“…These modern-day mat ecosystems resemble life during the Precambrian era, when the biosphere was mostly microbial and benthic [ 5 , 6 , 7 , 8 ]. Fortunately, even today, microbial mats similar to life in the shallow, anoxic, sometimes euxinic (high hydrogen sulfide, low dissolved oxygen) seas of the early biosphere thrive in several globally distributed refugia under extreme conditions of moisture, salinity, pH, temperature, and oxygen [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Indeed, a great variety of living microbial mats with a diversity of structural and functional characteristics are found in extant extreme ecosystems all over the world ranging from subglacial lakes to deep sea thermal vents [ 14 ].…”