Cellular Origin, Life in Extreme Habitats and Astrobiology – serie

This volume covers the fields of origin, evolution and phylogenesis from prokaryotic to eukaryotic cells. The authors review the three kingdoms of life (archea, eubacteria and eukarya) from molecular evolutionary levels to ecological aspects in enigmatic habitats, including general reviews of puzzling pro- and eukaryotic organisms and their domains. Among the harshest conditions found on Earth discussed are dry habitats, thermophilic (cells in hot springs and undersea thermal vents up to 110C), psychrophilic (cryophiles) and halophilic (high salt concentrations) niches where microbial life is frequently detected. Some chapters deal with the organisms which grow in extreme pH conditions (acidity versus alkalinity), and under hydrostatic pressure in the deep sea, and microbial growth on petroleum. Other contributors present their research on aerobiology and microbes growing in various gases and various levels of radiation, including cellular morphological modification in these extremophilic microbes. This volume also includes the symbiotic association between two or more organisms on the endocellular and exocellular levels.The volume should be of interest to students and researchers of biology, evolutionary biology and chemistry, and other evolutionary fields, and the intelligent layman.

In this study of the wide-ranging habitats of microbes, the contributors present the diversity of micro-organisms, from the state of fossil microbes in Archaean age rocks to the possibilities of extraterrestrial life. This volume discusses the extremophiles living in harsh environments (from our anthropocentric point) and describes them in detail. Some chapters also review topics such as symbiosis, bacterial luminescence, methanogens, and petroleum-grown cells. The final chapters shed light on astrobiology and speculate on extremophiles as candidates for extraterrestrial life.

Astrobiology is a very broad interdisciplinary field covering the origin, evolution, distribution, and destiny of life in the universe, as well as the design and implementation of missions for solar system exploration. A review covering its complete spectrum has been missing at a level accessible even to the non-specialist. The last section of the book consists of a supplement, including a glossary, notes, and tables, which represent highly condensed "windows" into research ranging from basic sciences to earth and life sciences, as well as the humanities.

The is the fourth volume in the series "Cellular Origin and Life in Extreme Habitats" (COLE). Fifty experts, from over a dozen countries, review their studies on different approaches to these phenomena. The chapters present various aspects of symbiosis, from gene transfer, morphological features, and biodiversity, to individual organisms sharing mutual cellular habitats. The origin of the eukaryotic phase is discussed with emphasis on cyanelles, H syntrophy, N2 fixation, and S-based symbiosis (as well as the origin of mitochondrion, chloroplast, and nucleus). All members of the three domains of life are presented for sharing symbiotic associations. This volume brings the concept of living together as "One plus One (plus One) equals One". The purpose of this book is to introduce the teacher, researcher, scholar, and student as well as the open-minded and science-oriented reader to the global importance of this association.

The halophilic micro-organisms form a highly diverse group of organisms. They present the biochemist/physiologist with interesting questions on the strategies used to cope with high osmotic pressures exerted by hypersaline brines and often have a strong impact on the ecosystems in which they thrive. The first section of the book presents in-depth discussions of the taxonomy, cellular properties, metabolic diversity, pigments, ion metabolism and organic osmotic solutes, properties of halophilic proteins, genetics, and biotechnological uses of halophilic micro-organisms. It then goes on describes the occurrence and functioning of these organisms in the Great Salt Lake, the Dead Sea, solar saltern ponds, alkaline soda lakes, and other hypersaline environments worldwide.

This new volume of "ORIGINS: Genesis, Evolution and Biodiversity of Microbial Life in the Universe" is the sixth unit of the book series Cellular Origins, Life in Extreme Habitats and Astrobiology (COLE) edited by Joseph Seckbach. In this book forty eminent scientists review their studies in the fields of Life from the beginning to the "Fact of Life." The history of Origin of Life and Astrobiology is well covered by these authors. Reviews cover the standard and alternative scenarios of the genesis of Life, while the chapters of "The First Cells" leading to the biodiversity and extremophiles of microbial Life. Among these extremophiles are the microbes living in the Life's limits, such as in high temperature, psychrophilic, UV radiation, and halophilic environments. The origin and history of Martian water is discussed following by the possible biogeochemistry inside Titan. This new field of Astrobiology has been presented, from comets as a source of materials and Life on earth to the space for last Frontiers

