Rigorous fundaments of classification of light-induced behaviour from freely motile microorganisms

Abstract

. Rigorous fundamentals of classification of light-induced behaviour from freely motile microorganisms. The revision of terminology and classification principles of the types of light­dependent movement behaviour of freely motile organisms and their populations has demonstrated the presence of various classification systems being the source of the terminological confusion. It is shown that the present classification and definition of the terms had a number of logical mistakes. The primary meaning of the term "phototopotaxis" which implies any light-dependent movement behaviour of freely motile organisms is proposed. It is possible to use the restored term "phototopotaxis" for definition of the movement oriented relative to the light stimulus. The parametrical principle of the classification of the types of phototaxis for a single or a population of cells is recommended for the first time. According to this principle it is possible to put in order the available facts and terminology on the strict logical basis, to forecast the dependence of the movement parameters of the biological objects on the light stimulus characteristics which has been not established till now, and to develop the program of further research. The parametrical principle could also be used for the classification of taxa induced by any stimuli. The photoreaction (immediate response to any change of the light stimulus) of freely motile organisms is discussed as a part of the more general meaning - phototaxis.