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      Novel Genes Involved in Resistance to Both Ultraviolet Radiation and Perchlorate From the Metagenomes of Hypersaline Environments

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          Abstract

          Microorganisms that thrive in hypersaline environments on the surface of our planet are exposed to the harmful effects of ultraviolet radiation. Therefore, for their protection, they have sunscreen pigments and highly efficient DNA repair and protection systems. The present study aimed to identify new genes involved in UV radiation resistance from these microorganisms, many of which cannot be cultured in the laboratory. Thus, a functional metagenomic approach was used and for this, small-insert libraries were constructed with DNA isolated from microorganisms of high-altitude Andean hypersaline lakes in Argentina (Diamante and Ojo Seco lakes, 4,589 and 3,200 m, respectively) and from the Es Trenc solar saltern in Spain. The libraries were hosted in a UV radiation-sensitive strain of Escherichia coli ( recA mutant) and they were exposed to UVB. The resistant colonies were analyzed and as a result, four clones were identified with environmental DNA fragments containing five genes that conferred resistance to UV radiation in E. coli. One gene encoded a RecA-like protein, complementing the mutation in recA that makes the E. coli host strain more sensitive to UV radiation. Two other genes from the same DNA fragment encoded a TATA-box binding protein and an unknown protein, both responsible for UV resistance. Interestingly, two other genes from different and remote environments, the Ojo Seco Andean lake and the Es Trenc saltern, encoded two hypothetical proteins that can be considered homologous based on their significant amino acid similarity (49%). All of these genes also conferred resistance to 4-nitroquinoline 1-oxide (4-NQO), a compound that mimics the effect of UV radiation on DNA, and also to perchlorate, a powerful oxidant that can induce DNA damage. Furthermore, the hypothetical protein from the Es Trenc salterns was localized as discrete foci possibly associated with damaged sites in the DNA in cells treated with 4-NQO, so it could be involved in the repair of damaged DNA. In summary, novel genes involved in resistance to UV radiation, 4-NQO and perchlorate have been identified in this work and two of them encoding hypothetical proteins that could be involved in DNA damage repair activities not previously described.

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          Life in extreme environments.

          Each recent report of liquid water existing elsewhere in the Solar System has reverberated through the international press and excited the imagination of humankind. Why? Because in the past few decades we have come to realize that where there is liquid water on Earth, virtually no matter what the physical conditions, there is life. What we previously thought of as insurmountable physical and chemical barriers to life, we now see as yet another niche harbouring 'extremophiles'. This realization, coupled with new data on the survival of microbes in the space environment and modelling of the potential for transfer of life between celestial bodies, suggests that life could be more common than previously thought. Here we examine critically what it means to be an extremophile, and the implications of this for evolution, biotechnology and especially the search for life in the Universe.
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            Molecular Mechanisms of Ultraviolet Radiation-Induced DNA Damage and Repair

            DNA is one of the prime molecules, and its stability is of utmost importance for proper functioning and existence of all living systems. Genotoxic chemicals and radiations exert adverse effects on genome stability. Ultraviolet radiation (UVR) (mainly UV-B: 280–315 nm) is one of the powerful agents that can alter the normal state of life by inducing a variety of mutagenic and cytotoxic DNA lesions such as cyclobutane-pyrimidine dimers (CPDs), 6-4 photoproducts (6-4PPs), and their Dewar valence isomers as well as DNA strand breaks by interfering the genome integrity. To counteract these lesions, organisms have developed a number of highly conserved repair mechanisms such as photoreactivation, base excision repair (BER), nucleotide excision repair (NER), and mismatch repair (MMR). Additionally, double-strand break repair (by homologous recombination and nonhomologous end joining), SOS response, cell-cycle checkpoints, and programmed cell death (apoptosis) are also operative in various organisms with the expense of specific gene products. This review deals with UV-induced alterations in DNA and its maintenance by various repair mechanisms.
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              Genetic diversity in Sargasso Sea bacterioplankton.

