Journal of Microbiology

Journal Articles

Characterization of Marinilongibacter aquaticus gen. nov., sp. nov., a unique marine bacterium harboring four CRISPR-Cas systems in the phylum Bacteroidota: Dao-Feng Zhang , Yu-Fang Yao , Hua-Peng Xue , Zi-Yue Fu , Xiao-Mei Zhang , Zongze Shao; J. Microbiol. 2022;60(9):905-915. Published online August 1, 2022; DOI: https://doi.org/10.1007/s12275-022-2102-3

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Abstract: A novel bacterium, designated YYF0007T, was isolated from an agar-degrading co-culture. The strain was found harboring four CRISPR-Cas systems of two classes in the chromosome and subsequently subjected to a study on polyphasic taxonomy. Pairwise analyses of the 16S rRNA gene sequences indicated that strain YYF0007T had highest 16S rRNA gene sequence similarity (92.2%) to Jiulongibacter sediminis JN- 14-9T. The phylogenomic trees based on the 16S rRNA gene and 269 single-copy orthologous gene clusters (OCs) indicated that strain YYF0007T should be recognized as a novel genus of the family Spirosomaceae. The cells were Gramstain- negative, nonmotile, strictly aerobic, and straight long rods with no flagellum. Optimum growth occurred at 28°C and pH 7.0 with the presence of NaCl concentration 1.0–3.0% (w/v). The strain showed oxidase and catalase activities. The major fatty acids were C16:1ω5c, iso-C15:0 and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c). The predominant isoprenoid quinone was MK-7. The complete genome size was 4.64 Mb with a DNA G + C content of 44.4%. Further typing of CRISPR-Cas systems in the family Spirosomaceae and the phylum Bacteroidota indicated that it was remarkable for strain YYF0007T featured by such a set of CRISPR-Cas systems. This trait highlights the applications of strain YYF- 0007T in studies on the evolutionary dynamics and bacterial autoimmunity of CRISPR-Cas system as a potential model. The name Marinilongibacter aquaticus gen. nov., sp. nov. is proposed, and the type strain is YYF0007T (= MCCC 1K06017T = GDMCC 1.2428T = JCM 34683T).

Gut microbiota metabolic characteristics in coronary artery disease patients with hyperhomocysteine: Ran Tian , Hong-Hong Liu , Si-Qin Feng , Yi-Fei Wang , Yi-Yang Wang , Yu-Xiong Chen , Hui Wang , Shu-Yang Zhang; J. Microbiol. 2022;60(4):419-428. Published online March 4, 2022; DOI: https://doi.org/10.1007/s12275-022-1451-2

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Abstract: Hyperhomocysteine (HHcy) is known as a risk factor for coronary artery disease (CAD). Despite the knowledge that gut microbiota related metabolism pathway shares metabolites with that of Hcy, little has been shown concerning the association between HHcy and gut microbiota. To explore their relationship in the context of CAD, 105 patients and 14 healthy controls were recruited from one single medical center located in Beijing, China. Their serum and fecal samples were collected, with multi-omics analyses performed via LC/MS/ MS and 16S rRNA gene V3-V4 region sequencing, respectively. Participants from the prospective cohort were divided into CAD, CAD & HHcy and healthy controls (HC) groups based on the diagnosis and serum Hcy concentration. The
results
revealed significant different metabolic signatures between CAD and CAD & HHcy groups. CAD patients with HHcy suffered a heavier atherosclerotic burden compared to CAD patients, and the difference was closely associated to betaine-homocysteine S-methyltransferase (BHMT)-related metabolites and trimethylamine N-oxide (TMAO)-related metabolites. Dimethylglycine (DMG) exhibited a strong positive correlation with serum total Hcy (tHcy), and TMAO and trimethylysine (TML) were associated with heavier atherosclerotic burden. Multiple other metabolites were also identified to be related to distinct cardiovascular risk factors. Additionally, Clostridium cluster IV and Butyricimonas were enriched in CAD patients with elevated tHcy. Our study suggested that CAD patients with elevated tHcy were correlated with higher atherosclerotic burden, and the impaired Hcy metabolism and cardiovascular risk were closely associated with BHMT-related metabolites, TMAO-related metabolites and impaired gut microbiota homeostasis.

