Life | March 2013 - Browse Articles

223 KiB

Open AccessReview

Microorganism Response to Stressed Terrestrial Environments: A Raman Spectroscopic Perspective of Extremophilic Life Strategies

by Susana E. Jorge-Villar and Howell G.M. Edwards

Life 2013, 3(1), 276-294; https://doi.org/10.3390/life3010276 - 13 Mar 2013

Cited by 18 | Viewed by 8565

Abstract

Raman spectroscopy is a valuable analytical technique for the identification of biomolecules and minerals in natural samples, which involves little or minimal sample manipulation. In this paper, we evaluate the advantages and disadvantages of this technique applied to the study of extremophiles. Furthermore, [...] Read more.

Raman spectroscopy is a valuable analytical technique for the identification of biomolecules and minerals in natural samples, which involves little or minimal sample manipulation. In this paper, we evaluate the advantages and disadvantages of this technique applied to the study of extremophiles. Furthermore, we provide a review of the results published, up to the present point in time, of the bio- and geo-strategies adopted by different types of extremophile colonies of microorganisms. We also show the characteristic Raman signatures for the identification of pigments and minerals, which appear in those complex samples. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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845 KiB

Open AccessArticle

Quorum Sensing in Some Representative Species of Halomonadaceae

by Ali Tahrioui, Melanie Schwab, Emilia Quesada and Inmaculada Llamas

Life 2013, 3(1), 260-275; https://doi.org/10.3390/life3010260 - 5 Mar 2013

Cited by 22 | Viewed by 8980

Abstract

Cell-to-cell communication, or quorum-sensing (QS), systems are employed by bacteria for promoting collective behaviour within a population. An analysis to detect QS signal molecules in 43 species of the Halomonadaceae family revealed that they produced N-acyl homoserine lactones (AHLs), which suggests that [...] Read more.

Cell-to-cell communication, or quorum-sensing (QS), systems are employed by bacteria for promoting collective behaviour within a population. An analysis to detect QS signal molecules in 43 species of the Halomonadaceae family revealed that they produced N-acyl homoserine lactones (AHLs), which suggests that the QS system is widespread throughout this group of bacteria. Thin-layer chromatography (TLC) analysis of crude AHL extracts, using Agrobacterium tumefaciens NTL4 (pZLR4) as biosensor strain, resulted in different profiles, which were not related to the various habitats of the species in question. To confirm AHL production in the Halomonadaceae species, PCR and DNA sequencing approaches were used to study the distribution of the luxI-type synthase gene. Phylogenetic analysis using sequence data revealed that 29 of the species studied contained a LuxI homolog. Phylogenetic analysis showed that sequences from Halomonadaceae species grouped together and were distinct from other members of the Gammaproteobacteria and also from species belonging to the Alphaproteobacteria and Betaproteobacteria. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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293 KiB

Open AccessArticle

Properties of Halococcus salifodinae, an Isolate from Permian Rock Salt Deposits, Compared with Halococci from Surface Waters

by Andrea Legat, Ewald B. M. Denner, Marion Dornmayr-Pfaffenhuemer, Peter Pfeiffer, Burkhard Knopf, Harald Claus, Claudia Gruber, Helmut König, Gerhard Wanner and Helga Stan-Lotter

Life 2013, 3(1), 244-259; https://doi.org/10.3390/life3010244 - 28 Feb 2013

Cited by 11 | Viewed by 10344

Abstract

Halococcus salifodinae BIp^T DSM 8989^T, an extremely halophilic archaeal isolate from an Austrian salt deposit (Bad Ischl), whose origin was dated to the Permian period, was described in 1994. Subsequently, several strains of the species have been isolated, some from [...] Read more.

