Journal of Microbiology

Journal Article

Metformin Regulates Gut Microbiota Abundance to Suppress M2 Skewing of Macrophages and Colorectal Tumorigenesis in Mice: Linfeng Fan , Xiangfu Zeng , Guofeng Xu; J. Microbiol. 2023;61(1):109-120. Published online January 26, 2023; DOI: https://doi.org/10.1007/s12275-022-00010-8

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Abstract: The correlation of imbalanced gut microbiota with the onset and progression of colorectal cancer (CRC) has become clear. This work investigates the effect of metformin on gut microbiota and genesis of CRC in mice. Human fecal samples were collected from healthy control (HC) donors and CRC patients. Compared to HC donors, CRC patients had reduced abundance of gut microbiota; however, they had increased abundance of detrimental Bacteroidetes. Mice were injected with azomethane (AOM) to induce colorectal tumorigenesis models. Treatment of CRC patients-sourced fecal microbiota promoted tumorigenesis, and it increased the expression of Ki67, β-catenin, COX-2, and Cyclin D1 in mouse colon tissues. Further treatment of metformin blocked the colorectal tumorigenesis in mice. Fecal microbiota from the metformin-treated mice was collected, which showed decreased Bacteroidetes abundance and suppressed AOM-induced colorectal tumorigenesis in mice as well. Moreover, the metformin- modified microbiota promoted the M1 macrophage-related markers IL-6 and iNOS but suppressed the M2 macrophage-related markers IL-4R and Arg1 in mouse colon tissues. In conclusion, this study suggests that metformin-mediated gut microbiota alteration suppresses macrophage M2 polarization to block colorectal tumorigenesis.

Review

MINIREVIEW] Fungi in salterns: Dawoon Chung† , Haryun Kim† , Hyun Seok Choi; J. Microbiol. 2019;57(9):717-724. Published online August 27, 2019; DOI: https://doi.org/10.1007/s12275-019-9195-3

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53 Citations

Abstract: Salterns are hypersaline extreme environments with unique physicochemical properties such as a salinity gradient. Although the investigation of microbiota in salterns has focused on archaea and bacteria, diverse fungi also thrive in the brine and soil of salterns. Fungi isolated from salterns are represented by black yeasts (Hortaea werneckii, Phaeotheca triangularis, Aureobasidium pullulans, and Trimmatostroma salinum), Cladosporium, Aspergillus, and Penicillium species. Most studies on saltern-derived fungi gave attention to black yeasts and their physiological characteristics, including growth under various culture conditions. Since then, biochemical and molecular tools have been employed to explore adaptation of these fungi to salt stress. Genome databases of several fungi in salterns are now publicly available and being used to elucidate salt tolerance mechanisms and discover the target genes for agricultural and industrial applications. Notably, the number of enzymes and novel metabolites known to be produced by diverse saltern-derived fungi has increased significantly. Therefore, fungi in salterns are not only interesting and important subjects to study fungal biodiversity and adaptive mechanisms in extreme environments, but also valuable bioresources with potential for biotechnological applications.

Journal Article

Growth of cyanobacterial soil crusts during diurnal freeze-thaw cycles: Steven K. Schmidt , Lara Vimercati; J. Microbiol. 2019;57(4):243-251. Published online February 5, 2019; DOI: https://doi.org/10.1007/s12275-019-8359-5

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16 Citations

Abstract: Various Nostoc spp. and related cyanobacteria are able to survive extreme temperatures and are among the most successful colonists of high-elevation sites being exposed due to glacial retreat. It is unclear, however, if cyanobacteria can grow during the extreme freeze-thaw cycles that occur on a yearround basis at high-elevation, peri-glacial sites or if they only grow during the rare periods when freeze-thaw cycles do not occur. We conducted several experiments to determine if cyanobacteria that form biological soil crusts (BSCs) at highelevation sites (> 5,000 m.a.s.l.) in the Andes can grow during diurnal freeze-thaw cycles on a par with those that occur in the field. Here we show that a soil crust that had been frozen at -20°C for five years was able to increase from 40% to 100% soil coverage during a 45-day incubation during which the soil temperature cycled between -12°C and 26°C every day. In a second, experiment an undeveloped soil with no visible BSCs showed a statistically significant shift in the bacterial community from one containing few cyanobacterial sequences (8% of sequences) to one dominated (27%) by Nostoc, Microcoleus, and Leptolyngbya phylotypes during a 77-day incubation with daily freeze-thaw cycles. In addition, counts of spherical Nostoc-like colonies increased significantly on the soil surface during the experiment, especially in microcosms receiving phosphorus. Taken together these results show that freeze-thaw cycles alone do not limit the growth of BSCs in high-elevation soils, and provide new insight into how life is able to thrive in one of the most extreme terrestrial environments on Earth.