Modern methods and approaches, such as the analysis of molecular sequences to infer evolutionary relationships among organisms, have provided vast new sets of data to further our understanding ofliving organisms, but there remain enigmas in the biological world that will keep scientists working and thinking for decades. Microorganisms by virtue of their small size and almost unbounded diversity provide ample examples of intriguing mysteries that are being challenged with all of the techniques the modern scientific arsenal can provide. One whole arena of this battle to resolve puzzling mysteries about various microorganisms is the almost unbelievable ability of many micro-organisms to live in extreme environments. Whether the challenge is extreme heat, cold, pressure, hyper­ salinity, alkalinity or acidity, some micro-organisms live now where no life might seem possible. This fascinating state of affairs is the context for this present volume edited by Joseph Seckbach. This Volume is a compilation of many of the especially interesting questions and biological challenges that arise in the consideration of microorganisms in general and the extremophiles in particular.

Astrobiology is a very broad interdisciplinary field covering the origin, evolution, distribution, and destiny of life in the universe, as well as the design and implementation of missions for solar system exploration. A review covering its complete spectrum has been missing at a level accessible even to the non-specialist. The last section of the book consists of a supplement, including a glossary, notes, and tables, which represent highly condensed `windows' into research ranging from basic sciences to earth and life sciences, as well as the humanities. These additions should make The New Science of Astrobiology accessible to a wide readership: scientists, humanists, and the general reader will have an opportunity to participate in one of the most rewarding activities of contemporary culture.

H. BALTSCHEFFSKYChairman Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, S-106 91 Stockholm, Sweden. Professor Stanley Miller, Professor K. R. Srinivasan, Organizers and Sponsors of this Conference, Ladies and Gentlemen; WearegettingreadyfortheAbdusSalamLecture,honoringtwomostdistinguishedsci- tists. Bothhaveverysigni?cantlycontributedtotherapidgrowthofthesphereoffun- mentalknowledgeinthesecondhalfofthetwentiethcentury. Abdus Salam,theoreticalphysicist,NobelPrizewinner,creatorandlongtimeleader of The Abdus Salam Center of Theoretical Physics. With his active interest in the origin oflifeheplayedaleadingroleininstigatingtheseconferencesonChemicalEvolutionand theOriginofLifehereinTrieste,whichstillareofsuchprimaryimportanceinthis?eld. Heleftthisworldin1996. And Stanley Miller,whomostgenerously,astheAbdusSalamLecturer,isgoingto giveushis"Recollectionsofthebeginningofchemicalevolutionexperiments": DearStanley,itisagreatprivilege,andindeedapleasuretointroduceyou.Thisisina wayaquiteeasytask,becauseweallalreadyknowthat"theMillerexperiment",whichis mostappropriatelyplacedinthetitleofthisconference,in1953,exactly50yearsago,was amajorbreakthrough,openingupanewresearch?eldwith,andfor,rationalandadvanced chemicalexperimentationonthemolecularoriginoflife. Itwouldtaketoomuchtimetotrytodescribehereyourscienti?ccarrier,yourprices, yourPresidencyofISSOLandyourmanyothersuccesses. SoIratherwillendthisint- ductionwithacoupleofpersonalrecollections. First I would like to combine something of Abdus Salam and Stanley Miller. Abdus Salamgavethevery?rstinvitedlectureoftheUniversityofStockholmInternationalL- turesonHuman,GlobalandUniversalProblems,in1975. And10yearslater,atLidingo .. closetoStockholm,StanleyMillergavetheopeninglectureofaconferenceontheMol- ularEvolutionofLife. OnapictureItook,asaco-arrangeroftheseevents,Stanleyisseen approachinginhisusual,modestway,morefocussedonscienti?cdiscussionthanonthe camera. Last but not least, I shall tell you the true story about when we learned that Stanley isanenthusiasticenvironmentalist,inthebestsenseoftheword. About25yearsago,in Stockholm, Stanley, my wife and I strolled in the King's Garden.Its elmtrees were full 7 J. Seckbach et al. (eds. ), Life in the Universe,7-8. C 2004 Kluwer Academic Publishers. Printed in the Netherlands. 8 of young people who, some even spending nights in the trees, prevented the authorities from removing the elmtrees, by ax and saw. Also Stanley signed a petition to save the elmtrees-andtheyweresaved! Stanley, I believe that your greatness as a scientist and as a friend must be linked to the many facets of your wonderful personality. We much look forward to your lecture. THE BEGINNING OF CHEMICAL EVOLUTION EXPERIMENTS Recollections and Perspectives 1 2 3 S. L. MILLER , J. L. BADA , and A.