Halococcus salifodinae BIp^T DSM 8989^T, an extremely halophilic archaeal isolate from an Austrian salt deposit (Bad Ischl), whose origin was dated to the Permian period, was described in 1994. Subsequently, several strains of the species have been isolated, some from similar but geographically separated salt deposits. Hcc. salifodinae may be regarded as one of the most ancient culturable species which existed already about 250 million years ago. Since its habitat probably did not change during this long period, its properties were presumably not subjected to the needs of mutational adaptation. Hcc. salifodinae and other isolates from ancient deposits would be suitable candidates for testing hypotheses on prokaryotic evolution, such as the molecular clock concept, or the net-like history of genome evolution. A comparison of available taxonomic characteristics from strains of Hcc. salifodinae and other Halococcus species, most of them originating from surface waters, is presented. The cell wall polymer of Hcc. salifodinae was examined and found to be a heteropolysaccharide, similar to that of Hcc. morrhuae. Polyhydroxyalkanoate granules were present in Hcc. salifodinae, suggesting a possible lateral gene transfer before Permian times. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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438 KiB

Open AccessReview

Molecular Mechanisms of Adaptation of the Moderately Halophilic Bacterium Halobacillis halophilus to Its Environment

by Inga Hänelt and Volker Müller

Life 2013, 3(1), 234-243; https://doi.org/10.3390/life3010234 - 27 Feb 2013

Cited by 36 | Viewed by 11008

Abstract

The capability of osmoadaptation is a prerequisite of organisms that live in an environment with changing salinities. Halobacillus halophilus is a moderately halophilic bacterium that grows between 0.4 and 3 M NaCl by accumulating both chloride and compatible solutes as osmolytes. Chloride is [...] Read more.

The capability of osmoadaptation is a prerequisite of organisms that live in an environment with changing salinities. Halobacillus halophilus is a moderately halophilic bacterium that grows between 0.4 and 3 M NaCl by accumulating both chloride and compatible solutes as osmolytes. Chloride is absolutely essential for growth and, moreover, was shown to modulate gene expression and activity of enzymes involved in osmoadaptation. The synthesis of different compatible solutes is strictly salinity- and growth phase-dependent. This unique hybrid strategy of H. halophilus will be reviewed here taking into account the recently published genome sequence. Based on identified genes we will speculate about possible scenarios of the synthesis of compatible solutes and the uptake of potassium ion which would complete our knowledge of the fine-tuned osmoregulation and intracellular osmolyte balance in H. halophilus. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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698 KiB

Open AccessArticle

A Laboratory of Extremophiles: Iceland Coordination Action for Research Activities on Life in Extreme Environments (CAREX) Field Campaign

by Viggó Marteinsson, Parag Vaishampayan, Jana Kviderova, Francesca Mapelli, Mauro Medori, Carlo Calfapietra, Angeles Aguilera, Domenica Hamisch, Eyjólfur Reynisson, Sveinn Magnússon, Ramona Marasco, Sara Borin, Abigail Calzada, Virginia Souza-Egipsy, Elena González-Toril, Ricardo Amils, Josef Elster and Robert Hänsch

Life 2013, 3(1), 211-233; https://doi.org/10.3390/life3010211 - 25 Feb 2013

Cited by 3 | Viewed by 10744

Abstract

Existence of life in extreme environments has been known for a long time, and their habitants have been investigated by different scientific disciplines for decades. However, reports of multidisciplinary research are uncommon. In this paper, we report an interdisciplinary three-day field campaign conducted [...] Read more.

Existence of life in extreme environments has been known for a long time, and their habitants have been investigated by different scientific disciplines for decades. However, reports of multidisciplinary research are uncommon. In this paper, we report an interdisciplinary three-day field campaign conducted in the framework of the Coordination Action for Research Activities on Life in Extreme Environments (CAREX) FP7EU program, with participation of experts in the fields of life and earth sciences. In situ experiments and sampling were performed in a 20 m long hot springs system of different temperature (57 °C to 100 °C) and pH (2 to 4). Abiotic factors were measured to study their influence on the diversity. The CO₂ and H₂S concentration varied at different sampling locations in the system, but the SO₂ remained the same. Four biofilms, mainly composed by four different algae and phototrophic protists, showed differences in photosynthetic activity. Varying temperature of the sampling location affects chlorophyll fluorescence, not only in the microbial mats, but plants (Juncus), indicating selective adaptation to the environmental conditions. Quantitative polymerase chain reaction (PCR), DNA microarray and denaturing gradient gel electrophoresis (DGGE)-based analysis in laboratory showed the presence of a diverse microbial population. Even a short duration (30 h) deployment of a micro colonizer in this hot spring system led to colonization of microorganisms based on ribosomal intergenic spacer (RISA) analysis. Polyphasic analysis of this hot spring system was possible due to the involvement of multidisciplinary approaches. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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1069 KiB

