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Bratkic A, Jazbec A, Toplak N, Koren S, Lojen S, Tinta T, Kostanjsek R, Snoj L. The colonization of an irradiated environment: the case of microbial biofilm in a nuclear reactor. Int J Radiat Biol 2024; 100:108-121. [PMID: 37812192 DOI: 10.1080/09553002.2023.2258206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 08/19/2023] [Indexed: 10/10/2023]
Abstract
The investigation of the microbial community change in the biofilm, growing on the walls of a containment tank of TRIGA nuclear reactor revealed a thriving community in an oligotrophic and heavy-metal-laden environment, periodically exposed to high pulses of ionizing radiation (IR). We observed a vertical IR resistance/tolerance stratification of microbial genera, with higher resistance and less diversity closer to the reactor core. One of the isolated Bacillus strains survived 15 kGy of combined gamma and proton radiation, which was surprising. It appears that there is a succession of genera that colonizes or re-colonizes new or IR-sterilized surfaces, led by Bacilli and/or Actinobacteria, upon which a photoautotrophic and diazotrophic community is established within a fortnight. The temporal progression of the biofilm community was evaluated also as a proxy for microbial response to radiological contamination events. This indicated there is a need for better dose-response models that could describe microbial response to contamination events. Overall, TRIGA nuclear reactor offers a unique insight into IR microbiology and provides useful means to study relevant microbial dose-thresholds during and after radiological contamination.
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Affiliation(s)
- Arne Bratkic
- Department of Environmental Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Anze Jazbec
- Reactor Physics Division, Jožef Stefan Institute, Ljubljana, Slovenia
| | | | | | - Sonja Lojen
- Department of Environmental Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Tinkara Tinta
- Marine Biology Station Piran, National Institute of Biology, Piran, Slovenia
| | - Rok Kostanjsek
- Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Luka Snoj
- Reactor Physics Division, Jožef Stefan Institute, Ljubljana, Slovenia
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Kouřilová X, Schwarzerová J, Pernicová I, Sedlář K, Mrázová K, Krzyžánek V, Nebesářová J, Obruča S. The First Insight into Polyhydroxyalkanoates Accumulation in Multi-Extremophilic Rubrobacter xylanophilus and Rubrobacter spartanus. Microorganisms 2021; 9:909. [PMID: 33923216 PMCID: PMC8146576 DOI: 10.3390/microorganisms9050909] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 04/19/2021] [Accepted: 04/20/2021] [Indexed: 12/27/2022] Open
Abstract
Actinobacteria belonging to the genus Rubrobacter are known for their multi-extremophilic growth conditions-they are highly radiation-resistant, halotolerant, thermotolerant or even thermophilic. This work demonstrates that the members of the genus are capable of accumulating polyhydroxyalkanoates (PHA) since PHA-related genes are widely distributed among Rubrobacter spp. whose complete genome sequences are available in public databases. Interestingly, all Rubrobacter strains possess both class I and class III synthases (PhaC). We have experimentally investigated the PHA accumulation in two thermophilic species, R. xylanophilus and R. spartanus. The PHA content in both strains reached up to 50% of the cell dry mass, both bacteria were able to accumulate PHA consisting of 3-hydroxybutyrate and 3-hydroxyvalerate monomeric units, none other monomers were incorporated into the polymer chain. The capability of PHA accumulation likely contributes to the multi-extremophilic characteristics since it is known that PHA substantially enhances the stress robustness of bacteria. Hence, PHA can be considered as extremolytes enabling adaptation to extreme conditions. Furthermore, due to the high PHA content in biomass, a wide range of utilizable substrates, Gram-stain positivity, and thermophilic features, the Rubrobacter species, in particular Rubrobacter xylanophilus, could be also interesting candidates for industrial production of PHA within the concept of Next-Generation Industrial Biotechnology.
