Vol 5, No 2 (2007)

Horizontal gene transfer as well as mutations, ge- nomic reorganization and gene loss is one of major driving forces of speciation and evolution of bacteria. A notion of definition of "species genome" is presented. The role of various types of mobile elements in distant gene transfer is considered. The nature of barriers for suc- cessful gene transfer on the level of molecular, cell and population processes is uncovered. A special attention is paid to the contribution of different systems of recombination. Hypothesis on the decisive role of horizontal gene transfer in genetic and ecological diversification of bacteria is discussed.

Chemosignaling is widespread among animals as tool for regulation of synecological interactions. Evolutional conservatism of such signaling allows us to suggest that same chemosignals play an important role in different animal species including human beings. Aversion/attraction of mouse pheromone 2,5- dimethylpyrazine (2,5-DMP) and 2,3-dimethylpyrazine (2,3-DMP) for CBA and C57BL/6 mice was studied in T-maze. It is shown that intact males and females of both strains under choice condition prefer 2,3-DMP to water and 2,5-DMP. They also prefer water to 2,5-DMP Stress after swimming modifies behavior in T-maze: all preferences disappear in C57BL/6 males and remain without changes in CBA males. Importance of behavioral changes obtained here under stress condition is discussed. Detailed studies of the preference modulation with recently shown other effects of 2,5-DMP could connect specific sensitivity to chemosignals with the pheromone, stress and genotype.

Intraspecific genetic polymorphism of a Baikal Lake endemic, big Baikal oilfish (Comephorus baicalensis Pallas, 1776), was evaluated based on microsatellite analysis. The obtained results have compared to the results received earlier for a little Baikal oilfish (C. dybowski Korotneff, 1905). Six microsatellite loci designed for the European sculpin, Cottus gobio, were used. Big Baikal oilfish samples were tested from the three Baikal trenches (southern, middle, northern). Average values of F_ST and R_STindexes between the samples did not exceed 0,02 that point to weak intraspecific genetic differentiation. Big Baikal oilfish had the smaller allele variety, the greater deficit of heterozygotes and presence of low-molecular alleles in comparison with little Baikal oilfish. The values of genetic differentiation were equaled F_ST = 0,138 and R_ST = 0,244 for all loci between cumulative samples of little and big Baikal oilfish. Analysis of microsatellite polymorphism has showed that both a big and little Baikal oilfishes are represented by single populations. The factor promoting panmixia within the Baikal oilfish species is apparently a passive transfer of juvenile and adult fishes by water currents.