Journal of Microbiology

Journal Article

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).

Editorial

Editorial] Bacterial Regulatory Mechanisms for the Control of Cellular Processes: Simple Organisms’ Complex Regulation: Jin-Won Lee; J. Microbiol. 2023;61(3):273-276. Published online April 3, 2023; DOI: https://doi.org/10.1007/s12275-023-00036-6

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Abstract: Bacteria employ a diverse array of cellular regulatory mechanisms to successfully adapt and thrive in ever-changing environments, including but not limited to temperature changes, fluctuations in nutrient availability, the presence or absence of electron acceptors such as oxygen, the availability of metal ions crucial for enzyme activity, and the existence of antibiotics. Bacteria can virtually modulate any step of gene expression from transcr!ptional initiation to posttranslational modification of a protein for the control of cellular processes. Furthermore, one gene regulator often controls another in a complex gene regulatory network. Thus, it is not easy to fully understand the intricacies of bacterial regulatory mechanisms in various environments. In this special issue, while acknowledging the challenge of covering all aspects of bacterial regulatory mechanisms across diverse environments, seven review articles are included to provide insight into the recent progress in understanding such mechanisms from different perspectives: positive regulatory mechanisms by secondary messenger (cAMP receptor protein), two-component signal transduction mechanisms (Rcs and Cpx), diverse regulatory mechanisms by a specific environmental factor in specific bacteria (oxygen availability in Mycobacterium and manganese ion availability in Salmonella), diverse regulatory mechanisms by a specific environmental factor (temperature and antibiotics), and regulatory mechanisms by antibiotics in cell wall synthesis. Bacteria, as ubiquitous organisms that can be found in almost every environment, carry out complex cellular processes that allow them to survive and thrive in a variety of different conditions despite their small size and relative simplicity. One of the key factors that allows bacteria to carry out these complex processes is their ability to regulate gene expression through various mechanisms. Gene expression is a fundamental biological process by which the genetic information encoded in a gene is transcribed into an RNA molecule and subsequently translated into a functional gene product, often a protein. Furthermore, the activity levels of proteins may further be altered by posttranslational modification. Regulation of gene expression refers to the control of the amount and timing of gene expression, and thus it can be divided into transcr!ptional, translational, and posttranslational levels.

Journal Articles

Construction of high-density transposon mutant library of Staphylococcus aureus using bacteriophage ϕ11: Wonsik Lee; J. Microbiol. 2022;60(12):1123-1129. Published online November 24, 2022; DOI: https://doi.org/10.1007/s12275-022-2476-2

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Abstract: Transposon mutant libraries are an important resource to study bacterial metabolism and pathogenesis. The fitness analysis of mutants in the libraries under various growth conditions provides important clues to study the physiology and biogenesis of structural components of a bacterial cell. A transposon library in conjunction with next-generation sequencing techniques, collectively named transposon sequencing (Tnseq), enables high-throughput genome profiling and synthetic lethality analysis. Tn-seq has also been used to identify essential genes and to study the mode of action of antibacterials. To construct a high-density transposon mutant library, an efficient delivery system for transposition in a model bacterium is essential. Here, I describe a detailed protocol for generating a high-density phage-based transposon mutant library in a Staphylococcus aureus strain, and this protocol is readily applicable to other S. aureus strains including USA300 and MW2.

Correlation between fat accumulation and fecal microbiota in crossbred pigs: Xin Li , Mengyu Li , Jinyi Han , Chuang Liu , Xuelei Han , Kejun Wang , Ruimin Qiao , Xiu-Ling Li , Xin-Jian Li; J. Microbiol. 2022;60(11):1077-1085. Published online September 9, 2022; DOI: https://doi.org/10.1007/s12275-022-2218-5

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Abstract: Backfat thickness (BF) is an important indicator of fat deposition capacity and lean meat rate in pigs and is very important in porcine genetics and breeding. Intestinal microbiota plays a key role in nutrient digestion and utilization with a profound impact on fat deposition of livestock animals. To investigate the relationship between the pig gut microbiome and BF, 20 low-BF (L-BF) and 20 high-BF (H-BF) pigs were selected as two groups from Yunong Black pigs in the present study. Fecal samples from pigs were analyzed for microbial diversity, composition, and predicted functionality using 16S rRNA gene sequencing. The results showed that there were significant differences in microbial β diversity between the two groups. LEfSe analysis revealed a number of bacterial features being differentially enriched in either L-BF or H-BF pigs. Spearman correlation analysis identified the abundance of Oscillospira, Peptococcus, and Bulleidia were significantly positive correlations with BF (P < 0.05), while Sutterella and Bifidobacterium were significantly negatively correlated with BF (P < 0.05). Importantly, the bacteria significantly positively correlated with BF mainly belong to Clostridium, which can ferment host-indigestible plant polysaccharides into shortchain fatty acid (SCFA) and promote fat synthesis and deposition. Predictive functional analysis indicated that the pathway abundance of cell motility and glycan biosynthesis were significantly widespread in the microbiota of the H-BF group. The results of this study will be useful for the development of microbial biomarkers for predicting and improving porcine BF, as well as for the investigation of targets for dietary strategies.

