Peritrikhisesti

Peritrikhisesti is a Finnish adverb used in microbiology to describe the flagellar arrangement known in English as peritrichous. In bacteria described this way, numerous flagella are distributed around the entire cell surface rather than being confined to a single pole or to small tufts.

This arrangement enables propulsion in many directions and facilitates rapid changes in movement. The flagella form rotating motors powered by the proton motive force, and their rotation is coordinated to produce smooth swimming, known as runs, interspersed with reorientation events called tumbles. Chemotactic signals can modulate the frequency and duration of runs and tumbles, guiding the cell toward favorable conditions.

Peritrichous flagellation is common in several well-studied bacteria, including Escherichia coli and Bacillus subtilis, though flagellation patterns vary across species and environmental contexts. It is often contrasted with monotrichous (a single flagellum at one end), lophotrichous (tufts at one end), and amphitrichous (flagella at both ends) arrangements, which confer different locomotion strategies.

Etymology-wise, the Finnish term peritrikhisesti derives from the same roots as the English peritrichous: peri- meaning around and trichos meaning hair, with the suffix -isesti forming an adverb. In scientific Finnish literature, the word is used to describe how cells move or how their flagella are distributed, providing a precise descriptor for microbial motility patterns.