The role of chitin and its hydrolysis products generated by Vibrio cholerae chitinases in mechanisms of its adaptation in water environments, metabolism, preservation, acquisition of pathogenic potential, and its epidemiological value are reviewed. Chitin utilization by V. cholerae as a source of energy, carbon, and nitrogen is described. Chitin association promotes biofilm formation on natural chitinous surfaces, increasing V. cholerae resistance to adverse factors in ecological niches: the human body and water environments with its inhabitants. Hydrolytic enzymes regulated by the corresponding genes result in complete chitin biodegradation by a chitinolytic catabolic cascade. Consequences of V. cholerae cell and chitin interaction at different hierarchical levels include metabolic and physiological cell reactions such as chemotaxis, cell division, biofilm formation, induction of genetic competence, and commensalic and symbiotic mutual relations with higher organisms, nutrient cycle, pathogenicity for humans, and water organisms that is an example of successful interrelation of bacteria and substratum in the ecology of the microorganism.

The morphology of the diatom genus Epithemia from ecosystems of Central Asia (Russia and Mongolia) is studied. It is shown that in the studied ecosystems there are species with local or endemic distribution, like in Lake Baikal, and taxa known from the Holarctic. Original morphological descriptions and pictures of 13 taxa are given. Three new taxa are described. They are E. compacta Kulikovskiy & Lange-Bertalot sp. nov. from Lake Baikal; E. selengaensis Vishnjakov, Kulikovskiy & Genkal sp. nov. from the Selenga River; and E. perlongicornis Vishnjakov, Kulikovskiy & Genkal sp. nov. from water bodies of the Great Lakes Depression in Mongolia.

A new dioecious species of Tolypella, T. mongolica sp. nov. from the section Tolypella, was described using an integrative taxonomy. It was found in three distant localities – shallows of a brackish small lake and a channel in the midland steppe in Mongolia and the Altai Mountains, and a small brackish water body in the dry steppe in Southeast Europe. It differs from other species in rbcL and ITS sequences and in distinct complex ornamentation of the oospore surface, varying from sparsely coarsely tuberculate to having the appearance of an aerial view of mountain landscape with acute to mostly sharp edges of elements at probably the ripest stage. Wide intrapopulation variability of expression of this trait, only partly explainable by oospore ripening stage, was found and illustrated for two populations, indicating previous underestimation of this phenomenon in taxonomic research. T. mongolica is richly fertile and appears to be ephemeral as most species of this genus. Only female plants were found in all localities. The absence of male plants could be referred to either their earlier development during the growing season or, less likely, parthenogenesis in this species. The description of the new species suggests taxonomic changes for two dioecious species of charophytes. Tolypella porteri stat. et comb. nov. was validated here. T. jwalae was recognized as a species of Nitella, N. jwalae comb. nov.