Journal of Microbiology

Journal Articles

Whole-genome sequencing analysis of Shiga toxin-producing Escherichia coli O22:H8 isolated from cattle prediction pathogenesis and colonization factors and position in STEC universe phylogeny: Wanderson Marques Da Silva , Mariano Larzabal , Flavia Figueira Aburjaile , Nahuel Riviere , Luisina Martorelli , James Bono , Ariel Amadio , Angel Cataldi; J. Microbiol. 2022;60(7):689-704. Published online June 22, 2022; DOI: https://doi.org/10.1007/s12275-022-1616-z

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Abstract: Shiga toxin-producing Escherichia coli (STEC) is a foodborne pathogen capable of causing illness in humans. In a previous study, our group showed that a STEC isolate belonging to O22:H8 serotype (strain 154) can interfere with STEC O157:H7 colonization both in vitro and in vivo. Using whole-genome sequencing and genomic comparative, we predicted a subset of genes acquired by O22:H8 strain 154 through horizontal gene transfer that might be responsible for the phenotype previously described by our group. Among them were identified genes related to the pathogenesis of non-LEE (locus of enterocyte effacement) STEC, specific metabolic processes, antibiotic resistance and genes encoding for the T6SS-1 that is related to inter-bacterial competition. In addition, we showed that this strain carries stx1c and stx2dact, a mucus-inducible variant. The results obtained in this study provide insights into STEC genomic plasticity and the importance of genomic islands in the adaptation and pathogenesis of this pathogen.

Lipocalin2 as a potential antibacterial drug against Acinetobacter baumannii infection: Daejin Lim , Su-Jin Park , Ha Young Kim , Minsang Shin , Miryoung Song; J. Microbiol. 2022;60(4):444-449. Published online March 28, 2022; DOI: https://doi.org/10.1007/s12275-022-2007-1

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Abstract: Available antibiotics to treat Acinetobacter baumannii infection is limited due to increasing resistance and the emergence of multiple drug-resistant strains. Hence, discovering effective agents against A. baumannii to reduce the number of infectionrelated deaths is imperative. In search of novel and alternative antibiotics, the antibacterial function of lipocalin2 (Lcn2) was investigated to treat systemic infections of A. baumannii using a mouse neutropenia model. We observed a significant increase in serum Lcn2 levels upon bacterial injection into the mouse, and the administration of recombinant Lcn2 (rmLcn2) extended their survival. Such protective effects were also observed in rmLcn2-pretreated macrophages, where rmLcn2 reduced the survival of the pathogen inside the macrophages. The underlying molecular mechanism of Lcn2 protection was also investigated. We observed that pretreatment of the Raw- 264.7 macrophages with rmLcn2 markedly altered the expression of tonB3, which encodes a component of the transporter for ferrisiderophores in A. baumannii. However, the expression of katG, the gene encoding catalase, remained unaffected. These indicate that Lcn2-mediated defense against the pathogen is related to nutritional immunity rather than reactive oxygen species (ROS) production. Furthermore, the addition of rmLcn2 in infected mice diminished bacterial burden in multiple organs and enhanced the expression of tonB3 in the liver, spleen, and lungs of the infected mice. Increased survival rate due to rmLcn2 treatment declined when the infection model was established using lcn2-defective (lcn2-/-) mice, which indicated the necessity of endogenous Lcn2. Therefore, the antibacterial function of Lcn2 can be exploited to develop an alternative therapeutic agent against A. baumannii.

An in vitro study of the antifungal activity of Trichoderma virens 7b and a profile of its non-polar antifungal components released against Ganoderma boninense: Lee Pei Lee Angel , Mohd Termizi Yusof , Intan Safinar Ismail , Bonnie Tay Yen Ping , Intan Nur Ainni Mohamed Azni , Norman Hj Kamarudin , Shamala Sundram; J. Microbiol. 2016;54(11):732-744. Published online October 29, 2016; DOI: https://doi.org/10.1007/s12275-016-6304-4

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47 Citations

Abstract: Ganoderma boninense is the causal agent of a devastating disease affecting oil palm in Southeast Asian countries. Basal stem rot (BSR) disease slowly rots the base of palms, which radically reduces productive lifespan of this lucrative crop. Previous reports have indicated the successful use of Trichoderma as biological control agent (BCA) against G. boninense and isolate T. virens 7b was selected based on its initial screening. This study attempts to decipher the mechanisms responsible for the inhibition of G. boninense by identifying and characterizing the chemical compounds as well as the physical mechanisms by T. virens 7b. Hexane extract of the isolate gave 62.60% ± 6.41 inhibition against G. boninense and observation under scanning electron microscope (SEM) detected severe mycelial deformation of the pathogen at the region of inhibition. Similar mycelia deformation of G. boninense was observed with a fungicide treatment, Benlate® indicating comparable fungicidal effect by T. virens 7b. Fraction 4 and 5 of hexane active fractions through preparative thin layer chromatography (P-TLC) was identified giving the best inhibition of the pathogen. These fractions comprised of ketones, alcohols, aldehydes, lactones, sesquiterpenes, monoterpenes, sulphides, and free fatty acids profiled through gas chromatography mass spectrometry detector (GC/MSD). A novel antifungal compound discovery of phenylethyl alcohol (PEA) by T. virens 7b is reported through this study. T. virens 7b also proved to be an active siderophore producer through chrome azurol S (CAS) agar assay. The study demonstrated the possible mechanisms involved and responsible in the successful inhibition of G. boninense.

