Journal of Microbiology

Volume 60(5); May 2022

Review

The crosstalk between bacteria and host autophagy: host defense or bacteria offense: Lin Zheng , Fang Wei , Guolin Li; J. Microbiol. 2022;60(5):451-460. Published online April 29, 2022; DOI: https://doi.org/10.1007/s12275-022-2009-z

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Abstract: Xenophagy is a specific selective autophagy for the elimination of intracellular bacteria. Current evidence suggests that the processes for host autophagy system to recognize and eliminate invading bacteria are complex, and vary according to different pathogens. Although both ubiquitin-dependent and ubiquitin-independent autophagy exist in host to defense invading bacteria, successful pathogens have evolved diverse strategies to escape from or paralyze host autophagy system. In this review, we discuss the mechanisms of host autophagy system to recognize and eliminate intracellular pathogens and the mechanisms of different pathogens to escape from or paralyze host autophagy system, with a particular focus on the most extensively studied bacteria.

Journal Articles

Comparative analysis of the colistin resistance-regulating gene cluster in Klebsiella species: Sun Ju Kim , Hongbaek Cho , Kwan Soo Ko; J. Microbiol. 2022;60(5):461-468. Published online April 18, 2022; DOI: https://doi.org/10.1007/s12275-022-1640-z

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Abstract: CrrAB two-component regulatory system is associated with colistin resistance in Klebsiella pneumoniae. Recently, some K. pneumoniae isolates lacking crrAB genes have been identified. In this study, we investigated the distribution and structural variation of the crrBAC-kexD cluster. To evaluate the structural variation of the crrBAC-kexD cluster, we explored 59 clinical K. pneumoniae isolates from Korea, and 508 whole genomes of K. pneumoniae and other strains of Klebsiella sp. Significant structural variations in crrBAC-kexD and its surrounding regions were identified among K. pneumoniae genomes. Within the genus Klebsiella, the cluster was identified only in K. pneumoniae, K. variicola, and K. quasipneumoniae, which form the K. pneumoniae complex. Among the 304 available K. pneumoniae genomes, an intact crrBAC-kexD cluster was identified in 178 isolates (58.6%), while the cluster was absent in 90 isolates (29.6%). Partial deletions within the cluster were identified in 22 genomes (7.2%). The most diverse structural patterns of the crrBAC-kexD cluster were observed in ST11 strains. Some clades lacked the crrBAC-kexD cluster. The crrBAC-kexD cluster was identified in the genomes of other bacterial species, including Citrobacter freundii and Enterobacter ludwigii. The crrBAC-kexD cluster is proposed to have been acquired by the ancestor of the K. pneumoniae complex from other bacterial species and the cluster may have been lost and re-acquired repeatedly in K. pneumoniae strains according to the phylogenetic analysis. The dynamic evolution of the crrBAC-kexD cluster suggests that it may have other roles, in addition to colistin resistance, in bacterial physiology.

Lysobacter ciconiae sp. nov., and Lysobacter avium sp. nov., isolated from the faeces of an Oriental stork: So-Yeon Lee , Pil Soo Kim , Hojun Sung , Dong-Wook Hyun , Jin-Woo Bae; J. Microbiol. 2022;60(5):469-477. Published online March 31, 2022; DOI: https://doi.org/10.1007/s12275-022-1647-5

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Abstract: Two Gram-stain-negative, mesophilic, strictly aerobic, nonspore forming, and yellow-pigmented strains with rod-shaped cells, designated H21R20T and H23M41T, were isolated from the faeces of an Oriental stork (Ciconia boyciana). Based on 16S rRNA gene sequences, both strains showed the highest similarity (98.3−98.4%) to the type strain of Lysobacter concretionis. Phylogenetic analysis based on the 16S rRNA genes and 92 bacterial core genes showed that strains H21R20T and H23M41T were robustly clustered with L. concretionis Ko07T. Whole genome sequencing revealed that the genomes of both strains were approximately 2.9 Mb in size. The DNA G + C contents of the H21R20T and H23M41T strains were 67.3 and 66.6%, respectively. The two strains showed 80.1−81.7% average nucleotide identity with L. concretionis Ko07T. Strain H21R20T grew optimally at 30°C and pH 8.0 and in the presence of 0.5–3% (wt/vol) NaCl, while strain H23M41T grew optimally at 30°C and pH 7.0–8.0 and in the presence of 0–3% (wt/vol) NaCl. Both strains possessed iso-C15:0, iso-C16:0 and summed feature 9 (iso-C17:1 ω9c and/or C16:0 10-methyl) as the major cellular fatty acids, ubiquinone Q-8 as a predominant quinone, and diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine as the major polar lipids. A multifaceted investigation demonstrated that strains H21R20T and H23M41T represent novel species of the genus Lysobacter, for which we propose the names Lysobacter ciconiae sp. nov. and Lysobacter avium sp. nov. for strains H21R20T (= KCTC 82316T = JCM 34832T) and H23M41T (= KCTC 62676T = JCM 33223T), respectively.

