研究者詳細 - 前田　憲成

論文 - 前田　憲成

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Alcaligenaceae and Chromatiaceae as pollution bacterial bioindicators in palm oil mill effluent (POME) final discharge polluted rivers 査読有り

Zolkefli N., Ramli N., Mohamad-Zainal N., Mustapha N., Yusoff M., Hassan M., Maeda T.

Ecological Indicators 111 2020年04月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019 Elsevier Ltd Microorganisms are progressively adopted as reliable and specific bioindicators of pollution, with Alcaligenaceae and Chromatiaceae being recently proposed to indicate contamination in river water due to palm oil mill effluent (POME) final discharge. This study was conducted to evaluate the reliability of these bacteria to act as specific bioindicators by assessing their detections in correlation with environmental factors in rivers polluted by POME final discharge when compared to by other pollution sources. By using the Illumina MiSeq high throughput sequencing platform, bacterial diversities and compositions were compared among unpolluted (upstream) river, polluted rivers due to POME final discharge and other rivers polluted by mining, chemical and automotive industries. To correlate between bacterial compositions and metabolisms in rivers subjected to different pollutants sources, the viability and the ratio of the high and low nucleic acids (HNA/LNA) bacterial cells were also compared by using a double staining assay based on flow cytometry. Interestingly, Alcaligenaceae and Chromatiaceae were found only in POME final discharge polluted rivers (>0.15%) but were not detected in rivers polluted by other pollutants. Higher bacterial cell viability was detected in rivers polluted by POME final discharge (86–91%) as compared to the other polluted rivers (15–80%). From the viable fractions of the bacterial cells, higher HNA cells (91–93%) were quantified in the POME final discharge receiving rivers but with only 5–18% in the other rivers. These trends indicated that the nutrients carried by the POME final discharge enhanced the growth of bacteria in the receiving river water that might include Alcaligenaceae and Chromatiaceae. These results suggested that either Alcaligenaceae or Chromatiaceae or both were unique in the POME final discharge polluted rivers but not in the others. They could function as specific and reliable bacterial bioindicators relevant for the establishment of a complementary monitoring system for POME pollutant discharge.

DOI： 10.1016/j.ecolind.2019.106048

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Toxicity identification and evaluation of palm oil mill effluent and its effects on the planktonic crustacean Daphnia magna 査読有り

Hashiguchi Y., Zakaria M.R., Maeda T., Yusoff M.Z.M., Hassan M.A., Shirai Y.

Science of the Total Environment 710 2020年03月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019 Elsevier B.V. Palm oil mill effluent (POME) contains complex and highly biodegradable organic matters so discharging it without appropriate treatment may lead to environmental problems. POME final discharge quality is normally determined based on conventional chemical detection such as by biological oxygen demand (BOD) and chemical oxygen demand (COD). The novelty of the present study is that the toxicity effects of the POME final discharge samples were evaluated based on whole effluent toxicity (WET) and toxicity identification evaluation (TIE) tests using Daphnia magna. The toxicity unit (TU) values were recorded to be in the range from TU = 1.1–11 obtained from WET, and the TIE manipulation tests suggested that a substantial amount of toxic compounds was contained in the POME final discharge. Phenol, 2,6-bis (1,1-dimethylethyl)- and heavy metals such as Cu and Zn were detected in all the effluents and were recognized as being the main toxicants in the POME final discharge. GC/MS analyses also successfully identified cyclic volatile methyl siloxanes; cyclotetrasiloxane, octamethyl- (D4), cyclopentasiloxane, decamethyl- (D5), cyclohexasiloxane, dodecamethyl- (D6). D4 was detected at 0.0148–0.0357 mg/L, which could be potentially toxic. The palm oil industry used only water in the form of steam to process the fruits, and the presence of these compounds might be derived from the detergents and grease used in palm oil mill cleaning and maintenance operations. An appropriate treatment process is thus required to eliminate these toxicants from the POME final discharge. It is recommended that two approaches, chemical-based monitoring as well as biological toxicity-based monitoring, should be utilized for achieving an acceptable quality of POME final discharge in the future.

