Researchers Database

Ikegami Akihiko

    EnviromentalandPreventiveMedicine Research Associate
Last Updated :2022/05/19

Researcher Information

J-Global ID

Research Interests

  • 予防医学   

Research Areas

  • Life sciences / Healthcare management, medical sociology

Academic & Professional Experience

  • 2015/03 - Today  Jichi Medical UniversitySchool of Medicine助教
  • 2013/09 - 2015/02  Jichi Medical UniversitySchool of Medicine客員研究員

Association Memberships


Published Papers

  • Ohtsu M, Mise N, Ikegami A, Mizuno A, Kobayashi Y, Nakagi Y, Nohara K, Yoshida T, Kayama F
    Environmental health and preventive medicine 24 (1) 72 - 72 1342-078X 2019/12 [Refereed][Not invited]
    BACKGROUND: Lead is a toxic metal abundant in the environment. Consumption of food contaminated at low levels of lead, especially by small children and pregnant women, raises a health concern. METHODS: Duplicated food portions and drinking water were collected over 3 days from 88 children and 87 pregnant women in Shimotsuke, Tochigi, Japan. Participants were recruited in this study between January 2014 and October 2015. Dust was also collected from their homes. Lead concentrations were measured and consequent oral lead exposure levels were estimated for this population at high risk to environmental toxicants. Lead concentrations of peripheral and cord blood, taken from children and pregnant women, and were also analyzed. RESULTS: Lead concentrations in food, drinking water, and house dust were low in general. Oral lead exposure to lead was higher for children (Mean ± SEM; 5.21 ± 0.30 μg/kg BW/week) than in pregnant women (1.47 ± 0.13 μg/kg BW/week). Food and house dust were main sources of lead contamination, but the contribution of house dust widely varied. Means ± SEM of peripheral and cord blood lead concentrations were 0.69 ± 0.04 μg/dL and 0.54 ± 0.05 μg/dL, respectively for pregnant women and 1.30 ± 0.07 μg/dL (peripheral only) in children. We detect no correlation between smoking situations and blood lead concentration in pregnant women. CONCLUSION: We conclude that oral lead exposure levels for Japanese children and pregnant women were generally low, with higher concentrations and exposure for children than for pregnant women. More efforts are necessary to clarify the sources of lead contamination and reduce lead exposure of the population at high risk even in Japan.
  • Hiroshi Kitazawa, Kiwako Yamamoto-Hanada, Mayako Saito-Abe, Tadayuki Ayabe, Hidetoshi Mezawa, Kazue Ishitsuka, Mizuho Konishi, Shoji F. Nakayama, Takehiro Michikawa, Ayako Senju, Mayumi Tsuji, Koichi Kusuhara, Masafumi Sanefuji, Shouichi Ohga, Masako Oda, Hiroshi Mitsubuchi, Takahiko Katoh, Akihiko Ikegami, Natan Mise, Kenji Matsumoto, Hirohisa Saito, Yukihiro Ohya
    Allergology International 68 (3) 391 - 393 1323-8930 2019/07 [Refereed][Not invited]
  • Mise N, Ohtsu M, Ikegami A, Mizuno A, Cui X, Kobayashi Y, Nakagi Y, Nohara K, Yoshida T, Kayama F
    Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment 36 (1) 84 - 95 1944-0049 2019/01 [Refereed][Not invited]
  • Fukatsu H, Koide N, Tada-Oikawa S, Izuoka K, Ikegami A, Ichihara S, Ukaji T, Morita N, Naiki Y, Komatsu T, Umezawa K
    Molecular medicine reports 18 (6) 5279 - 5285 1791-2997 2018/12 [Refereed][Not invited]
  • Zafar Fatmi, Ambreen Sahito, Akihiko Ikegami, Atsuko Mizuno, Xiaoyi Cui, Nathan Mise, Mai Takagi, Yayoi Kobayashi, Fujio Kayama
    International Journal of Environmental Research and Public Health 14 (4) 1660-4601 2017/04 [Refereed][Not invited]
    Lead (Pb) in petrol has been banned in developed countries. Despite the control of Pb in petrol since 2001, high levels were reported in the blood of pregnant women and children in Pakistan. However, the identification of sources of Pb has been elusive due to its pervasiveness. In this study, we assessed the lead intake of pregnant women and one- to three-year-old children from food, water, house dust, respirable dust, and soil. In addition, we completed the fingerprinting of the Pb isotopic ratios (LIR) of petrol and secondary sources (food, house-dust, respirable dust, soil, surma (eye cosmetics)) of exposure within the blood of pregnant women, newborns, and children. Eight families, with high (~50 µg/dL), medium (~20 µg/dL), and low blood levels (~10 µg/dL), were selected from 60 families. The main sources of exposure to lead for children were food and house-dust, and those for pregnant women were soil, respirable dust, and food. LIR was determined by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) with a two sigma uncertainty of ±0.03%. The LIR of mothers and newborns was similar. In contrast, surma, and to a larger extent petrol, exhibited a negligible contribution to both the child’s and mother’s blood Pb. Household wet-mopping could be effective in reducing Pb exposure. This intake assessment could be replicated for other developing countries to identify sources of lead and the burden of lead exposure in the population.
