of new taxa, the SCM method resulted in the cultivation of 80 potential new strains, including one at the family, 16 at the genus, and 63 at the species level, with a novelty ratio of ~ 35% (80/219). In contrast, the TC method allowed the isolation of ~ 10% (19/171) novel strains at species level only. These findings suggest that the SCM approach improved the cultivation of novel and diverse bacteria.

Description of Deefgea piscis sp. nov., and Deefgea tanakiae sp. nov., isolated from the gut of Korean indigenous fish: Do-Hun Gim , So-Yeon Lee , Jeong Eun Han , Jae-Yun Lee , Seo Min Kang , Jin-Woo Bae; J. Microbiol. 2022;60(11):1061-1069. Published online September 1, 2022; DOI: https://doi.org/10.1007/s12275-022-2250-5

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2 Citations

Abstract: Three novel strains, (D17T, D13, and D25T) isolated from the gut of the Korean dark sleeper (Odontobutis platycephala), Kumgang fat minnow (Rhynchocypris kumgangensis), and the Korean oily bitterling (Tanakia koreensis) were identified as two novel species. Strains D17T and D13 showed the highest similarities in 16S rRNA gene and complete genome sequences to Deefgea rivuli WB 3.4-79T (98.0% and 97.9%, respectively, of 16S rRNA gene sequence similarity, 77.8% and 77.7%, respectively, of orthologous average nucleotide identity, Ortho- ANI, and 21.9% and 21.9%, respectively, of digital DNA-DNA hybridization, dDDH). Strain D17T showed the highest similarities in 16S rRNA gene and complete genome sequences to D13 (99.9% of 16S rRNA gene sequence similarity, 91.8% of OrthoANI, and 45.1% of dDDH); therefore, strains D17T and D13 were assigned as the same species. Strain D25T showed the highest similarities in 16S rRNA gene and complete genome sequences to D. chitinilytica Nsw-4T (98.2% of 16S rRNA gene sequence similarity, 82.4% of OrthoANI, and 25.1% of dDDH). Strains D17T and D13 were Gram-stain-negative, facultative anaerobes, rod-shaped, non-motile, and non-flagellated. Strain D25T was Gram-stain-negative, facultative anaerobe, rodshaped, and motile by a single polar flagellum. These strains had C16:0 and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c) as the major cellular fatty acids and possessed Q-8 as a major respiratory ubiquinone. All three strains contained phosphatidylethanolamine and phosphatidylglycerol as the major polar lipids. Based on polyphasic taxonomic data, strains D17T, D13, and D25T represent two novel species of the genus Deefgea. We propose the name Deefgea piscis sp. nov. for strains D17T (= KCTC 82958T = JCM 34941T) and D13 (= KCTC 92368), and Deefgea tanakiae sp. nov. for strain D25T (= KCTC 82959T = JCM 34942T).

Review

Transmissibility and pathogenicity of SARS-CoV-2 variants in animal models: Young-Il Kim , Mark Anthony B. Casel , Young Ki Choi; J. Microbiol. 2022;60(3):255-267. Published online March 2, 2022; DOI: https://doi.org/10.1007/s12275-022-2033-z

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8 Citations

Abstract: As of February 2022, SARS-CoV-2 is still one of the most serious public health threats due to its high mortality rate and rapid spread of novel variants. Since the first outbreak in 2019, general understanding of SARS-CoV-2 has been improved through basic and clinical studies; however, knowledge gaps still exist in our understanding of the emerging novel SARSCoV- 2 variants, which impacts the corresponding development of vaccines and therapeutics. Especially, accumulation of mutations in SARS-CoV-2 and rapid spread in populations with previous immunity has resulted in selection of variants that evade the host immune response. This phenomenon threatens to render current SARS-CoV-2 vaccines ineffective for controlling the pandemic. Proper animal models are essential for detailed investigations into the viral etiology, transmission and pathogenesis mechanisms, as well as evaluation of the efficacy of vaccine candidates against recent SARS-CoV-2 variants. Further, the choice of animal model for each research topic is important for researchers to gain better knowledge of recent SARS-CoV-2 variants. Here, we review the advantages and limitations of each animal model, including mice, hamsters, ferrets, and non-human primates, to elucidate variant SARS-CoV-2 etiology and transmission and to evaluate therapeutic and vaccine efficacy.

