The Oligosaccharyltransferase AglB Supports Surface-Associated Growth and Iron Oxidation in Methanococcus maripaludis

Abstract

Most microbial organisms grow as surface-attached communities known as biofilms. However, the mechanisms whereby methanogenic archaea grow attached to surfaces have remained understudied. Here, we show that the oligosaccharyltransferase AglB is essential for growth of Methanococcus maripaludis strain JJ on glass or metal surfaces. AglB glycosylates several cellular structures such as pili, archaella, and the cell surface layer (S-layer). We show that the S-layer of strain JJ, but not strain S2, is a glycoprotein, that only strain JJ was capable of growth on surfaces, and that deletion of aglB blocked S-layer glycosylation and abolished surface-associated growth. A strain JJ mutant lacking structural components of the type IV-like pilus did not have a growth defect under any conditions tested, while a mutant lacking the pre-flagellin peptidase (Δ flaK ) was only defective for surface growth when formate was provided as the sole electron donor. Finally, for strains that are capable of Fe 0 oxidation, we show that deletion of aglB decreases the rate of anaerobic Fe 0 oxidation, presumably due to decreased association of biomass with the Fe 0 surface. Together, these data provide an initial characterization of surface-associated growth in a member of the methanogenic archaea. Importance Methanogenic archaea are responsible for producing the majority of methane on Earth and catalyze the terminal reactions in the degradation of organic matter in anoxic environments. Methanogens often grow as biofilms associated with surfaces or partner organisms; however, the molecular details of surface-associated growth remain uncharacterized. We have found evidence that glycosylation of the cell surface layer is essential for growth of M. maripaludis on surfaces and can enhance rates of anaerobic iron corrosion. These results provide insight into the physiology of surface-associated methanogenic organisms and highlight the importance of surface association to anaerobic iron corrosion.

Adaptation of a methanogen to the constructed environment

“…We suspect that glycosylated [NiFe]-hydrogenases could be anchored onto glycosylated S-layer proteins previously reported in this methanogen 5 . For this, the cells require glycosyl transferases such as AglB to glycosylate the hydrogenases and the S-layer proteins 5 . While AglB is not unique to corrosive strains, seven glycosyl transferases and four additional enzyme possibly catalyzing the biosynthesis of unusual sugars and deoxy-sugars for cell wall synthesis 11 and S-layer glycosylations 12 , were encoded in a genomic-region no.…”

“…We suspect that glycosylated [NiFe]-hydrogenases could be anchored onto glycosylated S-layer proteins previously reported in this methanogen 5 . For this, the cells require glycosyl transferases such as AglB to glycosylate the hydrogenases and the S-layer proteins 5 .…”

“…Moreover, when a segment of the MIC-island that included the [NiFe]-hydrogenases and the Tat-system was transplanted from the corrosive strain OS7 to a non-corrosive strain JJ, the resulting mutant exhibited some corrosive properties 5 , albeit an order of magnitude lower than corrosive OS7. This suggests there might be additional factors required for full corrosive potency.…”

“…Complementing this insight, Holten et al . 5 showed that glycosylated S-layer proteins facilitate the attachment of M. maripaludis to surfaces, including Fe 0 .…”

The Targeted Deletion of Genes Responsible for Expression of the Mth60 Fimbriae Leads to Loss of Cell-Cell Connections in Methanothermobacter thermautotrophicus ΔH

“…Because the raised antibodies against Mth60-fimbriae potentially bound mostly glycosylated proteins, we hypothesized that attachment of the anti-Mth60-fimbria antibody had an effect similar to that of the deletion of oligosaccharyltransferase AglB in M. maripaludis . This deletion led to the loss of glycosylation of M. maripaludis pilus structures, and therefore the deletion strain was deficient in surface attachment ( 45 ). Further investigations of the glycosylation of Mth60 fimbriae will be required in M. thermautotrophicus ΔH.…”