Open AccessArticle

Evolution of Microbial “Streamer” Growths in an Acidic, Metal-Contaminated Stream Draining an Abandoned Underground Copper Mine

by Catherine M. Kay, Owen F. Rowe, Laura Rocchetti, Kris Coupland, Kevin B. Hallberg and D. Barrie Johnson

Life 2013, 3(1), 189-210; https://doi.org/10.3390/life3010189 - 7 Feb 2013

Cited by 69 | Viewed by 8985

Abstract

A nine year study was carried out on the evolution of macroscopic “acid streamer” growths in acidic, metal-rich mine water from the point of construction of a new channel to drain an abandoned underground copper mine. The new channel became rapidly colonized by [...] Read more.

A nine year study was carried out on the evolution of macroscopic “acid streamer” growths in acidic, metal-rich mine water from the point of construction of a new channel to drain an abandoned underground copper mine. The new channel became rapidly colonized by acidophilic bacteria: two species of autotrophic iron-oxidizers (Acidithiobacillus ferrivorans and “Ferrovum myxofaciens”) and a heterotrophic iron-oxidizer (a novel genus/species with the proposed name “Acidithrix ferrooxidans”). The same bacteria dominated the acid streamer communities for the entire nine year period, with the autotrophic species accounting for ~80% of the micro-organisms in the streamer growths (as determined by terminal restriction enzyme fragment length polymorphism (T-RFLP) analysis). Biodiversity of the acid streamers became somewhat greater in time, and included species of heterotrophic acidophiles that reduce ferric iron (Acidiphilium, Acidobacterium, Acidocella and gammaproteobacterium WJ2) and other autotrophic iron-oxidizers (Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans). The diversity of archaea in the acid streamers was far more limited; relatively few clones were obtained, all of which were very distantly related to known species of euryarchaeotes. Some differences were apparent between the acid streamer community and planktonic-phase bacteria. This study has provided unique insights into the evolution of an extremophilic microbial community, and identified several novel species of acidophilic prokaryotes. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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472 KiB

Open AccessCommunication

Pivotal Enzyme in Glutamate Metabolism of Poly-g-Glutamate-Producing Microbes

by Makoto Ashiuchi, Takashi Yamamoto and Tohru Kamei

Life 2013, 3(1), 181-188; https://doi.org/10.3390/life3010181 - 6 Feb 2013

Cited by 5 | Viewed by 6405

Abstract

The extremely halophilic archaeon Natrialba aegyptiaca secretes the L-homo type of poly-g-glutamate (PGA) as an extremolyte. We examined the enzymes involved in glutamate metabolism and verified the presence of L-glutamate dehydrogenases, L-aspartate aminotransferase, and L-glutamate synthase. However, neither glutamate racemase nor D-amino acid [...] Read more.

The extremely halophilic archaeon Natrialba aegyptiaca secretes the L-homo type of poly-g-glutamate (PGA) as an extremolyte. We examined the enzymes involved in glutamate metabolism and verified the presence of L-glutamate dehydrogenases, L-aspartate aminotransferase, and L-glutamate synthase. However, neither glutamate racemase nor D-amino acid aminotransferase activity was detected, suggesting the absence of sources of D-glutamate. In contrast, D-glutamate-rich PGA producers mostly possess such intracellular sources of D-glutamate. The results of our present study indicate that the D-glutamate-anabolic enzyme “glutamate racemase” is pivotal in the biosynthesis of PGA. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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775 KiB

Open AccessArticle

Predator Avoidance in Extremophile Fish

by David Bierbach, Matthias Schulte, Nina Herrmann, Claudia Zimmer, Lenin Arias-Rodriguez, Jeane Rimber Indy, Rüdiger Riesch and Martin Plath

Life 2013, 3(1), 161-180; https://doi.org/10.3390/life3010161 - 6 Feb 2013

Cited by 8 | Viewed by 8847

Abstract

Extreme habitats are often characterized by reduced predation pressures, thus representing refuges for the inhabiting species. The present study was designed to investigate predator avoidance of extremophile populations of Poecilia mexicana and P. sulphuraria that either live in hydrogen sulfide-rich (sulfidic) springs or [...] Read more.