Molecular characterization of the Saccharomycopsis fibuligera ATF genes, encoding alcohol acetyltransferase for volatile acetate ester formation: Hye Yun Moon , Hyeon Jin Kim , Ki Seung Kim , Su Jin Yoo , Dong Wook Lee , Hee Je Shin , Jeong Ah Seo , Hyun Ah Kang; J. Microbiol. 2021;59(6):598-608. Published online May 29, 2021; DOI: https://doi.org/10.1007/s12275-021-1159-8

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Abstract: Aroma ester components produced by fermenting yeast cells via alcohol acetyltransferase (AATase)-catalyzed intracellular reactions are responsible for the fruity character of fermented alcoholic beverages, such as beer and wine. Acetate esters are reportedly produced at relatively high concentrations by non-Saccharomyces species. Here, we identified 12 ATF orthologues (SfATFs) encoding putative AATases, in the diploid genome of Saccharomycopsis fibuligera KJJ81, an isolate from wheat-based Nuruk in Korea. The identified SfATF proteins (SfAtfp) display low sequence identities with S. cerevisiae Atf1p (between 13.3 and 27.0%). All SfAtfp identified, except SfAtf(A)4p and SfAtf(B)4p, contained the activation domain (HXXXD) conserved in other Atf proteins. Culture supernatant analysis using headspace gas chromatography mass spectrometry confirmed that the recombinant S. cerevisiae strains expressing SfAtf(A)2p, SfAtf(B)2p, and SfAtf(B)6p produced high levels of isoamyl and phenethyl acetates. The volatile aroma profiles generated by the SfAtf proteins were distinctive from that of S. cerevisiae Atf1p, implying difference in the substrate preference. Cellular localization analysis using GFP fusion revealed the localization of SfAtf proteins proximal to the lipid particles, consistent with the presence of amphipathic helices at their N- and C-termini. This is the first report that systematically characterizes the S. fibuligera ATF genes encoding functional AATases responsible for acetate ester formation using higher alcohols as substrate, demonstrating their biotechnological potential for volatile ester production.

Mst1/2-ALK promotes NLRP3 inflammasome activation and cell apoptosis during Listeria monocytogenes infection: Aijiao Gao , Huixin Tang , Qian Zhang , Ruiqing Liu , Lin Wang , Yashan Liu , Zhi Qi , Yanna Shen; J. Microbiol. 2021;59(7):681-692. Published online April 20, 2021; DOI: https://doi.org/10.1007/s12275-021-0638-2

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Abstract: Listeria monocytogenes (L. monocytogenes) is a Gram-positive intracellular foodborne pathogen that causes severe diseases, such as meningitis and sepsis. The NLR family pyrin domain-containing 3 (NLRP3) inflammasome has been reported to participate in host defense against pathogen infection. However, the exact molecular mechanisms underlying NLRP3 inflammasome activation remain to be fully elucidated. In the present study, the roles of mammalian Ste20- like kinases 1/2 (Mst1/2) and Anaplastic Lymphoma Kinase (ALK) in the activation of the NLRP3 inflammasome induced by L. monocytogenes infection were investigated. The expression levels of Mst1/2, phospho (p)-ALK, p-JNK, Nek7, and NLRP3 downstream molecules including activated caspase- 1 (p20) and mature interleukin (IL)-1β (p17), were upregulated in L. monocytogenes-infected macrophages. The ALK inhibitor significantly decreased the expression of p-JNK, Nek7, and NLRP3 downstream molecules in macrophages infected with L. monocytogenes. Furthermore, the Mst1/2 inhibitor markedly inhibited the L. monocytogenes-induced activation of ALK, subsequently downregulating the expression of p-JNK, Nek7, and NLRP3 downstream molecules. Therefore, our study demonstrated that Mst1/2-ALK mediated the activation of the NLRP3 inflammasome by promoting the interaction between Nek7 and NLRP3 via JNK during L. monocytogenes infection, which subsequently increased the maturation and release of proinflammatory cytokine to resist pathogen infection. Moreover, Listeriolysin O played a key role in the process. In addition, we also found that the L. monocytogenes-induced apoptosis of J774A.1 cells was reduced by the Mst1/2 or ALK inhibitor. The present study reported, for the first time, that the Mst1/2-ALK-JNK-NLRP3 signaling pathway plays a vital proinflammatory role during L. monocytogenes infection.

