Journal of Microbiology

Journal Articles

Hydroxychloroquine an Antimalarial Drug, Exhibits Potent Antifungal Efficacy Against Candida albicans Through Multitargeting.: Sargun Tushar Basrani, Tanjila Chandsaheb Gavandi, Shivani Balasaheb Patil, Nandkumar Subhash Kadam, Dhairyasheel Vasantrao Yadav, Sayali Ashok Chougule, Sankunny Mohan Karuppayil, Ashwini Khanderao Jadhav; J. Microbiol. 2024;62(5):381-391. Published online April 8, 2024; DOI: https://doi.org/10.1007/s12275-024-00111-6

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Abstract: Candida albicans is the primary etiological agent associated with candidiasis in humans. Unrestricted growth of C. albicans can progress to systemic infections in the worst situation. This study investigates the antifungal activity of Hydroxychloroquine (HCQ) and mode of action against C. albicans. HCQ inhibited the planktonic growth and yeast to hyphal form morphogenesis of C. albicans significantly at 0.5 mg/ml concentration. The minimum inhibitory concentrations (MIC(50)) of HCQ for C. albicans adhesion and biofilm formation on the polystyrene surface was at 2 mg/ml and 4 mg/ml respectively. Various methods, such as scanning electron microscopy, exploration of the ergosterol biosynthesis pathway, cell cycle analysis, and assessment of S oxygen species (ROS) generation, were employed to investigate HCQ exerting its antifungal effects. HCQ was observed to reduce ergosterol levels in the cell membranes of C. albicans in a dose-dependent manner. Furthermore, HCQ treatment caused a substantial arrest of the C. albicans cell cycle at the G0/G1 phase, which impeded normal cell growth. Gene expression analysis revealed upregulation of SOD2, SOD1, and CAT1 genes after HCQ treatment, while genes like HWP1, RAS1, TEC1, and CDC 35 were downregulated. The study also assessed the in vivo efficacy of HCQ in a mice model, revealing a reduction in the pathogenicity of C. albicans after HCQ treatment. These results indicate that HCQ holds for the development of novel antifungal therapies.

Flavobacterium psychrotrophum sp. nov. and Flavobacterium panacagri sp. nov., Isolated from Freshwater and Soil: Yong-Seok Kim , Eun-Mi Hwang , Chang-Myeong Jeong , Chang-Jun Cha; J. Microbiol. 2023;61(10):891-901. Published online October 18, 2023; DOI: https://doi.org/10.1007/s12275-023-00081-1

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Abstract: Two novel bacterial strains CJ74T and CJ75T belonging to the genus Flavobacterium were isolated from freshwater of Han River and ginseng soil, South Korea, respectively. Strain CJ74T was Gram-stain-negative, aerobic, rod-shaped, non-motile, and non-flagellated, and did not produce flexirubin-type pigments. Strain CJ75T was Gram-stain-negative, aerobic, rodshaped, motile by gliding, and non-flagellated, and produced flexirubin-type pigments. Both strains were shown to grow optimally at 30 °C in the absence of NaCl on R2A medium. Phylogenetic analysis based on 16S rRNA gene sequences showed that strains CJ74T and CJ75T belonged to the genus Flavobacterium and were most closely related to Flavobacterium niveum TAPW14T and Flavobacterium foetidum CJ42T with 96.17% and 97.29% 16S rRNA sequence similarities, respectively. Genomic analyses including the reconstruction of phylogenomic tree, average nucleotide identity, and digital DNA-DNA hybridization suggested that they were novel species of the genus Flavobacterium. Both strains contained menaquinone 6 (MK-6) as the primary respiratory quinone and phosphatidylethanolamine as a major polar lipid. The predominant fatty acids of both strains were iso-C15:0 and summed feature 3 ( C16:1 ω7c and/or C16: 1 ω6c). Based on the polyphasic taxonomic study, strains CJ74T and CJ75T represent novel species of the genus Flavobacterium, for which names Flavobacterium psychrotrophum sp. nov. and Flavobacterium panacagri sp. nov. are proposed, respectively. The type strains are CJ74T (=KACC 19819T =JCM 32889T) and CJ75T (=KACC 23149T =JCM 36132T).

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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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.

Transcriptome‑based Mining of the Constitutive Promoters for Tuning Gene Expression in Aspergillus oryzae: Kobkul Laoteng , Jutamas Anantayanon , Chanikul Chutrakul , Sarocha Panchanawaporn , Sukanya Jeennor; J. Microbiol. 2023;61(2):199-210. Published online February 6, 2023; DOI: https://doi.org/10.1007/s12275-023-00020-0

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Abstract: Transcriptional regulation has been adopted for developing metabolic engineering tools. The regulatory promoter is a crucial genetic element for strain optimization. In this study, a gene set of Aspergillus oryzae with highly constitutive expression across different growth stages was identified through transcriptome data analysis. The candidate promoters were functionally characterized in A. oryzae by transcriptional control of β-glucuronidase (GUS) as a reporter. The results showed that the glyceraldehyde triphosphate dehydrogenase promoter (PgpdA1) of A. oryzae with a unique structure displayed the most robust strength in constitutively controlling the expression compared to the PgpdA2 and other putative promoters tested. In addition, the ubiquitin promoter (Pubi) of A. oryzae exhibited a moderate expression strength. The deletion analysis revealed that the 5' untranslated regions of gpdA1 and ubi with the length of 1028 and 811 nucleotides, counted from the putative translation start site (ATG), respectively, could efficiently drive the GUS expression. Interestingly, both promoters could function on various carbon sources for cell growth. Glucose was the best fermentable carbon source for allocating high constitutive expressions during cell growth, and the high concentrations (6–8% glucose, w/v) did not repress their functions. It was also demonstrated that the secondary metabolite gene coding for indigoidine could express under the control of PgpdA1 or Pubi promoter. These strong and moderate promoters of A. oryzae provided beneficial options in tuning the transcriptional expression for leveraging the metabolic control towards the targeted products.

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