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Affiliation(s)
- Xenie Kouřilová
- Department of Food Chemistry and Biotechnology, Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00 Brno, Czech Republic; (X.K.); (I.P.)
| | - Jana Schwarzerová
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Technicka 12, 616 00 Brno, Czech Republic; (J.S.); (K.S.)
| | - Iva Pernicová
- Department of Food Chemistry and Biotechnology, Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00 Brno, Czech Republic; (X.K.); (I.P.)
| | - Karel Sedlář
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Technicka 12, 616 00 Brno, Czech Republic; (J.S.); (K.S.)
| | - Kateřina Mrázová
- Institute of Scientific Instruments of the Czech Academy of Sciences, v.v.i., Kralovopolska 147, 612 64 Brno, Czech Republic; (K.M.); (V.K.)
| | - Vladislav Krzyžánek
- Institute of Scientific Instruments of the Czech Academy of Sciences, v.v.i., Kralovopolska 147, 612 64 Brno, Czech Republic; (K.M.); (V.K.)
| | - Jana Nebesářová
- Biology Centre, The Czech Academy of Sciences, v.v.i., Branisovska 31, 370 05 Ceske Budejovice, Czech Republic;
- Faculty of Science, Charles University, Vinicna 7, 128 44 Prague 2, Czech Republic
| | - Stanislav Obruča
- Department of Food Chemistry and Biotechnology, Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00 Brno, Czech Republic; (X.K.); (I.P.)
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Ogwu MC, Srinivasan S, Dong K, Ramasamy D, Waldman B, Adams JM. Community Ecology of Deinococcus in Irradiated Soil. MICROBIAL ECOLOGY 2019; 78:855-872. [PMID: 30980101 DOI: 10.1007/s00248-019-01343-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 02/12/2019] [Indexed: 05/24/2023]
Abstract
Deinococcus is a genus of soil bacteria known for radiation resistance. However, the effects of radiation exposure on its community structure are unknown. We exposed soil to three levels of gamma radiation, 0.1 kGy/h (low), 1 kGy/h (medium), and 3 kGy/h (high), once a week for 6 weeks and then extracted soil DNA for 16S rRNA amplicon sequencing. We found the following: (1) Increasing radiation dose produced a major increase in relative abundance of Deinococcus, reaching ~ 80% of reads at the highest doses. Differing abundances of the various Deinococcus species in relation to exposure levels indicate distinct "radiation niches." At 3 kGy/h, a single OTU identified as D. ficus overwhelmingly dominated the mesocosms. (2) Corresponding published genome data show that the dominant species at 3 kGy/h, D. ficus, has a larger and more complex genome than other Deinococcus species with a greater proportion of genes related to DNA and nucleotide metabolism, cell wall, membrane, and envelope biogenesis as well as more cell cycle control, cell division, and chromosome partitioning-related genes. Deinococcus ficus also has a higher guanine-cytosine ratio than most other Deinococcus. These features may be linked to genome stability and may explain its greater abundance in this apparently competitive system, under high-radiation exposures. (3) Genomic analysis suggests that Deinococcus, including D. ficus, are capable of utilizing diverse carbon sources derived from both microbial cells killed by the radiation (including C5-C12-containing compounds, like arabinose, lactose, N-acetyl-D-glucosamine) and plant-derived organic matter in the soil (e.g., cellulose and hemicellulose). (4) Overall, based on its metagenome, even the most highly irradiated (3 kGy/h) soil possesses a wide range of the activities necessary for a functional soil system. Future studies may consider the resilience and sustainability of such soils in a high-radiation environment.
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Affiliation(s)
- Matthew Chidozie Ogwu
- School of Biological Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea
- Department of Plant Biology and Biotechnology, University of Benin, PMB 1154, Ugbowo, Benin City, Edo State, Nigeria
| | - Sathiyaraj Srinivasan
- Department of Bio and Environmental Technology, Division of Environmental and Life Science, College of Natural Science, Seoul Women's University, 623 Hwarangno, Nowon-gu, Seoul, 139-774, Republic of Korea
| | - Ke Dong
- Department of Life Sciences, Kyonggi University, Suwon, 443-760, Republic of Korea
| | - Dhamodharan Ramasamy
- School of Biological Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea
| | - Bruce Waldman
- School of Biological Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic of Korea.
- Department of Integrative Biology, Oklahoma State University, 501 Life Sciences West, Stillwater, OK, 74078, USA.
| | - Jonathan M Adams
- School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing, 210023, Qixia District, Jiangsu Province, People's Republic of China.
