Stäbchen

Stäbchen is a German term used in biology with several related meanings. Most commonly it denotes rod-shaped cells or organisms. In bacteriology, Stäbchenbakterien are bacteria whose cells are cylindrical and longer than they are wide, also called bacilli in English. They range in size roughly from 0.5 to several micrometers in length. Bacilli include both Gram-positive and Gram-negative groups; notable examples are Bacillus and Clostridium (Gram-positive, some spore-forming) and Enterobacteriaceae (Gram-negative, rod-shaped). The rod shape contributes to certain growth patterns and colony morphologies and is used as a basic criterion in microscopic identification.

In anatomy, Stäbchen refers to rod photoreceptor cells in the retina. Rods are highly sensitive to light and enable vision under low-light conditions (scotopic vision); they do not mediate color vision. Rods are more numerous in the peripheral retina, have outer segments containing the photopigment rhodopsin, and work together with cone cells, which mediate daylight and color vision.

The term derives from the German Stab, meaning rod or staff, and Stäbchen is the diminutive form. The word is used in both biological contexts; the term reflects morphological similarity and is not restricted to a single discipline. In scientific writing, it is usually clarified by context to avoid ambiguity between bacterial rods and retinal rods.