DOI： 10.1016/j.scitotenv.2019.136277

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Fate of Escherichia coli O157 spiked into commercially available fermented soybean paste (MISO) 査読有り

Hosotani Y., Kawasaki S., Maeda T., Inatsu Y.

Nippon Shokuhin Kagaku Kogaku Kaishi 67 ( 10 ) 376 - 383 2020年01月

記述言語：日本語掲載種別：研究論文（学術雑誌）

Copyright© 2020, Japanese Society for Food Science and Technology This study investigated the fate of Escherichia coli (E. coli) O157 spiked into 24 commercially available fermented soybean paste (miso) samples. Viable cell numbers of the inoculated E. coli O157 at storage conditions of 5, 10, 20, or 30 ℃ were measured by the agar plate method or most probable number method. Cell numbers of E. coli O157 decreased gradually in all tested samples. The decreases in E. coli O157 numbers depended mainly on the water activity of samples. Decreases in the contamination level of E. coli O157 did not depend on the ingredients of miso samples (malted rice, wheat, and soybean). The obtained results suggest that the commercial risk of accidental E. coli O157 contamination is practically negligible because of high cell mortality during transportation and storage processes at room temperature.

DOI： 10.3136/NSKKK.67.376

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市販味噌に混入させた大腸菌O157の消長査読有り

細谷幸恵, 川崎晋, 前田憲成, 稲津康弘

日本食品科学工学会誌 ( 公益社団法人日本食品科学工学会 ) 67 ( 10 ) 376 - 383 2020年01月

記述言語：日本語掲載種別：研究論文（学術雑誌）

<p>味噌に混入させた大腸菌O157の消長を明らかにするために，市販味噌24検体を対象に複数の保存試験区（5，10，20，30 °C）における大腸菌O157生菌数の変動を寒天平板法およびMPN法により観察した．全保存試験区において，味噌混入下の大腸菌O157は増殖することなく段階的に死滅し，その死滅速度と味噌原料（米，麦，大豆）に関連は見られなかった．一方，味噌検体の水分活性値が大腸菌O157の死滅速度に影響を与える可能性を示した．本結果により，大腸菌O157が意図せず味噌に混入した場合であっても，常温での流通，保存の期間に死滅することから，そのリスクは実質的に無視しうるものであると推察された．</p>

DOI： 10.3136/nskkk.67.376

その他リンク： https://ci.nii.ac.jp/naid/130007934533

Evaluation of hydrogen metabolism by Escherichia coli strains possessing only a single hydrogenase in the genome 査読有り

Shekhar C., Kai T., Garcia-Contreras R., Sanchez-Torres V., Maeda T.

International Journal of Hydrogen Energy 2020年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020 Hydrogen Energy Publications LLC The four hydrogenase isozymes; hydrogenase 1 (Hyd-1), hydrogenase 2 (Hyd-2), hydrogenase 3 (Hyd-3) and hydrogenase 4 (Hyd-4) of Escherichia coli have been reported for their crucial functions in the hydrogen metabolism; however, their distinctive roles could not be completely understood. In this study, four ideal hydrogenase operon mutants, Δhyb hyc hyf, Δhya hyc hyf, Δhya hyb hyf, and Δhya hyb hyc, in which only a single hydrogenase is intact in the genome, were constructed as well as one quadruple mutant (Δhya hyb hyc hyf) that all four hydrogenase operons were deleted. First, single operon mutants and single-gene mutants for each hydrogenase showed different hydrogen productivity and growth in the anaerobic fermentation, indicating that bacterial phenotype regarding the hydrogen metabolism via the deletion of each operon is different with that of each single gene. Then, 4 triple hydrogenase operon mutants and one quadruple mutant were investigated to evaluate the hydrogen metabolism (hydrogen production and uptake) using glucose or glycerol as a substrate of hydrogen fermentation. With both the carbon sources, only Hyd-2 and Hyd-3 were able to produce hydrogen. Furthermore, all the hydrogenases showed hydrogen uptake activity. In addition, no hydrogen production and hydrogen uptake were detected in the quadruple mutant which does not have all 4 hydrogenases. Hydrogen production from Hyd-2 and Hyd-3 was further confirmed by complementing their operons in the cloning vector pBR322.