  • Akihiko Ikegami, Mai Takagi, Zafar Fatmi, Yayoi Kobayashi, Mayumi Ohtsu, Xiaoyi Cui, Nathan Mise, Atsuko Mizuno, Ambreen Sahito, Aneeta Khoso, Fujio Kayama
    ENVIRONMENTAL POLLUTION 218 723 - 727 0269-7491 2016/11 [Refereed][Not invited]
    Adverse health effects of heavy metals are a public health concern, especially lead may cause negative health impacts to human fetal and infantile development. The lead concentrations in Pakistani pregnant women's nails, used as a biomarker, were measured to estimate the lead exposure. Thirteen nail samples out of 84 nails analyzed contained lead higher than the concentration (13.6 mu g/g) of the fatal lead poisoning case, raising the possibility of an external contamination. Eye cosmetics such as surma are recognized as one of the important sources of lead exposure in Pakistan. We collected in Pakistan 30 eye cosmetics made in Pakistan, Saudi Arabia and western countries. As the metal composition analysis by energy dispersive X-ray fluorescence spectrometry revealed that some surma samples contained lead more than 96%, the surma might contaminate the nail specimen. Scanning electron microscopy observations showed that lead-containing surma consists of fine particle of galena (ore of lead sulfide) in respirable dust range (less than 10 mu m). In addition, relative in vitro bioavailability of lead in the surma was determined as 5.2%. Thus, lead-containing surma consists of inhalable and bioavailable particles, and it contributes an increased risk of lead exposure. Moreover, the relationship between the surma and the lead-contaminated nails by lead isotope ratios analysis indicated the potential of lead contamination in nails by surma. These results suggest that lead in the nails was derived both from body burden of lead and external contamination by lead-containing surma. Therefore, nail is not suited as a biomarker for lead exposure in the countries where surma used, because we may overestimate lead exposure by surface lead contamination in the nail by surma. (C) 2016 Elsevier Ltd. All rights reserved.
  • Xiaoyi Cui, Mayumi Ohtsu, Nathan Mise, Akihiko Ikegami, Atsuko Mizuno, Takako Sakamoto, Masanori Ogawa, Munehito Machida, Fujio Kayama
    SPRINGERPLUS 5 (1) 885  2193-1801 2016/06 [Refereed][Not invited]
    This study aimed to evaluate the relationships between oxidative stress and heavy metal exposure (lead [Pb] and cadmium [Cd]), as well as co-factors such as physical activity and age, in Japanese women. This study was conducted with female subjects from a rural agricultural community in Japan. Subjects were asked to complete lifestyle-related questionnaires and undergo a group health examination. Physical activity, alcohol consumption, body mass index, and other demographic information were collected. Blood and urine samples were collected to measure urinary 8-hydroxydeoxyguanosine (8-OHdG) levels and blood and urinary Cd and Pb concentrations. Urine samples were analyzed using high performance liquid chromatography and flameless atomic absorption spectrometry; blood samples were analyzed using inductively coupled plasma-mass spectrometry. Age, physical activity, and blood and urinary Cd and Pb concentrations were included in structural equation modeling analysis. Two latent factors for heavy metal exposure and physical activity were produced to predict the total influence of the variables. The final model was good: CMIN/DF = 0.775, CFI = 1.000, GFI = 0.975, AGFI = 0.954, RMSEA = 0.000. 8-OHdG levels were positively associated with heavy metal exposure, physical activity, and age (standard beta of path analysis: 0.33, 0.38, and 0.20, respectively). Therefore, oxidative stress is associated with both, environmental and lifestyle factors, in combination with aging.
  • Fujio Kayama, Zafar Fatmi, Akihiko Ikegami, Atsuko Mizuno, Mayumi Ohtsu, Nathern Mise, Xiaoyi Cui, Masanori Ogawa, Takako Sakamoto, Yoshiko Nakagi, Takahiko Yoshida, Ambreen Sahito, Shahla Naeem, Kulsoom Ghias, Hina Zuberi, Kanwal Tariq, Yayoi Kobayashi, Keiko Nohara
