Cells are thin nonmotile rods of variable length, 0.2-0.3 × 2–10 μm, with the thin monolayer cell-wall structure forming spherical terminal endospores. In the pre-spore state cells are filled with microcompartment-like bodies. The colonies in soft agar with amorphous cellulose are sphaerical and surrounded by cellulose clearance zones. Forms cell-bound yellow-orange pigment. Strictly anaerobic, fermentative, saccharolytic bacterium growing actively only with various forms of insoluble cellulose and less actively with soluble barley beta-glucan, xylan and lichenan. Growth in liquid culture is only possible with a saccharolytic partner from the genus Natronincola. Ammonium (but not urea or nitrate) and (potentially) N2 can serve as the nitrogen source during growth on cellulose. Obligately alkaliphilic, with a pH range for growth between 8.2 and 10.2 (opt. at 9.5) and moderately salt-tolerant, with a total Na+ range for growth from 0.3 to 1.75 M (opt. at 0.6-1.0 M). Mesophilic, with a maximum growth temperature at 43oC. G + C content of the genomic DNA is 31.5%.