DOI： 10.1016/j.ijhydene.2020.10.070

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Dark fermentative biohydrogen production from palm oil mill effluent: Operation factors and future progress of biohydrogen energy 査読有り

Rosman F.S., Yusoff M.Z.M., Zakaria M.R., Maeda T., Hassan M.A.

Pertanika Journal of Science and Technology 28 ( Special issue 2 ) 243 - 258 2020年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Malaysia is one of the largest producers and exporters of palm oil, thus, a large amount of palm oil mill effluent (POME) is generated through this process. POME contributes to environmental pollution if it is not properly treated. This complex effluent consists of colloidal matters and mainly organic components with more than 90% water. Thus, it is useful to be used as a substrate for fermentative processes, including biohydrogen production. Biohydrogen from POME is a renewable source that can potentially serve as an alternative to substitute fossil fuels. The abundance of POME and the rising price of fossil fuels in the global market create a demand for this source of energy. However, the complexity of the substituents in POME makes the optimisation of this effluent as a substrate in dark fermentation a challenge. This review article explores the important parameters that need to be considered for optimal biohydrogen production, such as the bioreactor operational parameters and the microbial consortium. Besides, the potential of metabolic engineering as a tool to overcome the limitations of the microbial strains to metabolise POME for increased biohydrogen production was also reviewed. However, further research and development are needed to increase the biohydrogen yield on par with commercial demand.

DOI： 10.47836/pjst.28.S2.19

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AiiM Lactonase Strongly Reduces Quorum Sensing Controlled Virulence Factors in Clinical Strains of Pseudomonas aeruginosa Isolated From Burned Patients 査読有り

López-Jácome L.E., Garza-Ramos G., Hernández-Durán M., Franco-Cendejas R., Loarca D., Romero-Martínez D., Nguyen P.T.D., Maeda T., González-Pedrajo B., Díaz-Guerrero M., Sánchez-Reyes J.L., Díaz-Ramírez D., García-Contreras R.

Frontiers in Microbiology 10 2019年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

© Copyright © 2019 López-Jácome, Garza-Ramos, Hernández-Durán, Franco-Cendejas, Loarca, Romero-Martínez, Nguyen, Maeda, González-Pedrajo, Díaz-Guerrero, Sánchez-Reyes, Díaz-Ramírez and García-Contreras. Pseudomonas aeruginosa is an opportunistic bacterium associated with healthcare infections in intensive care units (ICUs), ventilator-associated pneumonia (VAP), surgical site infections, and burns. This bacterium causes 75% of death in burned patients, since it can develop a persistent biofilm associated with infections, express several virulence factors, and antibiotic-resistance mechanisms. Some of these virulence factors are proteases such as elastase and alkaline protease, or toxic metabolites such as pyocyanin and is one of the few microorganisms able to produce cyanide, which inhibits the cytochrome oxidase of host cells. These virulence factors are controlled by quorum sensing (QS). In this work, 30 P. aeruginosa clinical strains isolated from burned patients from a tertiary hospital in Mexico City were studied. Antibiotic susceptibility tests were done, and virulence factors (elastase, alkaline protease, HCN, and pyocyanin) were determined in presence of an N-acylhomoserine lactonase, AiiM able to hydrolyze a wide range of acyl homoserine lactones. The treatment reduced significantly the activities of elastase and alkaline protease, and the production of pyocyanin and HCN in all producer strains but not the secretion of toxins through the type III secretion system. Our work suggests that AiiM treatment may be an effective therapy to combat P. aeruginosa infection in burn patients.

