Journal of Microbiology

Journal Articles

Fleagrass (Adenosma buchneroides Bonati) Acts as a Fungicide Against Candida albicans by Damaging Its Cell Wall.: Youwei Wu, Hongxia Zhang, Hongjie Chen, Zhizhi Du, Qin Li, Ruirui Wang; J. Microbiol. 2024;62(8):661-670. Published online July 3, 2024; DOI: https://doi.org/10.1007/s12275-024-00146-9

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Abstract: Fleagrass, a herb known for its pleasant aroma, is widely used as a mosquito repellent, antibacterial agent, and for treating colds, reducing swelling, and alleviating pain. The antifungal effects of the essential oils of fleagrass and carvacrol against Candida albicans were investigated by evaluating the growth and the mycelial and biofilm development of C. albicans. Transmission electron microscopy was used to evaluate the integrity of the cell membrane and cell wall of C. albicans. Fleagrass exhibited high fungicidal activity against C. albicans at concentrations of 0.5% v/v (via the Ras1/cAMP/PKA pathway). Furthermore, transmission electron microscopy revealed damage to the cell wall and membrane after treatment with the essential oil, which was further confirmed by the increased levels of β-1,3-glucan and chitin in the cell wall. This study showed that fleagrass exerts good fungicidal and hyphal growth inhibition activity against C. albicans by disrupting its cell wall, and thus, fleagrass may be a potential antifungal drug.

Licochalcone A Protects Vaginal Epithelial Cells Against Candida albicans Infection Via the TLR4/NF-κB Signaling Pathway.: Wei Li, Yujun Yin, Taoqiong Li, Yiqun Wang, Wenyin Shi; J. Microbiol. 2024;62(7):525-533. Published online May 31, 2024; DOI: https://doi.org/10.1007/s12275-024-00134-z

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Abstract: Vulvovaginal candidiasis (VVC) is a prevalent condition affecting a significant portion of women worldwide. Licochalcone A (LA), a natural compound with diverse biological activities, holds promise as a protective agent against Candida albicans (C. albicans) infection. This study aims to investigate the potential of LA to safeguard vaginal epithelial cells (VECs) from C. albicans infection and elucidate the underlying molecular mechanisms. To simulate VVC in vitro, VK2-E6E7 cells were infected with C. albicans. Candida albicans biofilm formation, C. albicans adhesion to VK2-E6E7 cells, and C. albicans-induced cell damage and inflammatory responses were assessed by XTT reduction assay, fluorescence assay, LDH assay, and ELISA. CCK-8 assay was performed to evaluate the cytotoxic effects of LA on VK2-E6E7 cells. Western blotting assay was performed to detect protein expression. LA dose-dependently hindered C. albicans biofilm formation and adhesion to VK2-E6E7 cells. Furthermore, LA mitigated cell damage, inhibited the Bax/Bcl-2 ratio, and attenuated the secretion of pro-inflammatory cytokines in C. albicans-induced VK2-E6E7 cells. The investigation into LA's impact on the Toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) pathway revealed that LA downregulated TLR4 expression and inhibited NF-κB activation in C. albicans-infected VK2-E6E7 cells. Furthermore, TLR4 overexpression partially abated LA-mediated protection, further highlighting the role of the TLR4/NF-κB pathway. LA holds the potential to safeguard VECs against C. albicans infection, potentially offering therapeutic avenues for VVC management.

Those Nematode‑Trapping Fungi That are not Everywhere: Hints Towards Soil Microbial Biogeography: Wei Deng , Fa Zhang , Davide Fornacca , Xiao-Yan Yang , Wen Xiao; J. Microbiol. 2023;61(5):511-523. Published online April 6, 2023; DOI: https://doi.org/10.1007/s12275-023-00043-7

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2 Citations

Abstract: The existence of biogeography for microorganisms is a raising topic in ecology and researchers are employing better distinctions between single species, including the most rare ones, to reveal potential hidden patterns. An important volume of evidence supporting heterogeneous distributions for bacteria, archaea and protists is accumulating, and more recently a few efforts have targeted microscopic fungi. We propose an insight into this latter kingdom by looking at a group of soil nematode-trapping fungi whose species are well-known and easily recognizable. We chose a pure culture approach because of its reliable isolation procedures for this specific group. After morphologically and molecularly identifying all species collected from 2250 samples distributed in 228 locations across Yunnan province of China, we analyzed occurrence frequencies and mapped species, genera, and richness. Results showed an apparent cosmopolitan tendency for this group of fungi, including species richness among sites. However, only four species were widespread across the region, while nonrandom heterogeneous distributions were observed for the remaining 40 species, both in terms of statistical distribution of species richness reflected by a significant variance-to-mean ratio, as well as in terms of visually discernible spatial clusters of rare species and genera on the map. Moreover, several species were restricted to only one location, raising the question of whether endemicity exists for this microbial group. Finally, environmental heterogeneity showed a marginal contribution in explaining restricted distributions, suggesting that other factors such as geographical isolation and dispersal capabilities should be explored. These findings contribute to our understanding of the cryptic geographic distribution of microorganisms and encourage further research in this direction.