    Reviews on Environmental Health 31 (1) 33 - 35 0048-7554 2016/03 [Not refereed][Not invited]
    Aim: Exposure assessment of lead (Pb) and Arsenic (As) from food, water, and house dust intake were assessed among pregnant women, their children and fetuses in Pakistan and Japan, as well as their body burden of the metals in their blood. Method: Fifty families which included a pregnant woman, a fetus and the 1-3-year-old siblings were recruited in Karachi and Khairpur in Pakistan, and Shimotsuke and Asahikawa in Japan, respectively. Their dietary exposure to Pb and As was measured in 3-day food duplicates and drinking water by ICP-MP. Pb in house dust and respirable dust was evaluated with an energy dispersive X-ray fluorescence spectrometry. Nonradioactive isotope Pb profiles of blood specimens will be compared with those of the exposure origins, such as food duplicates, respirable house dust, the soils nearby, and gasoline. Results: Judging from the data collected and analyzed so far, contribution from dietary intake is highly correlated to higher body burden of Pb among Pakistani mothers. Additional data analyses will reveal the status of Pb and As body burden in Pakistani mothers, fetuses and their siblings, and causal sources of high body burden is delineated by Pb isotope profile analysis of different sources of Pb exposure.
  • Cimi Ilmiawati, Takahiko Yoshida, Toshihiro Itoh, Yoshihiko Nakagi, Yasuaki Saijo, Yoshihiko Sugioka, Mineshi Sakamoto, Akihiko Ikegami, Masanori Ogawa, Fujio Kayama
    ENVIRONMENTAL HEALTH AND PREVENTIVE MEDICINE 20 (1) 18 - 27 1342-078X 2015/01 [Refereed][Not invited]
    To measure current Hg, Cd, and Pb exposure in Japanese children, and to estimate dietary intakes of foods responsible for high body burden. Blood, hair, and urine samples were collected from 9 to 10-year-old 229 children in Asahikawa and measured for Hg, Cd, and Pb in these matrices. Diet history questionnaire was used to estimate intake of marine foods and other food items. Hg level was measured by cold vapor atomic absorption spectrometry. Cd and Pb levels were determined with inductively coupled plasma mass spectrometry. Geometric mean (GM) of blood Hg, Cd, and Pb was 4.55 mu g/L, 0.34 mu g/L, and 0.96 mu g/dL, respectively. Urinary Cd level was 0.34 mu g/g creatinine (GM) and hair Hg was 1.31 mu g/g (GM). Approximately one-third (35 %) of blood samples had Hg level above the U.S. EPA reference dose (RfD; 5.8 mu g/L). Hair Hg level exceeded U.S. EPA RfD (1.2 mu g/g) in 59 % samples. Children in the upper quartile of blood Hg level had significantly higher intake of large predatory fish species compared to those in the lower quartile of blood Hg. Those with high blood Hg level may be explained by more frequent intake of big predatory fish. Cd and Pb exposure is generally low among Japanese children. As no safety margin exists for Pb exposure and high exposure to MeHg is noted in Japanese population; periodic biomonitoring and potential health risk assessment should continue in high-risk populations, notably among children.
  • Akihiko Ikegami, Peter Chung, Yiping W. Han
    INFECTION AND IMMUNITY 77 (7) 3075 - 3079 0019-9567 2009/07 [Refereed][Not invited]
    Fusobacterium nucleatum is a gram-negative oral anaerobe implicated in periodontal disease and adverse pregnancy outcome. The organism colonizes the mouse placenta, causing localized infection and inflammation. The mechanism of placental colonization has not been elucidated. Previous studies identified a novel adhesin from F. nucleatum, FadA, as being involved in the attachment and invasion of host cells. The fadA deletion mutant F. nucleatum 12230 US1 was defective in host cell attachment and invasion in vitro, but it also exhibited pleiotropic effects with altered cell morphology and growth rate. In this study, a fadA-complementing clone, F. nucleatum 12230 USF81, was constructed. The expression of FadA on USF81 was confirmed by Western blotting and immunofluorescent labeling. USF81 restored host cell attachment and invasion activities. The ability of F. nucleatum 12230, US1, and USF81 to colonize the mouse placenta was examined. US1 was severely defective in placental colonization compared to the wild type and USF81. Thus, FadA plays an important role in F. nucleatum colonization in vivo. These results also represent the first complementation studies for F. nucleatum. FadA may be a therapeutic target for preventing F. nucleatum colonization of the host.
