Journal of Microbiology

Volume 55(10); October 2017

Review

[Minireview] Antibiofilm agents: A new perspective for antimicrobial strategy: Xi-Hui Li , Joon-Hee Lee; J. Microbiol. 2017;55(10):753-766. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7274-x

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135 Citations

Abstract: Biofilms are complex microbial architectures that attach to surfaces and encase microorganisms in a matrix composed of self-produced hydrated extracellular polymeric substances (EPSs). In biofilms, microorganisms become much more resistant to antimicrobial treatments, harsh environmental conditions, and host immunity. Biofilm formation by microbial pathogens greatly enhances survival in hosts and causes chronic infections that result in persistent inflammation and tissue damages. Currently, it is believed over 80% of chronic infectious diseases are mediated by biofilms, and it is known that conventional antibiotic medications are inadequate at eradicating these biofilm-mediated infections. This situation demands new strategies for biofilm-associated infections, and currently, researchers focus on the development of antibiofilm agents that are specific to biofilms, but are nontoxic, because it is believed that this prevents the development of drug resistance. Here, we review the most promising antibiofilm agents undergoing intensive research and development.

Journal Articles

Rhodoferax koreense sp. nov, an obligately aerobic bacterium within the family Comamonadaceae, and emended description of the genus Rhodoferax: Mohamed El-Agamy Farh , Yeon-Ju Kim , Priyanka Singh , Sun Young Jung , Jong-Pyo Kang , Deok-Chun Yang; J. Microbiol. 2017;55(10):767-774. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7033-z

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13 Citations

Abstract: Gram-staining-negative, uniflagellated, rod-shaped, designated as DCY110T, was isolated from sludge located in Gangwon province, Republic of Korea. The phylogenetic tree of 16S rRNA gene sequence showed that the strain DCY110T belonged to the genus Rhodoferax with a close similarity to Rhodoferax saidenbachensis DSM 22694T (97.7%), Rhodoferax antarcticus DSM 24876T (97.5%), Rhodoferax ferrireducens DSM 15236T (97.3%), and Rhodoferax fermentans JCM 7819T (96.7%). The predominant isoprenoid quinine was ubiquinone (Q-8). DNA G + C content was 62.8 mol%. The major polar lipids were phosphatidylethanolamine and two unidentified phospholipids. The major fatty acids (> 10%) were C12:0, C16:0, summed feature 3 (which comprised C16:1 ω7c and/or C16:1 ω6c). The DNA-DNA relatedness values between the strain DCY110T and the closely related relatives used in this study were lower than 70%. Based on the following polyphasic analysis, the strain DCY110T is considered as a novel species of the genus Rhodoferax, for which the name Rhodoferax koreense sp. nov. is proposed. The type strain is DCY- 110T (= KCTC 52288T = JCM 31441T).

A novel methanotroph in the genus Methylomonas that contains a distinct clade of soluble methane monooxygenase: Ngoc-Loi Nguyen , Woon-Jong Yu , Hye-Young Yang , Jong-Geol Kim , Man-Young Jung , Soo-Je Park , Seong-Woon Roh , Sung-Keun Rhee; J. Microbiol. 2017;55(10):775-782. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7317-3

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22 Citations

Abstract: Aerobic methane oxidation is a key process in the global carbon cycle that acts as a major sink of methane. In this study, we describe a novel methanotroph designated EMGL16-1 that was isolated from a freshwater lake using the floating filter culture technique. Based on a phylogenetic analysis of 16S rRNA gene sequences, the isolate was found to be closely related to the genus Methylomonas in the family Methylococcaceae of the class Gammaproteobacteria with 94.2–97.4% 16S rRNA gene similarity to Methylomonas type strains. Comparison of chemotaxonomic and physiological properties further suggested that strain EMGL16-1 was taxonomically distinct from other species in the genus Methylomonas. The isolate was versatile in utilizing nitrogen sources such as molecular nitrogen, nitrate, nitrite, urea, and ammonium. The genes coding for subunit of the particulate form methane monooxygenase (pmoA), soluble methane monooxygenase (mmoX), and methanol dehydrogenase (mxaF) were detected in strain EMGL16-1. Phylogenetic analysis of mmoX indicated that mmoX of strain EMGL16-1 is distinct from those of other strains in the genus Methylomonas. This isolate probably represents a novel species in the genus. Our study provides new insights into the diversity of species in the genus Methylomonas and their environmental adaptations.

