Extremely Radiation-Resistant Mutants of a Halophilic Archaeon with Increased Single-Stranded DNA-Binding Protein (RPA) Gene Expression

DeVeaux, Linda C.; Müller, Jochen A.; Smith, Jonathon E.; Petrisko, Jill E.; Wells, Douglas P.; DasSarma, Shiladitya

doi:10.1667/rr0935.1

Cited by 84 publications

(91 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…H. salinarum is also very resistant to ionizing radiation and to desiccation, and it has been shown that it is also able to restore intact chromosomes from fragmented chromosomes (20). Mutants of H. salinarum could be isolated that show a considerably higher radiation resistance than D. radiodurans (9). Several species of methanogenic archaea have been shown to be very resistant against desiccation (17,23).…”

Section: Discussionmentioning

confidence: 99%

Genome Copy Numbers and Gene Conversion in Methanogenic Archaea

et al. 2011

View full text Add to dashboard Cite

Previous studies revealed that one species of methanogenic archaea, Methanocaldococcus jannaschii, is polyploid, while a second species, Methanothermobacter thermoautotrophicus, is diploid. To further investigate the distribution of ploidy in methanogenic archaea, species of two additional genera-Methanosarcina acetivorans and Methanococcus maripaludis-were investigated. M. acetivorans was found to be polyploid during fast growth (t D ‫؍‬ 6 h; 17 genome copies) and oligoploid during slow growth (doubling time ‫؍‬ 49 h; 3 genome copies). M. maripaludis has the highest ploidy level found for any archaeal species, with up to 55 genome copies in exponential phase and ca. 30 in stationary phase. A compilation of archaeal species with quantified ploidy levels reveals a clear dichotomy between Euryarchaeota and Crenarchaeota: none of seven euryarchaeal species of six genera is monoploid (haploid), while, in contrast, all six crenarchaeal species of four genera are monoploid, indicating significant genetic differences between these two kingdoms. Polyploidy in asexual species should lead to accumulation of inactivating mutations until the number of intact chromosomes per cell drops to zero (called "Muller's ratchet"). A mechanism to equalize the genome copies, such as gene conversion, would counteract this phenomenon. Making use of a previously constructed heterozygous mutant strain of the polyploid M. maripaludis we could show that in the absence of selection very fast equalization of genomes in M. maripaludis took place probably via a gene conversion mechanism. In addition, it was shown that the velocity of this phenomenon is inversely correlated to the strength of selection.

show abstract

Section: Discussionmentioning

confidence: 99%

Genome Copy Numbers and Gene Conversion in Methanogenic Archaea

et al. 2011

View full text Add to dashboard Cite

show abstract

“…strain NRC-1) can resist very harsh conditions, such as extreme doses of (UV and ionizing) radiation and desiccation (8,11). Recent culture-based and molecular studies have shown that the microbial diversity on spacecraft and within the clean rooms is extraordinarily high and does include extremotolerant bacteria and even archaea (25,30).…”

mentioning

confidence: 99%

Cultivation of Anaerobic and Facultatively Anaerobic Bacteria from Spacecraft-Associated Clean Rooms

Stieglmeier

Wirth²,

Kminek

et al. 2009

Appl Environ Microbiol

View full text Add to dashboard Cite

In the course of this biodiversity study, the cultivable microbial community of European spacecraft-associated clean rooms and the Herschel Space Observatory located therein were analyzed during routine assembly operations. Here, we focused on microorganisms capable of growing without oxygen. Anaerobes play a significant role in planetary protection considerations since extraterrestrial environments like Mars probably do not provide enough oxygen for fully aerobic microbial growth. A broad assortment of anaerobic media was used in our cultivation strategies, which focused on microorganisms with special metabolic skills. The majority of the isolated strains grew on anaerobic, complex, nutrient-rich media. Autotrophic microorganisms or microbes capable of fixing nitrogen were also cultivated. A broad range of facultatively anaerobic bacteria was detected during this study and also, for the first time, some strictly anaerobic bacteria (Clostridium and Propionibacterium) were isolated from spacecraft-associated clean rooms. The multiassay cultivation approach was the basis for the detection of several bacteria that had not been cultivated from these special environments before and also led to the discovery of two novel microbial species of Pseudomonas and Paenibacillus.The major issue of planetary protection is to prevent the contamination of extraterrestrial environments by terrestrial biomolecules and life forms. Furthermore, reverse contamination of Earth by extraterrestrial material is also a fundamental concern (1). In order not to affect or even to confound future life detection missions on celestial bodies, which are of interest for their chemical and biological evolution, spacecraft are constructed in so-called clean rooms and are subject to severe cleaning processes and microbiological controls before launch (9). Therefore, these clean rooms are considered extreme environments for microorganisms (47).Detailed planetary protection protocols for missions to Mars were designed for the Viking missions, which were launched in 1975, and about 7,000 samples were taken from the two Viking spacecraft during prelaunch activities in order to determine the cultivable microbial load (37). Besides human-associated bacteria (pathogens and opportunistic pathogens), which were predominant among the microbes detected in these samples, aerobic spore-forming microorganisms (Bacillus) were found frequently on spacecraft and within the facilities.Spores are the resting states of bacteria and are often highly resistant to heat, desiccation, and other abiotic stresses. These multiresistance properties of such spore-forming microorganisms make them perfect candidates for surviving a space flight, and thus, the main focus of attention has been on them. Furthermore, only the detection of aerobic spore-forming bacteria is currently included in space agencies' planetary protection protocols for the quantitative determination of microbial burden on spacecraft.

show abstract

“…This homolog, encoded by the rfa3 operon, is one of two eukaryotic-like RPAs present in H. salinarum. Constitutive upregulation of this operon was found as the only transcriptomic difference among multiple radiation-resistant mutants of H. salinarum (DeVeaux, et al, 2007). This homolog is significantly up-regulated following IR-treatment of wild type H. salinarum, but not in the radiation-resistant mutants, presumably because the protein is being constitutively expressed at the induced level.…”

Section: Transcriptional Regulationmentioning

confidence: 95%

“…In H. salinarum, Rfa3, Rfa8, and Ral, and Rfa2 and Rfa7 resemble the P. furiosis RPA with respect to operon structure and sequence homology to eukaryotic RPA (Figure 1). Rfa6 resembles the crenarchaeal SSB/RPA in gene and OB-fold structure, while Rfa1 appears more uniquely archaeal, with three OB-folds (DeVeaux, et al, 2007;Robbins, et al, 2005). The roles of the RPA-like homologs in H. salinarum will be discussed further below.…”

Section: Multiplicity Of Homologsmentioning

confidence: 98%