Description Microbial mat

1 description

1.1 structure
1.2 types of environment colonized
1.3 ecological , geological importance

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stromatolites formed microbial mats microbes move upwards avoid being smothered sediment.

microbial mats have been referred algal mats , bacterial mats in older scientific literature. type of biofilm large enough see naked eye , robust enough survive moderate physical stresses. these colonies of bacteria form on surfaces @ many types of interface, example between water , sediment or rock @ bottom, between air , rock or sediment, between soil , bed-rock, etc. such interfaces form vertical chemical gradients, i.e. vertical variations in chemical composition, make different levels suitable different types of bacteria , divide microbial mats layers, may sharply defined or may merge more gradually each other. variety of microbes able transcend limits of diffusion using nanowires shuttle electrons metabolic reactions 2 centimetres deep in sediment – example, electrons can transferred reactions involving hydrogen sulfide deeper within sediment oxygen in water, acts electron acceptor.

the best-known types of microbial mat may flat laminated mats, form on approximately horizontal surfaces, , stromatolites, stubby pillars built microbes move upwards avoid being smothered sediment deposited on them water. however, there spherical mats, on outside of pellets of rock or other firm material , others inside spheres of sediment.

structure

a microbial mat consists of several layers, each of dominated specific types of microorganism, bacteria. although composition of individual mats varies depending on environment, general rule by-products of each group of microorganisms serve food other groups. in effect each mat forms own food chain, 1 or few groups @ top of food chain by-products not consumed other groups. different types of microorganism dominate different layers based on comparative advantage living in layer. in other words, live in positions can out-perform other groups rather absolutely comfortable — ecological relationships between different groups combination of competition , co-operation. since metabolic capabilities of bacteria (what can eat , conditions can tolerate) depend on phylogeny (i.e. closely related groups have similar metabolisms), different layers of mat divided both different metabolic contributions community , phylogenetic relationships.

in wet environment sunlight main source of energy, uppermost layers dominated aerobic photosynthesizing cyanobacteria (blue-green bacteria color caused having chlorophyll), while lowest layers dominated anaerobic sulfate-reducing bacteria. there intermediate (oxygenated in daytime) layers inhabited facultative anaerobic bacteria. example, in hypersaline ponds near guerrero negro (mexico) various kind of mats explored. there mats middle purple layer inhabited photosynthesizing purple bacteria. other mats have white layer inhabited chemotrophic sulfide-oxidizing bacteria , beneath them olive layer inhabited photosynthesizing green sulfur bacteria , heterotrophic bacteria. however, layer structure not changeless during day: species of cyanobacteria migrate deeper layers @ morning, , go @ evening, avoid intensive solar light , uv radiation @ mid-day.

microbial mats held , bound substrates slimy extracellular polymeric substances secrete. in many cases of bacteria form filaments (threads), tangle , increase colonies structural strength, if filaments have sheaths (tough outer coverings).

this combination of slime , tangled threads attracts other microorganisms become part of mat community, example protozoa, of feed on mat-forming bacteria, , diatoms, seal surfaces of submerged microbial mats thin, parchment-like coverings.

marine mats may grow few centimeters in thickness, of top few millimeters oxygenated.

types of environment colonized

underwater microbial mats have been described layers live exploiting , extent modifying local chemical gradients, i.e. variations in chemical composition. thinner, less complex biofilms live in many sub-aerial environments, example on rocks, on mineral particles such sand, , within soil. have survive long periods without liquid water, in dormant state. microbial mats live in tidal zones, such found in sippewissett salt marsh, contain large proportion of similar microorganisms can survive several hours without water.

microbial mats , less complex types of biofilm found @ temperature ranges –40 °c +120 °c, because variations in pressure affect temperatures @ water remains liquid.

they appear endosymbionts in animals, example in hindguts of echinoids.

ecological , geological importance

wrinkled kinneyia-type sedimentary structures formed beneath cohesive microbial mats in peritidal zones. image shows location, in burgsvik beds of sweden, texture first identified evidence of microbial mat.



kinneyia-like structure in grimsby formation (silurian) exposed in niagara gorge, new york.

microbial mats use of types of metabolism , feeding strategy have evolved on earth—anoxygenic , oxygenic photosynthesis; anaerobic , aerobic chemotrophy (using chemicals rather sunshine source of energy); organic , inorganic respiration , fermentation (i..e converting food energy , without using oxygen in process); autotrophy (producing food inorganic compounds) , heterotrophy (producing food organic compounds, combination of predation , detritivory).

most sedimentary rocks , ore deposits have grown reef-like build-up rather falling out of water, , build-up has been @ least influenced , perhaps caused actions of microbes. stromatolites, bioherms (domes or columns similar internally stromatolites) , biostromes (distinct sheets of sediment) among such microbe-influenced build-ups. other types of microbial mat have created wrinkled elephant skin textures in marine sediments, although many years before these textures recognized trace fossils of mats. microbial mats have increased concentration of metal in many ore deposits, , without not feasible mine them—examples include iron (both sulfide , oxide ores), uranium, copper, silver , gold deposits.