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Insight Into Anaerobic Methanotrophy from 13C/12C- Amino Acids and 14C/12C-ANME Cells in Seafloor Microbial Ecology

Penelitian - Researchers of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) show methanotrophic pathways were analyzed to trace 13C-depleted amino acid biosynthesis in two clades of ANME (ANME-1 and ANME-2) from the Black Sea.

Microorganisms play a central role in both methane production and consumption in the global carbon cycle. The anaerobic oxidation of methane (AOM) is an important microbial process that controls the release of greenhouse gas from oceanic sediment.

Penelitian Insight Into Anaerobic Methanotrophy from 13C12C- Amino Acids and 14C12C-ANME Cells in Seafloor Microbial Ecology

“Since the discovery of extremely 13C-depleted lipids produced by modern anaerobic methanotrophic archaea (ANME) in deep-sea sediments, we have recognized the 13C-depleted isotopic signatures as an ongoing AOM process from biogeochemical models for lipid biomarker records, even in hydrothermally active seafloor settings,” Yoshinori Takano of the JAMSTEC.

Three phylogenetic groups of anaerobic methanotrophic archaea (ANME) have currently been identified, namely, ANME-1 (with subgroups a and b), ANME-2 (with subgroups a, b, c, and d), and ANME-3, which mediate AOM via sulfate, nitrate, iron, and manganese. AOM requires methyl coenzyme M reductase, which catalyzes anaerobic methanotrophy through reverse methanogenesis.

Because obtaining pure cultures in the laboratory and isolating ANME are difficult, the biochemical mechanisms that control the AOM process, especially the pathways leading to 13C-depleted cell biomass, remain largely unknown.

To better define the AOM process by focusing on biogeochemistry, Takano and team investigated the carbon isotopic composition of amino acids, the fundamental building blocks of proteins in ANME-1- and ANME-2-dominated mats collected from the northwestern Black Sea.

ANME-1 and ANME-2 are observed in tall reef-like chimney structures (up to ca. 5 m height, 1 m diameter) composed of carbonates and dense microbial biomass (~1010 cells cm−3) where the methane seep rises vertically through the porous calcified interior.

“We conducted compound-specific carbon isotope (13C/12C) analysis of 10 individual amino acids in the form of N-pivaloyl isopropyl ester derivatives and archaeal isoprenoid lipids together with radiocarbon (14C/12C) analysis of ANME cell using an accelerator mass spectrometry,” said Takano.

Journal : Yoshinori Takano et al. Insight into anaerobic methanotrophy from 13C/12C- amino acids and 14C/12C-ANME cells in seafloor microbial ecology, Scientific Reports, 24 September 2018, DOI:10.1038/s41598-018-31004-5



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