We also discuss confounding factors that we find crucial to the development of the field, such as the ability to protect and restrict intellectual property in the field, or the challenges involved in educating bioinformatics users.

H. BALTSCHEFFSKYChairman Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, S-106 91 Stockholm, Sweden. Professor Stanley Miller, Professor K. R. Srinivasan, Organizers and Sponsors of this Conference, Ladies and Gentlemen; WearegettingreadyfortheAbdusSalamLecture,honoringtwomostdistinguishedsci- tists. Bothhaveverysigni?cantlycontributedtotherapidgrowthofthesphereoffun- mentalknowledgeinthesecondhalfofthetwentiethcentury. Abdus Salam,theoreticalphysicist,NobelPrizewinner,creatorandlongtimeleader of The Abdus Salam Center of Theoretical Physics. With his active interest in the origin oflifeheplayedaleadingroleininstigatingtheseconferencesonChemicalEvolutionand theOriginofLifehereinTrieste,whichstillareofsuchprimaryimportanceinthis?eld. Heleftthisworldin1996. And Stanley Miller,whomostgenerously,astheAbdusSalamLecturer,isgoingto giveushis"Recollectionsofthebeginningofchemicalevolutionexperiments": DearStanley,itisagreatprivilege,andindeedapleasuretointroduceyou.Thisisina wayaquiteeasytask,becauseweallalreadyknowthat"theMillerexperiment",whichis mostappropriatelyplacedinthetitleofthisconference,in1953,exactly50yearsago,was amajorbreakthrough,openingupanewresearch?eldwith,andfor,rationalandadvanced chemicalexperimentationonthemolecularoriginoflife. Itwouldtaketoomuchtimetotrytodescribehereyourscienti?ccarrier,yourprices, yourPresidencyofISSOLandyourmanyothersuccesses. SoIratherwillendthisint- ductionwithacoupleofpersonalrecollections. First I would like to combine something of Abdus Salam and Stanley Miller. Abdus Salamgavethevery?rstinvitedlectureoftheUniversityofStockholmInternationalL- turesonHuman,GlobalandUniversalProblems,in1975. And10yearslater,atLidingo .. closetoStockholm,StanleyMillergavetheopeninglectureofaconferenceontheMol- ularEvolutionofLife. OnapictureItook,asaco-arrangeroftheseevents,Stanleyisseen approachinginhisusual,modestway,morefocussedonscienti?cdiscussionthanonthe camera. Last but not least, I shall tell you the true story about when we learned that Stanley isanenthusiasticenvironmentalist,inthebestsenseoftheword. About25yearsago,in Stockholm, Stanley, my wife and I strolled in the King's Garden.Its elmtrees were full 7 J. Seckbach et al. (eds. ), Life in the Universe,7-8. C 2004 Kluwer Academic Publishers. Printed in the Netherlands. 8 of young people who, some even spending nights in the trees, prevented the authorities from removing the elmtrees, by ax and saw. Also Stanley signed a petition to save the elmtrees-andtheyweresaved! Stanley, I believe that your greatness as a scientist and as a friend must be linked to the many facets of your wonderful personality. We much look forward to your lecture. THE BEGINNING OF CHEMICAL EVOLUTION EXPERIMENTS Recollections and Perspectives 1 2 3 S. L. MILLER , J. L. BADA , and A.

Salt is an essential requirement of life. Already from ancient times (e. g. , see the books of the Bible) its importance in human life has been known. For example, salt symbolizes destruction (as in Sodom and Gomorra), but on the other hand it has been an ingredient of every sacrifice during the Holy Temple periods. Microbial life in concentrated salt solutions has fascinated scientists since its discovery. Recently there have been several international meetings and books devoted entirely to halophiles. This book includes the proceedings of the “Halophiles 2004” conference held in Ljubljana, Slovenia, in September 2004 (www. u- lj. si/~bfbhaloph/index. html). This meeting was attended by 120 participants from 25 countries. The editors have selected presentations given at the meeting for this volume, and have also invited a number of contributions from experts who had not been present in Ljubljana. This book complements “Halophilic Microorganisms”, edited by A. Ventosa and published by Springer-Verlag (2004), “Halophilic Microorganism and their Environments” by A. Oren (2002), published by Kluwer Academic Publishers as volume 5 of “Cellular Origins, Life in Extreme Habitats and Astrobiology” (COLE), and “Microbiology and Biogeochemistry of Hypersaline Environments” edited by A. Oren, and published by CRC Press, Boca Raton (1999). Salt-loving (halophilic) microorganisms grow in salt solutions above seawater salinity (~3. 5% salt) up to saturation ranges (i. e. , around 35% salt). High concentrations of salt occur in natural environments (e. g.