  • Stanley Nithianantham, Minghua Xu, Mitsunori Yamada, Akihiko Ikegami, Menachem Shoham, Yiping W. Han
    JOURNAL OF BIOLOGICAL CHEMISTRY 284 (6) 3865 - 3872 0021-9258 2009/02 [Refereed][Not invited]
    Many bacterial appendages have filamentous structures, often composed of repeating monomers assembled in a head-to-tail manner. The mechanisms of such linkages vary. We report here a novel protein oligomerization motif identified in the FadA adhesin from the Gram-negative bacterium Fusobacterium nucleatum. The 2.0 angstrom crystal structure of the secreted form of FadA (mFadA) reveals two antiparallel alpha-helices connected by an intervening 8-residue hairpin loop. Leucine-leucine contacts play a prominent dual intra- and intermolecular role in the structure and function of FadA. First, they comprise the main association between the two helical arms of the monomer; second, they mediate the head-to-tail association of monomers to form the elongated polymers. This leucine-mediated filamentous assembly of FadA molecules constitutes a novel structural motif termed the "leucine chain." The essential role of these residues in FadA is corroborated by mutagenesis of selected leucine residues, which leads to the abrogation of oligomerization, filament formation, and binding to host cells.
  • Yiping W. Han, Akihiko Ikegami, Peter Chung, Lei Zhang, Cheri X. Deng
    APPLIED AND ENVIRONMENTAL MICROBIOLOGY 73 (11) 3677 - 3683 0099-2240 2007/06 [Refereed][Not invited]
    Studies of microorganisms are often hindered by a lack of effective genetic tools. One such example is Fusobacterium nucleatum, a gram-negative anaerobe associated with various human infections, including those causing periodontal disease and preterm birth. The first double-crossover allelic-exchange mutant in F. nucleatum was recently constructed using sonoporation, a novel ultrasound-mediated intracellular delivery method, demonstrating potential for bacterial gene transfection. To better unveil its mechanism, the current study examines the factors affecting the outcome of sonoporation. Delivery of Texas Red-conjugated dextran into F. nucleatum by sonoporation was at least twice as efficient as that by electroporation, and sonoporation was nonbactericidal, unlike electroporation. The delivery efficiency was affected by the acoustic pressure amplitude, the duty cycle, and the quantity of microbubbles used to initiate cavitation but not by the pulse repetition frequency of ultrasound application. To examine the involvement of homologous recombination in sonoporation-mediated mutant construction, the highly conserved recA gene, which carried most of the consensus residues, including the P loop, was identified in F. nucleatum, and a double-crossover recA mutant of F. nucleatum 12230, US1610, was constructed by sonoporation. The mutant exhibited increased sensitivity to UV exposure compared with that of the wild type, indicating that the RecA function in F. nucleatum was conserved. Interestingly, US1610 was also sensitive to ultrasound treatment, suggesting the likely involvement of RecA in postsonoporation repair and survival. Since sonoporation has consistently generated one-step double-crossover mutants in F. nucleatum by use of intact suicide plasmids, this technology may be developed into an efficient tool for streamlining mutant construction in bacteria.
  • YPW Han, A Ikegami, NF Bissada, M Herbst, RW Redline, GG Ashmead
    JOURNAL OF CLINICAL MICROBIOLOGY 44 (4) 1475 - 1483 0095-1137 2006/04 [Refereed][Not invited]
    intrauterine infection is a recognized cause of preterm birth. The infectious organisms are believed to originate primarily from the vaginal tract and secondarily from other parts of the body. It is plausible that microbes in the oral cavity can be transmitted to the pregnant uterus. However, direct evidence supporting such a transmission is lacking. In this study, amniotic fluids of 34 pregnant women were examined by PCR using 16S and 23S rRNA universally conserved primers. Bacterial DNA was amplified from the only patient with clinical intrauterine infection and histologic necrotizing acute and chronic chorioamnionitis. One strain, Bergeyella sp. clone AF14, was detected and was 99.7% identical to a previously reported uncultivated oral Bergeyella strain, clone AK152, at the 16S rRNA level. The same strain was detected in the subgingival plaque of the patient but not in her vaginal tract. The 16S-23S rRNA sequence of clone AF14 matched exactly with the sequences amplified