Review

REVIEW] The development of fluconazole resistance in Candida albicans – an example of microevolution of a fungal pathogen: Joachim Morschhäuser; J. Microbiol. 2016;54(3):192-201. Published online February 27, 2016; DOI: https://doi.org/10.1007/s12275-016-5628-4

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94 Citations

Abstract: The yeast Candida albicans is a member of the microbiota in the gastrointestinal and urogenital tracts of most healthy persons, but it can also cause symptomatic infections, especially in immunocompromised patients. During the life-long association with its human host, C. albicans generates genetically altered variants that are better adapted to changes in their environment. A prime example of this microevolution is the development of resistance to the commonly used drug fluconazole, which inhibits ergosterol biosynthesis, during antimycotic therapy. Fluconazole resistance can be caused by mutations in the drug target, by changes in the sterol biosynthesis pathway, and by gain-of-function mutations in transcription factors that result in the constitutive upregulation of ergosterol biosynthesis genes and multidrug efflux pumps. Fluconazole also induces genomic rearrangements that result in gene amplification and loss of heterozygosity for resistance mutations, which further increases drug resistance. These genome alterations may affect extended chromosomal regions and have additional phenotypic consequences. A striking case is the loss of heterozygosity for the mating type locus MTL in many fluconazole-resistant clinical isolates, which allows the cells to switch to the mating-competent opaque phenotype. This, in turn, raises the possibility that sexual recombination between different variants of an originally clonal, drug-susceptible population may contribute to the generation of highly fluconazole-resistant strains with multiple resistance mechanisms. The gain-of-function mutations in transcription factors, which result in deregulated gene expression, also cause reduced fitness. In spite of this, many clinical isolates that contain such mutations do not exhibit fitness defects, indicating that they have overcome the costs of drug resistance with further evolution by still unknown mechanisms.

Research Support, U.S. Gov't, Non-P.H.S.

Description of Pseudomonas asuensis sp. nov. from biological soil crusts in the Colorado plateau, United States of America: Gundlapally Sathyanarayana Reddy , # , Ferran Garcia-Pichel; J. Microbiol. 2015;53(1):6-13. Published online January 4, 2015; DOI: https://doi.org/10.1007/s12275-015-4462-4

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9 Citations

Abstract: A Gram-negative, aerobic, non spore-forming, non-motile, rod-shaped, yellow pigmented bacterium CP155-2T was isolated from a biological soil crusts sample collected in the Colorado plateau, USA and subjected to polyphasic taxonomic characterization. Strain CP155-2T contained summed feature 3 (C16:1ω5c/C16:1ω7c) and C18:1ω7c as major fatty acids and diphosphatidylglycerol (DPG) along with phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) as major polar lipids. Based on these characteristics CP155-2T was assigned to the genus Pseudomonas. Phylogenetic analysis based on 16S rRNA gene sequence further confirmed the affiliation of CP155-2T to the genus Pseudomonas and showed a 16S rRNA gene sequence similarity of less than 98.7% with already described species of the genus. Pseudomonas luteola, Pseudomonas zeshuii, and Pseudomonas duriflava were identified as the closest species of the genus Pseudomonas with 16S rRNA gene sequence similarities of 98.7%, 98.6%, and 96.9%, respectively. The values for DNA–DNA relatedness between CP155-2T and Pseudomonas luteola and Pseudomonas zeshuii were 23% and 14% respectively a value below the 70% threshold value, indicating that strain CP155-2T belongs to a novel taxon of the genus Pseudomonas lineage. The novel taxon status was strengthened by a number of phenotypic differences wherein CP155-2T was positive for oxidase, negative for gelatin hydrolysis, could utilize D-cellobiose, D-raffinose, L-rhamnose, D-sorbitol but not L-aspartic acid and L-glutamic acid. Based on the collective differences strain CP155-2T exhibited, it was identified as a novel species and the name Pseudomonas asuensis sp. nov. was proposed. The type strain of Pseudomonas asuensis sp. nov. is CP155- 2T (DSM 17866T =ATCC BAA-1264T =JCM13501T =KCTC 32484T).