Extreme habitats are often characterized by reduced predation pressures, thus representing refuges for the inhabiting species. The present study was designed to investigate predator avoidance of extremophile populations of Poecilia mexicana and P. sulphuraria that either live in hydrogen sulfide-rich (sulfidic) springs or cave habitats, both of which are known to have impoverished piscine predator regimes. Focal fishes that inhabited sulfidic springs showed slightly weaker avoidance reactions when presented with several naturally occurring predatory cichlids, but strongest differences to populations from non-sulfidic habitats were found in a decreased shoaling tendency with non-predatory swordtail (Xiphophorus hellerii) females. When comparing avoidance reactions between P. mexicana from a sulfidic cave (Cueva del Azufre) and the adjacent sulfidic surface creek (El Azufre), we found only slight differences in predator avoidance, but surface fish reacted much more strongly to the non-predatory cichlid Vieja bifasciata. Our third experiment was designed to disentangle learned from innate effects of predator recognition. We compared laboratory-reared (i.e., predator-naïve) and wild-caught (i.e., predator-experienced) individuals of P. mexicana from a non-sulfidic river and found no differences in their reaction towards the presented predators. Overall, our results indicate (1) that predator avoidance is still functional in extremophile Poecilia spp. and (2) that predator recognition and avoidance reactions have a strong genetic basis. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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551 KiB

Open AccessReview

Periplasmic Binding Proteins in Thermophiles: Characterization and Potential Application of an Arginine-Binding Protein from Thermotoga maritima: A Brief Thermo-Story

by Alessio Ausili, Maria Staiano, Jonathan Dattelbaum, Antonio Varriale, Alessandro Capo and Sabato D'Auria

Life 2013, 3(1), 149-160; https://doi.org/10.3390/life3010149 - 5 Feb 2013

Cited by 13 | Viewed by 7563

Abstract

Arginine-binding protein from the extremophile Thermotoga maritima is a 27.7 kDa protein possessing the typical two-domain structure of the periplasmic binding proteins family. The protein is characterized by a very high specificity and affinity to bind to arginine, also at high temperatures. Due [...] Read more.

Arginine-binding protein from the extremophile Thermotoga maritima is a 27.7 kDa protein possessing the typical two-domain structure of the periplasmic binding proteins family. The protein is characterized by a very high specificity and affinity to bind to arginine, also at high temperatures. Due to its features, this protein could be taken into account as a potential candidate for the design of a biosensor for arginine. It is important to investigate the stability of proteins when they are used for biotechnological applications. In this article, we review the structural and functional features of an arginine-binding protein from the extremophile Thermotoga maritima with a particular eye on its potential biotechnological applications. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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205 KiB

Open AccessReview

Quorum Sensing in Extreme Environments

by Kate Montgomery, James C. Charlesworth, Rebecca LeBard, Pieter T. Visscher and Brendan P. Burns

Life 2013, 3(1), 131-148; https://doi.org/10.3390/life3010131 - 29 Jan 2013

Cited by 85 | Viewed by 12524

Abstract

Microbial communication, particularly that of quorum sensing, plays an important role in regulating gene expression in a range of organisms. Although this phenomenon has been well studied in relation to, for example, virulence gene regulation, the focus of this article is to review [...] Read more.

