Anammoxosomes are enriched in the ladderane lipids shown at right. Analysis of the anammoxosome membranes from the bacterial species Brocadia anammoxidans and Kuenenia stuttgartiensis has revealed that ladderanes constitute more than 50% of membrane lipids. The high abundance of ladderane lipids in the anammoxosome results in an exceptionally dense membrane with reduced permeability. The reduced permeability may decrease the passive diffusion of protons across the membrane that would dissipate the electrochemical gradient. This would be especially detrimental to anammox bacteria, due to the relatively slow anammox metabolism. The decreased permeability has also been hypothesized to sequester the highly toxic and mutagenic intermediates, hydrazine and hydroxylamine, which can readily diffuse through biomembranes. The loss of these key intermediates would damage key cellular components such as DNA, as well as reduce the catabolic efficiency of the cell.