Journal Articles

Characterization of a cold-adapted debranching enzyme and its role in glycogen metabolism and virulence of Vibrio vulnificus MO6-24/O: Ah-Reum Han , Haeyoung Kim , Jong-Tae Park , Jung-Wan Kim; J. Microbiol. 2022;60(4):375-386. Published online February 14, 2022; DOI: https://doi.org/10.1007/s12275-022-1507-3

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Abstract: Vibrio vulnificus MO6-24/O has three genes annotated as debranching enzymes or pullulanase genes. Among them, the gene encoded by VVMO6_03032 (vvde1) shares a higher similarity at the amino acid sequence level to the glycogen debranching enzymes, AmyX of Bacillus subtilis (40.5%) and GlgX of Escherichia coli (55.5%), than those encoded by the other two genes. The vvde1 gene encoded a protein with a molecular mass of 75.56 kDa and purified Vvde1 efficiently hydrolyzed glycogen and pullulan to shorter chains of maltodextrin and maltotriose (G3), respectively. However, it hydrolyzed amylopectin and soluble starch far less efficiently, and β-cyclodextrin (β-CD) only rarely. The optimal pH and temperature of Vvde1 was 6.5 and 25°C, respectively. Vvde1 was a cold-adapted debranching enzyme with more than 60% residual activity at 5°C. It could maintain stability for 2 days at 25°C and 1 day at 35°C, but it destabilized drastically at 40°C. The Vvde1 activity was inhibited considerably by Cu2+, Hg2+, and Zn2+, while it was slightly enhanced by Co2+, Ca2+, Ni2+, and Fe2+. The vvde1 knock-out mutant accumulated more glycogen than the wild-type in media supplemented with 1.0% maltodextrin; however, the side chain length distribution of glycogen was similar to that of the wild-type except G3, which was much more abundant in the mutant. Therefore, Vvde1 seemed to debranch glycogen with the degree of polymerization 3 (DP3) as the specific target branch length. Virulence of the pathogen against Caenorhabditis elegans was attenuated significantly by the vvde1 mutation. These results suggest that Vvde1 might be a unique glycogen debranching enzyme that is involved in both glycogen utilization and shaping of glycogen molecules, and contributes toward virulence of the pathogen.

Differences in seroprevalence between epicenter and non-epicenter areas of the COVID-19 outbreak in South Korea: Hye Won Jeong , Hyun-Ha Chang , Eun Ji Kim , Yu Kyung Kim , Se-Mi Kim , Eun-Ha Kim , Young-Il Kim , Mark Anthony B. Casel , Seong-Gyu Kim , Rare Rollon , Seung-Gyu Jang , Kwang-Min Yu , Hee-Sung Kim , Hee Sue Park , Su-Jin Park , Yong-Dae Kim , Eung-Gook Kim , Young Ki Choi; J. Microbiol. 2021;59(5):530-533. Published online April 28, 2021; DOI: https://doi.org/10.1007/s12275-021-1095-7

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Abstract: To compare the standardized severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence of high epicenter region with non-epicenter region, serological studies were performed with a total of 3,268 sera from Daegu City and 3,981 sera from Chungbuk Province. Indirect immunofluorescence assay (IFA) for SARS-CoV-2 IgG results showed a high seroprevalence rate in the Daegu City (epicenter) compared with a non-epicenter area (Chungbuk Province) (1.27% vs. 0.91%, P = 0.0358). It is noteworthy that the highest seroprevalence in Daegu City was found in elderly patients (70’s) whereas young adult patients (20’s) in Chungbuk Province showed the highest seroprevalence. Neutralizing antibody (NAb) titers were found in three samples from Daegu City (3/3, 268, 0.09%) while none of the samples from Chungbuk Province were NAb positive. These results demonstrated that even following the large outbreak, the seropositive rate of SARS-CoV-2 in the general population remained low in South Korea.

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