DOI： 10.3389/fmicb.2019.02657

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Endolithic microbial habitats hosted in carbonate nodules currently forming within sediment at a high methane flux site in the sea of Japan 査読有り

Yanagawa K., Shiraishi F., Tanigawa Y., Maeda T., Mustapha N., Owari S., Tomaru H., Matsumoto R., Kano A.

Geosciences (Switzerland) 9 ( 11 ) 2019年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. Concretionary carbonates in deep-sea methane seep fields are formed as a result of microbial methane degradation, called anaerobic oxidation of methane (AOM). Recently, active microorganisms, including anaerobic methanotrophic archaea, were discovered from methane seep-associated carbonate outcroppings on the seafloor. However sedimentary buried carbonate nodules are a hitherto unknown microbial habitat. In this study, we investigated the microbial community structures in two carbonate nodules collected from a high methane flux site in a gas hydrate field off the Oki islands in the Sea of Japan. The nodules were formed around sulfate-methane interfaces (SMI) corresponding to 0.7 and 2.2 m below the seafloor. Based on a geochemical analysis, light carbon isotopic values ranging from -54.91% to -37.32% were found from the nodules collected at the shallow SMI depth, which were attributed to the high contributions of AOM-induced carbonate precipitation. Signatures of methanotrophic archaeal populations within the sedimentary buried nodule were detected based on microbial community composition analyses and quantitative real-time PCR targeted 16S rRNA, and functional genes for AOM. These results suggest that the buried carbonate nodule currently develops AOM-related microbial communities, and grows depending on the continued AOM under high methane flux conditions.

DOI： 10.3390/geosciences9110463

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Seeding Public Goods Is Essential for Maintaining Cooperation in Pseudomonas aeruginosa 査読有り

Loarca D., Díaz D., Quezada H., Guzmán-Ortiz A., Rebollar-Ruiz A., Presas A., Ramírez-Peris J., Franco-Cendejas R., Maeda T., Wood T., García-Contreras R.

Frontiers in Microbiology 10 2019年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

© Copyright © 2019 Loarca, Díaz, Quezada, Guzmán-Ortiz, Rebollar-Ruiz, Presas, Ramírez-Peris, Franco-Cendejas, Maeda, Wood and García-Contreras. Quorum sensing in Pseudomonas aeruginosa controls the production of costly public goods such as exoproteases. This cooperative behavior is susceptible to social cheating by mutants that do not invest in the exoprotease production but assimilate the amino acids and peptides derived by the hydrolysis of proteins in the extracellular media. In sequential cultures with protein as the sole carbon source, these social cheaters are readily selected and often reach equilibrium with the exoprotease producers. Nevertheless, an excess of cheaters causes the collapse of population growth. In this work, using the reference strain PA14 and a clinical isolate from a burn patient, we demonstrate that the initial amount of public goods (exoprotease) that comes with the inoculum in each sequential culture is essential for maintaining population growth and that eliminating the exoprotease in the inoculum leads to rapid population collapse. Therefore, our results suggest that sequential washes should be combined with public good inhibitors to more effectively combat P. aeruginosa infections.

DOI： 10.3389/fmicb.2019.02322

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Cytocompatible and antibacterial properties of chitosan-siloxane hybrid spheres 査読有り

Shirosaki Y., Nakatsukasa M., Yasutomi S., Cruz-Neves S., Hayakawa S., Osaka A., Maeda T., Miyazaki T.

Polymers 11 ( 10 ) 2019年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. Microporous spheres in a hybrid system consisting of chitosan and γ-glycidoxypropyltrimethoxysilane (GPTMS) have advantages in a range of applications, e.g., as vehicles for cell transplantation and soft tissue defect filling materials, because of their excellent cytocompatibility with various cells. In this study, microporous chitosan-GPTMS spheres were prepared by dropping chitosan-GPTMS precursor sols,with orwithout a ceriumchloride, into liquid nitrogen using a syringe pump. The droplets were then freeze dried to give the pores of size 10 to 50 μm. The cell culture tests showed that L929 fibroblast-like cells migrated into the micropores larger than 50 μm in diameter, whereasMG63 osteoblast-like cells proliferated well and covered the granule surfaces. The spheres with cerium chloride showed antibacterial properties against both gram-negative and gram-positive bacteria.

