Etymology: N.L. neut. n. proteinum, protein; N.L. adj. clasticus -a -um (from Gr. adj. klastos -ê -on, broken in pieces), breaking; N.L. neut. adj. proteoclasticum, protein breaking.

Cells are gram-positive, straight to slightly curved rods that are 0.4 to 0.6 pm wide and 1.3 to 3.0 pm long and do not form endospores. Cells occur in short chains and have tapered ends, and each cell possesses a single, subterminal flagellum, although cells are not motile in liquid culture. After overnight incubation, cells form a ropy sediment, which is easily dispersed with shaking. Colonies grown overnight on CC-glucose medium are 0.5 mm in diameter, tan, irregular, convex with undulate margins, and transparent with smooth surfaces and a viscous texture. Older colonies (2 to 3 days) are 1 mm in diameter and become granular. Growth characteristics. Growth is supported by amygdalin, arabinose, cellobiose, fructose, galactose, glucose, inulin, lactose, maltose, melibiose, rhamnose, salicin, starch, sucrose, xylan, and xylose, while glycogen and mannose support weak growth. The substrates adonitol, cellulose, dextrin, dulcitol, erythritol, galacturonic acid, glycerol, inositol, lactate, mannitol, melizitose, sorbitol, sorbose, and trehalose do not support growth. The fermentation products from growth on CC rnedium include formate, butyrate, acetate, propionate, and a trace of succinate. Hydrogen is produced from growth on CCglucose medium. Growth is stimulated by the presence of 20% rumen fluid, is inhibited by bile, and is not affected by Tween 80 or hemin. There is no growth aerobically. Characterization tests and G+C content. C. proteoclasticum hydrolyzes gelatin and casein, and proteolytic activity against casein is almost totally inhibited by phenylmethylsulfonyl fluoride and is inhibited to lesser degrees by merthiolate, N-tosyl- 1-lysine chloromethyl ketone,p-chloromercuribenzote, EDTA, and o-phenanthroline. This organism also exhibits a curd reaction with milk and hydrolyzes esculin. C. proteoclasticum does not produce indole or ammonia, does not exhibit catalase, lipase, or lecithinase activity, and does not reduce nitrate. The heat test data, spore strain results, and growth on sporulation medium all indicate that no endospores are formed, while colonies on blood agar are nonhemolytic. The G+C content of the DNA is 28 mol% (as determined by the thermal denaturation method).

C. proteoclasticum strain B316 is the type strain and has been deposited in the American Type Culture Collection as strain ATCC 51982.