Life As we Know It ["LAKI"] covers several aspects of Life, ranging from the prebiotic level, origin of life, evolution of prokaryotes to eukaryotes and finally to various affairs of human beings.

Algae and Cyanobacteria in Extreme Environments is a unique collection of essays, contributed by leading scientists from around the world, devoted to algae – and some related microbes – observed in unexpected harsh habitats, which it seems are an oasis or Garden of Eden for these organisms.

From Fossils to Astrobiology reviews developments in paleontology and geobiology that relate to the rapidly-developing field of Astrobiology, the study of life in the Universe. Many traditional areas of scientific study, including astronomy, chemistry and planetary science, contribute to Astrobiology, but the study of the record of life on planet Earth is critical in guiding investigations in the rest of the cosmos.  In this varied book, expert scientists from 15 countries present peer-reviewed, stimulating reviews of paleontological and astrobiological studies.  The overviews of established and emerging techniques for studying modern and ancient microorganisms on Earth and beyond, will be valuable guides to evaluating biosignatures which could be found in the extraterrestrial surface or subsurface within the Solar System and beyond.  This volume also provides discussion on the controversial reports of "nanobacteria" in the Martian meteorite ALH84001.  It is a unique volume among Astrobiology monographs in focusing on fossil evidence from the geological record and will be valuable to students and researchers alike.

r ed Algae in Genome Age book most people reading this book have childhood memories about being enthralled at the beach with those rare and mysterious living forms we knew as seaweeds. We were fascinated at that time by their range of red hues and textures, and most of all, their exotic beauty. t o a scientist, red algae represent much more than apparent features. t heir complex forms have attracted morphologists for centuries; their intricate life cycles have brought more than one surprise to plant biologists familiar only with ferns and fowering plants; their unusual tastes have been appreciated for mill- nia, and their valuable chemical constituents have been exploited for nearly as long, most recently by biotech companies; their diversity in marine, freshwater, and t- restrial environments has offered centuries of engaging entertainment for botanists eager to arrange them in orderly classifcation systems; still, the red algae continue to teach us how many more challenges need to be overcome in order to understand their biodiversity, biological functions, and evolutionary histories.

This book provides information about microbial mats, from early fossils to modern mats located in marine and terrestrial environments. Microbial mats – layered biofilms containing different types of cells – are most complex systems in which representatives of various groups of organisms are found together. Among them are cyanobacteria and eukaryotic phototrophs, aerobic heterotrophic and chemoautotrophic bacteria, protozoa, anoxygenic photosynthetic bacteria, and other types of microorganisms.These mats are perfect models for biogeochemical processes, such as the cycles of chemical elements, in which a variety of microorganisms cooperate and interact in complex ways. They are often found under extreme conditions and their study contributes to our understanding of extremophilic life. Moreover, microbial mats are models for Precambrian stromatolites; the study of modern microbial mats may provide information on the processes that may have occurred on Earth when prokaryotic life began to spread.

Bioinformatics has ignited the imagination of scientists, entrepreneurs and the general public. At the meeting place of two fast growth disciplines, biology and computer science Bioinformatics is one of the cornerstones of the new biology. It is clearly pivotal to the translation of high throughput projects such the human genome project into useful knowledge. Yet despite all this attention, there is no consensus on what exactly is Bioinformatics. There are several canonical topics, such as gene structure prediction, protein functional classification or structure prediction. The present book explores new frontiers in bioinformatics, such as Glycomics or the computational modeling of genetic processes. We also discuss confounding factors that we find crucial to the development of the field, such as the ability to protect and restrict intellectual property in the field, or the challenges involved in educating bioinformatics users. Finally, we touch upon some fundamental questions, such as what information is and how it is captured in biological systems. By bringing to the readers such a broad spectrum of reviews, we hope to capture the vibrant spirit of this young science and to truly represent the fast pace with which it is still developing.