from the patient's subgingival plaque. These observations suggest that the Bergeyella strain identified in the patient's intrauterine infection originated from the oral cavity. This is the first direct evidence of oral-utero microbial transmission. The patient's periodontal health during pregnancy was unclear. She did not have detectable periodontal disease during postpartum examination. Bergeyella spp. had not been previously associated with preterm birth and were detected in subgingival plaque of women without clinical levels of intrauterine infection. Uncultivated species may be overlooked opportunistic pathogens in preterm birth. This study sheds new light on the implication of oral bacteria in preterm birth.
  • Keiko Koga, Akihiko Ikegami, Kaoru Nakasone, Rikinori Murayama, Genki Akanuma, Yousuke Natori, Hideaki Nanamiya, Fujio Kawamura
    JOURNAL OF GENERAL AND APPLIED MICROBIOLOGY 52 (2) 119 - 124 0022-1260 2006/04 [Refereed][Not invited]
  • HK Kuramitsu, W Chen, A Ikegami
    JOURNAL OF PERIODONTOLOGY 76 (11) 2047 - 2051 0022-3492 2005/11 [Refereed][Not invited]
    Background: Periodontitis develops as a result of the interaction of the host with subgingival plaque bacteria. Both Porphyromonas gingivalis and Treponema denticola are frequently associated together in these oral biofilms. Methods: The molecular basis for in vitro biofilm formation was investigated for P. gingivalis 38 1, T. denticola. 35405, and mixtures of the two organisms using microtiter plate assays. In addition, the biofilms were examined following confocal laser scanning microscopy. Results: P. gingivalis 381, but not T. denticola strains, formed biofilms in vitro. This property was dependent, in part, on the strain 381 fimA, ppk, and usp genes. Microarray and Northern blot analyses suggested that the expression of the ppk gene was required for maximal expression of the uspA gene. P. gingivalis 381 formed synergistic biofilms when incubated with T. denticola strains. This process was dependent upon the strain 381 rgpB and fimA genes as well as the T. denticola flgE and cfpA genes. Conclusions: P. gingivalis 381 formed synergistic biofilms with T. denticola 35405. These results may be relevant to the previous observations that the two organisms are frequently observed together in subgingival plaque with the spirochetes localized to the exterior of the oral biofilms. It is suggested that other such synergistic effects may also occur between other plaque bacteria.
  • M Yamada, A Ikegami, HK Kuramitsu
    FEMS MICROBIOLOGY LETTERS 250 (2) 271 - 277 0378-1097 2005/09 [Refereed][Not invited]
    Biofilm formation is an important step in the etiology of periodontal diseases. In this study, in vitro biofilm formation by Treponema denticola and Porphyromonas gingivalis 381 displayed synergistic effects. Confocal microscopy demonstrated that P. gingivalis attaches to the substratum first as a primary colonizer followed by coaggregation with T denticola to form a mixed biofilm. The T denticola flagella mutant as well as the cytoplasmic filament mutant were shown to be essential for biofilm formation as well as coaggregation with P. gingivalis. The major fimbriae and Arg-gingipain B of P. gingivalis also play important roles in biofilm formation with T. denticola. (c) 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.
  • YW Han, A Ikegami, C Rajanna, HI Kawsar, Y Zhou, M Li, HT Sojar, RJ Genco, HK Kuramitsu, CX Deng
    JOURNAL OF BACTERIOLOGY 187 (15) 5330 - 5340 0021-9193 2005/08 [Refereed][Not invited]
    Fusobacterium nucleatum is a gram-negative anaerobe that is prevalent in periodontal disease and infections of different parts of the body. The organism has remarkable adherence properties, binding to partners ranging from eukaryotic and prokaryotic cells to extracellular macromolecules. Understanding its adherence is important for understanding the pathogenesis of F. nucleatum. In this study, a novel adhesin, FadA (Fusobacterium adhesin A), was demonstrated to bind to the surface proteins of the oral mucosal KB cells. FadA is composed of 129 amino acid (aa) residues, including an 18-aa signal peptide, with calculated molecular masses of 13.6 kDa for the intact form and 12.6 kDa for the secreted form. It is highly conserved among F. nucleatum, Fusobacterium periodonticum, and Fusobacterium simiae, the three most closely related oral species, but is absent in the nonoral species, including Fusobacterium gonidiaformans, Fusobacterium mortiferum, Fusobacterium