Journal of Microbiology

Volume 56(6); June 2018

Review

[MINIREVIEW] Antimicrobial actions of dual oxidases and lactoperoxidase: Demba Sarr , Eszter Tóth , Aaron Gingerich , Balázs Rada; J. Microbiol. 2018;56(6):373-386. Published online June 1, 2018; DOI: https://doi.org/10.1007/s12275-018-7545-1

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67 Citations

Abstract: The NOX/DUOX family of NADPH oxidases are transmembrane proteins generating reactive oxygen species as their primary enzymatic products. NADPH oxidase (NOX) 1–5 and Dual oxidase (DUOX) 1 and 2 are members of this family. These enzymes have several biological functions including immune defense, hormone biosynthesis, fertilization, cell proliferation and differentiation, extracellular matrix formation and vascular regulation. They are found in a variety of tissues such as the airways, salivary glands, colon, thyroid gland and lymphoid organs. The discovery of NADPH oxidases has drastically transformed our view of the biology of reactive oxygen species and oxidative stress. Roles of several isoforms including DUOX1 and DUOX2 in host innate immune defense have been implicated and are still being uncovered. DUOX enzymes highly expressed in the respiratory and salivary gland epithelium have been proposed as the major sources of hydrogen peroxide supporting mucosal oxidative antimicrobial defenses. In this review, we shortly present data on DUOX discovery, structure and function, and provide a detailed, upto- date summary of discoveries regarding antibacterial, antiviral, antifungal, and antiparasitic functions of DUOX enzymes. We also present all the literature describing the immune functions of lactoperoxidase, an enzyme working in partnership with DUOX to produce antimicrobial substances.

Journal Articles

Lysobacter pedocola sp. nov., a novel species isolated from Korean soil: Jun Hyeong Jang , Dongwook Lee , Taegun Seo; J. Microbiol. 2018;56(6):387-392. Published online June 1, 2018; DOI: https://doi.org/10.1007/s12275-018-8046-y

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8 Citations

Abstract: A Gram-negative, yellow-pigmented bacterial strain, designated IPC6T, was isolated from soil in an arid region of Goyang-si (Gyeonggi-do, South Korea). Cells were strictly aerobic, non-spore-forming, rod-shaped. The strain grew within a temperature range of 10–42°C (optimum, 30°C) and pH of 5.0–11.0 (optimum, pH 8.0) in the presence of 0–2% (w/v) NaCl. Phylogenetically, the novel strain was closely related to members of the Lysobacter genus based on 16S rRNA sequence similarity, and showed the highest sequence similarity to Lysobacter niastensis KACC 11588T (98.5%). The predominant fatty acids were iso-C15:0, iso-C16:0, and summed feature 9 (iso-C17:1 ω9c), with Q-8 identified as the major ubiquinone. The polar lipid content included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, an unknown aminophospholipid, and an unidentified phospholipid. DNA-DNA hybridization results indicated that the strain IPC6T was distinct from Lysobacter niastensis KACC 11588T (37.9 ± 0.14%), Lysobacter panacisoli KACC 17502T (56.4 ± 0.13%), Lysobacter soli KCTC 22011T (8.1 ± 0.04%), Lysobacter gummosus KCTC 12132T (9.6 ± 0.03%), and Lysobacter cavernae KCTC 42875T (37.5 ± 0.14%), respectively. The DNA G + C content of the novel strain was 71.1 mol%. Based on the collective phenotypic, genotypic and chemotaxonomic data, the IPC6T strain is considered to represent a novel species in the genus Lysobacter, for which the name Lysobacter pedocola sp. nov. (= KCTC 42811T = JCM 31020T) is proposed.

