Survival of Methanogens During Desiccation: Implications for Life on Mars

Kendrick, Michael G.; Kral, T. A.

doi:10.1089/ast.2006.6.546

Cited by 46 publications

(30 citation statements)

References 25 publications

(18 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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

“…Prior reports showed that Methanosarcina spp. and other methanogens could survive desiccation for limited periods of time (6,10,18,21,30). This report quantitatively assesses the survival rates of a methanogenic archaeon after desiccation and subsequent exposure to stress factors that simulate the driest environments on Earth, such as the Antarctic dry valleys and hyperarid core of the Atacama Desert in Chile (14,24).…”

Section: Recovery Of M Barkeri Desiccated Under Different Growth Conmentioning

confidence: 99%

Desiccation as a Long-Term Survival Mechanism for the Archaeon Methanosarcina barkeri

Anderson

Apolinario

Sowers

2012

Appl Environ Microbiol

View full text Add to dashboard Cite

Viable methanogens have been detected in dry, aerobic environments such as dry reservoir sediment, dry rice paddies and aerobic desert soils, which suggests that methanogens have mechanisms for long-term survival in a desiccated state. In this study, we quantified the survival rates of the methanogenic archaeon Methanosarcina barkeri after desiccation under conditions equivalent to the driest environments on Earth and subsequent exposure to different stress factors. There was no significant loss of viability after desiccation for 28 days for cells grown with either hydrogen or the methylotrophic substrates, but recovery was affected by growth phase, with cells desiccated during the stationary phase of growth having a higher rate of recovery after desiccation. Synthesis of methanosarcinal extracellular polysaccharide (EPS) significantly increased the viability of desiccated cells under both anaerobic and aerobic conditions compared with that of non-EPS-synthesizing cells. Desiccated M. barkeri exposed to air at room temperature did not lose significant viability after 28 days, and exposure of M. barkeri to air after desiccation appeared to improve the recovery of viable cells compared with that of desiccated cells that were never exposed to air. Desiccated M. barkeri was more resistant to higher temperatures, and although resistance to oxidative conditions such as ozone and ionizing radiation was not as robust as in other desiccation-resistant microorganisms, the protection mechanisms are likely adequate to maintain cell viability during periodic exposure events. The results of this study demonstrate that after desiccation M. barkeri has the innate capability to survive extended periods of exposure to air and lethal temperatures.A s more microorganisms are discovered in extreme environments on Earth that were previously considered to be devoid of life, we have been redefining the physical and chemical parameters for life to exist. One such extreme is the long-term storage of viable cells in a desiccated state, which imposes physiological constraints that many species cannot tolerate. A common characteristic of known desiccation-tolerant microorganisms, which include spore-forming bacteria, heterocyst-forming cyanobacteria, heteropolysaccharide-forming Beijerinckia, and Deinococcus, is the formation of relatively thick outer cell layers (32). The synthesis of an outer cell layer often composed of an extracellular polysaccharide (EPS), in conjunction with other mechanisms such as robust DNA repair and compatible solute formation, enables the cells to retain the minimal intracellular water activity required for survival (32).The methanogenic Archaea, despite their preference for highly reduced, anoxic conditions in order to grow, are globally distributed in a wide range of anaerobic, aquatic environments, including Antarctic lakes, submarine hydrothermal vents, rice paddies, sewage digestors, and as symbionts in rumen, termites, protozoa, and human large intestines (38). Among the least anticipated environments wher...

show abstract

“…Archaea were discussed as one of the most likely life forms on Earth to survive a space flight, and survive or even thrive on Mars (mainly methanogens and halophiles; Kendrick and Kral, 2006;Landis, 2001), but it was unclear, if Archaea even could be found in spacecraft-associated clean rooms.…”

Section: Introductionmentioning

confidence: 99%

Archaea in artificial environments: Their presence in global spacecraft clean rooms and impact on planetary protection

Moissl-Eichinger

2010

The ISME Journal

View full text Add to dashboard Cite

The presence and role of Archaea in artificial, human-controlled environments is still unclear. The search for Archaea has been focused on natural biotopes where they have been found in overwhelming numbers, and with amazing properties. However, they are considered as one of the major group of microorganisms that might be able to survive a space flight, or even to thrive on other planets. Although still concentrating on aerobic, bacterial spores as a proxy for spacecraft cleanliness, space agencies are beginning to consider Archaea as a possible contamination source that could affect future searches for life on other planets. This study reports on the discovery of archaeal 16S rRNA gene signatures not only in US American spacecraft assembly clean rooms but also in facilities in Europe and South America. Molecular methods revealed the presence of Crenarchaeota in all clean rooms sampled, while signatures derived from methanogens and a halophile appeared only sporadically. Although no Archaeon was successfully enriched in our multiassay cultivation approach thus far, samples from a European clean room revealed positive archaeal fluorescence in situ hybridization (FISH) signals of rod-shaped microorganisms, representing the first visualization of Archaea in clean room environments. The molecular and visual detection of Archaea was supported by the first quantitative PCR studies of clean rooms, estimating the overall quantity of Archaea therein. The significant presence of Archaea in these extreme environments in distinct geographical locations suggests a larger role for these microorganisms not only in natural biotopes, but also in human controlled and rigorously cleaned environments.

show abstract

Survival of Methanogens During Desiccation: Implications for Life on Mars

Cited by 46 publications

References 25 publications

Genome Copy Numbers and Gene Conversion in Methanogenic Archaea

Genome Copy Numbers and Gene Conversion in Methanogenic Archaea

Desiccation as a Long-Term Survival Mechanism for the Archaeon Methanosarcina barkeri

Archaea in artificial environments: Their presence in global spacecraft clean rooms and impact on planetary protection

Contact Info

Product

Resources

About