page_title: Microbial mat
section_title: Ecological and geological importance
hierarchical_section_title: Microbial mat / Description / Ecological and geological importance
caption_attribution_description: English: Blister-like microbial mat on ripple-marked surface of a Cambrian tidal flat; Elk Mound Group; Blackberry Hill, Wisconsin; photograph originally published in K.C. Gass, 2015. Solving the Mystery of the First Animals on Land: The Fossils of Blackberry Hill. Siri Scientific Press, Manchester, UK.
context_page_description: A microbial mat is a multi-layered sheet of microorganisms, mainly bacteria and archaea, and also just bacterial. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces, but a few survive in deserts. They colonize environments ranging in temperature from –40 °C to 120 °C. A few are found as endosymbionts of animals.
  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 by slimy substances secreted by the microorganisms, and in many cases some of the microorganisms form tangled webs of filaments which make the mat tougher. The best known physical forms are flat mats and stubby pillars called stromatolites, but there are also spherical forms.
context_section_description: Microbial mats use all of the types of metabolism and feeding strategy that have evolved on Earth—anoxygenic and oxygenic photosynthesis; anaerobic and aerobic chemotrophy (using chemicals rather than sunshine as a source of energy); organic and inorganic respiration and fermentation (i..e converting food into energy with and without using oxygen in the process); autotrophy (producing food from inorganic compounds) and heterotrophy (producing food only from organic compounds, by some combination of predation and detritivory).
  Most sedimentary rocks and ore deposits have grown by a reef-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) and biostromes (distinct sheets of sediment) are among such microbe-influenced build-ups. Other types of microbial mat have created wrinkled "elephant skin" textures in marine sediments, although it was many years before these textures were recognized as trace fossils of mats. 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.
caption: Blister-like microbial mat on ripple-marked surface of a Cambrian tidal flat at Blackberry Hill, Wisconsin
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