Journal of Microbiology

Research Article

LasB activation in Pseudomonas aeruginosa: Quorum sensing-mediated release of an auto-activation inhibitor: Cheol Seung Lee, Xi-Hui Li, Chae-Ran Jeon, Joon-Hee Lee; J. Microbiol. 2025;63(2):e2411005. Published online February 27, 2025; DOI: https://doi.org/10.71150/jm.2411005

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Abstract PDF: Pseudomonas aeruginosa secretes three major proteases: elastase B (LasB), protease IV (PIV), and elastase A (LasA), which play crucial roles in infection and pathogenesis. These proteases are activated sequentially from LasB in a proteolytic cascade, and LasB was previously thought to undergo auto-activation. However, our previous study suggested that LasB cannot auto-activate independently but requires additional quorum sensing (QS)-dependent factors for activation, as LasB remained inactive in QS-deficient P. aeruginosa (QS^-) even under artificial overexpression. In this study, we provide evidence for the existence of a LasB inhibitor in QS^- mutants: inactive LasB overexpressed in QS^- strains was in its processed form and could be reactivated upon purification; when full-length LasB was overexpressed in Escherichia coli, a heterologous bacterium lacking both LasB activators and inhibitors, the protein underwent normal processing and activation; and purified active LasB was significantly inhibited by culture supernatant (CS) from QS^- strains but not by CS from QS⁺ strains. These findings demonstrate that a LasB inhibitor exists in QS^- strains, and in its absence, LasB can undergo auto-activation without requiring an activator. Based on these results, we propose an updated hypothesis: the QS-dependent LasB activator functions by removing the LasB inhibitor rather than acting directly on LasB itself, thus preventing premature LasB activation until QS response is initiated.

Journal Articles

Functional analysis of ascP in Aeromonas veronii TH0426 reveals a key role in the regulation of virulence: Yongchao Guan , Meng Zhang , Yingda Wang , Zhongzhuo Liu , Zelin Zhao , Hong Wang , Dingjie An , Aidong Qian , Yuanhuan Kang , Wuwen Sun , Xiaofeng Shan; J. Microbiol. 2022;60(12):1153-1161. Published online November 10, 2022; DOI: https://doi.org/10.1007/s12275-022-2373-8

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Aeromonas veronii is a pathogen which can induce diseases in humans, animals and aquatic organisms, but its pathogenic mechanism and virulence factors are still elusive. In this study, we successfully constructed a mutant strain (ΔascP) by homologous recombination. The results showed that the deletion of the ascP gene significantly down-regulated the expression of associated effector proteins in A. veronii compared to its wild type. The adhesive and invasive abilities of ΔascP to EPC cells were 0.82-fold lower in contrast to the wild strain. The toxicity of ΔascP to cells was decreased by about 2.91-fold (1 h) and 1.74-fold (2 h). Furthermore, the LD50 of the mutant strain of crucian carp was reduced by 19.94-fold, and the virulence was considerably attenuated. In contrast to the wild strain, the ΔascP content in the liver and spleen was considerably lower. The titers of serum cytokines (IL-8, TNF-α, and IL-1β) in crucian carp after the infection of the ΔascP strain were considerably lower in contrast to the wild strain. Hence, the ascP gene is essential for the etiopathogenesis of A. veronii TH0426.

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Complete genome sequence and genome-wide transposon mutagenesis enable the determination of genes required for sodium hypochlorite tolerance and drug resistance in pathogen Aeromonas veronii GD2019
Yifan Bu, Chengyu Liu, Yabo Liu, Wensong Yu, Tingjin Lv, Yuanxing Zhang, Qiyao Wang, Yue Ma, Shuai Shao
Microbiological Research.2024; 284: 127731. CrossRef
Construction of the flagellin F mutant of Vibrio parahaemolyticus and its toxic effects on silver pomfret (Pampus argenteus) cells
Yang Li, Chao Liu, Yuechen Sun, Ruijun Wang, Choufei Wu, Hanqu Zhao, Liqin Zhang, Dawei Song, Quanxin Gao
International Journal of Biological Macromolecules.2024; 259: 129395. CrossRef
Ferric uptake regulator (fur) affects the pathogenicity of Aeromonas veronii TH0426 by regulating flagellar assembly and biofilm formation
Jin-shuo Gong, Ying-da Wang, Yan-long Jiang, Di Zhang, Ya-nan Cai, Xiao-feng Shan, He Gong, Hao Dong
Aquaculture.2024; 580: 740361. CrossRef