This book intends to provide an overview of current research on halophilic microorganisms, highlighting the diversity of life forms adapted to tolerate high salt concentrations and low water activities. Most of the 35 chapters are based on lectures presented during the international symposium "Halophiles 2004", held in Ljubljana, Slovenia, in September 2004. Descriptions of the diverse high-salt environments in which halophiles are found are followed by sections devoted to the properties of halophilic Archaea, of halophilic and halotolerant Bacteria, and of different groups of salt-loving Eukarya, including fungi, algae and protozoa. Extensive information is provided about fungi adapted to life at high salt concentrations, a group that was poorly known until very recently. This volume is intended for researchers and students interested in a wide range of disciplines in the life sciences: from microbial ecology and adaptation of microorganisms to life in extreme environments to genomics, biotechnology, and astrobiology.

Life As we Know It ["LAKI"] covers several aspects of Life, ranging from the prebiotic level, origin of life, evolution of prokaryotes to eukaryotes and finally to various affairs of human beings. Although it is hard to define Life, one can, however, characterize it and describe its features. Topics treated are categories of bacteria, algae and fungi, conscience, philosophy, theology, aesthetics, appearance of sport and life destiny, life after clinical death, and thoughts of the world to come ("Olam Haba"). The various chapters have been written so that they are accessible to all - from the avid lay reader to the specialist – and make available multidisciplinary sources of information about Life.  The information presented here on the various phenomena of Life were all written by highly qualified authors including scientists, public leaders, a professional athelete and three Nobel Laureates.

Global warming is accelerating faster than the ability for natural repair, and environmental stresses are damaging ecosystems, all affecting physical and biological systems on Earth. A new Nasa-led study shows that human activity has caused climate changes resulting in permafrost thawing, acid rain, and lower productivity in lakes as well as increased emissions of greenhouse gases, including CO2, N20, CH4, CF3, and CFC. Marine plants play a vital role in maintaining the balance of marine environments, while serving as a source of food for humankind and important chemical compounds. Microalgae and seaweed have enormous potential for reducing global warming and climate change. During photosynthesis algae grow, draw CO2 from the atmosphere, release oxygen, and produce solar biofuel. Experts in the life of marine plant ecosystems in globally changing environments contributed chapters to this book. The target readers are phycologists, ecologists, atmospheric scholars, conservationists, environmentalists, and ecologically aware laymen.

This new book takes us through a journey from early life to modern agriculture. The thirty eight authors present current studies on the interrelation of plants-animals. This topic has always fascinated man, as evidenced even by the first chapters of Genesis. The world of aqueous and terrestrial fauna appeared on early earth only after the flora covered the areas with the green pigmentation. Almost all life depends upon sunlight via the photosynthesis of the botanical world. We read abut the harnessing of bee pollination of crops to make it an essential component of modern agriculture endeavor. Some plants seduce insects for pollination by their appearance (e.g., disguised orchids entice visitors); there is the production of sweet nectar as a bribe in flowers to attract bees, butterflies, and honey-sucking birds. A particular outstanding phenomena are the carnivorous plants that have developed trapping and digesting systems of insects and higher animals.

When one picks up a multiauthored book in a series like this, one wonders what will be distinctive about its contents. one wonders about the "Concept of Symbiosis. " does it have the same meaning for all authors and all potential readers? one is further tempted to question the concept of stress. What is the meaning of the c- cept of stress? Some change in the biotic or abiotic aspects of the environment or habitat of the symbiotic partners? many might support the more general def- tion of symbiosis credited to de bary (1879), that symbiosis is the living together of separately named organisms. Something like Smith's (1992) more restricted PoLLnPia (P ermanent or Long-Lived intimate associations between diffe- ent organisms, usually of different sizes, in which the larger organism, the host, exploits the capabilities of one or more smaller organisms) seems to be a better ft for a book centered on the effects of stress on symbiosis. PoLLnPia implies an integrated holobiont system that has adapted itself to living successfully in a particular environment that could be construed as harsh for nonsymbiotic s- tems. often, when queried for examples, one thinks of lichens, of corals living in oligotrophic tropical waters, of Pompeii worms living in association with che- lithotrophic bacteria, and of all sorts of herbivorous animals living in associations with microorganisms.Presumably, the hosts could not survive, or thrive, in their habitats without their smaller partners doing their trophic work for their holo- otic systems.

