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Rezumat articol ediţie STUDIA UNIVERSITATIS BABEŞ-BOLYAI
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Rezumat: Microbial mats in most extreme settings, as found at the coastline of the subtropical-arid Arabian Peninsula, have been rarely studied. We used next-generation Illumina MiSeq sequencing, microsensors, stable isotopes and qPCR to study the diversity and carbon and nitrogen cycling in hypersaline microbial mats from Oman and UAE. Highly adapted bacterial specialists were mainly found at the most extreme, upper tidal sites and less specialized organisms with wide tolerance ranges in intermediate and lower sites of the transect. Up to 40% of the archaeal sequences represented so far unknown phyla. Rates of photosynthesis and respiration at the ambient salinities of the mats revealed a decrease from the lower to the upper tidal zone. All mats, regardless of their tidal location, exhibited a decrease in photosynthesis and respiration rates at salinities > 100‰. With respect to nitrogen cycle, these mats had potential rates of ammonia oxidation and denitrification of 0.8±0.4 and 2.0±1.0 nmol N g-1 h-1, respectively, whereas anammox was not detectable. The N2O production rate under anoxic conditions accounted for ca. 5% of total denitrification. Based on qPCR assays, amoA genes had the highest copy number while narG and nirS genes exhibited comparable estimates. Sequences of nirS gene were novel whereas nirK sequences were related to sequences from the Rhizobiales. Sequences of the nosZ gene were the most diverse and clustered with sequences from various genera. We conclude that the mats in the Arabian Peninsula have adjusted the diversity and function of their microbial communities to cope with extreme conditions.
Keywords: cyanobacterial mats, denitrification, microsensors, photosynthesis, respiration. |
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