Core promoter mutation of nucleotides A1762T and G1764A of hepatitis B virus increases core promoter transactivation by hepatocyte nuclear factor 1: Mi So Seong , Hyeon Jeong Hwang , Eun Ah Jang , Jeong Ah Jang , Wah Wah Aung , Yi Yi Kyaw , JaeHun Cheong; J. Microbiol. 2022;60(10):1039-1047. Published online September 27, 2022; DOI: https://doi.org/10.1007/s12275-022-1675-1

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Abstract

Hepatitis B virus (HBV) infection highly increases the risk for liver cirrhosis and hepatocellular carcinoma (HCC). The clinical manifestation of HBV infection is determined by the mutual interplay of the viral genotype, host genetic factors, mode of transmission, adaptive mutations, and environmental factors. Core promoter activation plays a critical role in the pre-genomic RNA transcription of HBV for HBV replication. The mutations of core promoter have been implicated in HCC development. We had obtained HBV genes from Myanmar HBV infectants and identified gene variations at the core promoter region. For measuring the relative transactivation activity on core promoter, we prepared the core-promoter reporter construct. Both of A1762T and G1764A mutation were consistently found in the HBV genes with hepatocellular carcinoma. The A1762T/G1764A mutation was corresponding to K130M/V131I of HBx protein. We prepared the core promoter- luciferase reporter construct containing the double A1762T/G1764A mutation and the K130M/V131I HBx protein expression construct. The A1762T/G1764A mutation highly was responsive to core promoter transactivation by HBx, regardless of HBx mutation. The A1762T/G1764A mutation newly created hepatocyte nuclear factor 1 (HNF1) responsive element. Ectopic expression of HNF1 largely increased the HBV core promoter containing A1762T/G1764A mutation. In addition, hepatic rich fatty acid, palmitic acid and oleic acid, increased K130M/V131I HBx level by core promoter activation. These results provide biological properties and clinical significance of specific HBV core promoter mutants related with HCC development.

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A Survey of HBV Core/Pre-Core Mutations in Iraqi Patients with Chronic Hepatitis
Abdulhussain Kadhim Jwaziri, Maryam Esghaei, Mohammad Hadi Karbalaie Niya, Hadi Sayah, Mohammad Hossein Razizadeh, Ali Gholami, Leila Mousavizadeh, Hossein Keyvani
Hepatitis Monthly.2023;[Epub] CrossRef
The A1762T/G1764A mutations enhance HBV replication by alternating viral transcriptome
Danli Yang, Jun Zou, Guiwen Guan, Xiaoyu Feng, Ting Zhang, Guixin Li, Hui Liu, Huiling Zheng, Jingyuan Xi, Guangxin Yu, Lizhong Dai, Fengmin Lu, Xiangmei Chen
Journal of Medical Virology.2023;[Epub] CrossRef
Clinical application value of hepatitis B virus basal core promoter 1762/1764 and GGTII and GGT in patients with HBV-DNA-positive primary liver cancer
Shunhua Qiu, Lifen Jin, Dan Yang, Dewen Zhang
Medicine.2023; 102(43): e35699. CrossRef

Mutational analysis on stable expression and LasB inhibition of LasB propeptide in Pseudomonas aeruginosa: Youngsun Shin , Xi-Hui Li , Cheol Seung Lee , Joon-Hee Lee; J. Microbiol. 2022;60(7):727-734. Published online May 25, 2022; DOI: https://doi.org/10.1007/s12275-022-1671-5