The periplasmic chaperone protein Psg_2795 contributes to the virulence of Pseudomonas savastanoi pv. glycinea: the causal agent of bacterial blight of soybean: Xiuhua Wang , Xiaoyan Zhang , Bao-Hui Lu , Jie Gao; J. Microbiol. 2022;60(5):478-487. Published online March 4, 2022; DOI: https://doi.org/10.1007/s12275-022-1469-5

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Abstract: Pseudomonas savastanoi pv. glycinea (Psg, also named P. syringae pv. glycinea and P. amygdali pv. glycinea) is the causative agent of bacterial blight in soybean. The identification of virulence factors is essential for understanding the pathogenesis of Psg. In this study, a mini-Tn5 transposon mutant library of Psg strain PsgNC12 was screened on soybean, and one low-virulent mini-Tn5 mutant, designated as 4573, was identified. Sequence analysis of the 4573-mutant revealed that the mini-Tn5 transposon was inserted in the Psg_2795 gene. Psg_2795 encodes a FimC-domain protein that is highly conserved in Pseudomonas. Further analysis revealed that the mutation and knockout of Psg_2795 results in a reduced virulence phenotype on soybean, decreased motility, weakened bacterial attachment to a glass surface and delayed the population growth within soybean leaves. The phenotype of the 4573-mutant could be complemented nearly to wild-type levels using an intact Psg_2795 gene. Collectively, our results demonstrate that Psg_2795 plays an important role in the virulence, motility, attachment and the population growth of PsgNC12 in soybean. This finding provides a new insight into the function of periplasmic chaperone proteins in a type I pilus and provides reference information for identifying Psg_2795 homologues in P. savastanoi and other bacteria.

Randomized Controlled Trial

A split face study on the effect of an anti-acne product containing fermentation products of Enterococcus faecalis CBT SL-5 on skin microbiome modification and acne improvement: Hye Sung Han , Sun Hye Shin , Bo-Yun Choi , Nayeon Koo , Sanghyun Lim , Dooheon Son , Myung Jun Chung , Kui Young Park , Woo Jun Sul; J. Microbiol. 2022;60(5):488-495. Published online March 14, 2022; DOI: https://doi.org/10.1007/s12275-022-1520-6

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Abstract: Antibiotic-resistant Cutibacterium acnes and dysbiosis of the skin microbiome are of increasing concern in acne treatment. Enterococcus faecalis, a widely used probiotic, has shown benefits for acne treatment by exerting antimicrobial activity against C. acnes. Therefore, this study aimed to investigate the efficacy and safety of an E. faecalis CBT SL-5-extract-containing lotion in patients with mild-to-moderate acne. Twenty patients were enrolled in this randomized, placebo-controlled, split-face comparative study. Patients were treated with E. faecalis lotion on one side of the face and a vehicle lotion on the other side for 4 weeks. The efficacy outcome measures included improvement in the investigators’ assessment of acne severity, patient satisfaction, changes in skin parameters and diversity of the skin microbiome. The investigators’ assessment score was significantly improved on the test side compared to the control side, after 2 weeks (p = 0.009) and 6 weeks (p < 0.0005). However, TEWL and skin hydration were not significantly different between the two groups. The phylogenetic diversity of the skin microbiota decreased over time in the skin samples of test side. In conclusion, E. faecalis CBT SL-5 extract can be a feasible and well-tolerated option for improving acne severity and skin microbiome dysbiosis in mild-to-moderate acne patients.