DOI： 10.3390/polym11101676

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Pseudogene YdfW in Escherichia coli decreases hydrogen production through nitrate respiration pathways 査読有り

Mokhtar M., Mohd Yusoff M., Mohamad Ali M., Mustapha N., Wood T., Maeda T.

International Journal of Hydrogen Energy 44 ( 31 ) 16212 - 16223 2019年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019 Hydrogen Energy Publications LLC Escherichia coli has approximately 4300 open reading frames and about 178 of them are annotated as pseudogenes. The existence of the pseudogenes in E. coli had raised the question of whether they contribute to any cell function. Recently, several pseudogenes have been studied; however, these genes are still considered rare and tend to be ignored as so-called junk. Our recent study has shown several pseudogenes in E. coli are essential in hydrogen metabolism. ydfW is one of the pseudogenes associated with hydrogen metabolism. Here, we found carbon dioxide and nitrate in the fermentation medium of mutant ydfW suggesting that this strain may induce nitrate pathways. The Fdh-N complex is comprised of FdnG, FdnH, and FdnI subunits which correspond to the nitrate-nitrite pathway. This finding is supported by transcription analysis that shows formate dehydrogenase (fdnG) and nitrate reductase (narG) are significantly induced (25- and 18-fold, respectively). FdnG and NarG play a significant role in the reduction of nitrate into nitrite; hence, their genes are induced by the build-up of nitrate. Based on in silico docking analysis, we predict that YdfW is covalently bound to the Fdh-N complex in the cytoplasm. Hence, deletion of ydfW is expected has influenced the nitrate-nitrite pathway. Subsequently, the situation will affect the hydrogen production in E. coli.

DOI： 10.1016/j.ijhydene.2019.04.228

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Quorum sensing between Gram-negative bacteria responsible for methane production in a complex waste sewage sludge consortium 査読有り

Nguyen P., Mustapha N., Kadokami K., Garcia-Contreras R., Wood T., Maeda T.

Applied Microbiology and Biotechnology 103 ( 3 ) 1485 - 1495 2019年02月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Quorum sensing (QS) plays a key role in activating bacterial functions through small molecules called autoinducers. In this study, the QS of Gram-negative bacteria in waste sewage sludge (WSS) was downregulated by adding the quorum quenching enzyme, AiiM lactonase, which cleaved the acyl-homoserine lactone (AHL) autoinducer signals from Gram-negative bacteria, and subsequently methane production was inhibited by over 400%. The pH was lowered after 2 days in the anaerobic fermentation whereas protease activity at the hydrolysis step was almost the same with or without AiiM. The production of acetic acid significantly increased during the fermentation in the presence of AiiM. The bacterial community at day 2 indicated that the population of Gram-positive bacteria increased in the presence of AiiM, and the percentage of Gram-negative bacteria decreased in the WSS containing AiiM. The change in the bacterial community in the presence of AiiM may be due to the different antimicrobial agents produced in the WSS because some of the Gram-positive bacteria were killed by adding the solid-phase extraction (SPE) fraction from the WSS without AiiM. In contrast, the SPE fraction with AiiM had reduced bactericidal activity against Gram-negative bacteria. Thus, bacterial signaling between Gram-negative bacteria is critical for methane production by the microbial consortia.

DOI： 10.1007/s00253-018-9553-9

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Dynamics of microbial populations responsible for biodegradation during the full-scale treatment of palm oil mill effluent 査読有り

Mohd-Nor D., Ramli N., Sharuddin S., Hassan M., Mustapha N., Ariffin H., Sakai K., Tashiro Y., Shirai Y., Maeda T.

