Microbial mat

A microbial mat is a layered community of microorganisms growing on a surface. Its strata often reflect gradients in light, oxygen, and chemical compounds.

Microbial stratification: The vertical arrangement of microbial groups according to environmental conditions and metabolic capabilities. Different strata occupy zones with distinct light and chemical conditions.
Biofilm: A community of microorganisms attached to a surface and embedded in a self-produced matrix. Microbial mats are structured, often conspicuously layered forms of surface-associated microbial growth.
Stromatolite: A layered sedimentary structure formed through microbial activity and sediment trapping or mineral precipitation. Some stromatolites record successive growth of ancient microbial mats.
Astrobiology: The study of life’s origin, evolution, distribution, and potential beyond Earth. Mats provide analogues for interpreting possible biosignatures in ancient or extraterrestrial settings.
Oxygenic photosynthesis: Photosynthesis that uses water as an electron donor and releases oxygen. Surface phototrophs can oxygenate upper layers during daylight.
Extracellular polymeric substance: A matrix of polymers released by microorganisms that surrounds cells and helps bind them to surfaces. The matrix stabilizes mat layers and traps particles.
Shark Bay stromatolites: Modern stromatolites in Western Australia, including examples growing in hypersaline coastal settings. These living structures provide a well-studied setting for modern mat-building communities.
Biosignature: A measurable feature that provides evidence of past or present biological activity. Mat textures and mineral products can preserve candidate biosignatures.
Anoxygenic photosynthesis: Photosynthesis that uses electron donors other than water and does not release oxygen. Anoxygenic phototrophs can use light beneath oxygenated surface zones.
Redox gradient: A spatial change in the availability of electron donors and acceptors that alters oxidation-reduction conditions. Overlapping redox zones sort metabolisms through the mat.

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