Journal Articles

Note] Antifungal Chitinase against Human Pathogenic Yeasts from Coprinellus congregatus: Yeeun Yoo Hyoung T. Choi; J. Microbiol. 2014;52(5):441-443. Published online February 17, 2014; DOI: https://doi.org/10.1007/s12275-014-3257-3

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Abstract: The inky cap, Coprinellus congregatus, produces mushrooms which become autolyzed rapidly to generate black liquid droplets, in which no cell wall is detected by microscopy. A chitinase (Chi2) which is synthesized during the autolytic phase of C. congregatus inhibits the growths of Candida al-bicans and Cryptococcus neoformans up to 10% at the con-centration of 10 μg/ml, about 50% at concentration of 20 μg/ml, and up to 95% at the concentration of 70 μg/ml. Upon treatment these yeast cells are observed to be severely de-formed, with the formation of large holes in the cell wall. The two yeast species show no growth inhibition at the concen-tration of 5 μg/ml, which means the minimum inhibitory concentrations for both yeast species are 10 μg/ml under these experimental conditions.

Evaluation of Antibacterial Activity against Salmonella Enteritidis: Gaëlle Legendre , Fabienne Faÿ , Isabelle Linossier , Karine Vallée-Réhel; J. Microbiol. 2011;49(3):349-354. Published online June 30, 2011; DOI: https://doi.org/10.1007/s12275-011-0162-x

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Abstract: Salmonella enterica serovar Enteritidis is a well-known pathogenic bacterium responsible for human gastrointestinal enteritis mainly due to the consumption of eggs and egg-products. The first aim of this work was to study several virulence factors of a strain isolated from egg content: SEovo. First, bacterial growth was studied at several temperatures and cell morphology was observed by scanning electronic microscopy. These experiments showed Salmonella’s ability to grow at low temperatures and to produce exoproducts. Next, Salmonella motility was observed performing swimming, twitching, and swarming tests. Results indicated a positive flagellar activity and the cell ability to differentiate and become hyperflagellated under specific conditions. Moreover, SEovo adherence and biofilm formation was carried out. All of these tests enabled us to conclude that SEovo is a potential pathogen, thus it can be used as a model to perform antibacterial experiments. The second part of the study was dedicated to the evaluation of the antibacterial activity of different molecules using several methods. The antibacterial effect of silver and copper aluminosilicates was tested by two different kinds of methods. On the one hand, the effect of these two antibacterial agents was determined using microbiological methods: viable cell count and agar-well diffusion. And on the other hand, the antibacterial activity was evaluated using CLSM and SYTO Red/SYTOX Green dyeing. CLSM allowed for the evaluation of the biocide on sessile cells, whereas the first methods did not. Results showed that adhered bacteria were more resistant than planktonic counterparts and that CLSM was a good alternative to evaluate antibacterial activity on fixed bacteria without having to carry out a removing step.

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

Multilocus Sequence Typing and Virulence Factors Analysis of Escherichia coli O157 Strains in China: Xiao W. Ji , Ya L. Liao , Ye F. Zhu , Hai G. Wang , Ling Gu , Jiang Gu , Chen Dong , Hong L. Ding , Xu H. Mao , Feng C. Zhu , Quan M. Zou; J. Microbiol. 2010;48(6):849-855. Published online January 9, 2011; DOI: https://doi.org/10.1007/s12275-010-0132-8

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Abstract: Escherichia coli O157:H7, an important food-borne pathogen, has become a major public health concern worldwide. The aim of this study was to investigate the molecular epidemiologic feature of E. coli O157:H7 strains in China. 105 E. coli O157:H7 isolates were collected from various hosts and places over 9 years. A multilocus sequence typing scheme (MLST) was applied for bacteria genotyping and polymerase chain reaction (PCR) was used for virulence factor identification. Seven new MLST sequence types (STs), namely ST836, ST837, ST838, ST839, ST840, ST841, and ST842 were identified, which grouped into two lineages. Phylogenetic analysis suggested that the most two frequent STs in China, ST837 and ST836, may be the derivatives of E. coli O157:H7 Sakai or E. coli O157:H7 EDL933. Geographical diversity and host variety of E. coli O157:H7 were observed in China. In addition, the different distribution of tccp was detected. The data presented herein provide new insights into the molecular epidemiologic feature of E. coli O157:H7, and aid in the investigation of the transmission regularity and evolutionary mechanism of E. coli O157:H7.

