The concept of pelobionts (Peloflagelatea class): A brief history and current status [Review] [Russian]

摘要

Pedobionts is a peculiar group of amitochondrial amoeboid protests possessing flagella. They are free-living microaerobic and anaerobic organisms. The ideas of the nature, composition, and taxonomic status of pelobionts radically changed time and again. The modern concept of pelobionts originates in Griffin's publication (1988), although most of the species comprising this group were known long ago. Pelomyxa palustris, the type species and genus of the group, was described by R. Greef in 1887. Other pelobionts, which were referred to "mastigamoebids", belong to three nominal genera Mastigamoeba, Mastigina, and Mastigella. They have a number of similar features of cell organization (unique in their combination) and represent a homogenous group of related organisms. Pelobionts are united into the class Peloflagellatea Seravin et Goodkov 1991 with the only order Pelobiontida (Page 1976) Griffin 1988. The results of few molecular and biological studies on phylogenetic relations between pelobionts and other protests are quite controversial. However, they attest definitely to the secondary loss of pelobionts' mitochondria in the course of their evolution. Atypical (deflected from the standard microtubular pattern) structure of axoneme and flagellar basal body in some pelobionts are also attributed to the loss of the initial locomotion function of the flagellar apparatus in the course of evolutionary transition to a different type of cell organization. The species composition of pelobionts has been poorly studied. Therefore, their taxonornic identification is unreliable. Among 200 nominal pelobiont species described in the late 19(th)-early 20(th) centuries, less than 10 species were reisolated and redescribed using modern methods of studies. Pelomyxa palustris, the best known and a single valid species in this genus, is suggested to be a complex of closely related independent species.