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Complete Genome Sequence of Rubrobacter xylanophilus Strain AA3-22, Isolated from Arima Onsen in Japan. Microbiol Resour Announc 2019; 8:8/34/e00818-19. [PMID: 31439702 PMCID: PMC6706694 DOI: 10.1128/mra.00818-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rubrobacter xylanophilus strain AA3-22, belonging to the phylum Actinobacteria, was isolated from nonvolcanic Arima Onsen (hot spring) in Japan. Here, we report the complete genome sequence of this organism, which was obtained by combining Oxford Nanopore long-read and Illumina short-read sequencing data. Rubrobacter xylanophilus strain AA3-22, belonging to the phylum Actinobacteria, was isolated from nonvolcanic Arima Onsen (hot spring) in Japan. Here, we report the complete genome sequence of this organism, which was obtained by combining Oxford Nanopore long-read and Illumina short-read sequencing data.
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Draft Genome Sequence of Kocuria rhizophila RF, a Radiation-Resistant Soil Isolate. GENOME ANNOUNCEMENTS 2016; 4:4/2/e00095-16. [PMID: 26966202 PMCID: PMC4786658 DOI: 10.1128/genomea.00095-16] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Kocuria rhizophila RF, a soil isolate from Iran, is a radiation-resistant bacterium. Only a limited amount of genomic information for radiation-resistant bacteria is currently available. Here, we report the draft genome sequence of this bacterium, providing knowledge to aid in the discovery of the genomic basis of its resistance to radiation.
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Sun J, Zhang Q, Zhou J, Wei Q. Illumina amplicon sequencing of 16S rRNA tag reveals bacterial community development in the rhizosphere of apple nurseries at a replant disease site and a new planting site. PLoS One 2014; 9:e111744. [PMID: 25360786 PMCID: PMC4216118 DOI: 10.1371/journal.pone.0111744] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2014] [Accepted: 10/03/2014] [Indexed: 11/24/2022] Open
Abstract
We used a next-generation, Illumina-based sequencing approach to characterize the bacterial community development of apple rhizosphere soil in a replant site (RePlant) and a new planting site (NewPlant) in Beijing. Dwarfing apple nurseries of 'Fuji'/SH6/Pingyitiancha trees were planted in the spring of 2013. Before planting, soil from the apple rhizosphere of the replant site (ReSoil) and from the new planting site (NewSoil) was sampled for analysis on the Illumina MiSeq platform. In late September, the rhizosphere soil from both sites was resampled (RePlant and NewPlant). More than 16,000 valid reads were obtained for each replicate, and the community was composed of five dominant groups (Proteobacteria, Acidobacteria, Bacteroidetes, Gemmatimonadetes and Actinobacteria). The bacterial diversity decreased after apple planting. Principal component analyses revealed that the rhizosphere samples were significantly different among treatments. Apple nursery planting showed a large impact on the soil bacterial community, and the community development was significantly different between the replanted and newly planted soils. Verrucomicrobia were less abundant in RePlant soil, while Pseudomonas and Lysobacter were increased in RePlant compared with ReSoil and NewPlant. Both RePlant and ReSoil showed relatively higher invertase and cellulase activities than NewPlant and NewSoil, but only NewPlant soil showed higher urease activity, and this soil also had the higher plant growth. Our experimental results suggest that planting apple nurseries has a significant impact on soil bacterial community development at both replant and new planting sites, and planting on new site resulted in significantly higher soil urease activity and a different bacterial community composition.
