By Alexander BORONIN, RAS Corresponding Member, Vitaly DUDA, Dr. Sc. (Biol.), Natalya SUZINA, Cand. Sc. (Biol.), G. Skryabin Institute of Biochemistry and Physiology of Microorganisms, RAS The ideas of the biological diversity and molecular genetic bases on the biological cell structure, functioning, and evolution have changed appreciably due to the progress in studies of the world of microorganisms, attained during the recent decade.An important result of studies of many new and rare microbiotic species is an ample information on the range of bacterial cell sizes; ultrasmall forms attract special attention of specialists. NOT RANDOM INTEREST Today the largest bacteria discovered are Thiomargarita namibiensis, a giant spherical aero-biobacterium, - 750 μm in diameter, and Epulopiscium sp., an anaerobic bacillus, - 80 μm diameter, which are larger than even some multicellular eukaryotes*. It is noteworthy that previously it was assumed that an extremely small diameter of a prokaryotic cell * Eukaryotes - uni- or multicellular plants, animals and some microorganisms, whose cell body is differentiated by cytoplasm and nucleus, limited by a membrane. Prokaryotes are microorganisms that have no typical cell nucleus and chromosome system. - Auth. стр. 31 can serve as the main phenotypical distinction of bacteria. By the way, it has become known recently (from publications by Claude Courties et al. in 1994 and 1998, as well as by Motomichi Matsuzaki in 2004, from the Tokyo State University, Japan) that the smallest one-cell independent eukaryotic organisms (Ostreococcus tauri and Cyanidoschizon merolae algae) are not larger than 0.6 - 2.0 μ. The smallest prokaryotes are Mycoplasma genitalium and Pelagibacter ubique bacteria, which are < 0.3 μm (300 nm). Let us note that the largest virus is 0.4 μm, while the majority of bacterial cells are 1 -2 um in size. The interest of scientists in ultrasmall b ... Read more