Journal of Microbiology

Journal Articles

Transcription Factors Tec1 and Tec2 Play Key Roles in the Hyphal Growth and Virulence of Mucor lusitanicus Through Increased Mitochondrial Oxidative Metabolism: Viridiana Alejandre-Castañeda , J. Alberto Patiño-Medina , Marco I. Valle-Maldonado , Alexis García , Rafael Ortiz-Alvarado , León F. Ruíz-Herrera , Karla Viridiana Castro-Cerritos , Joel Ramírez-Emiliano , Martha I. Ramírez-Díaz , Victoriano Garre , Soo Chan Lee , Víctor Meza-Carmen; J. Microbiol. 2023;61(12):1043-1062. Published online December 19, 2023; DOI: https://doi.org/10.1007/s12275-023-00096-8

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Abstract: Mucormycosis is a lethal and difficult-to-treat fungal infection caused by fungi of the order Mucorales. Mucor lusitanicus, a member of Mucorales, is commonly used as a model to understand disease pathogenesis. However, transcriptional control of hyphal growth and virulence in Mucorales is poorly understood. This study aimed to investigate the role of Tec proteins, which belong to the TEA/ATTS transcription factor family, in the hyphal development and virulence of M. lusitanicus. Unlike in the genome of Ascomycetes and Basidiomycetes, which have a single Tec homologue, in the genome of Mucorales, two Tec homologues, Tec1 and Tec2, were found, except in that of Phycomyces blakesleeanus, with only one Tec homologue. tec1 and tec2 overexpression in M. lusitanicus increased mycelial growth, mitochondrial content and activity, expression of the rhizoferrin synthetase-encoding gene rfs, and virulence in nematodes and wax moth larvae but decreased cAMP levels and protein kinase A (PKA) activity. Furthermore, tec1- and tec2-overexpressing strains required adequate mitochondrial metabolism to promote the virulent phenotype. The heterotrimeric G beta subunit 1-encoding gene deletant strain (Δgpb1) increased cAMP-PKA activity, downregulation of both tec genes, decreased both virulence and hyphal development, but tec1 and tec2 overexpression restored these defects. Overexpression of allele-mutated variants of Tec1(S332A) and Tec2(S168A) in the putative phosphorylation sites for PKA increased both virulence and hyphal growth of Δgpb1. These findings suggest that Tec homologues promote mycelial development and virulence by enhancing mitochondrial metabolism and rhizoferrin accumulation, providing new information for the rational control of the virulent phenotype of M. lusitanicus.

Crystal structure of the phage-encoded N-acetyltransferase in complex with acetyl-CoA, revealing a novel dimeric arrangement: Nayeon Ki , Inseong Jo , Yongseong Hyun , Jinwook Lee , Nam-Chul Ha , Hyun-Myung Oh; J. Microbiol. 2022;60(7):746-755. Published online July 4, 2022; DOI: https://doi.org/10.1007/s12275-022-2030-2

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Abstract: Bacteriophages employ diverse mechanisms to facilitate the proliferation of bacteriophages. The Salmonella-infecting phage SPN3US contains a putative N-acetyltransferase, which is widely found in bacteriophages. However, due to low sequence similarity to the N-acetyltransferases from bacteria and eukaryotic cells, the structure and function of phage-encoded acetyltransferases are mainly unknown. This study determines the crystal structure of the putative N-acetyltransferase of SPN3US in complex with acetyl-CoA. The crystal structure showed a novel homodimeric arrangement stabilized by exchanging the C-terminal α-helix within the dimer. The following biochemical analyses suggested that the phageencoded acetyltransferase might have a very narrow substrate specificity. Further studies are required to reveal the biochemical activity, which would help elucidate the interaction between the phage and host bacteria in controlling pathogenic bacteria.