Microbes and Environments 34 ( 2 ) 121 - 128 2019年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019, Japanese Society of Microbial Ecology. All rights reserved. Despite efforts to address the composition of the microbial community during the anaerobic treatment of palm oil mill effluent (POME), its composition in relation to biodegradation in the full-scale treatment system has not yet been extensively examined. Therefore, a thorough analysis of bacterial and archaeal communities was performed in the present study using MiSeq sequencing at the different stages of the POME treatment, which comprised anaerobic as well as facultative anaerobic and aerobic processes, including the mixed raw effluent (MRE), mixing pond, holding tank, and final discharge phases. Based on the results obtained, the following biodegradation processes were suggested to occur at the different treatment stages: (1) Lactobacillaceae (35.9%) dominated the first stage, which contributed to high lactic acid production; (2) the higher population of Clostridiaceae in the mixing pond (47.7%) and Prevotellaceae in the holding tank (49.7%) promoted acetic acid production; (3) the aceticlastic methanogen Methanosaetaceae (0.6–0.8%) played a role in acetic acid degradation in the open digester and closed reactor for methane generation; (4) Syntrophomonas (21.5–29.2%) appeared to be involved in the degradation of fatty acids and acetic acid by syntrophic cooperation with the hydrogenotrophic methanogen, Methanobacteriaceae (0.6–1.3%); and (5) the phenols and alcohols detected in the early phases, but not in the final discharge phase, indicated the successful degradation of lignocellulosic materials. The present results contribute to a better understanding of the biodegradation mechanisms involved in the different stages of the full-scale treatment of POME.

DOI： 10.1264/jsme2.ME18104

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Alcaligenaceae and Chromatiaceae as reliable bioindicators present in palm oil mill effluent final discharge treated by different biotreatment processes 査読有り

Mohd-Nor D., Ramli N., Sharuddin S., Hassan M., Mustapha N., Amran A., Sakai K., Shirai Y., Maeda T.

Ecological Indicators 95 468 - 473 2018年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018 Elsevier Ltd This study was undertaken to confirm the reliability of the proposed potential bioindicators, Alcaligenaceae and Chromatiaceae to specifically indicate contamination in river water by palm oil mill effluent (POME) final discharge. The use of bioindicators could assist in determining the specific cause of contamination in water bodies. Alcaligenaceae and Chromatiaceae were shown by a previous study to be present in river water contaminated with the final discharge from the treatment of POME. In the present study, the compositions of the bacterial communities in the POME final discharge obtained from four different palm oil mills which used different biotreatments of POME were elucidated using high-throughput MiSeq. The four POME final discharges studied showed different species richness and evenness among them. However, the bacterial community compositions in the different final discharges exhibited almost similar patterns in that the phylum Proteobacteria was dominant in all the samples. The proposed bioindicators, the Alcaligenaceae and Chromatiaceae families, were found to be present in all the four final discharges despite the different characteristics of the mills and the different biotreatment processes used by them. These bioindicators were also strongly and positively correlated with the biochemical oxygen demand (BOD5) concentration. This makes them reliable bacterial indicators to detect the presence of POME final discharge in river water.

DOI： 10.1016/j.ecolind.2018.08.007

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Pseudogene product YqiG is important for pflB expression and biohydrogen production in Escherichia coli BW25113 査読有り

Zakaria M.

3 Biotech 8 ( 10 ) 2018年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Pseudogenes in the Escherichia coli genome are assumed to be non-functional. In this study, Keio collection BW25113∆yqiG and YqiG-producing strain (BW25113/pCA24N-YqiG) were used to evaluate the importance of pseudogene yqiG in hydrogen metabolism. Our results show pseudogene protein YqiG was identified as an essential protein in the production of biohydrogen from glucose. The mutant yqiG decreased biohydrogen production from 37 µmol mg−1protein to 6 µmol mg−1protein compared to the wild-type strain, and glucose consumption was reduced by 80%. Through transcriptional analysis, we found that the yqiG mutation represses pflB transcription tenfold; pflB encodes pyruvate-formate lyase, one of the key enzymes in the anaerobic metabolism of E. coli. Moreover, production of YqiG stimulated glycolysis and increased biohydrogen productivity 1.5-fold compared to that of the wild-type strain. Thus, YqiG is important for the central glycolysis reaction and is able to influence hydrogen metabolism activity in E. coli.