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Abstract: Three major proteases, elastase B (LasB), protease IV (PIV), and elastase A (LasA) expressed in Pseudomonas aeruginosa play important roles in infections and pathogeneses. These are activated by a proteolytic cascade initiated by the activation of LasB. In this study, we investigated whether LasB could be inhibited using its propeptide (LasBpp). Although LasA and PIV were inhibited by their propeptides, LasB was not inhibited by purified LasBpp because LasB degraded LasBpp. To address this problem, mutant LasBpp variants were constructed to obtain a mutant LasBpp resistant to LasB degradation. A C-terminal deletion series of LasBpp was tested in vivo, and two positive candidates, T2 and T2-1, were selected. However, both caused growth retardation and were unstably expressed in vivo. Since deleting the C-terminal end of LasBpp significantly affected its stable expression, substitution mutations were introduced at the two amino acids near the truncation site of T2-1. The resulting mutants, LasBppE172D, LasBppG173A, and LasBppE172DG173A, significantly diminished LasB activity when overexpressed in vivo and were stably expressed in MW1, a quorum sensing mutant that does not produce LasB. In vitro analysis showed that purified LasBppE172DG173A inhibited LasB activity to a small extent. Summarizing, Cterminal modification of LasBpp profoundly affected the stable expression of LasBpp, and little enhanced the ability of LasBpp to resist degradation by LasB.

Functional characterization of HigBA toxin-antitoxin system in an Arctic bacterium, Bosea sp. PAMC 26642: Eunsil Choi , Ahhyun Huh , Changmin Oh , Jeong-Il Oh , Ho Young Kang , Jihwan Hwang; J. Microbiol. 2022;60(2):192-206. Published online February 1, 2022; DOI: https://doi.org/10.1007/s12275-022-1619-9

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Abstract

Toxin-antitoxin (TA) systems are growth-controlling genetic elements consisting of an intracellular toxin protein and its cognate antitoxin. TA systems have been spread among microbial genomes through horizontal gene transfer and are now prevalent in most bacterial and archaeal genomes. Under normal growth conditions, antitoxins tightly counteract the activity of the toxins. Upon stresses, antitoxins are inactivated, releasing activated toxins, which induce growth arrest or cell death. In this study, among nine functional TA modules in Bosea sp. PAMC 26642 living in Arctic lichen, we investigated the functionality of BoHigBA2. BohigBA2 is located close to a genomic island and adjacent to flagellar gene clusters. The expression of BohigB2 induced the inhibition of E. coli growth at 37°C, which was more manifest at 18°C, and this growth defect was reversed when BohigA2 was co-expressed, suggesting that this BoHigBA2 module might be an active TA module in Bosea sp. PAMC 26642. Live/dead staining and viable count analyses revealed that the BoHigB2 toxin had a bactericidal effect, causing cell death. Furthermore, we demonstrated that BoHigB2 possessed mRNA-specific ribonuclease activity on various mRNAs and cleaved only mRNAs being translated, which might impede overall translation and consequently lead to cell death. Our study provides the insight to understand the cold adaptation of Bosea sp. PAMC 26642 living in the Arctic.

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Evaluating the Contribution of the Predicted Toxin–Antitoxin System HigBA to Persistence, Biofilm Formation, and Virulence in Burkholderia pseudomallei
Itziar Chapartegui-González, Nittaya Khakhum, Jacob L. Stockton, Alfredo G. Torres, Igor E. Brodsky
Infection and Immunity.2022;[Epub] CrossRef
Chronicle of Research into Lichen-Associated Bacteria
Zichen He, Takeshi Naganuma
Microorganisms.2022; 10(11): 2111. CrossRef
Degradation of amoxicillin by newly isolated Bosea sp. Ads-6
Lei Yan, Ning Yan, Xi-Yan Gao, Ying Liu, Zhi-Pei Liu
Science of The Total Environment.2022; 828: 154411. CrossRef

Short-chain fatty acids inhibit the biofilm formation of Streptococcus gordonii through negative regulation of competence-stimulating peptide signaling pathway: Taehwan Park , Jintaek Im , A Reum Kim , Dongwook Lee , Sungho Jeong , Cheol-Heui Yun , Seung Hyun Han; J. Microbiol. 2021;59(12):1142-1149. Published online December 4, 2021; DOI: https://doi.org/10.1007/s12275-021-1576-8