Microbial co-occurrence network in the rhizosphere microbiome: its association with physicochemical properties and soybean yield at a regional scale: Sarbjeet Niraula , Meaghan Rose , Woo-Suk Chang; J. Microbiol. 2022;60(10):986-997. Published online September 27, 2022; DOI: https://doi.org/10.1007/s12275-022-2363-x

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5 Citations

Abstract: Microbial communities in the rhizosphere play a crucial role in determining plant growth and crop yield. A few studies have been performed to evaluate the diversity and co-occurrence patterns of rhizosphere microbiomes in soybean (Glycine max) at a regional scale. Here, we used a culture-independent
method
to compare the bacterial communities of the soybean rhizosphere between Nebraska (NE), a high-yield state, and Oklahoma (OK), a low-yield state. It is well known that the rhizosphere microbiome is a subset of microbes that ultimately get colonized by microbial communities from the surrounding bulk soil. Therefore, we hypothesized that differences in the soybean yield are attributed to the variations in the rhizosphere microbes at taxonomic, functional, and community levels. In addition, soil physicochemical properties were also evaluated from each sampling site for comparative study. Our result showed that distinct clusters were formed between NE and OK in terms of their soil physicochemical property. Among 3 primary nutrients (i.e., nitrogen, phosphorus, and potassium), potassium is more positively correlated with the high-yield state NE samples. We also attempted to identify keystone communities that significantly affected the soybean yield using co-occurrence network patterns. Network analysis revealed that communities formed distinct clusters in which members of modules having significantly positive correlations with the soybean yield were more abundant in NE than OK. In addition, we identified the most influential bacteria for the soybean yield in the identified modules. For instance, included are class Anaerolineae, family Micromonosporaceae, genus Plantomyces, and genus Nitrospira in the most complex module (ME9) and genus Rhizobium in ME23. This research would help to further identify a way to increase soybean yield in low-yield states in the U.S. as well as worldwide by reconstructing the microbial communities in the rhizosphere.

Complete gammaproteobacterial endosymbiont genome assembly from a seep tubeworm Lamellibrachia satsuma: Ajit Kumar Patra , Yong min Kwon , Youngik Yang; J. Microbiol. 2022;60(9):916-927. Published online August 1, 2022; DOI: https://doi.org/10.1007/s12275-022-2057-4

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1 Citations

Abstract: Siboglinid tubeworms thrive in hydrothermal vent and seep habitats via a symbiotic relationship with chemosynthetic bacteria. Difficulties in culturing tubeworms and their symbionts in a laboratory setting have hindered the study of host-microbe interactions. Therefore, released symbiont genomes are fragmented, thereby limiting the data available on the genome that affect subsequent analyses. Here, we present a complete genome of gammaproteobacterial endosymbiont from the tubeworm Lamellibrachia satsuma collected from a seep in Kagoshima Bay, assembled using a hybrid approach that combines sequences generated from the Illumina and Oxford Nanopore platforms. The genome consists of a single circular chromosome with an assembly size of 4,323,754 bp and a GC content of 53.9% with 3,624 protein-coding genes. The genome is of high quality and contains no assembly gaps, while the completeness and contamination are 99.33% and 2.73%, respectively. Comparative genome analysis revealed a total of 1,724 gene clusters shared in the vent and seep tubeworm symbionts, while 294 genes were found exclusively in L. satsuma symbionts such as transposons, genes for defense mechanisms, and inorganic ion transportations. The addition of this complete endosymbiont genome assembly would be valuable for comparative studies particularly with tubeworm symbiont genomes as well as with other chemosynthetic microbial communities.