Analysis of Expressed Sequence Tags from the Red Alga Griffithsia okiensis: Hyoungseok Lee , Hong Kum Lee , Gynheung An , Yoo Kyung Lee; J. Microbiol. 2007;45(6):541-546.; DOI: https://doi.org/2611 [pii]

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Abstract: Red algae are distributed globally, and the group contains several commercially important species. Griffithsia okiensis is one of the most extensively studied red algal species. In this study, we conducted expressed sequence tag (ESTs) analysis and synonymous codon usage analysis using cultured G. okiensis samples. A total of 1,104 cDNA clones were sequenced using a cDNA library made from samples collected from Dolsan Island, on the southern coast of Korea. The clustering analysis of these sequences allowed for the identification of 1,048 unigene clusters consisting of 36 consensus and 1,012 singleton sequences. BLASTX searches generated 532 significant hits (E-value <10-4) and via further Gene Ontology analysis, we constructed a functional classification of 434 unigenes. Our codon usage analysis showed that unigene clusters with more than three ESTs had higher GC contents (76.5%) at the third position of the codons than the singletons. Also, the majority of the optimal codons of G. okiensis and Chondrus crispus belonging to Bangiophycidae were C-ending, whereas those of Porphyra yezoensis belonging to Florideophycidae were G-ending. An orthologous gene search for the P. yezoensis EST database resulted in the identification of 39 unigenes commonly expressed in two rhodophytes, which have putative functions for structural proteins, protein degradation, signal transduction, stress response, and physiological processes. Although experiments have been conducted on a limited scale, this study provides a material basis for the development of microarrays useful for gene expression studies, as well as useful information for the comparative genomic analysis of red algae.

Diversity of Yeasts Associated with Natural Environments in Korea: Soon Gyu Hong , Kang Hyun Lee , Kyung Sook Bae; J. Microbiol. 2002;40(1):55-62.

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Abstract: Biodiversity of yeasts in various natural environments including soils, swamps and plants was investigated. By molecular identification methods based on the partial sequences of 26S rDNA, 69 isolates were assigned to 44 taxa including 27 known species. The remaining 17 taxa could potentially form new species. All of them were classified into Ascomycota, Hymenomycetes, Urediniomycetes and Ustilaginomycetes. Ascomycetous and ustilaginomycetous yeasts were generally isolated from flower samples, and hymenomycetous and urediniomycetous yeasts were generally isolated from soil samples. Distribution of yeast groups exhibited geographical variation. Yeast biodiversity of root soil also varied according to the associated plant species.

Laboratory Diagnosis of Invasive Candidiasis: Arjuna N.B. Ellepola , Christine J. Morrison; J. Microbiol. 2005;43(1):65-84.

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Abstract: Invasive candidiasis is associated with high morbidity and mortality. Clinical diagnosis is complicated by a lack of specific clinical signs and symptoms of disease. Laboratory diagnosis is also complex because circulating antibodies to Candida species may occur in normal individuals as the result of commensal colonization of mucosal surfaces thereby reducing the usefulness of antibody detection for the diagnosis of this disease. In addition, Candida species antigens are often rapidly cleared from the circulation so that antigen detection tests often lack the desired level of sensitivity. Microbiological confirmation is difficult because blood cultures can be negative in up to 50% of autopsy-proven cases of deep-seated candidiasis or may only become positive late in the infection. Positive cultures from urine or mucosal surfaces do not necessarily indicate invasive disease although can occur during systemic infection. Furthermore, differences in the virulence and in the susceptibility of the various Candida species to antifungal drugs make identification to the species level important for clinical management. Newer molecular biological tests have generated interest but are not yet standardized or readily available in most clinical laboratory settings nor have they been validated in large clinical trials. Laboratory surveillance of at-risk patients could result in earlier initiation of antifungal therapy if sensitive and specific diagnostic tests, which are also cost effective, become available. This review will compare diagnostic tests currently in use as well as those under development by describing their assets and limitations for the diagnosis of invasive candidiasis. <br><br><br>

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