Silencing the cleavage factor CFIm25 as a new strategy to control Entamoeba histolytica parasite: Juan David Ospina-Villa , Nancy Guillén , Cesar Lopez-Camarillo , Jacqueline Soto-Sanchez , Esther Ramirez-Moreno , Raul Garcia-Vazquez , Carlos A. Castañon-Sanchez , Abigail Betanzos , Laurence A. Marchat; J. Microbiol. 2017;55(10):783-791. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7259-9

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16 Citations

Abstract: The 25 kDa subunit of the Clevage Factor Im (CFIm25) is an essential factor for messenger RNA polyadenylation in human cells. Therefore, here we investigated whether the homologous protein of Entamoeba histolytica, the protozoan responsible for human amoebiasis, might be considered as a biochemical target for parasite control. Trophozoites were cultured with bacterial double-stranded RNA molecules targeting the EhCFIm25 gene, and inhibition of mRNA and protein expression was confirmed by RT-PCR and Western blot assays, respectively. EhCFIm25 silencing was associated with a significant acceleration of cell proliferation and cell death. Moreover, trophozoites appeared as larger and multinucleated cells. These morphological changes were accompanied by a reduced mobility, and erythrophagocytosis was significantly diminished. Lastly, the knockdown of EhCFIm25 affected the poly(A) site selection in two reporter genes and revealed that EhCFIm25 stimulates the utilization of downstream poly(A) sites in E. histolytica mRNA. Overall, our data confirm that targeting the polyadenylation process represents an interesting strategy for controlling parasites, including E. histolytica. To our best knowledge, the present study is the first to have revealed the relevance of the cleavage factor CFIm25 as a biochemical target in parasites.

Construction of a genetic linkage map and QTL mapping of agronomic traits in Auricularia auricula-judae: Li-Xin Lu , Fang-Jie Yao , Peng Wang , Ming Fang , You-Min Zhang , Wei-Tong Zhang , Xiang-Hui Kong , Jia Lu; J. Microbiol. 2017;55(10):792-799. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7241-6

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19 Citations

Abstract: Auricularia auricula-judae is a traditional edible fungus that is cultivated widely in China. In this study, a genetic linkage map for A. auricula-judae was constructed using a mapping population consisting of 138 monokaryons derived from a hybrid strain (A119-5). The monokaryotic parent strains A14-5 and A18-119 were derived from two cultivated varieties, A14 (Qihei No. 1) and A18 (Qihei No. 2), respectively. In total, 130 simple sequence repeat markers were mapped. These markers were developed using the whole genome sequence of A. auricula-judae and amplified in A14-5, A18- 119, and the mapping population. The map consisted of 11 linkage groups (LGs) spanning 854 cM, with an average interval length of 6.57 cM. A testcross population was derived from crossing between the monokaryon A184-57 (from the wild strain A184 as a tester strain) and the mapping population. Important agronomic trait-related QTLs, including mycelium growth rate on potato dextrose agar for the mapping population, mycelium growth rate on potato dextrose agar and sawdust for the testcross population, growth period (days from inoculation to fruiting body harvesting), and yield for the testcross population, were identified using the composite interval mapping method. Six mycelium growth raterelated QTLs were identified on LG1 and LG4, two growth period-related QTLs were identified on LG2, and three yieldrelated QTLs were identified on LG2 and LG6. The results showed no linkage relationship between mycelium growth rate and growth period. The present study provides a foundation for locating genes for important agronomic characteristics in A. auricula-judae in the future.