Antiviral effects of human placenta hydrolysate (Laennec) against SARS-CoV-2 in vitro and in the ferret model: Eun-Ha Kim , Young-il Kim , Seung-Gyu Jang , Minju Im , Kyeongsoo Jeong , Young Ki Choi , Hae-Jung Han; J. Microbiol. 2021;59(11):1056-1062. Published online October 6, 2021; DOI: https://doi.org/10.1007/s12275-021-1367-2

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Abstract: The COVID-19 pandemic has caused unprecedented health, social, and economic crises worldwide. However, to date, there is an only a limited effective treatment for this disease. Human placenta hydrolysate (hPH) has previously been shown to be safe and to improve the health condition in patients with hyperferritinemia and COVID-19. In this study, we aimed to determine the antiviral effects of hPH against SARS-CoV-2 in vitro and in vivo models and compared with Remdesivir, an FDA-approved drug for COVID-19 treatment. To assess whether hPH inhibited SARS-CoV-2 replication, we determined the CC50, EC50, and selective index (SI) in Vero cells by infection with a SARS-CoV-2 at an MOI of 0.01. Further, groups of ferrets infected with 105.8 TCID50/ml of SARS-CoV-2 and treated with hPH at 2, 4, 6 dpi, and compared their clinical manifestation and virus titers in respiratory tracts with PBS control-treated group. The mRNA expression of immunerelated cytokines was determined by qRT-PCR. hPH treatment attenuated virus replication in a dose-dependent manner in vitro. In a ferret infection study, treatment with hPH resulted in minimal bodyweight loss and attenuated virus replication in the nasal wash, turbinates, and lungs of infected ferrets. In addition, qRT-PCR results revealed that the hPH treatment remarkably upregulated the gene expression of type I (IFN-α and IFN-β) and II (IFN-γ) IFNs in SARS-CoV-2 infected ferrets. Our data collectively suggest that hPH has antiviral efficacy against SARS-CoV-2 and might be a promising therapeutic agent for the treatment of SARS-CoV-2 infection.

Description of Ornithinimicrobium ciconiae sp. nov., and Ornithinimicrobium avium sp. nov., isolated from the faeces of the endangered and near-threatened birds: So-Yeon Lee , Hojun Sung , Pil Soo Kim , Hyun Sik Kim , Jae-Yun Lee , June-Young Lee , Yun-Seok Jeong , Euon Jung Tak , Jeong Eun Han , Dong-Wook Hyun , Jin-Woo Bae; J. Microbiol. 2021;59(11):978-987. Published online September 27, 2021; DOI: https://doi.org/10.1007/s12275-021-1323-1

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Abstract: Phenotypic and genomic analyses were performed to characterize two novel species, H23M54T and AMA3305T, isolated from the faeces of the Oriental stork (Ciconia boyciana) and the cinereous vulture (Aegypius monachus), respectively. Strains H23M54T and AMA3305T showed the highest similarities of 16S rRNA gene sequences and complete genome sequences with Ornithinimicrobium cavernae CFH 30183T (98.5% of 16S rRNA gene sequence similarity and 82.1% of average nucleotide identity, ANI) and O. pekingense DSM 21552T (98.5% of 16S rRNA gene sequence similarity and 82.3% of ANI), respectively. Both strains were Gram-stain-positive, obligate aerobes, non-motile, non-spore-forming, and coccoid- and rodshaped. Strain H23M54T grew optimally at 25–30°C and pH 8.0 and in the presence of 1.5–2% (wt/vol) NaCl, while strain AMA3305T grew optimally at 30°C and pH 7.0 and in the presence of 1–3% (wt/vol) NaCl. Both strains had iso-C15:0, iso- C16:0, and summed feature 9 (iso-C17:1 ω9c and/or C16:0 10- methyl) as major cellular fatty acids. MK-8 (H4) was identified as the primary respiratory quinone in both strains. Strains H23M54T and AMA3305T possessed diphosphatidylglycerol and phosphatidylglycerol as major polar lipids. Moreover, strains H23M54T and AMA3305T commonly contained ribose and glucose as major sugars and L-ornithine, L-alanine, glycine, and aspartic acid as major amino acids. The polyphasic taxonomic data indicate that strains H23M54T and AMA3305T represent novel species of the genus Ornithinimicrobium. We propose the names Ornithinimicrobium ciconiae sp. nov. and Ornithinimicrobium avium sp. nov. for strains H23M54T (= KCTC 49151T = JCM 33221T) and AMA3305T (= KCTC 49180T = JCM 32873T), respectively.

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