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Microbial mat

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Thecyanobacterialalgal mat,salty lake on theWhite Seaseaside

Amicrobial matis a multi-layered sheet ofmicroorganisms,mainlybacteriaandarchaea,or bacteria alone. Microbial mats grow atinterfacesbetween different types of material, mostly on submerged or moistsurfaces,but a few survive in deserts.[1]A few are found asendosymbiontsofanimals.

Although only a few centimetres thick at most, microbial mats create a wide range of internal chemical environments, and hence generally consist of layers of microorganisms that can feed on or at least tolerate the dominant chemicals at their level and which are usually of closely related species. In moist conditions mats are usually held together byslimy substancessecreted by the microorganisms. In many cases some of the bacteria form tangled webs offilamentswhich make the mat tougher. The best known physical forms are flat mats and stubby pillars calledstromatolites,but there are also spherical forms.

Microbial mats are the earliest form of life on Earth for which there is goodfossilevidence, from3,500million years ago,and have been the most important members and maintainers of the planet'secosystems.Originally they depended onhydrothermal ventsfor energy and chemical "food", but the development ofphotosynthesisallowed mats to proliferate outside of these environments by utilizing a more widely available energy source, sunlight. The final and most significant stage of this liberation was the development of oxygen-producing photosynthesis, since the main chemical inputs for this arecarbon dioxideand water.

As a result, microbial mats began to produce the atmosphere we know today, in which freeoxygenis a vital component. At around the same time they may also have been the birthplace of the more complexeukaryotetype ofcell,of which allmulticellularorganisms are composed.[2]Microbial mats were abundant on the shallow seabed until theCambrian substrate revolution,when animals living in shallow seas increased their burrowing capabilities and thus broke up the surfaces of mats and let oxygenated water into the deeper layers, poisoning the oxygen-intolerant microorganisms that lived there. Although this revolution drove mats off soft floors of shallow seas, they still flourish in many environments where burrowing is limited or impossible, including rocky seabeds and shores, and hyper-saline and brackish lagoons. They are found also on the floors of the deep oceans.

Because of microbial mats' ability to use almost anything as "food", there is considerable interest in industrial uses of mats, especially for water treatment and for cleaning uppollution.

Description[edit]

Stromatolitesare formed by some microbial mats as the microbes slowly move upwards to avoid being smothered by sediment.

Microbial mats may also be referred to asalgal matsandbacterialmats. They are a type ofbiofilmthat is large enough to see with the naked eye and robust enough to survive moderate physical stresses. These colonies ofbacteriaform on surfaces at many types ofinterface,for example between water and thesedimentor rock at the bottom, between air and rock or sediment, between soil and bed-rock, etc. Such interfaces form verticalchemical gradients,i.e. vertical variations in chemical composition, which make different levels suitable for different types of bacteria and thus divide microbial mats into layers, which may be sharply defined or may merge more gradually into each other.[3]A variety of microbes are able to transcend the limits of diffusion by using "nanowires" to shuttle electrons from their metabolic reactions up to two centimetres deep in the sediment – for example, electrons can be transferred from reactions involving hydrogen sulfide deeper within the sediment to oxygen in the water, which acts as an electron acceptor.[4]

The best-known types of microbial mat may be flat laminated mats, which form on approximately horizontal surfaces, andstromatolites,stubby pillars built as the microbes slowly move upwards to avoid being smothered by sediment deposited on them by water. However, there are also spherical mats, some on the outside of pellets of rock or other firm material and othersinsidespheres of sediment.[3]

Structure[edit]

A microbial mat consists of several layers, each of which is dominated by specific types ofmicroorganism,mainlybacteria.Although the composition of individual mats varies depending on the environment, as a general rule the by-products of each group of microorganisms serve as "food" for other groups. In effect each mat forms its ownfood chain,with one or a few groups at the top of the food chain as their by-products are not consumed by other groups. Different types of microorganism dominate different layers based on theircomparative advantagefor living in that layer. In other words, they live in positions where they can out-perform other groups rather than where they would absolutely be most comfortable — ecological relationships between different groups are a combination of competition and co-operation. Since themetaboliccapabilities of bacteria (what they can "eat" and what conditions they can tolerate) generally depend on theirphylogeny(i.e. the most closely related groups have the most similar metabolisms), the different layers of a mat are divided both by their different metabolic contributions to the community and by their phylogenetic relationships.

