論文 - 前田　憲成

A Novel Archaeal Lineage in Boiling Hot Springs around Oyasukyo Gorge (Akita, Japan) 査読有り

Asamatsu Katsuhiro, Yoshitake Kai, Saito Makoto, Prasitwuttisak Wipoo, Ishibashi Jun-ichiro, Tsutsumi Akihi, Mustapha Nurul Asyifah, Maeda Toshinari, Yanagawa Katsunori

Ｍｉｃｒｏｂｅｓ　ａｎｄ　ｅｎｖｉｒｏｎｍｅｎｔｓ ( 日本微生物生態学会 / 日本土壌微生物学会 / Taiwan Society of Microbial Ecology / 植物微生物研究会 / 極限環境微生物学会 )   36 ( 4 )   2021年01月

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記述言語：英語   掲載種別：研究論文（学術雑誌）

<p>A novel deep-branching archaeal lineage was discovered at high-temperature hot springs around Oyasukyo Gorge in Akita Prefecture, Japan. Actively boiling hot spring water contained >1×10⁴ microbes mL^–1. The microbial community composition assessed by analyzing 16S rRNA gene amplicons revealed that the dominant bacterial phyla were <i>Proteobacteria</i> and <i>Aquificae</i> (>50% of the microbial composition) in samples collected in 2016 and 2019, respectively. Approximately 10% of the reads obtained in both years were not assigned to any taxonomy. The more detailed phylogenetic positions of the unassigned sequences identified using a clone library and phylogenetic tree showed that they formed a clade that was independent, distantly related to known phyla, and had low similarity (<82%) to all other sequences in available databases. The present results suggest that this novel archaeal phylum-level lineage thrives in boiling hot springs in Japan.</p>

DOI： 10.1264/jsme2.ME21048

CiNii Article

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Effect of Aso limonite on anaerobic digestion of waste sewage sludge 査読有り

Mustapha N.A., Toya S., Maeda T.

AMB Express   10 ( 1 )   2020年12月

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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, The Author(s). The effect of Aso volcanic limonite was explored in anaerobic digestion using waste sewage sludge (WSS). In this study, methane and hydrogen sulfide were remarkably inhibited when Aso limonite was mixed with WSS as well as a significant reduction of ammonia. Although pH was lowered after adding Aso limonite, methane was still inhibited in neutralized pH condition at 7.0. Hydrolysis stage was not influenced by Aso limonite as supported by the result that a high protease activity was still detected in the presence of the material. However, acidogenesis stage was affected by Aso limonite as indicated by the different productions of organic acids. Acetic acid, was accumulated in the presence of Aso limonite due to the inhibition of methane production, except in the highest concentration of Aso limonite which the production of acetate may be inhibited. Besides, the production of propionate and butyrate reduced in accordance to the increased concentration of Aso limonite. In addition, Archaeal activity (methanogens) in WSS with Aso limonite was low in agreement with the low methane production. Thus, these results indicate that Aso limonite influences the acidogenesis and methanogenesis processes, by which the productions of methane and ammonia were inhibited. On the other hand, in the contactless of Aso limonite during the anaerobic digestion of WSS (Aso limonite was placed in the area of headspace in the vial), Aso limonite had the adsorptive ability for hydrogen sulfide from WSS, but not for methane. This contactless system of Aso limonite may be a practical means to remove hydrogen sulfide without inhibiting methane production as an important bioenergy source.

DOI： 10.1186/s13568-020-01010-w

Kyutacar

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A review of current and emerging approaches for water pollution monitoring 査読有り

Zolkefli N., Sharuddin S.S., Yusoff M.Z.M., Hassan M.A., Maeda T., Ramli N.

Water (Switzerland)   12 ( 12 )   1 - 30   2020年12月

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. The aquatic ecosystem is continuously threatened by the infiltration and discharge of anthropogenic wastewaters. This issue requires the unending improvement of monitoring systems to become more comprehensive and specific to targeted pollutants. This review intended to elucidate the overall aspects explored by researchers in developing better water pollution monitoring tools in recent years. The discussion is encircled around three main elements that have been extensively used as the basis for the development of monitoring methods, namely the dissolved compounds, bacterial indicator, and nucleic acids. The latest technologies applied in wastewater and surface water mapped from these key players were reviewed and categorized into physicochemical and compound characterizations, biomonitoring, and molecular approaches in taxonomical and functional analyses. Overall, researchers are continuously rallying to enhance the detection of causal source for water pollution through either conventional or mostly advanced approaches focusing on spectrometry, high-throughput sequencing, and flow cytometry technology among others. From this review’s perspective, each pollution evaluation technology has its own advantages and it would be beneficial for several aspects of pollutants assessments to be combined and established as a complementary package for better aquatic environmental management in the long run.

