 This, and other EM studies, confirmed that the cell envelope structure of the Methanosarcinales is composed of a cytoplasmic membrane (CM) with an additional barrier (the S-layer) external to the CM.Under conditions of low osmolarity the S-layer is extensively decorated with a polysaccharide, termed methanochondroitin, and the cells tend to grow in multicellular aggregates.Upon adaptation to high osmolarity conditions the cells disaggregate and grow as single cells that lack the methanochondroitin layer.