Desiccation as a long-term survival mechanism for the archaeon Methanosarcina barkeri.
01 Mar 2012-Applied and Environmental Microbiology (American Society for Microbiology)-Vol. 78, Iss: 5, pp 1473-1479
TL;DR: After desiccation M. barkeri has the innate capability to survive extended periods of exposure to air and lethal temperatures, and the protection mechanisms are likely adequate to maintain cell viability during periodic exposure events.
Abstract: 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.
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TL;DR: The environmental, physiological and molecular adaptations that enable xerotolerant bacteria to survive in environments in which water is scarce are discussed and insights from modern 'omics' technologies are highlighted.
Abstract: Water is vital for many biological processes and is essential for all living organisms. However, numerous macroorganisms and microorganisms have adapted to survive in environments in which water is scarce; such organisms are collectively termed xerotolerant. With increasing global desertification due to climate change and human-driven desertification processes, it is becoming ever more important to understand how xerotolerant organisms cope with a lack of water. In this Review, we discuss the environmental, physiological and molecular adaptations that enable xerotolerant bacteria to survive in environments in which water is scarce and highlight insights from modern 'omics' technologies. Understanding xerotolerance will inform and hopefully aid efforts to regulate and even reverse desertification.
169 citations
TL;DR: The purpose of anaerobic digestion is the production of a renewable energy source (biogas) and an odor free nutrient-rich fertilizer and if animal wastes are accidentally found in the environment, it can cause a drastic chain of environmental and public health complications.
Abstract: With an ever increasing population rate; a vast array of biomass wastes rich in organic and inorganic nutrients as well as pathogenic microorganisms will result from the diversified human, industrial and agricultural activities Anaerobic digestion is applauded as one of the best ways to properly handle and manage these wastes Animal wastes have been recognized as suitable substrates for anaerobic digestion process, a natural biological process in which complex organic materials are broken down into simpler molecules in the absence of oxygen by the concerted activities of four sets of metabolically linked microorganisms This process occurs in an airtight chamber (biodigester) via four stages represented by hydrolytic, acidogenic, acetogenic and methanogenic microorganisms The microbial population and structure can be identified by the combined use of culture-based, microscopic and molecular techniques Overall, the process is affected by bio-digester design, operational factors and manure characteristics The purpose of anaerobic digestion is the production of a renewable energy source (biogas) and an odor free nutrient-rich fertilizer Conversely, if animal wastes are accidentally found in the environment, it can cause a drastic chain of environmental and public health complications
158 citations
Cites background from "Desiccation as a long-term survival..."
...[44] also noted that after dessication process, M....
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Journal Article•
TL;DR: Maeder et al. as discussed by the authors compared the Methanosarcina barkeri genome with methanearcina mazei and showed extensive rearrangement within methanosarcinal genomes.
Abstract: LBNL-60247 Preprint Title: The Methanosarcina barkeri genome: comparative analysis with Methanosarcina acetivorans and Methanosarcina mazei reveals extensive rearrangement within methanosarcinal genomes Author(s): Dennis L. Maeder, Iain Anderson, et al Division: Genomics November 2006 Journal of Bacteriology
153 citations
Journal Article•
TL;DR: In this article, the formation of alginate appeared to play a decisive role in protecting the nitrogenase that is required for cell growth in this culture, which is not the prevailing mechanism for nitrogenase protection in A. vinelandii grown in phosphate-limited nitrogen free chemostat culture.
Abstract: ABSTRACT The activity of nitrogenase in the nitrogen-fixing bacteriumAzotobacter vinelandii grown diazotrophically under aerobic conditions is generally considered to be protected against O2 by a high respiration rate. In this work, we have shown that a high rate of respiration is not the prevailing mechanism for nitrogenase protection in A. vinelandii grown in phosphate-limited nitrogen-free chemostat culture. Instead, the formation of alginate appeared to play a decisive role in protecting the nitrogenase that is required for cell growth in this culture. Depending on the O2 tension and cell growth rate, the formation rate and composition of alginate released into the culture broth varied significantly. Furthermore, transmission electron microscopic analysis of cell morphology and the cell surface revealed the existence of an alginate capsule on the surface of A. vinelandii. The composition, thickness, and compactness of this alginate capsule also varied significantly. In general, increasing O2 tension led to the formation of alginate with a higher molecular weight and a greater l-guluronic acid content. The alginate capsule was accordingly thicker and more compact. In addition, the formation of the alginate capsule was found to be strongly affected by the shear rate in a bioreactor. Based on these experimental results, it is suggested that the production of alginate, especially the formation of an alginate capsule on the cell surface, forms an effective barrier for O2 transfer into the cell. It is obviously the quality, not the quantity, of alginate that is decisive for the protection of nitrogenase.