DOI： 10.3390/w12123417

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Effect of calcium acetate content on apatite-forming ability and mechanical property of pmma bone cement modified with quaternary ammonium 査読有り

Wang H., Maeda T., Miyazaki T.

Materials   13 ( 21 )   1 - 8   2020年11月

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© MDPI AG. All rights reserved. Polymethyl methacrylate (PMMA)-based bone cement is a popular biomaterial used for fixation of artificial joints. A next-generation bone cement having bone-bonding ability, i.e., bioactivity and antibacterial property is desired. We previously revealed that PMMA cement added with 2-(tert-butylamino)ethyl methacrylate, γ-methacryloxypropyltrimethoxysilane and calcium acetate showed in vitro bioactivity and antibacterial activity. This cement contains calcium acetate at 20% of the powder component. Lower content of the calcium acetate is preferable, because the release of a lot of calcium salt may degrade mechanical properties in the body environment. In the present study, we investigate the effects of calcium acetate content on the setting property and mechanical strength of the cement and apatite formation in simulated body fluid (SBF). The setting time increased and the compressive strength decreased with an increase in calcium acetate content. Although the compressive strength decreased after immersion in SBF for 7 d, all the cements still satisfied the requirements of ISO5833. Apatite was formed in SBF within 7 d on the samples where the calcium acetate content was 5% or more. Therefore, it was found that PMMA cement having antibacterial properties and bioactivity can be obtained even if the amount of the calcium acetate is reduced to 5%.

DOI： 10.3390/ma13214998

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Mechanism of carbon partitioning towards starch and triacylglycerol in Chlorella vulgaris under nitrogen stress through whole-transcriptome analysis 査読有り

Nordin N., Yusof N., Maeda T., Mustapha N.A., Mohd Yusoff M.Z., Raja Khairuddin R.F.

Biomass and Bioenergy   138   2020年07月

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2020 Elsevier Ltd This study aims to elucidate the mechanism of carbon partitioning towards starch and triacylglycerol (TAG) under nitrogen stress. Whole-transcriptome analysis was performed using RNA sequencing before being validated with qRT-PCR. The strain, Chlorella vulgaris UPSI-JRM01, exhibited a two-stage response to nitrogen stress: i) carbohydrate accumulation, plastid protein degradation and amino acid biosynthesis; and ii) lipid accumulation, carbohydrate degradation and DNA damage. In the first stage, the genes responsible for plastid protein degradation (CD4A), amino acid biosynthesis (arg, GLSN, AHCY, win1), carbon fixation (RuBisCO, GapC, fba, TK) and starch synthesis (SS, SBE2) were upregulated. In the second stage, the upregulation of genes responsible for starch degradation (SP), glycolysis (PFO, PK, ACS), fatty acid biosynthesis (FabH, accD) and TAG accumulation (DGAT2) were observed. By contrast, the components of photosystem I (PsbD, PsbC, PsbB), photosystem II (PsaA), cytochrome b6/f (PetA, PetG) and F-type ATPase (beta, alpha) were downregulated. The results suggested that nitrogen stress triggered high starch accumulation before the carbon was partitioned towards triacylglycerol (TAG) for long-term energy storage by two different pathways: chloroplastic TAG synthesis and glycerolipid metabolism. The starch build-up functions served as a rapid response to nitrogen stress, whereas subsequent lipid accumulation benefited the long-term storage of energy. This research provides in-depth understanding of the metabolic changes triggered by nitrogen stress.

DOI： 10.1016/j.biombioe.2020.105600

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Microalgae-bacteria interaction in palm oil mill effluent treatment 査読有り

Mohd Udaiyappan A.F., Hasan H.A., Takriff M.S., Abdullah S.R.S., Maeda T., Mustapha N.A., Mohd Yasin N.H., Nazashida Mohd Hakimi N.I.