In a wet environment where sunlight is the main source of energy, the uppermost layers are generally dominated byaerobicphotosynthesizingcyanobacteria(blue-green bacteria whose color is caused by their havingchlorophyll), while the lowest layers are generally dominated byanaerobicsulfate-reducing bacteria.[5]Sometimes there are intermediate (oxygenated only in the daytime) layers inhabited byfacultative anaerobicbacteria. For example, in hypersaline ponds near Guerrero Negro (Mexico) various kind of mats were explored. There are some mats with a middle purple layer inhabited by photosynthesizing purple bacteria.[6]Some other mats have a white layer inhabited by chemotrophicsulfur oxidizing bacteriaand beneath them an olive layer inhabited by photosynthesizinggreen sulfur bacteriaandheterotrophicbacteria.[7]However, this layer structure is not changeless during a day: some species of cyanobacteria migrate to deeper layers at morning, and go back at evening, to avoid intensive solar light and UV radiation at mid-day.[7][8]

Microbial mats are generally held together and bound to theirsubstratesby slimyextracellular polymeric substanceswhich they secrete. In many cases some of the bacteriaform filaments(threads), which tangle and thus increase the colonies' structural strength, especially if the filaments have sheaths (tough outer coverings).[3]

This combination of slime and tangled threads attracts other microorganisms which become part of the mat community, for exampleprotozoa,some of which feed on the mat-forming bacteria, anddiatoms,which often seal the surfaces of submerged microbial mats with thin,parchment-like coverings.[3]

Marine mats may grow to a few centimeters in thickness, of which only the top few millimeters are oxygenated.[9]

Types of environment colonized[edit]

Underwater microbial mats have been described as layers that live by exploiting and to some extent modifying localchemical gradients,i.e. variations in the chemical composition. Thinner, less complexbiofilmslive in manysub-aerialenvironments, for example on rocks, on mineral particles such as sand, and withinsoil.They have to survive for long periods without liquid water, often in a dormant state. Microbial mats that live in tidal zones, such as those found in theSippewissett salt marsh,often contain a large proportion of similar microorganisms that can survive for several hours without water.[3]

Microbial mats and less complex types of biofilm are found at temperature ranges from –40 °C to +120 °C, because variations in pressure affect the temperatures at which water remains liquid.[3]

They even appear asendosymbiontsin some animals, for example in the hindguts of someechinoids.[10]

Ecological and geological importance[edit]

Wrinkled Kinneyia-type sedimentary structures formed beneath cohesive microbial mats inperitidal zones.[11]The image shows the location, in theBurgsvik bedsofSweden,where the texture was first identified as evidence of a microbial mat.[12]
Kinneyia-like structure in the Grimsby Formation (Silurian) exposed in Niagara Gorge, New York
Blister-like microbial mat on ripple-marked surface of aCambriantidal flat atBlackberry Hill,Wisconsin

Microbial mats use all of the types of metabolism and feeding strategy that have evolved on Earth—anoxygenic and oxygenicphotosynthesis;anaerobic and aerobicchemotrophy(using chemicals rather than sunshine as a source of energy); organic and inorganicrespirationandfermentation(i..e converting food into energy with and without using oxygen in the process);autotrophy(producing food from inorganic compounds) andheterotrophy(producing food only from organic compounds, by some combination ofpredationanddetritivory).[3]

Most sedimentary rocks and ore deposits have grown by areef-like build-up rather than by "falling" out of the water, and this build-up has been at least influenced and perhaps sometimes caused by the actions of microbes.Stromatolites,bioherms(domes or columns similar internally to stromatolites) andbiostromes(distinct sheets of sediment) are among such microbe-influenced build-ups.[3]Other types of microbial mat have created wrinkled "elephant skin" textures in marine sediments, although it was many years before these textures were recognized astrace fossilsof mats.[12]Microbial mats have increased the concentration of metal in many ore deposits, and without this it would not be feasible to mine them—examples include iron (both sulfide and oxide ores), uranium, copper, silver and gold deposits.[3]