134 citations
TL;DR: This work aims to highlight the available information and indicate open questions in this field of biofilms, and to show how little molecular details are known about archaeal biofilm formation.
Abstract: Biofilms are currently viewed as the most common form in which microorganisms exist in nature. Bacterial biofilms play important roles in disease and industrial applications, and they have been studied in great detail. Although it is well accepted that archaea are not only the extremists they were thought to be as they occupy nearly every habitat where also bacteria are found, it is surprising how little molecular details are known about archaeal biofilm formation. Therefore, we aim to highlight the available information and indicate open questions in this field.
69 citations
References
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TL;DR: The present review considers a number of the features that appear to be critical to the withstanding of a long-term water deficit, including the elaboration of a conspicuous extracellular glycan, synthesis of abundant UV-absorbing pigments, and maintenance of protein stability and structural integrity.
1,259 citations
"Desiccation as a long-term survival..." refers background in this paper
...the formation of relatively thick outer cell layers (32)....
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TL;DR: E2F1 emerges as a key protein that integrates cell division and growth, both of which are essential for cell proliferation, and is complementary in activating the signal pathway.
Abstract: During cell proliferation, growth must occur to maintain homeostatic cell size. Here we show that E2F1 is capable of inducing growth by regulating mTORC1 activity. The activation of cell growth and mTORC1 by E2F1 is dependent on both E2F1's ability to bind DNA and to regulate gene transcription, demonstrating that a gene induction expression program is required in this process. Unlike E2F1, E2F3 is unable to activate mTORC1, suggesting that growth activity could be restricted to individual E2F members. The effect of E2F1 on the activation of mTORC1 does not depend on Akt. Furthermore, over-expression of TSC2 does not interfere with the effect of E2F1, indicating that the E2F1-induced signal pathway can compensate for the inhibitory effect of TSC2 on Rheb. Immunolocalization studies demonstrate that E2F1 induces the translocation of mTORC1 to the late endosome vesicles, in a mechanism dependent of leucine. E2F1 and leucine, or insulin, together affect the activation of S6K stronger than alone suggesting that they are complementary in activating the signal pathway. From these studies, E2F1 emerges as a key protein that integrates cell division and growth, both of which are essential for cell proliferation.
668 citations
TL;DR: The evidence presented suggests that D. radiodurans' ionizing radiation resistance is incidental, a consequence of this organism's adaptation to a common physiological stress, dehydration.
Abstract: Forty-one ionizing radiation-sensitive strains of Deinococcus radiodurans were evaluated for their ability to survive 6 weeks of desiccation. All exhibited a substantial loss of viability upon rehydration compared with wild-type D. radiodurans. Examination of chromosomal DNA from desiccated cultures revealed a time-dependent increase in DNA damage, as measured by an increase in DNA double-strand breaks. The evidence presented suggests that D. radiodurans9 ionizing radiation resistance is incidental, a consequence of this organism9s adaptation to a common physiological stress, dehydration.
649 citations
"Desiccation as a long-term survival..." refers background in this paper
...However, in the current report we show that the sensitivity of desiccated cells to ionizing radiation is similar to that of E. coli, indicating that the mechanisms of adaptation in M. barkeri are not linked to a robust DNA repair associated with desiccation-tolerant microorganisms such as Deinococcus and Halobacterium (20, 25)....
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...barkeri are not linked to a robust DNA repair associated with desiccation-tolerant microorganisms such as Deinococcus and Halobacterium (20, 25)....
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Uniformed Services University of the Health Sciences1, Harvard University2, University at Albany, SUNY3, J. Craig Venter Institute4, Pennsylvania State University5, Massachusetts Institute of Technology6, University of Wisconsin-Madison7, Virginia Tech8, University of Illinois at Urbana–Champaign9, Cornell University10, Columbia University11
TL;DR: The complete genome sequence of an acetate-utilizing methanogen, Methanosarcina acetivorans C2A, is reported, which indicates the likelihood of undiscovered natural energy sources for methanogenesis, whereas the presence of single-subunit carbon monoxide dehydrogenases raises the possibility of nonmethanogenic growth.