Journal Articles

Exploiting the antibacterial mechanism of phenazine substances from Lysobacter antibioticus 13-6 against Xanthomonas oryzae pv. oryzicola: Qi Liu , Jun Yang , Waqar Ahmed , Xiaoyan Wan , Lanfang Wei , Guanghai Ji; J. Microbiol. 2022;60(5):496-510. Published online March 31, 2022; DOI: https://doi.org/10.1007/s12275-022-1542-0

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Abstract: Bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola (Xoc) is one of the most destructive diseases affecting rice production worldwide. In this study, we extracted and purified phenazine substances from the secondary metabolites of Lysobacter antibioticus 13-6. The bacteriostatic mechanism of phenazine substances against Xoc was investigated through physiological response and transcriptomic analysis.
Results
showed that phenazine substances affects the cell membrane permeability of Xoc, which causes cell swelling and deformation, blockage of flagellum synthesis, and imbalance of intracellular environment. The changes in intracellular environment affect the physiological and metabolic functions of Xoc, which reduces the formation of pathogenic factors and pathogenicity. Through transcriptomic analysis, we found that among differentially expressed genes, the expression of 595 genes was induced significantly (275 up-regulated and 320 down-regulated). In addition, we observed that phenazine substances affects three main functions of Xoc, i.e., transmembrane transporter activity, DNA-mediated transposition, and structural molecular activity. Phenazine substances also inhibits the potassium ion transport system that reduces Xoc resistance and induces the phosphate ion transport system to maintain the stability of the internal environment. Finally, we conclude that phenazine substances could retard cell growth and reduce the pathogenicity of Xoc by affecting cell structure and physiological metabolism. Altogether, our study highlights latest insights into the antibacterial mechanism of phenazine substances against Xoc and provides basic guidance to manage the incidence of bacterial leaf streak of rice.

Integrated proteomic and metabolomic analyses reveal significant changes in chloroplasts and mitochondria of pepper (Capsicum annuum L.) during Sclerotium rolfsii infection: Hongdong Liao , Xiangyu Wen , Xuelei Deng , Yonghong Wu , Jianping Xu , Xin Li , Shudong Zhou , Xuefeng Li , Chunhui Zhu , Feng Luo , Yanqing Ma , Jingyuan Zheng; J. Microbiol. 2022;60(5):511-525. Published online March 31, 2022; DOI: https://doi.org/10.1007/s12275-022-1603-4

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Abstract: Infection by Sclerotium rolfsii will cause serious disease and lead to significant economic losses in chili pepper. In this study, the response of pepper during S. rolfsii infection was explored by electron microscopy, physiological determination and integrated proteome and metabolome analyses. Our results showed that the stomata of pepper stems were important portals for S. rolfsii infection. The plant cell morphology was significantly changed at the time of the fungal hyphae just contacting (T1) or surrounding (T2) the pepper. The chlorophyll, carotenoid, and MDA contents and the activities of POD, SOD, and CAT were markedly upregulated at T1 and T2. Approximately 4129 proteins and 823 metabolites were clearly identified in proteome and metabolome analyses, respectively. A change in 396 proteins and 54 metabolites in pepper stem tissues was observed at T1 compared with 438 proteins and 53 metabolites at T2. The proteins and metabolites related to photosynthesis and antioxidant systems in chloroplasts and mitochondria were disproportionally affected by S. rolfsii infection, impacting carbohydrate and amino acid metabolism. This study provided new insights into the response mechanism in pepper stems during S. rolfsii infection, which can guide future work on fungal disease resistance breeding in pepper.

Evaluation of Cyc1 protein stability in Acidithiobacillus ferrooxidans bacterium after E121D mutation by molecular dynamics simulation to improve electron transfer: Mahnaz Shojapour , Somayeh Farahmand , Faezeh Fatemi , Marzieh Dehghan Shasaltaneh; J. Microbiol. 2022;60(5):526-532. Published online March 14, 2022; DOI: https://doi.org/10.1007/s12275-022-1645-7