The novel antifungal agent AB-22 displays in vitro activity against hyphal growth and biofilm formation in Candida albicans and potency for treating systemic candidiasis: Kyung-Tae Lee , Dong-Gi Lee , Ji Won Choi , Jong-Hyun Park , Ki Duk Park , Jong-Seung Lee , Yong-Sun Bahn; J. Microbiol. 2022;60(4):438-443. Published online March 14, 2022; DOI: https://doi.org/10.1007/s12275-022-2016-0

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Abstract: Systemic candidiasis, which is mainly caused by Candida albicans, is a serious acute fungal infection in the clinical setting. In a previous study, we reported that compound 22h (designated as AB-22 in this study), a vinyl sulfate compound, is a fast-acting fungicidal agent against a broad spectrum of fungal pathogens. In this study, we aimed to further analyze the in vitro and in vivo efficacy of AB-22 against filamentation, biofilm formation, and virulence of C. albicans. Under in vitro hyphal growth-inducing condition, AB-22 effectively inhibited germ tube formation and hyphal growth, which are required for the initiation of biofilm formation. Indeed, AB-22 significantly suppressed C. albicans biofilm formation in a dose-dependent manner. Moreover, AB-22 treatment inhibited the normal induction of ALS3, HWP1, and ECE1, which are all required for hyphal transition in C. albicans. Furthermore, AB-22 treatment increased the survival of mice systemically infected with C. albicans. In conclusion, in addition to its fungicidal activity, AB-22 inhibits filamentation and biofilm formation in C. albicans, which could collectively contribute to its potent in vivo efficacy against systemic candidiasis.

Genetic diversity and population structure of the amylolytic yeast Saccharomycopsis fibuligera associated with Baijiu fermentation in China: Ju-Wei Wang , Pei-Jie Han , Da-Yong Han , Sen Zhou , Kuan Li , Peng-Yu He , Pan Zhen , Hui-Xin Yu , Zhen-Rong Liang , Xue-Wei Wang , Feng-Yan Bai; J. Microbiol. 2021;59(8):753-762. Published online July 5, 2021; DOI: https://doi.org/10.1007/s12275-021-1115-7

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Abstract: The amylolytic yeast Saccharomycopsis fibuligera is a predominant species in starters and the early fermentation stage of Chinese liquor (Baijiu). However, the genetic diversity of the species remains largely unknown. Here we sequenced the genomes of 97 S. fibuligera strains from different Chinese Baijiu companies. The genetic diversity and population structure of the strains were analyzed based on 1,133 orthologous genes and the whole genome single nucleotide polymorphisms (SNPs). Four main lineages were recognized. One lineage contains 60 Chinese strains which are exclusively homozygous with relatively small genome sizes (18.55–18.72 Mb) and low sequence diversity. The strains clustered in the other three lineages are heterozygous with larger genomes (21.85–23.72 Mb) and higher sequence diversity. The genomes of the homozygous strains showed nearly 100% coverage with the genome of the reference strain KPH12 and the sub-genome A of the hybrid strain KJJ81 at the above 98% sequence identity level. The genomes of the heterozygous strains showed nearly 80% coverage with both the sub-genome A and the whole genome of KJJ81, suggesting that the Chinese heterozygous strains are also hybrids with nearly 20% genomes from an unidentified source. Eighty-three genes were found to show significant copy number variation between different lineages. However, remarkable lineage specific variations in glucoamylase and α-amylase activities and growth profiles in different carbon sources and under different environmental conditions were not observed, though strains exhibiting relatively high glucoamylase activity were mainly found from the homozygous lineage.

Isolation of a novel strain, Sphingorhabdus sp. YGSMI21 and characterization of its enantioselective epoxide hydrolase activity: Jung-Hee Woo , Hae-Seon Kim , Nyun-Ho Park , Ho Young Suk; J. Microbiol. 2021;59(7):675-680. Published online June 1, 2021; DOI: https://doi.org/10.1007/s12275-021-1023-x