DOI： 10.1007/s13205-018-1461-2

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Electron carriers increase electricity production in methane microbial fuel cells that reverse methanogenesis 査読有り

Yamasaki R.

Biotechnology for Biofuels 11 ( 1 ) 2018年07月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018 The Author(s). Background: We previously reversed methanogenesis in microbial fuel cells (MFCs) to produce electricity for the first time from methane by combining an engineered archaeal strain that produces methyl-coenzyme M reductase from unculturable anaerobic methanotrophs (to capture methane and secrete acetate) with Geobacter sulfurreducens (to produce electrons from the generated acetate) and methane-acclimated sludge (to provide electron shuttles). Results: Here, the power density in MFCs was increased 77-fold to 5216 mW/m2and the current density in MFCs was increased 73-fold to 7.3 A/m2by reducing the surface area of the cathode (to make reasonable comparisons to other MFCs), by changing the order the strains of the consortium were added to the anode compartment, and by adding additional electron carriers (e.g., humic acids and cytochrome C). Conclusions: This power density and current density are comparable to the best for any MFC, including those with Shewanella and Geobacter spp. that utilize non-gaseous substrates. In addition, we demonstrate the methane MFC may be used to power a fan by storing the energy in a capacitor. Hence, MFCs that convert methane to electricity are limited by electron carriers.

DOI： 10.1186/s13068-018-1208-7

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Enhanced phagocytosis of Aggregatibacter actinomycetemcomitans cells by macrophages activated by a probiotic Lactobacillus strain 査読有り

Jaffar N., Okinaga T., Nishihara T., Maeda T.

Journal of Dairy Science 101 ( 7 ) 5789 - 5798 2018年07月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018 American Dairy Science Association The activation of phagocytosis is one important approach to clearing pathogenic cells in a host. This study evaluated the ability of probiotic lactobacilli to induce phagocytic activity as well as the clearance of a periodontal pathogen, Aggregatibacter actinomycetemcomitans. First, the activation of phagocytosis was found by using lyophilized dead cells. Probiotic Lactobacillus strains significantly enhanced the phagocytic activity of macrophage cells, indicating that the probiotic lactobacilli have a remarkable ability to stimulate the macrophages. Essentially, 3 Lactobacillus strains tested did not have any critical toxic effect on the murine macrophage, and Lactobacillus johnsonii NBRC 13952 showed the least cytotoxic effect on the RAW264.7 macrophages. The expression of classically activated macrophage markers, IL-1β, and cluster of differentiation 80 increased by L. johnsonii NBRC 13952; however, there was no significant difference for IL-18. The highest phagocytic activity by macrophages was found in a condition in which the macrophage activated by L. johnsonii NBRC 13952 functions to kill the cells of A. actinomycetemcomitans. Correlating with the result, a high amount of hypodiploid DNA (SubG1) was detected from the macrophage cells stimulated by L. johnsonii NBRC 13952. Taken together, the results suggest that macrophages activated by the Lactobacillus strain can facilitate the phagocytosis of A. actinomycetemcomitans cells by linking with enhanced apoptotic activities. In conclusion, L. johnsonii NBRC 13952 has a certain role in activating the RAW264.7 macrophages, thereby counteracting the infection of A. actinomycetemcomitans.

DOI： 10.3168/jds.2017-14355

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Pyocyanin restricts social cheating in Pseudomonas aeruginosa 査読有り

Castañeda-Tamez P., Ramírez-Peris J., Pérez-Velázquez J., Kuttler C., Jalalimanesh A., Saucedo-Mora M., Jiménez-Cortés J., Maeda T., González Y., Tomás M., Wood T., García-Contreras R.