Effect of biostimulation and bioaugmentation on hydrocarbon degradation and detoxification of diesel-contaminated soil: a microcosm study: Patricia Giovanella , Lídia de Azevedo Duarte , Daniela Mayumi Kita , Valéria Maia de Oliveira , Lara Durães Sette; J. Microbiol. 2021;59(7):634-643. Published online May 15, 2021; DOI: https://doi.org/10.1007/s12275-021-0395-2

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7 Citations

Abstract: Soil contamination with diesel oil is quite common during processes of transport and storage. Bioremediation is considered a safe, economical, and environmentally friendly approach for contaminated soil treatment. In this context, studies using hydrocarbon bioremediation have focused on total petroleum hydrocarbon (TPH) analysis to assess process effectiveness, while ecotoxicity has been neglected. Thus, this study aimed to select a microbial consortium capable of detoxifying diesel oil and apply this consortium to the bioremediation of soil contaminated with this environmental pollutant through different bioremediation approaches. Gas chromatography (GC-FID) was used to analyze diesel oil degradation, while ecotoxicological bioassays with the bioindicators Artemia sp., Aliivibrio fischeri (Microtox), and Cucumis sativus were used to assess detoxification. After 90 days of bioremediation, we found that the biostimulation and biostimulation/ bioaugmentation approaches showed higher rates of diesel oil degradation in relation to natural attenuation (41.9 and 26.7%, respectively). Phytotoxicity increased in the biostimulation and biostimulation/bioaugmentation treatments during the degradation process, whereas in the Microtox test, the toxicity was the same in these treatments as that in the natural attenuation treatment. In both the phytotoxicity and Microtox tests, bioaugmentation treatment showed lower toxicity. However, compared with natural attenuation, this approach did not show satisfactory hydrocarbon degradation. Based on the microcosm experiments results, we conclude that a broader analysis of the success of bioremediation requires the performance of toxicity bioassays.

Review

Microbial source tracking using metagenomics and other new technologies: Shahbaz Raza , Jungman Kim , Michael J. Sadowsky , Tatsuya Unno; J. Microbiol. 2021;59(3):259-269. Published online February 10, 2021; DOI: https://doi.org/10.1007/s12275-021-0668-9

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9 Citations

Abstract: The environment is under siege from a variety of pollution sources. Fecal pollution is especially harmful as it disperses pathogenic bacteria into waterways. Unraveling origins of mixed sources of fecal bacteria is difficult and microbial source tracking (MST) in complex environments is still a daunting task. Despite the challenges, the need for answers far outweighs the difficulties experienced. Advancements in qPCR and next generation sequencing (NGS) technologies have shifted the traditional culture-based MST approaches towards culture independent technologies, where communitybased MST is becoming a method of choice. Metagenomic tools may be useful to overcome some of the limitations of community-based MST methods as they can give deep insight into identifying host specific fecal markers and their association with different environments. Adoption of machine learning (ML) algorithms, along with the metagenomic based MST approaches, will also provide a statistically robust and automated platform. To compliment that, ML-based approaches provide accurate optimization of resources. With the successful application of ML based models in disease prediction, outbreak investigation and medicine prescription, it would be possible that these methods would serve as a better surrogate of traditional MST approaches in future.

Journal Article

Genetic linkage map construction and quantitative trait loci mapping of agronomic traits in Gloeostereum incarnatum: Wan-Zhu Jiang , Fang-Jie Yao , Li-Xin Lu , Ming Fang , Peng Wang , You-Min Zhang , Jing-Jing Meng , Jia Lu , Xiao-Xu Ma , Qi He , Kai-Sheng Shao; J. Microbiol. 2021;59(1):41-50. Published online November 17, 2020; DOI: https://doi.org/10.1007/s12275-021-0242-5

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7 Citations

Abstract: Gloeostereum incarnatum is an edible medicinal mushroom widely grown in China. Using the whole genome of G. incarnatum, simple sequence repeat (SSR) markers were developed and synthetic primers were designed to construct its first genetic linkage map. The 1,048.6 cm map is composed of 10 linkage groups and contains 183 SSR markers. In total, 112 genome assembly sequences were anchored, representing 16.43 Mb and covering 46.41% of the genome. Selfing populations were used for quantitative trait loci (QTL) targeting, and the composite interval mapping method was used to co-localize the mycelium growth rate (potato dextrose agar and sawdust), growth period, yield and fruiting body length, and width and thickness. The 14 QTLs of agronomic traits had LOD values of 3.20–6.51 and contribution rates of 2.22– 13.18%. No linkage relationship was found between the mycelium growth rate and the growth period, but a linkage relationship was observed among the length, width and thickness of the fruiting bodies. Using NCBI’s BLAST alignment, the genomic sequences corresponding to the QTL regions were compared, and a TPR-like protein candidate gene was selected. Using whole-genome data, 138 candidate genes were found in four sequence fragments of two SSR markers located in the same scaffold. The genetic map and QTLs established in this study will aid in developing selective markers for agronomic traits and identifying corresponding genes, thereby providing a scientific basis for the further gene mapping of quantitative traits and the marker-assisted selection of functional genes in G. incarnatum breeding programs.

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