Role in the history of life[edit]

Further information:Timeline of evolution

The earliest mats[edit]

Microbial mats are among the oldest clear signs of life, asmicrobially induced sedimentary structures (MISS)formed3,480million years agohave been found inwestern Australia.[3][13][14]At that early stage the mats' structure may already have been similar to that of modern mats that do not includephotosynthesizingbacteria. It is even possible that non-photosynthesizing mats were present as early as4,000million years ago.If so, their energy source would have beenhydrothermal vents(high-pressurehot springsaround submergedvolcanoes), and the evolutionary split betweenbacteriaandarcheamay also have occurred around this time.[15]

The earliest mats may have been small, single-speciesbiofilmsofchemotrophsthat relied on hydrothermal vents to supply both energy and chemical "food". Within a short time (by geological standards) the build-up of dead microorganisms would have created anecological nichefor scavengingheterotrophs,possiblymethane-emittingandsulfate-reducingorganisms that would have formed new layers in the mats and enriched their supply of biologically useful chemicals.[15]

Photosynthesis[edit]

It is generally thought thatphotosynthesis,the biological generation of chemical energy from light, evolved shortly after3,000million years ago(3 billion).[15]However anisotope analysissuggests that oxygenic photosynthesis may have been widespread as early as3,500million years ago.[15]There are several different types of photosynthetic reaction, andanalysis of bacterial DNAindicates that photosynthesis first arose in anoxygenicpurple bacteria,while theoxygenic photosynthesisseen incyanobacteriaand much later inplantswas the last to evolve.[16]

The earliest photosynthesis may have been powered byinfra-redlight, using modified versions ofpigmentswhose original function was to detect infra-red heat emissions from hydrothermal vents. The development of photosynthetic energy generation enabled the microorganisms first to colonize wider areas around vents and then to use sunlight as an energy source. The role of the hydrothermal vents was now limited to supplying reduced metals into the oceans as a whole rather than being the main supporters of life in specific locations.[16]Heterotrophic scavengers would have accompanied the photosynthesizers in their migration out of the "hydrothermal ghetto".[15]

The evolution of purple bacteria, which do not produce or use oxygen but can tolerate it, enabled mats to colonize areas that locally had relatively high concentrations of oxygen, which is toxic to organisms that are not adapted to it.[17]Microbial mats would have been separated into oxidized and reduced layers, and this specialization would have increased their productivity.[15]It may be possible to confirm this model by analyzing the isotope ratios of both carbon and sulfur in sediments laid down in shallow water.[15]

The last major stage in the evolution of microbial mats was the appearance ofcyanobacteria,photosynthesizers which both produce and use oxygen. This gave undersea mats their typical modern structure: an oxygen-rich top layer of cyanobacteria; a layer of photosynthesizing purple bacteria that could tolerate oxygen; and oxygen-free,H2S-dominated lower layers of heterotrophic scavengers, mainly methane-emitting and sulfate-reducing organisms.[15]

It is estimated that the appearance of oxygenic photosynthesis increased biological productivity by a factor of between 100 and 1,000. All photosyntheticreactionsrequire areducing agent,but the significance of oxygenic photosynthesis is that it useswateras a reducing agent, and water is much more plentiful than the geologically produced reducing agents on which photosynthesis previously depended. The resulting increases in the populations of photosynthesizing bacteria in the top layers of microbial mats would have caused corresponding population increases among thechemotrophicandheterotrophicmicroorganisms that inhabited the lower layers and which fed respectively on the by-products of the photosynthesizers and on the corpses and / or living bodies of the other mat organisms. These increases would have made microbial mats the planet's dominant ecosystems. From this point onwards life itself produced significantly more of the resources it needed than did geochemical processes.[18]

Oxygenic photosynthesis in microbial mats would also have increased the free oxygen content of the Earth's atmosphere, both directly by emitting oxygen and because the mats emitted molecular hydrogen (H2), some of which would have escaped from the Earth's atmosphere before it could re-combine with free oxygen to form more water. Microbial mats thus played a major role in the evolution of organisms which could first tolerate free oxygen and then use it as an energy source.[18]Oxygen is toxic to organisms that are not adapted to it, but greatly increases the metabolic efficiency of oxygen-adapted organisms[17]— for example anaerobicfermentationproduces a net yield of twomoleculesofadenosine triphosphate,cells' internal "fuel", per molecule ofglucose,whileaerobic respirationproduces a net yield of 36.[19]Theoxygenation of the atmospherewas a prerequisite for the evolution of the more complexeukaryotetype of cell, from which allmulticellularorganisms are built.[20]

