Revisão narrativa sobre a importância de esteiras microbianas na formação de estromatólitos e demais estruturas organosedimentares
Abstract
Microbial mats are complex benthic ecosystems that interact with sediments and form a range
of biostratification structures called MISS (“Microbially Induced Sedimentary Structure”),
which significantly influence the composition of sedimentary systems, commonly associated
with aquatic environments. Microrganisms that form biofilms play an important role in
formation of MISS by synthesizing EPS (“Extracellular Polymeric Substances”), trapping
and binding suspended sediment grains in the water column and the bioprecipitation of
minerals in the EPS structure and cell surfaces. The cells promote sediment biostabilization,
which reduces the likelihood of rupture and erosion. The diversity of metabolisms and
species found in the microbial mats influence the morphological patterns, as well as the mats'
potential to consolidate and subsequently lithify, which gives rise to microbialites.
Stromatolites are the best known structures resulting from the metabolism of microbial
ecosystems and have a characteristic internal lamination structure, which is a reflection of the
overlapping of numerous biofilms of different functional groups, in which there is
precipitation of different minerals that end up generating different layers of colors that
discriminate the lamination. The specific metabolism and behavior of the MISS-forming
bacteria made it possible to preserve part of the planet's past that has little information,
compared to geological periods in which there were more diverse and more complex forms of
life in terms of body structure. The mineral precipitation of microbial mats enabled the
formation of the extensive fossil record of microbialites that fill in paleontological gaps
associated with the Precambrian, due to the lack of body fossils. Bioprecipitation, as well as
the metabolic diversity and adaptation to extreme physicochemical conditions that
microrganisms in these ecosystems usually present, are also of interest in the field of
astrobiology, especially regarding the possibility that the soil of Mars harbors life similar to
bacteria mat-forming on Earth, or have harbored in the remote past.
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