Frontiers in Microbiology 9 ( JUN ) 2018年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018 Castañeda-Tamez, Ramírez-Peris, Pérez-Velázquez, Kuttler, Jalalimanesh, Saucedo-Mora, Jiménez-Cortés, Maeda, González, Tomás, Wood and García-Contreras. Quorum sensing (QS) in Pseudomonas aeruginosa coordinates the expression of virulence factors, such as exoproteases and siderophores, that are public goods utilized by the whole population of bacteria, regardless of whether they invested or not in their production. These public goods can be used by QS defective mutants for growth, and since these mutants do not contribute to public goods production, they are considered social cheaters. Pyocyanin is a phenazine that is a toxic, QS-controlled metabolite produced by P. aeruginosa. It is a redox-active compound and promotes the generation of reactive oxygen species; it also possesses antibacterial properties and increases fitness in competition with other bacterial species. Since QS-deficient individuals are less able to tolerate oxidative stress, we hypothesized that the pyocyanin produced by the wild-type population could promote selection of functional QS systems in this bacterium. Here, we demonstrate, using competition experiments and mathematical models, that, indeed, pyocyanin increases the fitness of the cooperative QS-proficient individuals and restricts the appearance of social cheaters. In addition, we also show that pyocyanin is able to select QS in other bacteria such as Acinetobacter baumannii.

DOI： 10.3389/fmicb.2018.01348

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Seeking key microorganisms for enhancing methane production in anaerobic digestion of waste sewage sludge 査読有り

Mustapha N., Hu A., Yu C., Sharuddin S., Ramli N., Shirai Y., Maeda T.

Applied Microbiology and Biotechnology 102 ( 12 ) 5323 - 5334 2018年06月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Efficient approaches for the utilization of waste sewage sludge have been widely studied. One of them is to use it for the bioenergy production, specifically methane gas which is well-known to be driven by complex bacterial interactions during the anaerobic digestion process. Therefore, it is important to understand not only microorganisms for producing methane but also those for controlling or regulating the process. In this study, azithromycin analogs belonging to macrolide, ketolide, and lincosamide groups were applied to investigate the mechanisms and dynamics of bacterial community in waste sewage sludge for methane production. The stages of anaerobic digestion process were evaluated by measuring the production of intermediate substrates, such as protease activity, organic acids, the quantification of bacteria and archaea, and its community dynamics. All azithromycin analogs used in this study achieved a high methane production compared to the control sample without any antibiotic due to the efficient hydrolysis process and the presence of important fermentative bacteria and archaea responsible in the methanogenesis stage. The key microorganisms contributing to the methane production may be Clostridia, Cladilinea, Planctomycetes, and Alphaproteobacteria as an accelerator whereas Nitrosomonadaceae and Nitrospiraceae may be suppressors for methane production. In conclusion, the utilization of antibiotic analogs of macrolide, ketolide, and lincosamide groups has a promising ability in finding the essential microorganisms and improving the methane production using waste sewage sludge.

DOI： 10.1007/s00253-018-9003-8

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Current state and perspectives in hydrogen production by Escherichia coli: roles of hydrogenases in glucose or glycerol metabolism 招待有り査読有り

Maeda T., Tran K., Yamasaki R., Wood T.

Applied Microbiology and Biotechnology 102 ( 5 ) 2041 - 2050 2018年03月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Escherichia coli has been a robust host strain for much biological research, in particular, research in metabolic engineering, protein engineering, and heterologous gene expression. In this mini review, to understand bacterial hydrogen production by E. coli, the effect of glucose and glycerol metabolism on hydrogen production is compared, and the current approaches to enhance hydrogen production from glycerol as a substrate are reviewed. In addition, the argument from past to present on the functions of E. coli hydrogenases, hydrogenase 1, hydrogenase 2, hydrogenase 3, and hydrogenase 4 is summarized. Furthermore, based on the literature that the E. coli formate-hydrogen lyase is essential for bacterial hydrogen production via recombinant hydrogenases, research achievements from the past regarding heterologous production of hydrogenase are rethought.

DOI： 10.1007/s00253-018-8752-8

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85040906850&origin=inward

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