Cyanobacteria have the most complete biochemical "toolkits" of all the mat-forming organisms: the photosynthesis mechanisms of bothgreen bacteriaand purple bacteria; oxygen production; and theCalvin cycle,which convertscarbon dioxideand water intocarbohydratesandsugars.It is likely that they acquired many of these sub-systems from existing mat organisms, by some combination ofhorizontal gene transferandendosymbiosisfollowed by fusion. Whatever the causes, cyanobacteria are the most self-sufficient of the mat organisms and were well-adapted to strike out on their own both as floating mats and as the first of thephytoplankton,which forms the basis of most marinefood chains.[15]

Origin of eukaryotes[edit]

The time at whicheukaryotesfirst appeared is still uncertain: there is reasonable evidence that fossils dated between1,600million years agoand2,100million years agorepresent eukaryotes,[21]but the presence ofsteranesinAustralianshalesmay indicate that eukaryotes were present2,700million years ago.[22]There is still debate about the origins of eukaryotes, and many of the theories focus on the idea that a bacterium first became an endosymbiont of an anaerobic archean and then fused with it to become one organism. If such endosymbiosis was an important factor, microbial mats would have encouraged it.[2]There are two known variations of this scenario:

  • The boundary between the oxygenated and oxygen-free zones of a mat would have moved up when photosynthesis shut down at night and back down when photosynthesis resumed after the next sunrise. Symbiosis between independent aerobic and anaerobic organisms would have enabled both to live comfortably in the zone that was subject to oxygen "tides", and subsequent endosymbiosis would have made such partnerships more mobile.[15]
  • The initial partnership may have been between anaerobic archea that requiredmolecular hydrogen(H2) and heterotrophic bacteria that produced it and could live both with and without oxygen.[15][23]

Life on land[edit]

Microbial mats from ~1,200million years agoprovide the first evidence of life in the terrestrial realm.[24]

The earliest multicellular "animals"[edit]

Before:
After:
Sessile organism
anchored in mat
Animal grazing
on mat
Animals embedded
in mat
Animals
burrowing
just under
mat
Firm, layered, anoxic, sulphidic substrate
Animals moving on / in
surface of sea-floor
Loose,
oxygenated
upper substrate
with
burrowing
animals
Before and after theCambrian substrate revolution

TheEdiacara biotaare the earliest widely accepted evidence of multicellular "animals". MostEdiacaranstrata with the "elephant skin" texture characteristic of microbial mats contain fossils, and Ediacaran fossils are hardly ever found in beds that do not contain these microbial mats.[25]Adolf Seilachercategorized the "animals" as: "mat encrusters", which were permanently attached to the mat; "mat scratchers", which grazed the surface of the mat without destroying it; "mat stickers", suspension feeders that were partially embedded in the mat; and "undermat miners", which burrowed underneath the mat and fed on decomposing mat material.[26]

The Cambrian substrate revolution[edit]

In the Early Cambrian, however, organisms began to burrow vertically for protection or food, breaking down the microbial mats, and thus allowing water and oxygen to penetrate a considerable distance below the surface and kill the oxygen-intolerant microorganisms in the lower layers. As a result of thisCambrian substrate revolution,marine microbial mats are confined to environments in which burrowing is non-existent or negligible:[27]very harsh environments, such as hyper-saline lagoons or brackish estuaries, which are uninhabitable for the burrowing organisms that broke up the mats;[28]rocky "floors" which the burrowers cannot penetrate;[27]the depths of the oceans, where burrowing activity today is at a similar level to that in the shallow coastal seas before the revolution.[27]

Current status[edit]

Although the Cambrian substrate revolution opened up new niches for animals, it was not catastrophic for microbial mats, but it did greatly reduce their extent.

