by Nikolai RAVIN, Dr. Sc. (Biol.), Vice-Director for Research, Laboratory Head, Molecular Cloning Systems, Bioengineering Center, Russian Academy of Sciences, Moscow The natural communities of microorganisms may include thousands of species, most of which cannot be cultured under laboratory conditions and thus cannot be properly studied. However, this problem has been solved with the development of new methods of genome analysis. Using these methods, we have studied the composition of bacterial communities of hot springs in Kamchatka and within methane hydrate deposits at the bottom of Lake Baikal. NUCLEOTIDE SEQUENCES HOLD THE KEYS One of the most important tasks of microbiology (as in other classical biological sciences) is identification and classification of research objects. Zoology and botany make use of the entire variety of morphological signs of animals and plants for this purpose, but this approach is not productive for microorganisms, as the number of differentiating external characteristics of unicellular organisms is scanty. That is why in addition to cell size and shape, the presence or absence of flagella, etc., the classification of bacteria is based on the variety of their functional characteristics, such as the capacity to grow on different substrates, to form certain metabolites, their oxygen dependence, etc. It is impossible to study these characteristics at the level of one стр. 9 cell--a whole organism per se--because of its very small size. This problem was solved with the development of culturing methods--reproduction of pure cultures of identical cells under laboratory conditions. Analysis of cell cultures reveals the diversity of metabolic and biochemical processes realized by microorganisms, and their ecological role in the biosphere; it enables scientists to develop methods for identification and classification of microorganisms. New trends, based on concepts of the functional characteristics of a ... Читать далее