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Affiliation(s)
- Jian Sun
- Institute of Forestry and Pomology, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Qiang Zhang
- Institute of Forestry and Pomology, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Jia Zhou
- Institute of Forestry and Pomology, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Qinping Wei
- Institute of Forestry and Pomology, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
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Gabani P, Singh OV. Radiation-resistant extremophiles and their potential in biotechnology and therapeutics. Appl Microbiol Biotechnol 2012; 97:993-1004. [PMID: 23271672 DOI: 10.1007/s00253-012-4642-7] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Revised: 12/03/2012] [Accepted: 12/05/2012] [Indexed: 10/27/2022]
Abstract
Extremophiles are organisms able to thrive in extreme environmental conditions. Microorganisms with the ability to survive high doses of radiation are known as radioresistant or radiation-resistant extremophiles. Excessive or intense exposure to radiation (i.e., gamma rays, X-rays, and particularly UV radiation) can induce a variety of mutagenic and cytotoxic DNA lesions, which can lead to different forms of cancer. However, some populations of microorganisms thrive under different types of radiation due to defensive mechanisms provided by primary and secondary metabolic products, i.e., extremolytes and extremozymes. Extremolytes (including scytonemin, mycosporine-like amino acids, shinorine, porphyra-334, palythine, biopterin, and phlorotannin, among others) are able to absorb a wide spectrum of radiation while protecting the organism's DNA from being damaged. The possible commercial applications of extremolytes include anticancer drugs, antioxidants, cell-cycle-blocking agents, and sunscreens, among others. This article aims to review the strategies by which microorganisms thrive in extreme radiation environments and discuss their potential uses in biotechnology and the therapeutic industry. The major challenges that lie ahead are also discussed.
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Affiliation(s)
- Prashant Gabani
- Division of Biological and Health Sciences, University of Pittsburgh, 300 Campus Drive, Bradford, PA 16701, USA
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Copeland E, Choy N, Gabani P, Singh OV. Biosynthesis of Extremolytes: Radiation Resistance and Biotechnological Implications. Extremophiles 2012. [DOI: 10.1002/9781118394144.ch15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Ragon M, Restoux G, Moreira D, Møller AP, López-García P. Sunlight-exposed biofilm microbial communities are naturally resistant to chernobyl ionizing-radiation levels. PLoS One 2011; 6:e21764. [PMID: 21765911 PMCID: PMC3135598 DOI: 10.1371/journal.pone.0021764] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Accepted: 06/06/2011] [Indexed: 02/06/2023] Open
Abstract
Background The Chernobyl accident represents a long-term experiment on the effects of exposure to ionizing radiation at the ecosystem level. Though studies of these effects on plants and animals are abundant, the study of how Chernobyl radiation levels affect prokaryotic and eukaryotic microbial communities is practically non-existent, except for a few reports on human pathogens or soil microorganisms. Environments enduring extreme desiccation and UV radiation, such as sunlight exposed biofilms could in principle select for organisms highly resistant to ionizing radiation as well. Methodology/Principal Findings To test this hypothesis, we explored the diversity of microorganisms belonging to the three domains of life by cultivation-independent approaches in biofilms developing on concrete walls or pillars in the Chernobyl area exposed to different levels of radiation, and we compared them with a similar biofilm from a non-irradiated site in Northern Ireland. Actinobacteria, Alphaproteobacteria, Bacteroidetes, Acidobacteria and Deinococcales were the most consistently detected bacterial groups, whereas green algae (Chlorophyta) and ascomycete fungi (Ascomycota) dominated within the eukaryotes. Close relatives to the most radio-resistant organisms known, including Rubrobacter species, Deinococcales and melanized ascomycete fungi were always detected. The diversity of bacteria and eukaryotes found in the most highly irradiated samples was comparable to that of less irradiated Chernobyl sites and Northern Ireland. However, the study of mutation frequencies in non-coding ITS regions versus SSU rRNA genes in members of a same actinobacterial operational taxonomic unit (OTU) present in Chernobyl samples and Northern Ireland showed a positive correlation between increased radiation and mutation rates. Conclusions/Significance Our results show that biofilm microbial communities in the most irradiated samples are comparable to non-irradiated samples in terms of general diversity patterns, despite increased mutation levels at the single-OTU level. Therefore, biofilm communities growing in sunlight exposed substrates are capable of coping with increased mutation rates and appear pre-adapted to levels of ionizing radiation in Chernobyl due to their natural adaptation to periodical desiccation and ambient UV radiation.