Journal of Water Process Engineering   35   2020年06月

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2020 Elsevier Ltd Palm oil mill effluent (POME) contains a substantial amount of nutrients and a significant amount of indigenous microorganisms that consume the nutrients for their growth. In this study, we demonstrated that cultivation of microalgae in POME was able to reduce its carbon and nutrient contents. Three native microalgae isolates, namely, Coelastrella sp. UKM4, Chlamydomonas sp. UKM6 and Scenedesmus sp. UKM9, were cultured in sterilized and unsterilized anaerobic POME to evaluate the microalgae-bacteria interactions for phycoremediation of POME. The results showed higher COD removal in unsterilized POME than in sterilized POME due to microalgae-bacteria consortia interaction. Of the three microalgae isolates, the interaction of Scenedesmus sp. UKM9 with bacteria showed the highest COD and PO43− removal percentages. For NH4+ removal, all three isolates showed removal of more than 80 % in both sterilized and unsterilized POME. Quantitative real-time polymerase chain reaction analysis showed that the quantities of bacteria were constant after the treatment, while the quantities of microalgae changed. Metagenomics analysis showed that the community of bacteria shifted after microalgae cultivation in POME, with Actinobacteria, Bacteroidetes, Planctomycetes and Proteobacteria being the major phyla.

DOI： 10.1016/j.jwpe.2020.101203

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Characterization of gallium resistance induced in a Pseudomonas aeruginosa cystic fibrosis isolate 査読有り

Tovar-García A., Angarita-Zapata V., Cazares A., Jasso-Chávez R., Belmont-Díaz J., Sanchez-Torres V., López-Jacome L.E., Coria-Jiménez R., Maeda T., García-Contreras R.

Archives of Microbiology   202 ( 3 )   617 - 622   2020年04月

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. The repurposing of gallium nitrate as an antibacterial, a drug used previously for the treatment of hypercalcemia, is a plausible alternative to combat infections by Pseudomonas aeruginosa, since it has antipseudomonal properties in vitro and in vivo in animal models and in human lung infections. Furthermore, gallium nitrate tolerance in clinical isolates is very rare. Nevertheless, studies on the reference strains PA14 and PAO1 show that resistance against gallium nitrate is achieved by decreasing gallium intracellular levels by increasing the production of pyocyanin. In this work, we induced resistance in a cystic fibrosis P. aeruginosa isolate and explored its resistance mechanisms. This isolated strain, INP-58M, was not a pyocyanin producer, and its pyoverdine levels remained unchanged upon gallium addition. However, it showed higher activities of NADPH-producing enzymes and the antioxidant enzyme SOD when gallium was added, which suggests a better antioxidant response. Remarkably, gallium intracellular levels in the resistant isolate were higher than those of the parental strain at 20 h but lower after 24 h of culture, suggesting that this strain is capable of gallium efflux.

DOI： 10.1007/s00203-019-01777-y

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Biochar enhanced the nitrifying and denitrifying bacterial communities during the composting of poultry manure and rice straw 査読有り

Zainudin M.H., Mustapha N.A., Maeda T., Ramli N., Sakai K., Hassan M.

Waste Management   106   240 - 249   2020年04月

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2020 Elsevier Ltd Biochar has proven to be a feasible additive for mitigating nitrogen loss during the composting process. This study aims to evaluate the influence of biochar addition on bacterial community and physicochemical properties changes, including ammonium (NH4+), nitrite (NO2−) and nitrate (NO3−) contents during the composting of poultry manure. The composting was carried out by adding 20% (w/w) of biochar into the mixture of poultry manure and rice straw with a ratio of 2:1, and the same treatment without biochar was prepared as a control. The finished product of control compost recorded the high contents of NO2− and NO3− (366 mg/kg and 600 mg/kg) with reduced the total NH4+ content to 10 mg/kg. Meanwhile, biochar compost recorded a higher amount of total NH4+ content (110 mg/kg) with low NO2− and NO3− (161 mg/kg and 137 mg/kg) content in the final composting material. The principal component analysis showed that the dynamics of dominant genera related to Halomonas, Pusillimonas, and Pseudofulvimonas, all of which were known as nitrifying and denitrifying bacteria, was significantly correlated with the dynamic of NO2− and NO3− content throughout the composting process. The genera related to Pusillimonas, and Pseudofulvimonas appeared as the dominant communities as the NO2− and NO3− increased. In contrast, as the NO2− and NO3− concentration decreased, the Halomonas genus were notably enriched in biochar compost. This study revealed the bacterial community shifts corresponded with the change of physicochemical properties, which provides essential information for a better understanding of monitoring and improving the composting process.

DOI： 10.1016/j.wasman.2020.03.029

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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

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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

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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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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

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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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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

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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

CiNii Article

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

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

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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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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

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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

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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

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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

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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

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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

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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

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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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