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Abstract

Streptococcus gordonii, a Gram-positive commensal bacterium, is an opportunistic pathogen closely related to initiation and progression of various oral diseases, such as periodontitis and dental caries. Its biofilm formation is linked with the development of such diseases by enhanced resistance against antimicrobial treatment or host immunity. In the present study, we investigated the effect of short-chain fatty acids (SCFAs) on the biofilm formation of S. gordonii. SCFAs, including sodium acetate (NaA), sodium propionate (NaP), and sodium butyrate (NaB), showed an effective inhibitory activity on the biofilm formation of S. gordonii without reduction in bacterial growth. SCFAs suppressed S. gordonii biofilm formation at early time points whereas SCFAs did not affect its preformed biofilm. A quorum-sensing system mediated by competence-stimulating peptide (CSP) is known to regulate biofilm formation of streptococci. Interestingly, SCFAs substantially decreased mRNA expression of comD and comE, which are CSP-sensor and its response regulator responsible for CSP pathway, respectively. Although S. gordonii biofilm formation was enhanced by exogenous synthetic CSP treatment, such effect was not observed in the presence of SCFAs. Collectively, these results suggest that SCFAs have an anti-biofilm activity on S. gordonii through inhibiting comD and comE expression which results in negative regulation of CSP quorum-sensing system. SCFAs could be an effective anti-biofilm agent against S. gordonii for the prevention of oral diseases.

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Menghe Liu, Ru Peng, Chunfang Tian, Jianping Shi, Jiannan Ma, Ruiwen Shi, Xiao Qi, Rongwei Zhao, Haibin Guan
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Georgy E. Leonov, Yurgita R. Varaeva, Elena N. Livantsova, Antonina V. Starodubova
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Lactiplantibacillus plantarum LRCC5314 includes a gene for serotonin biosynthesis via the tryptophan metabolic pathway: Jiseon Jeong , Yunjeong Lee , Seokmin Yoon , Jong-Hwa Kim , Wonyong Kim; J. Microbiol. 2021;59(12):1092-1103. Published online December 4, 2021; DOI: https://doi.org/10.1007/s12275-021-1472-2

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Abstract

As the functions of probiotics within the same species may not be shared, it is important to analyze the genetic characteristics of strains to determine their safety and usefulness before industrial applications. Hence the present study was undertaken to determine functional genes, and beneficial activities of strain LRCC5314, a bacterial strain isolated from kimchi through comparative genomic analysis. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain LRCC5314 was a member of the species L. plantarum. Whole genome size of strain LRCC5314 was sequence was 3.25 Mb long, with a G + C content of 44.5 mol% and 3,031 predicted genes. Strain LRCC5314 could metabolize hexoses through homofermentation, which produces only lactic acid from hexoses. According to gene annotation, strain LRCC- 5314 contained genes of EPS production and CRISPR. Moreover, the strain contained genes that could encode a complete biosynthetic pathway for the production of tryptophan, which can be used as a precursor of serotonin. Notably, the tryptophan and serotonin activities strain LRCC5314 were higher than those of reference strains, L. plantarum ATCC 14917T, DSM 20246, DSM 2601, and ATCC 8014, which reach tryptophan amount of 0.784 ± 0.045 μM/ml in MRS broth and serotonin concentration of 19.075 ± 0.295 ng/ml in HT-22 cells. These findings indicated that L. plantarum LRCC5314 could provide a source for serotonin production and could be used as a functional probiotic for stress regulation.