navi-forme, Fusobacterium russii, and Fusobacterium ulcerans. In addition to FadA, F. nucleatum ATCC 25586 and ATCC 49256 also encode two paralogues, FN1529 and FNV2159, each sharing 31% identity with FadA. A double-crossover fadA deletion mutant, F. nucleatum 12230-US1, was constructed by utilizing a novel sonoporation procedure. The mutant had a slightly slower growth rate, yet its binding to KB and Chinese hamster ovarian cells was reduced by 70 to 80% compared to that of the wild type, indicating that FadA plays an important role in fusobacterial colonization in the host. Furthermore, due to its uniqueness to oral Fusobacterium species, fadA may be used as a marker to detect orally related fusobacteria. F. nucleatum isolated from other parts of the body may originate from the oral cavity.
  • Kuramitsu HK, Chi B, Ikegami A
    Current protocols in microbiology Chapter 12 Unit 12B.2  1934-8525 2005/07 [Not refereed][Not invited]
  • 池上昭彦
    月刊海洋 36 (8) 633 - 637 0916-2011 2004/08 [Not refereed][Not invited]
  • A Ikegami, K Honma, A Sharma, HK Kuramitsu
    INFECTION AND IMMUNITY 72 (8) 4619 - 4627 0019-9567 2004/08 [Refereed][Not invited]
    The gene lrrA, encoding a leucine-rich repeat protein, LrrA, that contains eight consensus tandem repeats of 23 amino acid residues, has been identified in Treponema denticola ATCC 35405. A leucine-rich repeat is a generally useful protein-binding motif, and proteins containing this repeat are typically involved in protein-protein interactions. Southern blot analysis demonstrated that T. denticola ATCC 35405 expresses the lrrA gene, but the gene was not identified in T. denticola ATCC 33520. In order to analyze the functions of LrrA in T. denticola, an lrrA-inactivated mutant of strain ATCC 35405 and an lrrA gene expression transformant of strain ATCC 33520 were constructed. Characterization of the mutant and transformant demonstrated that LrrA is associated with the extracytoplasmic fraction of T. denticola and expresses multifunctional properties. It was demonstrated that the attachment of strain ATCC 35405 to HEp-2 cell cultures and coaggregation with Tannerella forsythensis were attenuated by the lrrA mutation. In addition, an in vitro binding assay demonstrated specific binding of LrrA to a portion of the Tannerella forsythensis leucine-rich repeat protein, BspA, which is mediated by the N-terminal region of LrrA. It was also observed that the lrrA mutation caused a reduction of swarming in T. denticola ATCC 35405 and consequently attenuated tissue penetration. These results suggest that the leucine-rich repeat protein LrrA plays a role in the attachment and penetration of human epithelial cells and coaggregation with Tannerella forsythensis. These properties may play important roles in the virulence of T. denticola.
  • H Kawano, A Ikegami, K Nakasone, C Kato, R Usami, K Horikoshi
    BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 67 (9) 1983 - 1985 0916-8451 2003/09 [Refereed][Not invited]
    NtrC protein of piezophilic Shewanella violacea was overexpressed and purified, to confirm the protein-DNA interaction. An electrophoretic mobility shift assay demonstrated that the NtrC recognizes the sequence for NtrC binding within the region upstream of the glnA operon. Western blot analysis also showed that the NtrC is expressed at a higher level under high-pressure conditions than under atmospheric pressure conditions.
  • K Nakasone, A Ikegami, H Kawano, C Kato, R Usami, K Horikoshi
    EXTREMOPHILES 6 (2) 89 - 95 1431-0651 2002/04 [Refereed][Not invited]
    Deep-sea bacteria have unique systems for gene and protein expression controlled by hydrostatic pressure. One of the sigma factors, sigma(54), was found to play an important role in pressure-regulated transcription in a deep-sea piezophilic bacterium, Shewanella violacea. A glutamine synthetase gene (glnA) has been targeted as a model for the pressure-regulated promoter to investigate transcriptional regulation by the sigma(54) factor. Recognition sites for sigma(54) and sigma(70) factors were observed at an upstream region of the glnA, and NtrC-binding sites were also identified at the same region. Primer extension analyses revealed that the transcription initiation sites of both promoters were determined and that transcription from the sigma(54) site was regulated by elevated pressure. The sigma(54) promoter is known to be activated by a two-component signal transduction system, the NtrB-NtrC phosphorylation relay. Our results suggested that this system might be regulated by deep-sea conditions and that the gene expression controlled by the sigma(54) promoter was actually regulated by pressure. We propose a possible model of the molecular mechanisms for pressure-regulated transcription.