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Abstract: Cyc1 (Cytochrome c552) is a protein in the electron transport chain of the Acidithiobacillus ferrooxidans (Af) bacteria which obtain their energy from oxidation Fe2+ to Fe3+. The electrons are directed through Cyc2, RCY (rusticyanin), Cyc1, and Cox aa3 proteins to O2. Cyc1 protein consists of two chains, A and B. In the present study, a novel mutation (E121D) in the A chain of Cyc1 protein was selected due to electron receiving from Histidine 143 of RCY. Then, the changes performed in the E121D mutant were evaluated by MD simulations analyzes. Cyc1 and RCY proteins were docked by a Patchdock server. By E121D mutation, the connection between Zn 1388 of chain B and aspartate 121 of chain A weaken. Asp 121 gets farther from Zn 1388. Therefore, the aspartate gets closer to Cu 1156 of the RCY leading to the higher stability of the RCY/ Cyc1 complex. Further, an acidic residue (Glu121) becomes a more acidic residue (Asp121) and improves the electron transfer to Cyc1 protein. The results of RMSF analysis showed further ligand flexibility in mutation. This leads to fluctuation of the active site and increases redox potential at the mutation point and the speed of electron transfer. This study also predicts that in all respiratory chain proteins, electrons probably enter the first active site via glutamate and exit histidine in the second active site of each respiratory chain protein.

Meta-Analysis

Proposal of a health gut microbiome index based on a meta-analysis of Korean and global population datasets: Hyun-Seok Oh , Uigi Min , Hyejin Jang , Namil Kim , Jeongmin Lim , Mauricio Chalita , Jongsik Chun; J. Microbiol. 2022;60(5):533-549. Published online March 31, 2022; DOI: https://doi.org/10.1007/s12275-022-1526-0

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Abstract: The disruption of the human gut microbiota has been linked to host health conditions, including various diseases. However, no reliable index for measuring and predicting a healthy microbiome is currently available. Here, the sequencing data of 1,663 Koreans were obtained from three independent studies. Furthermore, we pooled 3,490 samples from public databases and analyzed a total of 5,153 fecal samples. First, we analyzed Korean gut microbiome covariates to determine the influence of lifestyle on variation in the gut microbiota. Next, patterns of microbiota variations across geographical locations and disease statuses were confirmed using a global cohort and disease data. Based on comprehensive comparative analysis, we were able to define three enterotypes among Korean cohorts, namely, Prevotella type, Bacteroides type, and outlier type. By a thorough categorization of dysbiosis and the evaluation of microbial characteristics using multiple datasets, we identified a wide spectrum of accuracy levels in classifying health and disease states. Using the observed microbiome patterns, we devised an index named the gut microbiome index (GMI) that could consistently predict health conditions from human gut microbiome data. Compared to ecological metrics, the microbial marker index, and machine learning approaches, GMI distinguished between healthy and non-healthy individuals with a higher accuracy across various datasets. Thus, this study proposes a potential index to measure health status of gut microbiome that is verified from multiethnic data of various diseases, and we expect this model to facilitate further clinical application of gut microbiota data in future.

Journal Article

The efficacy of a 2,4-diaminoquinazoline compound as an intranasal vaccine adjuvant to protect against influenza A virus infection in vivo: Kyungseob Noh , Eun Ju Jeong , Timothy An , Jin Soo Shin , Hyejin Kim , Soo Bong Han , Meehyein Kim; J. Microbiol. 2022;60(5):550-559. Published online April 18, 2022; DOI: https://doi.org/10.1007/s12275-022-1661-7

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Abstract: Adjuvants are substances added to vaccines to enhance antigen- specific immune responses or to protect antigens from rapid elimination. As pattern recognition receptors, Toll-like receptors 7 (TLR7) and 8 (TLR8) activate the innate immune system by sensing endosomal single-stranded RNA of RNA viruses. Here, we investigated if a 2,4-diaminoquinazolinebased TLR7/8 agonist, (S)-3-((2-amino-8-fluoroquinazolin- 4-yl)amino)hexan-1-ol (named compound 31), could be used as an adjuvant to enhance the serological and mucosal immunity of an inactivated influenza A virus vaccine. The compound induced the production of proinflammatory cytokines in macrophages. In a dose-response analysis, intranasal administration of 1 μg compound 31 together with an inactivated vaccine (0.5 μg) to mice not only enhanced virus-specific IgG and IgA production but also neutralized influenza A virus with statistical significance. Notably, in a virus-challenge model, the combination of the vaccine and compound 31 alleviated viral infection-mediated loss of body weight and increased survival rates by 40% compared with vaccine only-treated mice. We suggest that compound 31 is a promising lead compound for developing mucosal vaccine adjuvants to protect against respiratory RNA viruses such as influenza viruses and potentially coronaviruses.

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