Use of microbial mats in paleontology[edit]

Most fossils preserve only the hard parts of organisms, e.g. shells. The rare cases where soft-bodied fossils are preserved (the remains of soft-bodied organisms and also of the soft parts of organisms for which only hard parts such as shells are usually found) are extremely valuable because they provide information about organisms that are hardly ever fossilized and much more information than is usually available about those for which only the hard parts are usually preserved.[29]Microbial mats help to preserve soft-bodied fossils by:

  • Capturing corpses on the sticky surfaces of mats and thus preventing them from floating or drifting away.[29]
  • Physically protecting them from being eaten by scavengers and broken up by burrowing animals, and protecting fossil-bearing sediments from erosion. For example, the speed of water current required to erode sediment bound by a mat is 20–30 times as great as the speed required to erode a bare sediment.[29]
  • Preventing or reducing decay both by physically screening the remains from decay-causing bacteria and by creating chemical conditions that are hostile to decay-causing bacteria.[29]
  • Preserving tracks and burrows by protecting them from erosion.[29]Many trace fossils date from significantly earlier than the body fossils of animals that are thought to have been capable of making them and thus improve paleontologists' estimates of when animals with these capabilities first appeared.[30]

Industrial uses[edit]

The ability of microbial mat communities to use a vast range of "foods" has recently led to interest in industrial uses. There have been trials of microbial mats for purifying water, both for human use and infish farming,[31][32]and studies of their potential for cleaning upoil spills.[33]As a result of the growing commercial potential, there have been applications for and grants ofpatentsrelating to the growing, installation and use of microbial mats, mainly for cleaning up pollutants and waste products.[34]

See also[edit]

Notes[edit]