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Fermented foods: Harnessing their potential to modulate the microbiota-gut-brain axis for mental health
Ramya Balasubramanian, Elizabeth Schneider, Eoin Gunnigle, Paul D. Cotter, John F. Cryan
Neuroscience & Biobehavioral Reviews.2024; 158: 105562. CrossRef
Effect of postbiotic Lactiplantibacillus plantarum LRCC5314 supplemented in powdered milk on type 2 diabetes in mice
J.-H. Kim, W. Kwak, Y. Nam, J. Baek, Y. Lee, S. Yoon, W. Kim
Journal of Dairy Science.2024; 107(8): 5301. CrossRef
The role of pharmacomicrobiomics in HIV prevention, treatment, and women’s health
Erik C. Swanson, Christopher M. Basting, Nichole R. Klatt
Microbiome.2024;[Epub] CrossRef
Whole-Genome Sequence of Lactococcus lactis Subsp. lactis LL16 Confirms Safety, Probiotic Potential, and Reveals Functional Traits
Justina Mileriene, Jurgita Aksomaitiene, Kristina Kondrotiene, Tora Asledottir, Gerd Elisabeth Vegarud, Loreta Serniene, Mindaugas Malakauskas
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The putative sensor histidine kinase VadJ coordinates development and sterigmatocystin production in Aspergillus nidulans: Yanxia Zhao , Mi-Kyung Lee , Jieyin Lim , Heungyun Moon , Hee-Soo Park , Weifa Zheng , Jae-Hyuk Yu; J. Microbiol. 2021;59(8):746-752. Published online July 5, 2021; DOI: https://doi.org/10.1007/s12275-021-1055-2

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Abstract

The VosA-VelB heterocomplex governs expression of several genes associated with fungal development and secondary metabolism. In this study, we have investigated the functions of one of the VosA-VelB-activated developmental genes vadJ in development and production of the mycotoxin sterigmatocystin in the model fungus Aspergillus nidulans. The vadJ gene is predicted to encode a 957-amino acid length protein containing a highly conserved sensor histidine kinase domain. The deletion of vosA or velB resulted in decreased mRNA levels of vadJ throughout the life cycle, suggesting that VosA and VelB are necessary for proper expression of vadJ. Nullifying vadJ led to highly restricted colony growth, lowered formation of asexual spores, and about two-fold reduction in conidial viability. Conversely, the deletion of vadJ resulted in elevated production of sexual fruiting bodies and sterigmatocystin. These suggest that VadJ is necessary for proper coordination of asexual and sexual development, and sterigmatocystin production. In accordance with this idea, the deletion of vadJ led to elevated mRNA levels of the two key sexual developmental activators esdC and nsdD. In summary, the putative sensor histidine kinase VadJ represses sexual development and sterigmatocystin production, but activates asexual development in A. nidulans.

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Involvement of LaeA and Velvet Proteins in Regulating the Production of Mycotoxins and Other Fungal Secondary Metabolites
Xuwen Hou, Liyao Liu, Dan Xu, Daowan Lai, Ligang Zhou
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Adaptative responses of Neurospora crassa by histidine kinases upon the attack of the arthropod Sinella curviseta
Ting Lu, Xiao-meng Wang, Peng-xu Chen, Juan Xi, Han-bing Yang, Wei-fa Zheng, Yan-xia Zhao
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Implication of VelB in the development, pathogenicity, and secondary metabolism of Penicillium expansum
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Regulators of the Asexual Life Cycle of Aspergillus nidulans
Ye-Eun Son, Jae-Hyuk Yu, Hee-Soo Park
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Kunlong Yang, Jun Tian, Nancy P. Keller
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Cells.2022; 11(24): 3998. CrossRef

Genetic changes in plaque-purified varicella vaccine strain Suduvax during in vitro propagation in cell culture: Hye Rim Hwang , Se Hwan Kang , Chan Hee Lee; J. Microbiol. 2021;59(7):702-707. Published online June 1, 2021; DOI: https://doi.org/10.1007/s12275-021-1062-3