STROMATOLITES: Interaction of Microbes with Sediments provides an overview and latest information about the formation of Stromatolites as a result of interaction of microbes with sediments. Eighty-three expert scientists from twenty-seven countries present the chapters in this volume which have been reviewed by thirty four referees. The volume deals with ancient to modern examples of stromatolites and microorganisms which are observed in various diverse environments, such as: marine, nonmarine, lacustrine and extreme geographical areas covering almost the whole earth. The reviews are original articles written by leading experienced experts, some chapters deal with latest instrumental techniques used for the study of microbes and Stromatolites. Other chapters have been contributed by young researchers who revealed updated data on Stromatolites. The astrobiological implications of early microbiota, sulfur isotopic ratios, microbialites in extreme conditions on earth has opened up new vistas in the search of extraterrestrial life.

Diatom biology, genomics and ecology are becoming more relevant to the human species. While there have been recent compilations of some of the applied aspects of diatoms, and the dizzying pace of taxonomic revisions, this new volume bring us up to date on their classification, biology and ecology, as well as covering the topics of genomics and applied uses. In this collection, some of the leaders in diatom research present either new information or summarize recent research efforts on a wide range of topics, including the tree of life of diatoms, their classifications, the wide habitats and ecological spectra the group exploits, as well as the beauty of their form. This volume celebrates the diversity, emerging areas of research and fascinating ecology of the diatoms bringing this group of world-renown and emerging research leaders together. 'The Diatom World' will foster greater appreciation and research contributions on this incredibly diverse and fascinating group of organisms.

Since the publication of The New Science of Astrobiology in the year 2001—the first edition of the present book—two significant events have taken place raising the subject from the beginning of the present century to its present maturity. Firstly, in 2001 the Galileo Mission still had two years to complete its task, which turned out to be an outstanding survey of the Jovian system, especially of its intriguing satellite Europa. Secondly, the Cassini Huygens Mission was still on its way to Saturn. Its present success has surpassed all expectations of ESA and NASA. Astrobiologists still did not know that Titan was the fifth body in the Solar System that possibly contained a water ocean (including the Earth and the three Galilean satellites other than Io). For these reasons the book includes overviews of the evolutionary and molecular biology that are necessary. There is a discussion of other sectors of culture that are the natural frontiers of astrobiology, especially the humanities.

ANOXIA defines the lack of free molecular oxygen in an environment. In the presence of organic matter, anaerobic prokaryotes produce compounds such as free radicals, hydrogen sulfide, or methane that are typically toxic to aerobes. The concomitance of suppressed respiration and presence of toxic substances suggests these habitats are inhospitable to Eukaryota. Ecologists sometimes term such environments 'Death Zones'. This book presents, however, a collection of remarkable adaptations to anoxia, observed in Eukaryotes such as protists, animals, plants and fungi. Case studies provide evidence for controlled beneficial use of anoxia by, for example, modification of free radicals, use of alternative electron donors for anaerobic metabolic pathways, and employment of anaerobic symbionts. The complex, interwoven existence of oxic and anoxic conditions in space and time is also highlighted as is the idea that eukaryotic inhabitation of anoxic habitats was established early in Earth history.

Genesis – In The Beginning deals with the origin and diversity of Life and early biological evolution and discusses the question of where (hot or cold sources) and when the beginning of Life took place.

This book provides information about microbial mats, from early fossils to modern mats located in marine and terrestrial environments. Microbial mats – layered biofilms containing different types of cells – are most complex systems in which representatives of various groups of organisms are found together. Among them are cyanobacteria and eukaryotic phototrophs, aerobic heterotrophic and chemoautotrophic bacteria, protozoa, anoxygenic photosynthetic bacteria, and other types of microorganisms.These mats are perfect models for biogeochemical processes, such as the cycles of chemical elements, in which a variety of microorganisms cooperate and interact in complex ways. They are often found under extreme conditions and their study contributes to our understanding of extremophilic life. Moreover, microbial mats are models for Precambrian stromatolites; the study of modern microbial mats may provide information on the processes that may have occurred on Earth when prokaryotic life began to spread.