Microbial communication, particularly that of quorum sensing, plays an important role in regulating gene expression in a range of organisms. Although this phenomenon has been well studied in relation to, for example, virulence gene regulation, the focus of this article is to review our understanding of the role of microbial communication in extreme environments. Cell signaling regulates many important microbial processes and may play a pivotal role in driving microbial functional diversity and ultimately ecosystem function in extreme environments. Several recent studies have characterized cell signaling in modern analogs to early Earth communities (microbial mats), and characterization of cell signaling systems in these communities may provide unique insights in understanding the microbial interactions involved in function and survival in extreme environments. Cell signaling is a fundamental process that may have co-evolved with communities and environmental conditions on the early Earth. Without cell signaling, evolutionary pressures may have even resulted in the extinction rather than evolution of certain microbial groups. One of the biggest challenges in extremophile biology is understanding how and why some microbial functional groups are located where logically they would not be expected to survive, and tightly regulated communication may be key. Finally, quorum sensing has been recently identified for the first time in archaea, and thus communication at multiple levels (potentially even inter-domain) may be fundamental in extreme environments. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

743 KiB

Open AccessReview

A Survey of Protein Structures from Archaeal Viruses

by Nikki Dellas, C. Martin Lawrence and Mark J. Young

Life 2013, 3(1), 118-130; https://doi.org/10.3390/life3010118 - 24 Jan 2013

Cited by 6 | Viewed by 7876

Abstract

Viruses that infect the third domain of life, Archaea, are a newly emerging field of interest. To date, all characterized archaeal viruses infect archaea that thrive in extreme conditions, such as halophilic, hyperthermophilic, and methanogenic environments. Viruses in general, especially those replicating in [...] Read more.

Viruses that infect the third domain of life, Archaea, are a newly emerging field of interest. To date, all characterized archaeal viruses infect archaea that thrive in extreme conditions, such as halophilic, hyperthermophilic, and methanogenic environments. Viruses in general, especially those replicating in extreme environments, contain highly mosaic genomes with open reading frames (ORFs) whose sequences are often dissimilar to all other known ORFs. It has been estimated that approximately 85% of virally encoded ORFs do not match known sequences in the nucleic acid databases, and this percentage is even higher for archaeal viruses (typically 90%–100%). This statistic suggests that either virus genomes represent a larger segment of sequence space and/or that viruses encode genes of novel fold and/or function. Because the overall three-dimensional fold of a protein evolves more slowly than its sequence, efforts have been geared toward structural characterization of proteins encoded by archaeal viruses in order to gain insight into their potential functions. In this short review, we provide multiple examples where structural characterization of archaeal viral proteins has indeed provided significant functional and evolutionary insight. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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1911 KiB

Open AccessReview

Surface Appendages of Archaea: Structure, Function, Genetics and Assembly

by Ken F. Jarrell, Yan Ding, Divya B. Nair and Sarah Siu

Life 2013, 3(1), 86-117; https://doi.org/10.3390/life3010086 - 24 Jan 2013

Cited by 43 | Viewed by 13893

Abstract

Organisms representing diverse subgroupings of the Domain Archaea are known to possess unusual surface structures. These can include ones unique to Archaea such as cannulae and hami as well as archaella (archaeal flagella) and various types of pili that superficially resemble their namesakes [...] Read more.

Organisms representing diverse subgroupings of the Domain Archaea are known to possess unusual surface structures. These can include ones unique to Archaea such as cannulae and hami as well as archaella (archaeal flagella) and various types of pili that superficially resemble their namesakes in Bacteria, although with significant differences. Major advances have occurred particularly in the study of archaella and pili using model organisms with recently developed advanced genetic tools. There is common use of a type IV pili-model of assembly for several archaeal surface structures including archaella, certain pili and sugar binding structures termed bindosomes. In addition, there are widespread posttranslational modifications of archaellins and pilins with N-linked glycans, with some containing novel sugars. Archaeal surface structures are involved in such diverse functions as swimming, attachment to surfaces, cell to cell contact resulting in genetic transfer, biofilm formation, and possible intercellular communication. Sometimes functions are co-dependent on other surface structures. These structures and the regulation of their assembly are important features that allow various Archaea, including thermoacidophilic, hyperthermophilic, halophilic, and anaerobic ones, to survive and thrive in the extreme environments that are commonly inhabited by members of this domain. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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425 KiB

