Nonmotility

Nonmotility is the absence of self-generated movement in cells, organisms, or tissues. It describes a property in which an entity does not propel itself, either permanently as a trait or temporarily as a physiological state. Nonmotile units may still be displaced by external forces such as fluid flow, currents, or mechanical disturbance.

In microbiology, motility is often achieved by structures such as flagella or cilia, or by amoeboid movement. Nonmotile bacteria lack these propulsion systems and generally depend on passive processes for dispersal. The distinction between motile and nonmotile species supports identification and informs ecological and clinical interpretation.

In eukaryotes, many cells are nonmotile. Red blood cells circulate without propulsion, and mature plant cells typically do not move by themselves. Fungal yeasts are usually nonmotile, although some life stages exhibit limited forms of movement when attached to substrates.

Some life-cycle stages, such as spores or cysts, are nonmotile, entering a dormant state until favorable conditions return.

Motility can be measured by observing movement in liquid media or using semi-solid, agar-based assays. Nonmotility influences ecological dispersal, host–pathogen interactions, and responses to environmental change, and is a key trait in taxonomy and physiology.