  1. ^Schieber, J.; Bose, P; Eriksson, P. G.; Banerjee, S.; Sarkar, S.; Altermann, W.; Catuneanu, O. (2007).Atlas of Microbial Mat Features Preserved within the Siliciclastic Rock Record.Elsevier.ISBN978-0-444-52859-9.Retrieved2008-07-01.
  2. ^abNobs, Stephanie-Jane; MacLeod, Fraser I.; Wong, Hon Lun; Burns, Brendan P. (2022-05-01)."Eukarya the chimera: eukaryotes, a secondary innovation of the two domains of life?".Trends in Microbiology.30(5): 421–431.doi:10.1016/j.tim.2021.11.003.ISSN0966-842X.PMID34863611.S2CID244823103.
  3. ^abcdefghijKrumbein, W.E.; Brehm, U.; Gerdes, G.; Gorbushina, A.A.; Levit, G.; Palinska, K.A. (2003). "Biofilm, Biodictyon, Biomat Microbialites, Oolites, Stromatolites, Geophysiology, Global Mechanism, Parahistology". In Krumbein, W.E.; Paterson, D.M.; Zavarzin, G.A. (eds.).Fossil and Recent Biofilms: A Natural History of Life on Earth(PDF).Kluwer Academic. pp. 1–28.ISBN978-1-4020-1597-7.Archived fromthe original(PDF)on January 6, 2007.Retrieved2008-07-09.
  4. ^Nielsen, L.; Risgaard-Petersen, N.; Fossing, H.; Christensen, P.; Sayama, M. (2010). "Electric currents couple spatially separated biogeochemical processes in marine sediment".Nature.463(7284): 1071–1074.Bibcode:2010Natur.463.1071N.doi:10.1038/nature08790.PMID20182510.S2CID205219761.
  5. ^Risatti, J. B.; Capman, W.C.; Stahl, D.A. (October 11, 1994)."Community structure of a microbial mat: the phylogenetic dimension".Proceedings of the National Academy of Sciences.91(21): 10173–7.Bibcode:1994PNAS...9110173R.doi:10.1073/pnas.91.21.10173.PMC44980.PMID7937858.
  6. ^Lucas J. Stal: Physiological ecology of cyanobacteria in microbial mats and other communities, New Phytologist (1995), 131, 1–32
  7. ^abGarcia-Pichel F., Mechling M., Castenholz R.W.,Diel Migrations of Microorganisms within a Benthic, Hypersaline Mat Community,Appl. and Env. Microbiology, May 1994, pp. 1500–1511
  8. ^Bebout B.M., Garcia-Pichel F.,UV B-Induced Vertical Migrations of Cyanobacteria in a Microbial Mat,Appl. Environ. Microbiol., Dec 1995, 4215–4222, Vol 61, No. 12
  9. ^Che, L.M.; Andréfouët. S.; Bothorel, V.; Guezennec, M.; Rougeaux, H.; Guezennec, J.; Deslandes, E.; Trichet, J.; Matheron, R.; Le Campion, T.; Payri, C.; Caumette, P. (2001)."Physical, chemical, and microbiological characteristics of microbial mats (KOPARA) in the South Pacific atolls of French Polynesia".Canadian Journal of Microbiology.47(11): 994–1012.doi:10.1139/cjm-47-11-994.PMID11766060.Retrieved2008-07-18.[permanent dead link]
  10. ^Temara, A.; de Ridder, C.; Kuenen, J.G.; Robertson, L.A. (February 1993)."Sulfide-oxidizing bacteria in the burrowing echinoid,Echinocardium cordatum(Echinodermata) ".Marine Biology.115(2): 179.Bibcode:1993MarBi.115..179T.doi:10.1007/BF00346333.S2CID85351601.
  11. ^Porada H.; Ghergut J.; Bouougri El H. (2008). "Kinneyia-Type Wrinkle Structures—Critical Review And Model Of Formation".PALAIOS.23(2): 65–77.Bibcode:2008Palai..23...65P.doi:10.2110/palo.2006.p06-095r.S2CID128464944.
  12. ^abManten, A. A. (1966)."Some problematic shallow-marine structures".Marine Geol.4(3): 227–232.Bibcode:1966MGeol...4..227M.doi:10.1016/0025-3227(66)90023-5.hdl:1874/16526.S2CID129854399.Archived fromthe originalon 2008-10-21.Retrieved2007-06-18.
  13. ^Borenstein, Seth (13 November 2013)."Oldest fossil found: Meet your microbial mom".AP News.Retrieved15 November2013.
  14. ^Noffke, Nora;Christian, Christian; Wacey, David; Hazen, Robert M. (8 November 2013)."Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia".Astrobiology.13(12): 1103–24.Bibcode:2013AsBio..13.1103N.doi:10.1089/ast.2013.1030.PMC3870916.PMID24205812.
  15. ^abcdefghijkNisbet, E.G. & Fowler, C.M.R. (December 7, 1999)."Archaean metabolic evolution of microbial mats".Proceedings of the Royal Society B.266(1436): 2375.doi:10.1098/rspb.1999.0934.PMC1690475.– abstract with link to free full content (PDF)
  16. ^abBlankenship, R.E. (1 January 2001). "Molecular evidence for the evolution of photosynthesis".Trends in Plant Science.6(1): 4–6.doi:10.1016/S1360-1385(00)01831-8.PMID11164357.
  17. ^abAbele, D. (7 November 2002)."Toxic oxygen: The radical life-giver"(PDF).Nature.420(27): 27.Bibcode:2002Natur.420...27A.doi:10.1038/420027a.PMID12422197.S2CID4317378.