Open AccessReview

Biohydrogen Production by the Thermophilic Bacterium Caldicellulosiruptor saccharolyticus: Current Status and Perspectives

by Abraham A. M. Bielen, Marcel R. A. Verhaart, John Van der Oost and Servé W. M. Kengen

Life 2013, 3(1), 52-85; https://doi.org/10.3390/life3010052 - 17 Jan 2013

Cited by 45 | Viewed by 10512

Abstract

Caldicellulosiruptor saccharolyticus is one of the most thermophilic cellulolytic organisms known to date. This Gram-positive anaerobic bacterium ferments a broad spectrum of mono-, di- and polysaccharides to mainly acetate, CO₂ and hydrogen. With hydrogen yields approaching the theoretical limit for dark fermentation [...] Read more.

Caldicellulosiruptor saccharolyticus is one of the most thermophilic cellulolytic organisms known to date. This Gram-positive anaerobic bacterium ferments a broad spectrum of mono-, di- and polysaccharides to mainly acetate, CO₂ and hydrogen. With hydrogen yields approaching the theoretical limit for dark fermentation of 4 mol hydrogen per mol hexose, this organism has proven itself to be an excellent candidate for biological hydrogen production. This review provides an overview of the research on C. saccharolyticus with respect to the hydrolytic capability, sugar metabolism, hydrogen formation, mechanisms involved in hydrogen inhibition, and the regulation of the redox and carbon metabolism. Analysis of currently available fermentation data reveal decreased hydrogen yields under non-ideal cultivation conditions, which are mainly associated with the accumulation of hydrogen in the liquid phase. Thermodynamic considerations concerning the reactions involved in hydrogen formation are discussed with respect to the dissolved hydrogen concentration. Novel cultivation data demonstrate the sensitivity of C. saccharolyticus to increased hydrogen levels regarding substrate load and nitrogen limitation. In addition, special attention is given to the rhamnose metabolism, which represents an unusual type of redox balancing. Finally, several approaches are suggested to improve biohydrogen production by C. saccharolyticus. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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154 KiB

Open AccessReview

Halophilic Bacteria as a Source of Novel Hydrolytic Enzymes

by María De Lourdes Moreno, Dolores Pérez, María Teresa García and Encarnación Mellado

Life 2013, 3(1), 38-51; https://doi.org/10.3390/life3010038 - 10 Jan 2013

Cited by 148 | Viewed by 16803

Abstract

Hydrolases constitute a class of enzymes widely distributed in nature from bacteria to higher eukaryotes. The halotolerance of many enzymes derived from halophilic bacteria can be exploited wherever enzymatic transformations are required to function under physical and chemical conditions, such as in the [...] Read more.

Hydrolases constitute a class of enzymes widely distributed in nature from bacteria to higher eukaryotes. The halotolerance of many enzymes derived from halophilic bacteria can be exploited wherever enzymatic transformations are required to function under physical and chemical conditions, such as in the presence of organic solvents and extremes in temperature and salt content. In recent years, different screening programs have been performed in saline habitats in order to isolate and characterize novel enzymatic activities with different properties to those of conventional enzymes. Several halophilic hydrolases have been described, including amylases, lipases and proteases, and then used for biotechnological applications. Moreover, the discovery of biopolymer-degrading enzymes offers a new solution for the treatment of oilfield waste, where high temperature and salinity are typically found, while providing valuable information about heterotrophic processes in saline environments. In this work, we describe the results obtained in different screening programs specially focused on the diversity of halophiles showing hydrolytic activities in saline and hypersaline habitats, including the description of enzymes with special biochemical properties. The intracellular lipolytic enzyme LipBL, produced by the moderately halophilic bacterium Marinobacter lipolyticus, showed advantages over other lipases, being an enzyme active over a wide range of pH values and temperatures. The immobilized LipBL derivatives obtained and tested in regio- and enantioselective reactions, showed an excellent behavior in the production of free polyunsaturated fatty acids (PUFAs). On the other hand, the extremely halophilic bacterium, Salicola marasensis sp. IC10 showing lipase and protease activities, was studied for its ability to produce promising enzymes in terms of its resistance to temperature and salinity. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