Paenibacillus albilobatus sp. nov., isolated from acidic soil on Jeju Island: Jae-Won Lee , Ye-Eun Kim , Myung-Suk Kang , Ki-Eun Lee , Eun-Young Lee , Soo-Je Park; J. Microbiol. 2018;56(6):393-398. Published online June 1, 2018; DOI: https://doi.org/10.1007/s12275-018-8158-4

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Abstract: A rod-shaped, white color colony with lobate architectures, strain h2T was isolated from a moderately acidic soil on Jeju Island, Republic of Korea. Comparative analysis of the 16S rRNA gene sequence showed that the strain h2T is closely related to Paenibacillus relictisesami DSM 25385T (97.4%, 16S rRNA gene sequence similarity), Paenibacillus azoreducens KACC 11244T (97.2%), and Paenibacillus cookii LMG 18419T (97.0%). DNA-DNA hybridization indicated that the strain h2T has relatively low levels of DNA-DNA relatedness with respect to P. relictisesami DSM 25385T (10.2%) and P. azoreducens KACC 11244T (13.7%). Additionally, the genomic DNA G + C content of h2T is 51.5 mol%. The isolated strain grew at pH 4.0–9.0 (optimum, pH 6.0–7.0) and 0–5% (w/v) NaCl (optimum, 0%) and a temperature of 15–45°C (optimum 35°C). The quinones in the strain are MK-6 and MK-7, and the predominant fatty acid is C15:0 anteiso (32.1%) followed by C17:0 anteiso (26.5%), and C16:0 iso (21.0%). Based on its phenotypic properties, genotypic distinctiveness, and chemotaxonomic features, strain h2T is proposed as a novel species in the genus Paenibacillus, for which the name Paenibacillus albilobatus sp. nov. is proposed (= KCCM 43269T = JCM 32395T = LMG 30408T). The type strain of Paenibacillus albilobatus is h2T.

Root-associated bacteria influencing mycelial growth of Tricholoma matsutake (pine mushroom): Seung-Yoon Oh , Young Woon Lim; J. Microbiol. 2018;56(6):399-407. Published online June 1, 2018; DOI: https://doi.org/10.1007/s12275-018-7491-y

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29 Citations

Abstract: Tricholoma matsutake is an ectomycorrhizal fungus usually associated with Pinus densiflora in South Korea. Fruiting bodies (mushrooms) of T. matsutake are economically important due to their attractive aroma; yet, T. matsutake is uncultivatable and its habitat is rapidly being eradicated due to global climate change. Root-associated bacteria can influence the growth of ectomycorrhizal fungi that co-exist in the host rhizosphere and distinctive bacterial communities are associated with T. matsutake. In this study, we investigated how these bacterial communities affect T. matsutake growth by isolating bacteria from the roots of P. densiflora colonized by ectomycorrhizae of T. matsutake and co-culturing rootassociated bacteria with T. matsutake isolates. Thirteen species of bacteria (27 isolates) were found in pine roots, all belonging to the orders Bacillales or Burkholderiales. Two species in the genus Paenibacillus promoted the growth of T. matsutake in glucose poor conditions, likely using soluble metabolites. In contrast, other bacteria suppressed the growth of T. matsutake using both soluble and volatile metabolites. Antifungal activity was more frequent in glucose poor conditions. In general, pine rhizospheres harbored many bacteria that had a negative impact on T. matsutake growth and the few Paenibacillus species that promoted T. matsutake growth. Paenibacillus species, therefore, may represent a promising resource toward successful cultivation of T. matsutake.

Metagenomic analysis reveals the prevalence and persistence of antibiotic- and heavy metal-resistance genes in wastewater treatment plant: Sachin Kumar Gupta , Hanseob Shin , Dukki Han , Hor-Gil Hur , Tatsuya Unno; J. Microbiol. 2018;56(6):408-415. Published online June 1, 2018; DOI: https://doi.org/10.1007/s12275-018-8195-z