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Affiliation(s)
- Marie Ragon
- Unité d'Ecologie, Systématique et Evolution - CNRS UMR8079, Université Paris-Sud, Orsay, France
| | - Gwendal Restoux
- Unité d'Ecologie, Systématique et Evolution - CNRS UMR8079, Université Paris-Sud, Orsay, France
| | - David Moreira
- Unité d'Ecologie, Systématique et Evolution - CNRS UMR8079, Université Paris-Sud, Orsay, France
| | - Anders Pape Møller
- Unité d'Ecologie, Systématique et Evolution - CNRS UMR8079, Université Paris-Sud, Orsay, France
| | - Purificación López-García
- Unité d'Ecologie, Systématique et Evolution - CNRS UMR8079, Université Paris-Sud, Orsay, France
- * E-mail:
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Singh O, Gabani P. Extremophiles: radiation resistance microbial reserves and therapeutic implications. J Appl Microbiol 2011; 110:851-61. [DOI: 10.1111/j.1365-2672.2011.04971.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Nucleotide excision repair and homologous recombination systems commit differentially to the repair of DNA-protein crosslinks. Mol Cell 2007; 28:147-58. [PMID: 17936711 DOI: 10.1016/j.molcel.2007.07.029] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Revised: 06/30/2007] [Accepted: 07/30/2007] [Indexed: 11/21/2022]
Abstract
DNA-protein crosslinks (DPCs)-where proteins are covalently trapped on the DNA strand-block the progression of replication and transcription machineries and hence hamper the faithful transfer of genetic information. However, the repair mechanism of DPCs remains largely elusive. Here we have analyzed the roles of nucleotide excision repair (NER) and homologous recombination (HR) in the repair of DPCs both in vitro and in vivo using a bacterial system. Several lines of biochemical and genetic evidence show that both NER and HR commit to the repair or tolerance of DPCs, but differentially. NER repairs DPCs with crosslinked proteins of sizes less than 12-14 kDa, whereas oversized DPCs are processed exclusively by RecBCD-dependent HR. These results highlight how NER and HR are coordinated when cells need to deal with unusually bulky DNA lesions such as DPCs.
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Chicote E, Moreno DA, Garcia AM, Sarro MI, Lorenzo PI, Montero F. Biofouling on the walls of a spent nuclear fuel pool with radioactive ultrapure water. BIOFOULING 2004; 20:35-42. [PMID: 15079891 DOI: 10.1080/08927010410001662670] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Microbial activity in spent nuclear fuel pools which contain ultrapure and radioactive water has been previously observed. The aim of the present research was to isolate and identify the microorganisms attached to the nuclear pool wall of a Spanish nuclear power plant. Amplification of 16S rDNA fragments from the culturable microorganisms by PCR using universal primers for the domain 'Bacteria', followed by Denaturing Gradient Gel Electrophoresis analysis revealed the presence of six different bacteria. The complete gene for 16S rDNA of each one was sequenced and identified as belonging to three different phylogenetic groups, viz. beta-Proteobacteria, Actinomycetales and the Bacillus/Staphylococcus group. A fungus was also found and identified as Aspergillus fumigatus by sequencing the D2 region of the large subunit rDNA gene. The isolation of these microorganisms in oligotrophic and radioactive conditions is of great interest due to the possibility of their use in bioremediation processes of radionuclide-contaminated environments.
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Affiliation(s)
- Eduardo Chicote
- Universidad Politécnica de Madrid, Departamento de Ingeniería y Ciencia de los Materiales, Escuela Técnica Superior de Ingenieros Industriales, José Gutiérrez Abascal 2, E-28006 Madrid, Spain
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Gánti T, Horváth A, Bérczi S, Gesztesi A, Szathmáry E. Dark Dune Spots: possible biomarkers on Mars? ORIGINS LIFE EVOL B 2003; 33:515-57. [PMID: 14604189 DOI: 10.1023/a:1025705828948] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Dark Dune Spots (DDSs) are transitional geomorphologic formations in the frost-covered polar regions of Mars. Our analysis of the transformations and arrangements of subsequent stages of DDSs into time sequence revealed their: (i) hole-like characteristics, (ii) development and formation from the bottom of the frosted layer till the disapperance of the latter, (iii) repeated (seasonal and annual) appearance in a pattern of multiple DDSs on the surface, and (iv) probable origin. We focused our studies on a model in which DDSs were interpreted as objects triggered by biological activity involved in the frosting and melting processes. We discuss two competing interpretations of DDSs: development by defrosting alone, and by defrosting and melting enhanced by the activity of Martian Surface Organisms (MSOs). MSOs are hypothetical Martian photosynthetic surface organisms thought to absorb sunlight. As a result they warm up by late winter and melt the ice around them, whereby their growth and reproduction become possible. The ice cover above the liquid water lens harbouring the MSOs provides excellent heat and UV insulation, prevents fast evaporation, and sustains basic living conditions until the ice cover exists. When the frost cover disappears MSOs go to a dormant, desiccated state. We propose further studies to be carried out by orbiters and landers travelling to Mars and by analysis of partial analogues on earth.