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Abstract: Infection by varicella-zoster virus (VZV) can be prevented by using live attenuated vaccines. VZV vaccine strains are known to evolve rapidly in vivo, however, their genetic and biological effects are not known. In this study, the plaque-purified vaccine strain Suduvax (PPS) was used to understand the genetic changes that occur during the process of propagation in in vitro cell culture. Full genome sequences of three different passages (p4, p30, and p60) of PPS were determined and compared for genetic changes. Mutations were found at 59 positions. The number of genetically polymorphic sites (GPS) and the average of minor allele frequency (MAF) at GPSs were not significantly altered after passaging in cell culture up to p60. The number of variant nucleotide positions (VNPs), wherein GPS was found in at least one passage of PPS, was 149. Overall, MAF changed by less than 5% at 52 VNPs, increased by more than 5% at 42 VNPs, and decreased by more than 5% at 55 VNPs in p60, compared with that seen in p4. More complicated patterns of changes in MAF were observed when genetic polymorphism at 149 VNPs was analyzed among the three passages. However, MAF decreased and mixed genotypes became unequivocally fixed to vaccine type in 23 vaccine-specific positions in higher passages of PPS. Plaque-purified Suduvax appeared to adapt to better replication during in vitro cell culture. Further studies with other vaccine strains and in vivo studies will help to understand the evolution of the VZV vaccine.

Identification and characterization of a new agar-degrading strain with the novel properties of saccharides inhibition and nitrogen fixation: Hao Wu , Guiguang Chen , Yaxi Bian , Wei Zeng , Bihong Sun , Zhiqun Liang; J. Microbiol. 2017;55(6):475-482. Published online May 28, 2017; DOI: https://doi.org/10.1007/s12275-017-6464-x

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Abstract

In this study, a new agar-degrading strain was isolated from soil with agar as a sole carbon source and energy. Based on its morphological, physiological, biochemical characterization and 16S rDNA sequence, the strain was identified as Strep-tomyces lavendulae UN-8. The extracellular agarase activity reached 0.03 U/ml after fermentation in shake flask (250 ml), which was close to other reported non-marine micro-organisms. Furthermore, it is interesting that the growth of UN-8 would be inhibited by glucose (40 g/L) and maltose (40 g/L) with the inhibitory rate of 100% and 70%, respec-tively. Besides, UN-8 could be grown on the solid medium without any nitrogen sources, then the possible nitrogen fix-ation gene nifU was cloned from its genomic DNA. The de-duced amino acid sequence of nifU has high similarity (98%) with nitrogen fixation protein NifU from Streptomyces sp. NRRL S-104 (KJY22454.1) and Streptomyces sp. NRRL F-4428 (KJK52526.1) based on NCBI blast. It is suggested that the nifU gene of UN-8 also encoded nitrogen fixation protein NifU. These results provided some new information for the further understanding of agar-degrading strain.

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A Novel Strategy to Regulate 1-Deoxynojirimycin Production Based on Its Biosynthetic Pathway in Streptomyces lavendulae
Hao Wu, Ye Guo, Lei Chen, Guiguang Chen, Zhiqun Liang
Frontiers in Microbiology.2019;[Epub] CrossRef

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Photosynthetic inhibition and oxidative stress to the toxic Phaeocystis globosa caused by a diketopiperazine isolated from products of algicidal bacterium metabolism: Shuo Tan , Xiaoli Hu , Pinghe Yin , Ling Zhao; J. Microbiol. 2016;54(5):364-375. Published online April 20, 2016; DOI: https://doi.org/10.1007/s12275-016-6012-0

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Abstract

Algicidal bacteria have been turned out to be available for inhibiting Phaeocystis globosa which frequently caused harmful algal blooms and threatened to economic development and ecological balance. A marine bacterium Bacillus sp. Ts-12 exhibited significant algicidal activity against P. globosa by indirect attack. In present study, an algicidal compound was isolated by silica gel column, Sephadex G-15 column and HPLC, further identified as hexahydropyrrolo[1,2-a]pyrazine- 1,4-dione, cyclo-(Pro-Gly), by GC-MS and 1H-NMR. Cyclo-(Pro-Gly) significantly increased the level of reactive oxygen species (ROS) within P. globosa cells, further activating the enzymatic and non-enzymatic antioxidant systems, including superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and ascorbic acid (AsA). The increase in methane dicarboxylic aldehyde (MDA) content showed that the surplus ROS induced lipid peroxidation on membrane system. Transmission electron microscope (TEM) and flow cytometry (FCM) analysis revealed that cyclo-(Pro-Gly) caused reduction of Chl-a content, destruction of cell membrane integrity, chloroplasts and nuclear structure. Real-time PCR assay showed that the transcriptions of photosynthesis related genes (psbA, psbD, rbcL) were significantly inhibited. This study indicated that cyclo-(Pro-Gly) from marine Bacillus sp. Ts-12 exerted photosynthetic inhibition and oxidative stress to P. globosa and eventually led to the algal cells lysis. This algicidal compound might be potential bio-agent for controlling P. globosa red tide.