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72 Citations

Abstract: The increased antibiotic resistance among microorganisms has resulted into growing interest for investigating the wastewater treatment plants (WWTPs) as they are reported to be the major source in the dissemination of antibiotic resistance genes (ARGs) and heavy metal resistance genes (HMRGs) in the environment. In this study, we investigated the prevalence and persistence of ARGs and HMRGs as well as bacterial diversity and mobile genetic elements (MGEs) in influent and effluent at the WWTP in Gwangju, South Korea, using high-throughput sequencing based metagenomic approach. A good number of broad-spectrum of resistance genes (both ARG and HMRG) were prevalent and likely persistent, although large portion of them were successfully removed at the wastewater treatment process. The relative abundance of ARGs and MGEs was higher in effluent as compared to that of influent. Our results suggest that the resistance genes with high abundance and bacteria harbouring ARGs and MGEs are likely to persist more through the treatment process. On analyzing the microbial community, the phylum Proteobacteria, especially potentially pathogenic species belonging to the genus Acinetobacter, dominated in WWTP. Overall, our study demonstrates that many ARGs and HMRGs may persist the treatment processes in WWTPs and their association to MGEs may contribute to the dissemination of resistance genes among microorganisms in the environment.

Diversity of A mating type in Lentinula edodes and mating type preference in the cultivated strains: Byeongsuk Ha , Sinil Kim , Minseek Kim , Yoon Jung Moon , Yelin Song , Jae-San Ryu , Hojin Ryu , Hyeon-Su Ro; J. Microbiol. 2018;56(6):416-425. Published online June 1, 2018; DOI: https://doi.org/10.1007/s12275-018-8030-6

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18 Citations

Abstract: Diversity of A mating type in Lentinula edodes has been assessed by analysis of A mating loci in 127 strains collected from East Asia. It was discovered that hypervariable sequence region with an approximate length of 1 kb in the A mating locus, spanning 5􍿁􀁇region of HD2-intergenic region-5􍿁􀁇region of HD1, could represent individual A mating type as evidenced by comprehensive mating analysis. The sequence analysis revealed 27 A mating type alleles from 96 cultivated strains and 48 alleles from 31 wild strains. Twelve of them commonly appeared, leaving 63 unique A mating type alleles. It was also revealed that only a few A mating type alleles such as A1, A4, A5, and A7 were prevalent in the cultivated strains, accounting for 62.5% of all A mating types. This implies preferred selection of certain A mating types in the process of strain development and suggests potential role of A mating genes in the expression of genes governing mushroom quality. Dominant expression of an A mating gene HD1 was observed from A1 mating locus, the most prevalent A allele, in A1-containing dikaryons. However, connections between HD1 expression and A1 preference in the cultivated strains remain to be verified. The A mating type was highly diverse in the wild strains. Thirty-six unique A alleles were discovered from relatively small and confined area of mountainous region in Korean peninsula. The number will further increase because no A allele has been recurrently observed in the wild strains and thus newly discovered strain will have good chances to contain new A allele. The high diversity in small area also suggests that the A mating locus has evolved rapidly and thus its diversity will further increase.

Photosynthetic and biochemical responses of the freshwater green algae Closterium ehrenbergii Meneghini (Conjugatophyceae) exposed to the metal coppers and its implication for toxicity testing: Hui Wang , Vinitha Ebenezer , Jang-Seu Ki; J. Microbiol. 2018;56(6):426-434. Published online June 1, 2018; DOI: https://doi.org/10.1007/s12275-018-8081-8

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26 Citations

Abstract: The freshwater green algae Closterium is sensitive to water quality, and hence has been suggested as ideal organisms for toxicity testing. In the present study, we evaluated the photosynthetic and biochemical responses of C. ehrenbergii to the common contaminants, coppers. The 72 h median effective concentrations (EC50) of CuSO4 and CuCl2 on the test organism were calculated to be 0.202 mg/L and 0.245 mg/L, respectively. Exposure to both coppers considerably decreased pigment levels and photosynthetic efficiency, while inducing the generation of reactive oxygen species (ROS) in cells with increased exposure time. Moreover, the coppers significantly increased the levels of lipid peroxidation and superoxide dismutase (SOD) activity, even at relatively lower concentrations. These suggest that copper contaminants may exert deleterious effects on the photosynthesis and cellular oxidative stress of C. ehrenbergii, representing its powerful potential in aquatic toxicity assessments.

