Press release

Press release (In Japanese only)

Marimo (lake ball) is an uncommon ball-like aggregation of the green alga, Aegagropila linnaei. Although A. linnaei is distributed in fresh and brackish waters in the northern hemisphere, marimo colonies are found only in particular habitats. Here, we report the bacterial communities inside various sizes and aggregating structures of natural marimo collected from Lake Akan, Japan. We observed multi-layers composed of sediment particles only in the sizeable radial-type marimo with a >20 cm diameter, not in the tangled-type marimo. The deeper layers were enriched by Nitrospira, potential sulphur-oxidizing bacteria, and sulphate-reducing bacteria. Microorganisms of the multi-layers would form biofilms incorporating nearby sediment, which would function as microbial “seals” within large radial-type marimo. We propose that the layer structure provides habitats for diverse bacterial communities, promotes airtightness of the marimo, and finally contributes to the massive growth of the aggregation. These findings provide clues to deciphering the growth of endangered marimo.

Source: R. Nakai, et al., iScience DOI:10.1016/j.isci.2021.102720