Methanogenic Archaea are the only organisms on Earth capable of reducing carbon dioxide to methane and are key players in the global carbon cycle where they convert over one billion tons of photosynthetically fixed carbon to methane annually. Methanogens are found in environments ranging from freshwater and marine sediments to the digestive tracts of termites and ruminants where they are the primary consumers of fermentatively produced hydrogen (H2). However, this presents a problem in that H2 is poorly soluble and easily diffuses away from producing cells. We hypothesize that surface associated biofilm communities can alleviate this problem by limiting diffusive loss of H2 to the environment. To test this hypothesis, we are working to understand the genetic basis of biofilm formation in the model organism Methanococcus maripaludis. Most biofilm forming organisms rely on flagella and pili for initial surface attachment and the early stages of biofilm formation; however, M. maripaludis strains lacking these appendages have only minor defects in biofilm formation. In contrast, glycosylation of the cell surface layer (s-layer) appears to be a primary determinant of a given strains ability to form a biofilm. In strains with glycosylated s-layers, deletion of the protein oligosaccharyltransferase aglB completely abolishes biofilm formation and inhibits the H2-dependent corrosion of Fe0, presumably due to a decreased association of cells with the Fe0 surface. Finally, we are testing the hypothesis that biofilm formation provides a growth advantage in other H2 limiting environments, such as when methanogens are growing syntrophically with H2 producing bacterial partners.

Biofilm formation in methanogenic archaea

ACS Spring 2022

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