Colistin resistance in Enterobacter spp. isolates in Korea: Yoon-Kyoung Hong , Ji-Young Lee , Kwan Soo Ko; J. Microbiol. 2018;56(6):435-440. Published online June 1, 2018; DOI: https://doi.org/10.1007/s12275-018-7449-0

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16 Citations

Abstract: We investigated the colistin resistance rate among 356 Enterobacter spp. clinical isolates from eight hospitals in Korea. Antibiotic susceptibility testing was performed by broth microdilution. While 51 of 213 (23.9%) Enterobacter cloacae isolates were colistin-resistant, only six of 143 (4.2%) E. aerogenes isolates showed resistance. We also identified the skip well phenotype in eight E. cloacae and three E. aerogenes isolates. Multilocus sequence typing for E. cloacae and randomly amplified polymorphic DNA analysis and enterobacterial repetitive intergenic consensus PCR for E. aerogenes revealed that clonal spreading of colistin-resistant and skip well Enterobacter spp. isolates had not occurred. In vitro time-kill assays were performed with three colistin-resistant, three skip well, and two colistin-susceptible isolates of E. cloacae and E. aerogenes. Inconsistent results were observed among isolates with skip well phenotypes; while some were eradicated by 2 mg/L colistin, others were not. This suggests that skip well isolates have differentiated into different categories. As the high rates of colistin resistance in E. cloacae detected are of clinical concern, continuous monitoring is warranted. In addition, the clinical implications and mechanisms of the skip well phenotype should be investigated to ensure the appropriate use of colistin against Enterobacter infections.

Analysis of IE62 mutations found in Varicella-Zoster virus vaccine strains for transactivation activity: Hyemin Ko , Gwang Myeong Lee , Ok Sarah Shin , Moon Jung Song , Chan Hee Lee , Young Eui Kim , Jin-Hyun Ahn; J. Microbiol. 2018;56(6):441-448. Published online June 1, 2018; DOI: https://doi.org/10.1007/s12275-018-8144-x

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Abstract: Live attenuated vaccine strains have been developed for Varicella- Zoster virus (VZV). Compared to clinically isolated strains, the vaccine strains contain several non-synonymous mutations in open reading frames (ORFs) 0, 6, 31, 39, 55, 62, and 64. In particular, ORF62, encoding an immediate-early (IE) 62 protein that acts as a transactivator for viral gene expression, contains six non-synonymous mutations, but whether these mutations affect transactivation activity of IE62 is not understood. In this study, we investigated the role of non-synonymous vaccine-type mutations (M99T, S628G, R958G, V1197A, I1260V, and L1275S) of IE62 in Suduvax, a vaccine strain isolated in Korea, for transactivation activity. In reporter assays, Suduvax IE62 showed 2- to 4-fold lower transactivation activity toward ORF4, ORF28, ORF29, and ORF68 promoters than wild-type IE62. Introduction of individual M99T, S628G, R958G, or V1197A/ I1260V/L1275S mutations into wild-type IE62 did not affect transactivation activity. However, the combination of M99T within the N-terminal Sp transcription factor binding region and V1197A/I1260V/L1275S within the C-terminal serineenriched acidic domain (SEAD) significantly reduced the transactivation activity of IE62. The M99T/V1197A/I1260V/ L1275S mutant IE62 did not show considerable alterations in intracellular distribution and Sp3 binding compared to wild-type IE62, suggesting that other alteration(s) may be responsible for the reduced transactivation activity. Collectively, our results suggest that acquisition of mutations in both Met 99 and the SEAD of IE62 is responsible for the reduced transactivation activity found in IE62 of the VZV vaccine strains and contributes to attenuation of the virus.

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