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

Cyclic Dipeptides from Lactic Acid Bacteria Inhibit the Proliferation of Pathogenic Fungi: Min-Kyu Kwak , Rui Liu , Min-Kyu Kim , Dohyun Moon , Andrew HyoungJin Kim , Sung-Hyun Song , Sa-Ouk Kang; J. Microbiol. 2014;52(1):64-70. Published online January 4, 2014; DOI: https://doi.org/10.1007/s12275-014-3520-7

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55 Citations

Abstract: Lactobacillus plantarum LBP-K10 was identified to be the most potent antifungal strain from Korean traditional fermented vegetables. The culture filtrate of this strain showed remarkable antifungal activity against Ganoderma boninense. Five fractions from the culture filtrate were observed to have an inhibitory effect against G. boninense. Also, the electron ionization and chemical ionization indicated that these compounds might be cyclic dipeptides. Of the five active fractions, two fractions showed the most significant anti-Ganoderma activity, and one of these fractions inhibited the growth of Candida albicans. These compounds were identified to be cis-cyclo(L-Val-L-Pro) and cis-cyclo(L-Phe-L-Pro), as confirmed by X-ray crystallography.

Symbiotic Interaction of Endophytic Bacteria with Arbuscular Mycorrhizal Fungi and Its Antagonistic Effect on Ganoderma boninense: Shamala Sundram , Sariah Meon , Idris Abu Seman , Radziah Othman; J. Microbiol. 2011;49(4):551-557. Published online September 2, 2011; DOI: https://doi.org/10.1007/s12275-011-0489-3

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48 Citations

Abstract: Endophytic bacteria (Pseudomonas aeruginosa UPMP3 and Burkholderia cepacia UPMB3), isolated from within roots of oil palm (Elaeis guineensis Jacq.), were tested for their presymbiotic effects on two arbuscular mycorrhizal fungi, (Glomus intraradices UT126 and Glomus clarum BR152B). These endophytic bacteria were also tested for antagonistic effects on Ganoderma boninense PER 71, a white wood rot fungal pathogen that causes a serious disease in oil palm. Spore germination and hyphal length of each arbuscular mycorrhizal fungal (AMF) pairing with endophytic bacteria was found to be significantly higher than spores plated in the absence of bacteria. Scanning electron microscopy (SEM) showed that the endophytic bacteria were scattered, resting or embedded on the surface hyaline layer or on the degraded walls of AMF spores, possibly feeding on the outer hyaline spore wall. The antagonistic effect of the endophytic bacteria was expressed as severe morphological abnormalities in the hyphal structures of G. boninense PER 71. The effects of the endophytic bacteria on G. boninense PER 71 hyphal structures were observed clearly under SEM. Severe inter-twisting, distortion, lysis and shrivelling of the hyphal structures were observed. This study found that the effect of endophytic bacteria on G. intraradices UT126 and G. clarum BR152B resembled that of a mycorrhiza helper bacteria (MHB) association because the association significantly promoted AMF spore germination and hyphal length. However, the endophytic bacteria were extremely damaging to G. boninense PER 71.

Cloning and Sequence Analysis of a Glyceraldehyde-3-phosphate Dehydrogenase Gene from Ganoderma lucidum: Xu Fei , Ming Wen Zhao , Yu Xiang Li; J. Microbiol. 2006;44(5):515-522.; DOI: https://doi.org/2446 [pii]

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Abstract: A cDNA library of Ganoderma lucidum has been constructed using a Zap Express cloning vector. A glyceraldehyde-3-phosphate dehydrogenase gene (gpd) was isolated from this library by hybridization of the recombinant phage clones with a gpd-specific gene probe generated by PCR. By comparison of the cDNA and the genomic DNA sequences, it was found that the complete nucleotide sequence encodes a putative polypeptide chain of 338 amino acids interrupted by 6 introns. The predicted amino acid sequence of this gene shows a high degree of sequence similarity to the GPD proteins from yeast and filamentous fungi. The promoter region contains a CT-rich stretch, two CAAT boxes, and a consensus TATA box. The possibility of using the gpd promoter in the construction of new transformation vectors is discussed.