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Abstract: Sphingorhabdus sp. YGSMI21, a novel microbial strain with an enantioselective epoxide hydrolase activity, was isolated from tidal samples contaminated by accidental oil spills subjected to enriched culture with polycyclic aromatic hydrocarbon. This strain was able to optically decompose (R)-styrene oxide (SO) and showed 100% optical purity. In addition, it showed a good enantioselectivity for the derivatives of (S)- SO, (S)-2-chlorostyrene oxide (CSO), (S)-3-CSO and (S)-4- CSO. For (S)-2-CSO, (S)-3-CSO and (S)-4-CSO, 99.9%ee was obtained with the yield of 26.2%, 24.8%, and 11.0%, respectively, when using 10 mg cells of Sphingorhabdus sp. YGSMI21 at pH 8.0 with 4 mM racemic substrates at pH 8.0 and 25°C. The values obtained in this study for (S)-2-CSO, particularly the yield of 26.2%, is noteworthy, considering that obtaining an enantiomerically pure form is difficult. Taken together, Sphingorhabdus sp. YGSMI21 can be regarded as a wholecell biocatalyst in the production of various (S)-CSO with the chlorine group at a different position.

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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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.

Fungal diversity in deep-sea sediments from Magellan seamounts environment of the western Pacific revealed by high-throughput Illumina sequencing: Shuai Yang , Wei Xu , Yuanhao Gao , Xiaoyao Chen , Zhu-Hua Luo; J. Microbiol. 2020;58(10):841-852. Published online September 2, 2020; DOI: https://doi.org/10.1007/s12275-020-0198-x

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Abstract: There are lots of seamounts globally whose primary production is disproportionally greater than the surrounding areas. Compared to other deep-sea environments, however, the seamounts environment is relatively less explored for fungal diversity. In the present study, we explored the fungal community structure in deep-sea sediments from four different stations of the Magellan seamounts environment by using high-throughput sequencing of the ITS1 region. A total of 1,897,618 ITS1 sequences were obtained. Among these sequences, fungal ITS1 sequences could be clustered into 1,662 OTUs. The majority of these sequences belonged to Ascomycota. In the genera level, the most abundant genus was Mortierella (4.79%), which was reported as a common fungal genus in soil and marine sediments, followed by Umbelopsis (3.80%), Cladosporium (2.98%), Saccharomycopsis (2.53%), Aspergillus (2.42%), Hortaea (2.36%), Saitozyma (2.20%), Trichoderma (2.12%), Penicillium (2.11%), Russula (1.86%), and Verticillium (1.40%). Most of these recovered genera belong to Ascomycota. The Bray-Curtis analysis showed that there was 37 to 85% dissimilarity of fungal communities between each two sediment samples. The Principal coordinates analysis clearly showed variations in the fungal community among different sediment samples. These results suggested that there was a difference in fungal community structures not only among four different sampling stations but also for different layers at the same station. The depth and geographical distance significantly affect the fungal community, and the effect of depth and geographical distance on the structure of the fungal community in the Magellan seamounts is basically same. Most of the fungi were more or less related to plants, these plant parasitic/symbiotic/endophytic fungi constitute a unique type of seamounts environmental fungal ecology, different from other marine ecosystems.

Short-term effects of returning granulated straw on soil microbial community and organic carbon fractions in dryland farming: Wei Fan , Jinggui Wu; J. Microbiol. 2020;58(8):657-667. Published online June 25, 2020; DOI: https://doi.org/10.1007/s12275-020-9266-5

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Abstract: We conducted a 2-year field experiment which was comprised of five treatments, namely no straw returning (CK), straw mulching (SM), straw plowed into the soil (SP), and straw returned in granulated form (SG). The aim of this study was to investigate the effects of different straw returning modes on soil bacterial and fungal community structure and their relationships to soil organic carbon (SOC) fractions at three different soil depths (0–20, 20–40, and 40–60 cm) in a dryland under maize cultivation in Northeast (NE) China. SM, SP, and SG treatments significantly increased SOC content. Compared with SM and SP treatments, SG treatment significantly increased the content of SOC and easily oxidizable carbon (EOC) in the topsoil (0–20 cm depth), and increased dissolved organic carbon (DOC) and SOC content of the light fraction (LFOC) in the 20–40 cm layer. Meanwhile, SG treatment exhibited the highest microbial biomass C (MBC) content in all of the three soil depths. SG treatment also enhanced bacterial richness as well as fungal richness and diversity in the upper 40 cm of soil. In addition, SG treatment increased the relative abundance of Proteobacteria in all depths, and had the highest relative abundance of Basidiomycota in the first 20 cm of soil. SP treatment showed the lowest soil organic carbon content in all fractions and soil microbial community composition. SM treatment exhibited similar results to SG treatment in SOC, DOC, and LFOC contents, and bacterial diversity in the topsoil and subsoil. As a whole, treatment SG improved soil quality and maize yield, hence we recommend returning granulated straw as the most effective practice for enhancing labile SOC fractions as well as maintaining soil diversity and microbial richness of arid farmlands in NE China.

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