Review

[MINIREVIEW]Regulation of gene expression by protein lysine acetylation in Salmonella: Hyojeong Koo , Shinae Park , Min-Kyu Kwak , Jung-Shin Lee; J. Microbiol. 2020;58(12):979-987. Published online November 17, 2020; DOI: https://doi.org/10.1007/s12275-020-0483-8

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Abstract: Protein lysine acetylation influences many physiological functions, such as gene regulation, metabolism, and disease in eukaryotes. Although little is known about the role of lysine acetylation in bacteria, several reports have proposed its importance in various cellular processes. Here, we discussed the function of the protein lysine acetylation and the post-translational modifications (PTMs) of histone-like proteins in bacteria focusing on Salmonella pathogenicity. The protein lysine residue in Salmonella is acetylated by the Pat-mediated enzymatic pathway or by the acetyl phosphate-mediated non-enzymatic pathway. In Salmonella, the acetylation of lysine 102 and lysine 201 on PhoP inhibits its protein activity and DNAbinding, respectively. Lysine acetylation of the transcriptional regulator, HilD, also inhibits pathogenic gene expression. Moreover, it has been reported that the protein acetylation patterns significantly differ in the drug-resistant and -sensitive Salmonella strains. In addition, nucleoid-associated proteins such as histone-like nucleoid structuring protein (H-NS) are critical for the gene silencing in bacteria, and PTMs in H-NS also affect the gene expression. In this review, we suggest that protein lysine acetylation and the post-translational modifications of H-NS are important factors in understanding the regulation of gene expression responsible for pathogenicity in Salmonella.

Journal Article

Omp16, a conserved peptidoglycan-associated lipoprotein, is involved in Brucella virulence in vitro: Feijie Zhi , Dong Zhou , Junmei Li , Lulu Tian , Guangdong Zhang , Yaping Jin , Aihua Wang; J. Microbiol. 2020;58(9):793-804. Published online September 1, 2020; DOI: https://doi.org/10.1007/s12275-020-0144-y

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Abstract: Brucella, the bacterial agent of common zoonotic brucellosis, primarily infects specific animal species. The Brucella outer membrane proteins (Omps) are particularly attractive for developing vaccine and improving diagnostic tests and are associated with the virulence of smooth Brucella strains. Omp16 is a homologue to peptidoglycan-associated lipoproteins (Pals), and an omp16 mutant has not been generated in any Brucella strain until now. Very little is known about the functions and pathogenic mechanisms of Omp16 in Brucella. Here, we confirmed that Omp16 has a conserved Pal domain and is highly conserved in Brucella. We attempted to delete omp16 in Brucella suis vaccine strain 2 (B. suis S2) without success, which shows that Omp16 is vital for Brucella survival. We acquired a B. suis S2 Omp16 mutant via conditional complementation. Omp16 deficiency impaired Brucella outer membrane integrity and activity in vitro. Moreover, inactivation of Omp16 decreased bacterial intracellular survival in macrophage RAW 264.7 cells. B. suis S2 and its derivatives induced marked expression of IL-1β, IL-6, and TNF-α mRNA in Raw 264.7 cells. Whereas inactivation of Omp16 in Brucella enhanced IL-1β and IL-6 expression in Raw 264.7 cells. Altogether, these findings show that the Brucella Omp16 mutant was obtained via conditional complementation and confirmed that Omp16 can maintain outer membrane integrity and be involved in bacterial virulence in Brucella in vitro and in vivo. These results will be important in uncovering the pathogenic mechanisms of Brucella.

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