  18. ^abHoehler, T.M.; Bebout, B.M.; Des Marais, D.J. (19 July 2001). "The role of microbial mats in the production of reduced gases on the early Earth".Nature.412(6844): 324–7.Bibcode:2001Natur.412..324H.doi:10.1038/35085554.PMID11460161.S2CID4365775.
  19. ^"Introduction to Aerobic Respiration".University of California, Davis. Archived fromthe originalon September 8, 2008.Retrieved2008-07-14.
  20. ^Hedges, S.B.; Blair, J.E; Venturi, M.L.; Shoe, J.L (28 January 2004)."A molecular timescale of eukaryote evolution and the rise of complex multicellular life".BMC Evolutionary Biology.4:2.doi:10.1186/1471-2148-4-2.PMC341452.PMID15005799.
  21. ^Knoll, Andrew H.; Javaux, E.J; Hewitt, D.; Cohen, P. (2006)."Eukaryotic organisms in Proterozoic oceans".Philosophical Transactions of the Royal Society B.361(1470): 1023–38.doi:10.1098/rstb.2006.1843.PMC1578724.PMID16754612.
  22. ^Brocks, J.J.; Logan, G.A.; Buick, R.; Summons, R.E. (13 August 1999). "Archean Molecular Fossils and the Early Rise of Eukaryotes".Science.285(5430): 1033–6.Bibcode:1999Sci...285.1033B.CiteSeerX10.1.1.516.9123.doi:10.1126/science.285.5430.1033.PMID10446042.
  23. ^Martin W. & Müller, M. (March 1998)."The hydrogen hypothesis for the first eukaryote".Nature.392(6671): 37–41.Bibcode:1998Natur.392...37M.doi:10.1038/32096.PMID9510246.S2CID338885.Retrieved2008-07-16.
  24. ^Prave, A. R. (2002). "Life on land in the Proterozoic: Evidence from the Torridonian rocks of northwest Scotland".Geology.30(9): 811–812.Bibcode:2002Geo....30..811P.doi:10.1130/0091-7613(2002)030<0811:LOLITP>2.0.CO;2.ISSN0091-7613.
  25. ^Runnegar, B.N.; Fedonkin, M.A. (1992). "Proterozoic metazoan body fossils". In Schopf, W.J.; Klein, C. (eds.).The Proterozoic biosphere.Cambridge University Press. pp. 369–388.ISBN978-0-521-36615-1.
  26. ^Seilacher, A. (1999)."Biomat-related lifestyles in the Precambrian".PALAIOS.14(1): 86–93.Bibcode:1999Palai..14...86S.doi:10.2307/3515363.JSTOR3515363.Retrieved2008-07-17.
  27. ^abcBottjer, D.J.; Hagadorn, J.W.; Dornbos, S.Q."The Cambrian substrate revolution"(PDF).Amherst College.Archived fromthe original(PDF)on 2006-09-09.Retrieved2008-06-28.
  28. ^Seilacher, Adolf; Luis A. Buatoisb; M. Gabriela Mángano (2005-10-07). "Trace fossils in the Ediacaran–Cambrian transition: Behavioral diversification, ecological turnover and environmental shift".Palaeogeography, Palaeoclimatology, Palaeoecology.227(4): 323–56.Bibcode:2005PPP...227..323S.doi:10.1016/j.palaeo.2005.06.003.
  29. ^abcdeBriggs, D.E.G. (2003). "The role of biofilms in the fossilization of non-biomineralized tissues". In Krumbein, W.E.; Paterson, D.M.; Zavarzin, G.A. (eds.).Fossil and Recent Biofilms: A Natural History of Life on Earth.Kluwer Academic. pp. 281–290.ISBN978-1-4020-1597-7.Retrieved2008-07-09.
  30. ^Seilacher, A. (1994). "How valid is Cruziana Stratigraphy?".International Journal of Earth Sciences.83(4): 752–8.Bibcode:1994GeoRu..83..752S.doi:10.1007/BF00251073.S2CID129504434.
  31. ^Potts, D.A.; Patenaude, E.L.; Görres, J.H.; Amador, J.A."Wastewater Renovation and Hydraulic Performance of a Low Profile Leaching System"(PDF).GeoMatrix, Inc.Retrieved2008-07-17.[dead link]
  32. ^Bender, J (August 2004)."A waste effluent treatment system based on microbial mats for black sea bass Centropristis striata recycled-water mariculture".Aquacultural Engineering.31(1–2): 73–82.Bibcode:2004AqEng..31...73B.doi:10.1016/j.aquaeng.2004.02.001.Retrieved2008-07-17.
  33. ^"Role of microbial mats in bioremediation of hydrocarbon polluted coastal zones".ISTworld. Archived fromthe originalon 2011-07-23.Retrieved2008-07-17.
  34. ^"Compositions and methods of use of constructed microbial mats – United States Patent 6033559".Retrieved2008-07-17.;"Silage-microbial mat system and method – United States Patent 5522985".Retrieved2008-07-17.;"GeoMat".GeoMatrix, Inc.Retrieved2008-07-17.[dead link]cites U.S. Patents 7351005 and 7374670

References[edit]

External links[edit]

  • Jürgen Schieber."Microbial Mat Page".Retrieved2008-07-01.– outline of microbial mats and pictures of mats in various situations and at various magnifications.
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