Abstract: The Archaea remain the most poorly understood domain of life despite their importance to the biosphere. Methanogenesis, which plays a pivotal role in the global carbon cycle, is unique to the Archaea. Each year, an estimated 900 million metric tons of methane are biologically produced, representing the major global source for this greenhouse gas and contributing significantly to global warming (Schlesinger 1997). Methanogenesis is critical to the waste-treatment industry and biologically produced methane also represents an important alternative fuel source. At least two-thirds of the methane in nature is derived from acetate, although only two genera of methanogens are known to be capable of utilizing this substrate. We report here the first complete genome sequence of an acetate-utilizing (acetoclastic) methanogen, Methanosarcina acetivorans C2A.
The Methanosarcineae are metabolically and physiologically the most versatile methanogens. Only Methanosarcina species possess all three known pathways for methanogenesis (Fig. (Fig.1)1) and are capable of utilizing no less than nine methanogenic substrates, including acetate. In contrast, all other orders of methanogens possess a single pathway for methanogenesis, and many utilize no more than two substrates. Among methanogens, the Methanosarcineae also display extensive environmental diversity. Individual species of Methanosarcina have been found in freshwater and marine sediments, decaying leaves and garden soils, oil wells, sewage and animal waste digesters and lagoons, thermophilic digesters, feces of herbivorous animals, and the rumens of ungulates (Zinder 1993).
Figure 1
Three pathways for methanogenesis. Methanogenesis is a form of anaerobic respiration using a variety of one-carbon (C-1) compounds or acetic acid as a terminal electron acceptor. All three pathways converge on the reduction of methyl-CoM to methane (CH ...
The Methanosarcineae are unique among the Archaea in forming complex multicellular structures during different phases of growth and in response to environmental change (Fig. (Fig.2).2). Within the Methanosarcineae, a number of distinct morphological forms have been characterized, including single cells with and without a cell envelope, as well as multicellular packets and lamina (Macario and Conway de Macario 2001). Packets and lamina display internal morphological heterogeneity, suggesting the possibility of cellular differentiation. Moreover, it has been suggested that cells within lamina may display differential production of extracellular material, a potential form of cellular specialization (Macario and Conway de Macario 2001). The formation of multicellular structures has been proposed to act as an adaptation to stress and likely plays a role in the ability of Methanosarcina species to colonize diverse environments.
Figure 2
Different morphological forms of Methanosarcina acetivorans. Thin-section electron micrographs showing M. acetivorans growing as both single cells (center of micrograph) and within multicellular aggregates (top left, bottom right). Cells were harvested ...
Significantly, powerful methods for genetic analysis exist for Methanosarcina species. These tools include plasmid shuttle vectors (Metcalf et al. 1997), very high efficiency transformation (Metcalf et al. 1997), random in vivo transposon mutagenesis (Zhang et al. 2000), directed mutagenesis of specific genes (Zhang et al. 2000), multiple selectable markers (Boccazzi et al. 2000), reporter gene fusions (M. Pritchett and W. Metcalf, unpubl.), integration vectors (Conway de Macario et al. 1996), and anaerobic incubators for large-scale growth of methanogens on solid media (Metcalf et al. 1998). Furthermore, and in contrast to other known methanogens, genetic analysis can be used to study the process of methanogenesis: Because Methanosarcina species are able to utilize each of the three known methanogenic pathways, mutants in a single pathway are viable (M. Pritchett and W. Metcalf, unpubl.). The availability of genetic methods allowing immediate exploitation of genomic sequence, coupled with the genetic, physiological, and environmental diversity of M. acetivorans make this species an outstanding model organism for the study of archaeal biology. For these reasons, we set out to study the genome of M. acetivorans.
626 citations
TL;DR: Whether transoceanic and transcontinental dust events inject a large pulse of microorganisms and pollen into the atmosphere and could therefore have a role in transporting pathogens or expanding the biogeographical range of some organisms by facilitating long-distance dispersal events is discussed.
Abstract: Desert winds aerosolize several billion tons of soil-derived dust each year, including concentrated seasonal pulses from Africa and Asia. These transoceanic and transcontinental dust events inject a large pulse of microorganisms and pollen into the atmosphere and could therefore have a role in transporting pathogens or expanding the biogeographical range of some organisms by facilitating long-distance dispersal events. As we discuss here, whether such dispersal events are occurring is only now beginning to be investigated. Huge dust events create an atmospheric bridge over land and sea, and the microbiota contained within them could impact downwind ecosystems. Such dispersal is of interest because of the possible health effects of allergens and pathogens that might be carried with the dust.
549 citations
"Desiccation as a long-term survival..." refers background in this paper
...to be disseminated in high-altitude dust clouds as a mechanism for explaining the ubiquitous nature of these species in both aqueous and terrestrial environments around the globe (17)....
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