  • Kawano Hiroaki, Nakasone Kaoru, Ikegami Akihiko
    Technical reports of Japan Marine Science and Technology Center 海洋科学技術センタ- (45) 1 - 6 0387-382X 2002/03 [Not refereed][Not invited]
  • 角田伸人, 池上昭彦, 加藤千明, 青野力三
    日本農芸化学会誌 75 104  0002-1407 2001/03 [Not refereed][Not invited]
  • K Nakasone, A Ikegami, C Kato, K Horikoshi
    BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 65 (1) 190 - 193 0916-8451 2001/01 [Refereed][Not invited]
    The gene encoding the principal a factor (rpoD) of the piezophilic bacterium Shewanella violacea was cloned and sequenced. The rpoD gene was found to encode a polypeptide consisting of 614 amino acid residues, showing 75.6 and 64.3% identity to those of Escherichia coli and Pseudomonas putida, respectively, Comparison with E, coli sigma (70) and P. putida sigma (70) showed that significant similarity exists in four conserved regions known to be required for promoter recognition and core binding. Using an expression plasmid harboring the rpoD gene, the S, violacea sigma (70) factor was overexpressed in E, coli and successfully purified to near homogeneity.
  • K Nakasone, A Ikegami, S Fujii, C Kato, K Horikoshi
    FEMS MICROBIOLOGY LETTERS 193 (2) 261 - 268 0378-1097 2000/12 [Refereed][Not invited]
    The rpoA gene encoding the alpha subunit of RNA polymerase from the deep-sea piezophilic bacterium Shewanella violacea DSS12 was cloned and sequenced. The rpoA gene was found to encode a polypeptide consisting of 329 amino acids with a molecular mass of 36 238 Da. S. violacea alpha protein was expressed in a ts Escherichia coli mutant. to confirm whether the rpoA gene is functional. It complemented this mutation, indicating a chimeric RNA polymerase is assembled at the non-permissive temperature. Recombinant alpha protein was overexpressed using an expression plasmid harboring the rpoA gene and purified to near homogeneity. Primer extension analysis revealed that two transcriptional initiation sites are recognized by sigma (70) RNA polymerase. It also indicated that pressure response (piezoresponse) in the alpha operon occurred at the transcriptional level. suggesting some positive regulators may interact with the transcriptional apparatus and regulate the expression of the operon at different pressure conditions. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
  • A Ikegami, K Nakasone, C Kato, Y Nakamura, Yoshikawa, I, R Usami, K Horikoshi
    FEMS MICROBIOLOGY LETTERS 192 (1) 91 - 95 0378-1097 2000/11 [Refereed][Not invited]
    A glutamine synthetase gene (glnA) was isolated from a deep-sea piezophilic bacterium, Shewanella violacea strain DSS12. A 7.5-kb SacI fragment containing the complete glnA gene was cloned and sequenced. The glnA gene was found to encode a protein consisting of 469 amino acid residues, showing 75.0% identity to the glutamine synthetase of Escherichia coli. Primer extension analyses revealed two transcription initiation sites in glnA and expression from each site was positively regulated by pressure. Putative promoters recognized by sigma (70) and sigma (54) were identified in the region upstream of glnA. An electrophoretic mobility shift assay demonstrated that S. violacea sigma (54) specifically binds to the promoter region of glnA, suggesting that sigma (54) may play an important role in pressure-regulated transcription in this piezophilic bacterium. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
  • Ikegami A, Nakasone K, Fujita M, Fujii S, Kato C, Usami R, Horikoshi K
    Biochimica et biophysica acta 1-3 1491 315 - 320 0006-3002 2000/04 [Refereed][Not invited]
  • A Ikegami, K Nakasone, C Kato, R Usami, K Horikoshi
    BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 64 (4) 915 - 918 0916-8451 2000/04 [Refereed][Not invited]
    The ntrBC genes coding for the bacterial signal-transducing protein NtrB and the bacterial enhancer-binding protein NtrC of deep-sea piezophilic Shewanella violacea were cloned and their nucleotide sequences were analyzed. The conserved regions of NtrB and those of NtrC are well conserved in the case of the ntrBC products of S. violacea.
  • 池上 昭彦, 仲宗根 薫, 藤田 昌也
    Technical reports of Japan Marine Science and Technology Center 海洋科学技術センタ- (40) 25 - 30 0387-382X 2000/02 [Not refereed][Not invited]
