Cell: Rod shaped cells.
Spore: The species are endospore formers. Shape of the spores varies with the species and maybe oval, ellipsoidal, cylindrical or spherical. The location maybe terminal, sub-terminal or central. The spores formed are quite heat resistant and retain viability even at temperatures as high as 100°C for one minute. Spore formation is usually observed in old cultures. Studies show that formation maybe enhanced in media containing 40mg/L manganese sulfate. Spores also shown to be resistant to 70°C for 10 minutes or to 95% ethanol for 20 minutes. Thus, they survive pasteurization temperatures in the heat stabilization of fortified wines. The spores are also resistant to acid and salt and can persist in the environment for long periods of time.
Colony: Colony morphology is highly variable and depends on various strains and the species. Large to very large, grey white colonies, maybe dry in appearance or may look wet and blistery have been observed.
Liquid growth: Growth is uniform and solution appears turbid.