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Journal Article

Kinetic characterization of a novel acid ectophosphatase from Enterobacter asburiae: Vanessa Sayuri Sato , Renato F. Galdiano Júnior , Gisele Regina Rodrigues , Eliana G. M. Lemos , João Martins Pizauro Junior; J. Microbiol. 2016;54(2):106-113. Published online February 2, 2016; DOI: https://doi.org/10.1007/s12275-015-5354-3

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Abstract

Expression of acid ectophosphatase by Enterobacter asburiae, isolated from Cattleya walkeriana (Orchidaceae) roots and identified by the 16S rRNA gene sequencing analysis, was strictly regulated by phosphorus ions, with its optimal activity being observed at an inorganic phosphate concentration of 7 mM. At the optimum pH 3.5, intact cells released p-nitrophenol at a rate of 350.76 ± 13.53 nmol of p-nitrophenolate (pNP)/min/108 cells. The membrane-bound enzyme was obtained by centrifugation at 100,000 × g for 1 h at 4°C. p-Nitrophenylphosphate (pNPP) hydrolysis by the enzyme follows “Michaelis-Menten” kinetics with V = 61.2 U/mg and K0.5 = 60 μM, while ATP hydrolysis showed V = 19.7 U/mg, K0.5 = 110 μM, and nH = 1.6 and pyrophosphate hydrolysis showed V = 29.7 U/mg, K0.5 = 84 μM, and nH = 2.3. Arsenate and phosphate were competitive inhibitors with Ki = 0.6 mM and Ki = 1.8 mM, respectively. p-Nitrophenyl phosphatase (pNPPase) activity was inhibited by vanadate, while p-hydroxymercuribenzoate, EDTA, calcium, copper, and cobalt had no inhibitory effects. Magnesium ions were stimulatory (K0.5 = 2.2 mM and nH = 0.5). Production of an acid ectophosphatase can be a mechanism for the solubilization of mineral phosphates by microorganisms such as Enterobacter asburiae that are versatile in the solubilization of insoluble minerals, which, in turn, increases the availability of nutrients for plants, particularly in soils that are poor in phosphorus.

Citations

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Potential inhibition of entomopathogenic nematodes and plant growth-promoting bacteria with exposure to selected herbicides and insecticides
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Md. Manjurul Haque, Md Khaled Mosharaf, Md. Amdadul Haque, Md. Zahid Hasan Tanvir, Md. Khairul Alam
Frontiers in Microbiology.2021;[Epub] CrossRef
Immunoglobulin Y in the diagnosis of Aeromonas hydrophila infection in Nile tilapia (Oreochromis niloticus)
Dayanne C. Fernandes, Silas F. Eto, Michelli I.G. Funnicelli, Camila C. Fernandes, Ives Charlie-Silva, Marco A.A. Belo, João M. Pizauro
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Scientific Reports.2017;[Epub] CrossRef

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

Growth Inhibition of the Yeast Transformant by the Expression of a Chitinase from Coprinellus congregatus: Hyangsoon Lim , Hyoung T. Choi; J. Microbiol. 2010;48(5):706-708. Published online November 3, 2010; DOI: https://doi.org/10.1007/s12275-010-0272-x