Mutation of the cyclic di-GMP phosphodiesterase gene in Burkholderia lata SK875 attenuates virulence and enhances biofilm formation: Hae-In Jung , Yun-Jung Kim , Yun-Jung Lee , Hee-Soo Lee , Jung-Kee Lee , Soo-Ki Kim; J. Microbiol. 2017;55(10):800-808. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7374-7

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11 Citations

Abstract: Burkholderia sp. is a gram-negative bacterium that commonly exists in the environment, and can cause diseases in plants, animals, and humans. Here, a transposon mutant library of a Burkholderia lata isolate from a pig with swine respiratory disease in Korea was screened for strains showing attenuated virulence in Caenorhabditis elegans. One such mutant was obtained, and the Tn5 insertion junction was mapped to rpfR, a gene encoding a cyclic di-GMP phosphodiesterase that functions as a receptor. Mutation of rpfR caused a reduction in growth on CPG agar and swimming motility as well as a rough colony morphology on Congo red agar. TLC analysis showed reduced AHL secretion, which was in agreement with the results from plate-based and bioluminescence assays. The mutant strain produced significantly more biofilm detected by crystal violet staining than the parent strain. SEM of the mutant strain clearly showed that the overproduced biofilm contained a filamentous structure. These results suggest that the cyclic di-GMP phosphodiesterase RpfR plays an important role in quorum sensing modulation of the bacterial virulence and biofilm formation.

The response of human bacteria to static magnetic field and radiofrequency electromagnetic field: David P. E. Crabtree , Brandon J. Herrera , Sanghoon Kang; J. Microbiol. 2017;55(10):809-815. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7208-7

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10 Citations

Abstract: Cell phones and electronic appliances and devices are inseparable from most people in modern society and the electromagnetic field (EMF) from the devices is a potential health threat. Although the direct health effect of a cell phone and its radiofrequency (RF) EMF to human is still elusive, the effect to unicellular organisms is rather apparent. Human microbiota, including skin microbiota, has been linked to a very significant role in the health of a host human body. It is important to understand the response of human skin microbiota to the RF-EMF from cell phones and personal electronic devices, since this may be one of the potential mechanisms of a human health threat brought about by the disruption of the intimate and balanced host-microbiota relationship. Here, we investigated the response of both laboratory culture strains and isolates of skin bacteria under static magnetic field (SMF) and RF-EMF. The growth patterns of laboratory cultures of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus epidermidis under SMF were variable per different species. The bacterial isolates of skin microbiota from 4 subjects with different cell phone usage history also showed inconsistent growth responses. These findings led us to hypothesize that cell phone level RF-EMF disrupts human skin microbiota. Thus, the results from the current study lay ground for more comprehensive research on the effect of RF-EMF on human health through the human-microbiota relationship.

Gly184 of the Escherichia coli cAMP receptor protein provides optimal context for both DNA binding and RNA polymerase interaction: Matt N. Hicks , Sanjiva Gunasekara , Jose Serate , Jin Park , Pegah Mosharaf , Yue Zhou , Jin-Won Lee , Hwan Youn; J. Microbiol. 2017;55(10):816-822. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7266-x

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3 Citations

Abstract: The Escherichia coli cAMP receptor protein (CRP) utilizes the helix-turn-helix motif for DNA binding. The CRP’s recognition helix, termed F-helix, includes a stretch of six amino acids (Arg180, Glu181, Thr182, Val183, Gly184, and Arg185) for direct DNA contacts. Arg180, Glu181 and Arg185 are known as important residues for DNA binding and specificity, but little has been studied for the other residues. Here we show that Gly184 is another F-helix residue critical for the transcriptional activation function of CRP. First, glycine was repeatedly selected at CRP position 184 for its unique ability to provide wild type-level transcriptional activation activity. To dissect the glycine requirement, wild type CRP and mutants G184A, G184F, G184S, and G184Y were purified and their in vitro DNA-binding activity was measured. G184A and G184F displayed reduced DNA binding, which may explain their low transcriptional activation activity. However, G184S and G184Y displayed apparently normal DNA affinity. Therefore, an additional factor is needed to account for the diminished transcriptional activation function in G184S and G184Y, and the best explanation is perturbations in their interaction with RNA polymerase. The fact that glycine is the smallest amino acid could not fully warrant its suitability, as shown in this study. We hypothesize that Gly184 fulfills the dual functions of DNA binding and RNA polymerase interaction by conferring conformational flexibility to the F-helix.

