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Ignicoccus hospitalis – understanding its extraordinary radiation tolerance and an unsolved archaeal repair system

Palomeque-Dominguez, H. and Beblo-Vranesevic, K. and Rettberg, P. (2021) Ignicoccus hospitalis – understanding its extraordinary radiation tolerance and an unsolved archaeal repair system. EANA 2021, 7.-10. September 2021, Virtual Conference.

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Abstract

Ignicoccus hospitalis is an obligate anaerobic, hyperthermophilic and chemolithoautotrophic archaeal microorganism that has exhibited an extraordinarily high tolerance against ionizing radiation (1). It was demonstrated by Koschnitzki, 2016 that I. hospitalis cells can remain viable after exposure to X-ray doses up to 12 kGy and it can completely repair DNA damages within one hour (2). I. hospitalis has a D10-value of ~5 kGy but it can remain metabolically active after being exposed up to 118 kGy (3). This exceptional radiotolerance is unexpected since ionizing radiation is not present in its natural environment - a submarine system of hydrothermal vents (4). Given that DNA damages induced by high temperature are similar to those induced by ionizing radiation (5), we hypothesize that the radiation tolerance of I. hospitalis is a consequence of the intrinsic biological properties it uses to cope the extreme conditions of its habitat. To unravel the mechanisms involved in the radiation tolerance of I. hospitalis, two approaches are currently being followed: exploring the intracellular-specific protection and monitoring the gene regulation of the DNA repair process. Having multiple genome copies (polyploidy) might allow microbes for genomic DNA protection, maintenance, and repair at extreme conditions (6). The possibility of polyploidy in I. hospitalis was addressed. The number of genome copies per cell under different growth stages was calculated based on the quantitation of the total DNA content and the cell density from a series of culture aliquots. It was found that during the beginning of Log phase, I. hospitalis cells have 0.85±0.35 genomes/cell, in the middle of Log phase this value doubles to 1.78±0.27 genomes/cell, and at the stationary phase it drops again to 0.59±0.37 genomes/cell. Compatible solutes have been extensively studied for their role in cellular protection against severe injuring influences like osmotic stress or heat shock, and for their function as radical scavenging molecules (7). A combination of different cultivation setups, like supra-optimal growth temperatures (92.5 – 95 ˚C) and high salinity (3 – 5 % w/v) were tested to influence the accumulation of compatible solutes. Then, desiccation survival was used as an indication of their presence within the cells. No cell survival after desiccation was detected, meaning there isn’t significant compatible solutes accumulation. An alternative intracellular protection mechanism in some microorganisms is based on the intracellular manganese/iron (Mn/Fe) ratio. It has been reported that Deinococcus radiodurans accumulates high amounts of intracellular manganese and low levels of iron (8). The determination of intracellular content of these two transition metals is currently ongoing, and it will be measured by ICP-MS. A set of transcriptomics experiments are currently in progress in order to investigate the up-or-downregulation of genes related with DNA repair mechanisms. We will use dRNA-seq analysis to contrast different irradiation conditions with pre-selected time points during the DNA repair process and optimal conditions. This project will help to gain knowledge on the DNA repair mechanisms in Archaea, and to better understand the limits of life.

Item URL in elib:https://elib.dlr.de/143864/
Document Type:Conference or Workshop Item (Speech)
Title:Ignicoccus hospitalis – understanding its extraordinary radiation tolerance and an unsolved archaeal repair system
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Palomeque-Dominguez, H.Radiation Biology Department, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, GermanyUNSPECIFIED
Beblo-Vranesevic, K.Radiation Biology Department, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany; kristina.beblo (at) dlr.dehttps://orcid.org/0000-0002-4834-7121
Rettberg, P.Radiation Biology Department, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany; petra.rettberg (at) dlr.dehttps://orcid.org/0000-0003-4439-2395
Date:September 2021
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:Ignicoccus hospitalis, ionizing radiation, DNA repair
Event Title:EANA 2021
Event Location:Virtual Conference
Event Type:international Conference
Event Dates:7.-10. September 2021
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Research under Space Conditions
DLR - Research theme (Project):R - Project ISS LIFE 2.0
Location: Köln-Porz
Institutes and Institutions:Institute of Aerospace Medicine > Radiation Biology
Deposited By: Kopp, Kerstin
Deposited On:17 Sep 2021 08:39
Last Modified:17 Sep 2021 08:39

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