  • 池上昭彦, 仲宗根薫, 宇佐美論, 加藤千明, 堀越弘毅
    JAMSTEC深海研究 1 生物学編 (15) 53 - 57 1340-7848 1999/11 [Not refereed][Not invited]
  • K Nakasone, A Ikegami, C Kato, R Usami, K Horikoshi
    FEMS MICROBIOLOGY LETTERS 176 (2) 351 - 356 0378-1097 1999/07 [Refereed][Not invited]
    Potential regulatory elements were identified upstream of the pressure-regulated operon in the deep-sea barophilic bacterium Shewanella violacea strain DSS12 and binding of cellular proteins to this region was studied under different pressure conditions. Sequence analysis revealed the existence of a region, designated region A, showing similarity to the consensus sequence for sigma(54) binding, when the region upstream of the operon was compared with several consensus sequences for sigma factors. A palindromic sequence AGTTAAAGATTAAACT, designated region B, was found further upstream beyond region A. In a region designated region C, just upstream of region B; a unique octamer motif AAGGTAAG, tandemly repeated 13 times, was found. By means of an electrophoretic mobility shift assay it was demonstrated that a sigma(54)-like factor recognized region A while other unknown factors recognized the sequences in regions B and C. Different shift patterns of protein-DNA complexes were observed when extracts of cells cultured at 0.1 MPa and 50 MPa were incubated with P-32-labeled DNA probes corresponding to region B or C. These results indicate that barophilic strain DSS12 expresses different DNA-binding factors capable of recognizing these elements upstream of the pressure-regulated operon under different pressure conditions. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
  • Nakasone K, Ikegami A, Kato C, Usami R, Horikoshi K
    Extremophiles : life under extreme conditions 3 2 149 - 154 1431-0651 1998/08 [Refereed][Not invited]
  • C Kato, A Ikegami, M Smorawinska, R Usami, K Horikoshi
    JOURNAL OF MARINE BIOTECHNOLOGY 5 (4) 210 - 218 0941-2905 1997 [Not refereed][Not invited]
    A pressure-regulated operon that displayed high homology with one present in the barophilic bacterium strain DB6705 was cloned and sequenced from a barotolerant bacterium strain DSS12. Two open reading frames, ORF1 and ORF2, which constituted the pressure-regulated operon, were identified within the sequence, DNA fragments from regions upstream and downstream of the pressure-regulated operon in strain DSS12 were also cloned and sequenced. Downstream of the pressure-regulated operon, three open reading frames, designated ORF3, ORF4, and ORF5 were found, and part of another ORF, designated UORF6, was located upstream of the operon. From the results of primer extension analysis, the gene expressions of the pressure-regulated operon (ORF1, 2) and downstream operon (ORF3, 4) were clearly regulated by elevated pressure at the transcription level, The deduced amino acid sequences of the gene products of ORF3, 4, 5, and UORF6 showed high homology with CydD, CydC, proline dehydrog enase, and ATP-dependent RNA helicase from Escherichia coli, respectively. These results indicate that the genes identified in the regions flanking the pressure-regulated operon are homologous to E. coli genes, although the genes within this operon are not.
  • 小川勇二郎, 藤倉克則, 岩淵洋, 能木裕一, 小寺透, 長井茂, 岡野肇, 池上昭彦, 桑野健
    JAMSTEC深海研究 (12) 1 - 22 1340-7848 1996/12 [Not refereed][Not invited]
  • C Kato, H Tamegai, A Ikegami, R Usami, K Horikoshi
    JOURNAL OF BIOCHEMISTRY 120 (2) 301 - 305 0021-924X 1996/08 [Refereed][Not invited]
    Escherichia coli strain JD518, a cydD-deficient mutant, displayed temperature-sensitive and pressure-sensitive growth, The defective cydD gene in this strain was complemented by open reading frame 3 (ORF3), previously identified in DNA from a barotolerant bacterium, strain DSS12, allowing growth of the cydD mutant under high temperature and high pressure conditions, Spectrophotometrical analysis indicated that the cytochrome bd complex which is assembled by the CydD protein was expressed in E. coli strain JD518 carrying the ORF3 gene at the same level as occurred in the wild-type strain, Our results indicate that the cydD gene functions are required for cell stability under the condition of high pressure stress in bacteria.

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  • 特許 9,181,592 B2:METHOD FOR DETECTING A BACTERIAL PATHOGEN    2015/11/10
    Yiping W. Han, Akihiko Ikegami
  • 特開平11-279409:機能性ワックス  1999/10/12
    池上 昭彦

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