Heterologous prime-boost immunization with live SPY1 and DnaJ protein of Streptococcus pneumoniae induces strong Th1 and Th17 cellular immune responses in mice: Yulan Qiu , Xuemei Zhang , Xinyuan Zhang , Yunjun Mo , Xiaoyu Sun , Jichao Wang , Yibing Yin , Wenchun Xu; J. Microbiol. 2017;55(10):823-829. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7262-1

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6 Citations

Abstract: diseases in children under 5-year-old. Vaccine has been used as an indispensable strategy to prevent S. pneumoniae infection for more than 30 years. Our previous studies confirmed that mucosal immunization with live attenuated strain SPY1 can protect mice against nasopharyngeal colonization of S. pneumoniae and lethal pneumococcal infection, and the protective effects are comparable with those induced by commercially available 23-valent polysaccharide vaccine. However, live attenuated vaccine SPY1 needs four inoculations to get satisfactory protective effect, which may increase the risk of virulence recovery. It is reported that heterologous primeboost approach is more effective than homologous primeboost approach. In the present study, to decrease the doses of live SPY1 and improve the safety of SPY1 vaccine, we immunized mice with SPY1 and DnaJ protein alternately. Our
results
showed that heterologous prime-boost immunization with SPY1 and DnaJ protein could significantly reduce the colonization of S. pneumoniae in the respiratory tract of mice, and induce stronger Th1 and Th17 cellular immune responses than SPY1 alone. These results indicate heterologous prime-boost immunization method not only elicits better protective effect than SPY1 alone, but also reduces the doses of live SPY1 and decreases the risk of SPY1 vaccine. This work is the first time to study the protective efficiency with two different forms of S. pneumoniae candidate vaccine, and provides a new strategy for the development of S. pneumoniae vaccine.

The synthetic human beta-defensin-3 C15 peptide exhibits antimicrobial activity against Streptococcus mutans, both alone and in combination with dental disinfectants: Ki Bum Ahn , A Reum Kim , Kee-Yeon Kum , Cheol-Heui Yun , Seung Hyun Han; J. Microbiol. 2017;55(10):830-836. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7362-y

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34 Citations

Abstract: Streptococcus mutans is a major etiologic agent of human dental caries that forms biofilms on hard tissues in the human oral cavity, such as tooth and dentinal surfaces. Human β-defensin-3 (HBD3) is a 45-amino-acid natural antimicrobial peptide that has broad spectrum antimicrobial activity against bacteria and fungi. A synthetic peptide consisting of the C-terminal 15 amino acids of HBD3 (HBD3-C15) was recently shown to be sufficient for its antimicrobial activity. Thus, clinical applications of this peptide have garnered attention. In this study, we investigated whether HBD3-C15 inhibits the growth of the representative cariogenic pathogen Streptococcus mutans and its biofilm formation. HBD3-C15 inhibited bacterial growth, exhibited bactericidal activity, and attenuated bacterial biofilm formation in a dose-dependent manner. HBD3-C15 potentiated the bactericidal and anti-biofilm activity of calcium hydroxide (CH) and chlorhexidine digluconate (CHX), which are representative disinfectants used in dental clinics, against S. mutans. Moreover, HBD3-C15 showed antimicrobial activity by inhibiting biofilm formation by S. mutans and other dentinophilic bacteria such as Enterococcus faecalis and Streptococcus gordonii, which are associated with dental caries and endodontic infection, on human dentin slices. These effects were observed for HBD3-C15 alone and for HBD3-C15 in combination with CH or CHX. Therefore, we suggest that HBD3-C15 is a potential alternative or additive disinfectant that can be used for the treatment of oral infectious diseases, including dental caries and endodontic infections.

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