1280 KiB

Open AccessArticle

Pavilion Lake Microbialites: Morphological, Molecular and Biochemical Evidence for a Cold-Water Transition to Colonial Aggregates

by Dirk Schulze-Makuch, Darlene Lim, Bernard Laval, Carol Turse, Marina Resendes de Sousa António, Olivia Chan, Stephen B. Pointing, Allyson Brady, Donnie Reid and Louis N. Irwin

Life 2013, 3(1), 21-37; https://doi.org/10.3390/life3010021 - 27 Dec 2012

Cited by 9 | Viewed by 9637

Abstract

The presence of microbialite structures in a freshwater, dimictic mid-latitudelake and their establishment after the last ice age about 10,000 years ago is puzzling.Freshwater calcite microbialites at Pavilion Lake, British Columbia, Canada, consist of acomplex community of microorganisms that collectively form large, ordered [...] Read more.

The presence of microbialite structures in a freshwater, dimictic mid-latitudelake and their establishment after the last ice age about 10,000 years ago is puzzling.Freshwater calcite microbialites at Pavilion Lake, British Columbia, Canada, consist of acomplex community of microorganisms that collectively form large, ordered structuredaggregates. This distinctive assemblage of freshwater calcite microbialites was studied through standard microbial methods, morphological observations, phospholipid fatty acid(PLFA) analysis, DNA sequencing and the identification of quorum sensing molecules.Our results suggest that the microbialites may represent a transitional form from theexclusively prokaryotic colonial precursors of stromatolites to the multicellular organismicaggregates that give rise to coral reefs. Full article

(This article belongs to the Section Microbiology)

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308 KiB

Open AccessReview

The Function of Gas Vesicles in Halophilic Archaea and Bacteria: Theories and Experimental Evidence

by Aharon Oren

Life 2013, 3(1), 1-20; https://doi.org/10.3390/life3010001 - 27 Dec 2012

Cited by 31 | Viewed by 13125

Abstract

A few extremely halophilic Archaea (Halobacterium salinarum, Haloquadratum walsbyi, Haloferax mediterranei, Halorubrum vacuolatum, Halogeometricum borinquense, Haloplanus spp.) possess gas vesicles that bestow buoyancy on the cells. Gas vesicles are also produced by the anaerobic endospore-forming halophilic Bacteria [...] Read more.

A few extremely halophilic Archaea (Halobacterium salinarum, Haloquadratum walsbyi, Haloferax mediterranei, Halorubrum vacuolatum, Halogeometricum borinquense, Haloplanus spp.) possess gas vesicles that bestow buoyancy on the cells. Gas vesicles are also produced by the anaerobic endospore-forming halophilic Bacteria Sporohalobacter lortetii and Orenia sivashensis. We have extensive information on the properties of gas vesicles in Hbt. salinarum and Hfx. mediterranei and the regulation of their formation. Different functions were suggested for gas vesicle synthesis: buoying cells towards oxygen-rich surface layers in hypersaline water bodies to prevent oxygen limitation, reaching higher light intensities for the light-driven proton pump bacteriorhodopsin, positioning the cells optimally for light absorption, light shielding, reducing the cytoplasmic volume leading to a higher surface-area-to-volume ratio (for the Archaea) and dispersal of endospores (for the anaerobic spore-forming Bacteria). Except for Hqr. walsbyi which abounds in saltern crystallizer brines, gas-vacuolate halophiles are not among the dominant life forms in hypersaline environments. There only has been little research on gas vesicles in natural communities of halophilic microorganisms, and the few existing studies failed to provide clear evidence for their possible function. This paper summarizes the current status of the different theories why gas vesicles may provide a selective advantage to some halophilic microorganisms. Full article

(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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Life, Volume 3, Issue 1 (March 2013) – 16 articles , Pages 1-294

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