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Abstract: Coprinellus congregatus generates several chitinases during its entire life cycle: at the growing hyphal stage and at the mushroom autolysis stage. We have isolated a chitinase gene (chi1) from the mushroom tissue at the autolysing stage, and constructed a chitinase expression vector to get large amount of enzyme protein. Chitinase 1 (chi1) cDNA was heterologously expressed in Saccharomyces cerevisiae by gal1 promoter. The transformants showed no specific change in growth characteristics under normal growth conditions. However the expression of the gene by the gal1 promoter in the yeast transformants resulted in complete growth inhibition, while laccase expression by the gal1 promoter showed normal growth. The chitinase activities from the transformants were also more than 3 times higher than that of the recipient strain, and the chitinase expression by the real time-PCR also showed increased expression of the chi1 in the yeast transformant. Expression of a chitinase which was produced at the mushroom autolysing stage of C. congregatus resulted in yeast growth inhibition.

Kinetic Evaluation of Products Inhibition to Succinic Acid Producers Escherichia coli NZN111, AFP111, BL21, and Actinobacillus succinogenes 130ZT: Qiang Li , Dan Wang , Yong Wu , Maohua Yang , Wangliang Li , Jianmin Xing , Zhiguo Su; J. Microbiol. 2010;48(3):290-296. Published online June 23, 2010; DOI: https://doi.org/10.1007/s12275-010-9262-2

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Abstract: Succinic acid is one of the platform compounds and its production via natural feedstocks has drawn worldwide concerns. To evaluate the inhibitory effects of fermentation products on the growth of Actinobacillus succinogenes 130ZT and Escherichia coli NZN111, AFP111, BL21, fermentations with addition of individual products in medium were carried out. The cell growth was inhibited when the concentrations of formate, acetate, lactate, and succinate were at range of 8.8-17.6 g/L, 10-40 g/L, 9-18 g/L, and 10-80 g/L, respectively. For these two species of bacteria, E. coli was more resistant to acid products than A. succinogenes, while both endured succinate rather than by-products. As a result of end product inhibition, succinate production yield by A. succinogenes decreased from 1.11 to 0.49 g/g glucose. Logistic and Monod mathematical models were presented to simulate the inhibition kinetics. The Logistic model was found more suitable for describing the overall synergistic inhibitory effects.

Journal Article

Melanogenesis Inhibitory Effects of Methanolic Extracts of Umbilicaria esculenta and Usnea longissima: Moo-Sung Kim , Hong-Bum Cho; J. Microbiol. 2007;45(6):578-582.; DOI: https://doi.org/2605 [pii]

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Abstract: The primary objective of this study was to assess the in vitro melanogenesis inhibitory effects of methanolic extracts of the edible and medicinal lichens, Umbilicaria (Gyrophora) esculenta and Usnea longissima. The quantities of the total phenolic compounds of methanolic extract of the two lichen extracts were determined to be 1.46% and 2.62%, respectively. In order to evaluate the antioxidative effects of the extracts, we also measured electron donating abilities (EDA) and lipid peroxidation rates. The EDA values measured by the reduction of 1.1''-diphenyl-2-picrylhydrazyl (DPPH) were 72.8% and 80.7% for the extracts, with SC50 (median scavenging concentration) values of 1.29±0.05 mg/ml and 1.03±0.06 mg/ml, respectively. The rates of inhibition of lipid peroxidation using linoleic acid were 92.1% and 97.3% for the extracts, with IC50 (median inhibitory concentration) values of 0.57±0.05 mg/ml and 0.53±0.06 mg/ml, respectively. The inhibitory rates of the extracts against tyrosinase were 67.4% and 84.8%, respectively. The extracts were shown to reduce melanin formation in human melanoma cells. Melanin contents in the samples treated with 0.01% and 0.1% U. esculenta were 47.1% and 31.2%, respectively, and those treated with 0.01% and 0.1% Usnea longissima were 51.1% and 34.9%, respectively, whereas a value of 54.0% was registered when ascorbic acid was utilized as a positive control. In addition to direct tyrosinase inhibition, it was determined that the lichen extracts affected the activity of tyrosinase via the inhibition of tyrosinase glycosylation. As a result, the methanolic extracts of U. esculenta and Usnea longissima evidenced melanogenesis inhibitory effects, which occurred via multiple routes.

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