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Affiliation(s)
- Tibor Gánti
- Collegium Budapest, Institute for Advanced Study, Budapest, Hungary
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Hirano T, Hirano H, Yamaguchi R, Asami S, Tsurudome Y, Kasai H. Sequence specificity of the 8-hydroxyguanine repair activity in rat organs. JOURNAL OF RADIATION RESEARCH 2001; 42:247-254. [PMID: 11840641 DOI: 10.1269/jrr.42.247] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The base excision repair system for 8-hydroxyguanine (8-OH-Gua) is believed to play a role in the prevention of mutations, such as GC-to-TA transversion, which leads to cancer development. However, the exact repair mechanism is still unclear. In this study, we examine whether the repair activity level for 8-hydroxyguanine, one of the major forms of oxidative DNA damage, depends on the sequence of the substrate DNA. We prepared six different oligonucleotides containing 8-hydroxyguanine as substrates and reacted them with crude extracts from the livers and kidneys of 8-week-old Sprague-Dawley rats. As a result, up to a 10-fold difference in the repair activity levels was observed, depending on the substrates used. Based on this observation, we suggest that the repair systems may act with sequence specificity on the damaged DNA.
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Affiliation(s)
- T Hirano
- Department of Environmental Oncology, University of Occupational and Environmental Health, Kitakyushu, 807-8555, Japan
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Abstract
All 21 of the Nudix hydrolase genes from the radiation-resistant organism Deinococcus radiodurans have been cloned into vectors under the control of T7 promoters and expressed as soluble proteins in Escherichia coli. Their sizes range from 9.8 kDa (91 amino acids) to 59 kDa (548 amino acids). Two novel proteins were identified, each with two Nudix boxes in its primary structure, unique among all other known Nudix hydrolases. Extracts of each of the expressed proteins were assayed by a generalized procedure that measures the hydrolysis of nucleoside diphosphate derivatives, and several enzymatic activities were tentatively identified. In addition to representatives of known Nudix hydrolase subfamilies active on ADP-ribose, NADH, dinucleoside polyphosphates or (deoxy)nucleoside triphosphates, two new enzymes, a UDP-glucose pyrophosphatase and a CoA pyrophosphatase, were identified.
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Affiliation(s)
- W Xu
- Department of Biology and the McCollum-Pratt Institute, The Johns Hopkins University, Baltimore, MD 21218, USA
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Kamiya H, Kasai H. 2-hydroxyadenine in DNA is a very poor substrate of the Escherichia coli MutY protein. JOURNAL OF RADIATION RESEARCH 2000; 41:349-354. [PMID: 11329883 DOI: 10.1269/jrr.41.349] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
To test the possibility that the Escherichia coli MutY or MutM protein acts as a 2-hydroxyadenine (2-OH-Ade) glycosylase, we treated double-stranded oligodeoxyribonucleotides containing 2-OH-Ade with the E. coli MutY or MutM protein in vitro. We found that a strand with 2-OH-Ade was a very poor substrate of MutY, irrespective of the base in the complementary strand. Moreover, a strand containing adenine or guanine opposite 2-OH-Ade was also rarely cleaved by MutY. The cleavage of oligonucleotides with 2-OH-Ade by MutM was not observed. These results indicate that neither MutY nor MutM plays an important role in the removal of 2-OH-Ade from DNA.
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Affiliation(s)
- H Kamiya
- Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan
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