Enhanced Production of Exopolysaccharides by Fed-batch Culture of Ganoderma resinaceum DG-6556: Hyun Mi Kim , Soon-Young Paik , Kyung Soo Ra , Kwang Bon Koo , Jong Won Yun , Jang Won Choi; J. Microbiol. 2006;44(2):233-242.; DOI: https://doi.org/2360 [pii]

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Abstract: The objectives of this study were to optimize submerged culture conditions of a new fungal isolate, Ganorderma resinaceum, and to enhance the production of bioactive mycelial biomass and exopolysaccharides (EPS) by fed-batch culture. The maximum mycelial growth and EPS production in batch culture were achieved in a medium containing 10 g/l glucose, 8 g/l soy peptone, and 5 mM MnCl2 at an initial pH 6.0 and temperature 31°C. After optimization of culture medium and environmental conditions in batch cultures, a fed-batch culture strategy was employed to enhance production of mycelial biomass and EPS. Five different EPS with molecular weights ranging from 53,000 to 5,257,000 g/mole were obtained from either top or bottom fractions of ethanol precipitate of culture filtrate. A fed-batch culture of G. resinaceum led to enhanced production of both mycelial biomass and EPS. The maximum concentrations of mycelial biomass (42.2 g/l) and EPS (4.6 g/l) were obtained when 50 g/l of glucose was fed at day 6 into an initial 10 g/l of glucose medium. It may be worth attempting with other mushroom fermentation processes for enhanced production of mushroom polysaccharides, particularly those with industrial potential.

Identification of Medicinal Mushroom Species Based on Nuclear Large Subunit rDNA Sequences: Ji Seon Lee , Mi Ok Lim , Kyoung Yeh Cho , Jung Hee Cho , Seung Yeup Chang , Doo Hyun Nam; J. Microbiol. 2006;44(1):29-34.; DOI: https://doi.org/2340 [pii]

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Abstract: The purpose of this study was to develop molecular identification method for medical mushrooms and their preparations based on the nucleotide sequences of nuclear large subunit (LSU) rDNA. Four specimens were collected of each of the three representative medicinal mushrooms used in Korea: Ganoderma lucidum, Coriolus versicolor, and Fomes fomentarius. Fungal material used in these experiments included two different mycelial cultures and two different fruiting bodies from wild or cultivated mushrooms. The genomic DNA of mushrooms were extracted and 3 nuclear LSU rDNA fragments were amplified: set 1 for the 1.1-kb DNA fragment in the upstream region, set 2 for the 1.2-kb fragment in the middle, and set 3 for the 1.3-kb fragment downstream. The amplified gene products of nuclear large subunit rDNA from 3 different mushrooms were cloned into E. coli vector and subjected to nucleotide sequence determination. The sequence thus determined revealed that the gene sequences of the same medicinal mushroom species were more than 99.48% homologous, and the consensus sequences of 3 different medicinal mushrooms were more than 97.80% homologous. Restriction analysis revealed no useful restriction sites for 6-bp recognition enzymes for distinguishing the 3 sequences from one another, but some distinctive restriction patterns were recognized by the 4-bp recognition enzymes AccII and HhaI. This analysis was also confirmed by PCR-RFLP experiments on medicinal mushrooms.

Journal Article

Isolation and Characterization of a-Glucosidase Inhibitor from the Fungus Ganoderma lucidum: Shin-Duk Kim , Hong Joon Nho; J. Microbiol. 2004;42(3):223-227.; DOI: https://doi.org/2085 [pii]

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Abstract: An [alpha]-glucosidase inhibitor, SKG-3, was isolated from the fruiting bodies of Ganoderma lucidum and its physico-chemical properties were characterized. It was a highly specific and effective reversible inhibitor of [alpha]-glucosidase. It showed very potent inhibitory activity against [alpha]-glucosidase with an IC_50 value of 4.6 mg/ml, but no activity for any other glycosidases tested. Enzyme activity could be recovered upon dialysis, thus providing evidence for the reversibility of the inhibition. A Lineweaver-Burk plot indicated that the SKG-3 inhibition of [alpha]-glucosidase was competitive.

Phylogenetic relationship of ganoderma species with the polyporaceae base don RFLP analysis of the nuclear ITS region: Park, Hong Je , Shin, Kee Sun , Yoon, Cheol Sik , Lee, Dong Hun , Bae, Kyung Sook; J. Microbiol. 1996;34(2):117-123.

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Abstract: Restriction-polymorphic patterns of nuclear-ITS were examined for the genetic relationships among 12 bisidiomycetous mushrooms to Aphyllophorales and Agaricales. The taxonomic affinity of Ganoderma species with the family Polyporaceae also was examined. With 13 restriction endonucleases, 159 restriction characters were generated form the 12 species examined. UPGMA and neighbor-joining analyses separated the 12 species into two genetically distinct groups that correspond to orders (Agaricales and Aphyllophorales) where each species is included. This result indicates that there is clear genetic demarcation between Agaricales and Aphyllophorales. Dendrograms constructed by several data analyses showed that even though Ganoderma species are somewhat in intermediate taxonomic position between the Polyporaceae and families of the Agaricales, they are genetically more related to the Polyporaceae. These results are consistent with morphological characters observed in those mushrooms. However, it is premature to conclude taxonomic status Ganoderma species in the present study employing small sample size.

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