              Bacterioplankton are recognized as important agents of biogeochemical change in marine ecosystems, yet relatively little is known about the species that make up these communities. Uncertainties about the genetic structure and diversity of natural bacterioplankton populations stem from the traditional difficulties associated with microbial cultivation techniques. Discrepancies between direct counts and plate counts are typically several orders of magnitude, raising doubts as to whether cultivated marine bacteria are actually representative of dominant planktonic species. We have phylogenetically analysed clone libraries of eubacterial 16S ribosomal RNA genes amplified from natural populations of Sargasso Sea picoplankton by the polymerase chain reaction. The analysis indicates the presence of a novel microbial group, the SAR11 cluster, which appears to be a significant component of this oligotrophic bacterioplankton community. A second cluster of lineages related to the oxygenic phototrophs--cyanobacteria, prochlorophytes and chloroplasts--was also observed. However, none of the genes matched the small subunit rRNA sequences of cultivated marine cyanobacteria from similar habitats. The diversity of 16S rRNA genes observed within the clusters suggests that these bacterioplankton may be consortia of independent lineages sharing surprisingly distant common ancestors.
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                Author and article information

                Contributors
                Journal
                Front Microbiol
                Front Microbiol
                Front. Microbiol.
                Frontiers in Microbiology
                Frontiers Media S.A.
                1664-302X
                26 March 2020
                2020
                : 11
                : 453
                Affiliations
                [1] 1Department of Molecular Evolution, Centro de Astrobiología (CSIC-INTA) , Madrid, Spain
                [2] 2Programa Institucional de Fomento a la Investigación, Desarrollo e Innovación, Universidad Tecnológica Metropolitana , Santiago, Chile
                [3] 3Laboratorio de Investigaciones Microbiológicas de Lagunas Andinas (LIMLA), Planta Piloto de Procesos Industriales y Microbiológicos (PROIMI), Centro Científico Tecnológico, Consejo Nacional de Investigaciones Científicas y Técnicas , San Miguel de Tucumán, Argentina
                [4] 4Marine Microbiology Group, Department of Ecology and Marine Resources, Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB) , Esporles, Spain
                Author notes

                Edited by: Jesse G. Dillon, California State University, Long Beach, United States

                Reviewed by: Haitham Sghaier, National Center for Nuclear Sciences and Technology, Tunisia; Wenyuan Han, Huazhong Agricultural University, China

                *Correspondence: José Eduardo González-Pastor, gonzalezpje@ 123456cab.inta-csic.es

                This article was submitted to Extreme Microbiology, a section of the journal Frontiers in Microbiology

                Article
                10.3389/fmicb.2020.00453
                7135895
                a1c4cb6d-5627-4717-8fcb-d0089ccd9ac8
                Copyright © 2020 Lamprecht-Grandío, Cortesão, Mirete, Benguigui de la Cámara, de Figueras, Pérez-Pantoja, White, Farías, Rosselló-Móra and González-Pastor.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 22 August 2019
                : 03 March 2020
                Page count
                Figures: 7, Tables: 2, Equations: 0, References: 74, Pages: 15, Words: 0
                Funding
                Funded by: Ministerio de Economía y Competitividad 10.13039/501100003329
                Award ID: CLG2015_66686-C3-2-P
                Award ID: CLG2015_66686-C3-1-P
                Funded by: Ministerio de Ciencia, Innovación y Universidades 10.13039/100014440
                Award ID: PGC2018-096956-B-C41
                Award ID: PGC2018-096956-B-C42
                Funded by: Horizon 2020 Framework Programme 10.13039/100010661
                Award ID: GA 685474
                Funded by: Comisión Nacional de Investigación Científica y Tecnológica 10.13039/501100002848
                Award ID: GAMBIO ACT172128
                Funded by: Fondo Nacional de Desarrollo Científico y Tecnológico 10.13039/501100002850
                Award ID: 1161750
                Categories
                Microbiology
                Original Research

                Microbiology & Virology
                uv resistance,perchlorate resistance,4-nitroquinoline 1-oxide,dna repair,functional metagenomics,hypersaline environments,andean highlands

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