[African wild cat (Felis lybica Forster, 1780) in the Saratov Transvolga Region].

Analysis of the area limits where African wild cat was found as well as of published data on its distribution in the Saratov Transvolga Region demonstrated that the local range of this species extended and its northwestern limit advanced almost 1000 km to the Volga zoogeographical boundary.

[Abundance of Trans-Volga population of the great bustard (Otis tarda L.)]. / Chislennost' zavolzhskoi populiatsii drofy (Otis tarda L.).

We studied the abundance, spatial structure, and democratic parameters of the Trans-Volga population of great bustard as well as this species connection to the habitats during premigratory movements. The data were obtained by monitoring a test area of 1,200,000 hectares in 1998-2000. Time-related changes in the structure of great bustard habitats in Saratov Trans-Volga Region during the 20th century are described and the mechanisms underlying the changes in this species connection to the habitats under the influence of anthropogenic factors are proposed.

Analysis of Yersinia pestis chromosomal determinants Pgm+ and Psts associated with virulence.

The ability to absorb exogenous pigments (Pgm+) has, until now, been considered an established virulence factor of Yersinia pestis, the causative agent of plague. This property correlates with the sensitivity to the bacteriocin pesticin (Psts). Both functions are chromosomally encoded. In the present study, using Hfr donors and isogenic Pgm-Psts and Pgm-Pstr mutants, these functions were shown to be determined by discrete but closely linked genes. These markers designated pgm and psn, respectively, were preliminarily located within a linkage group including 11 loci. It was also found that pigmentation is not essential for mouse virulence but is necessary for survival of Y. pestis in the flea, the plague vector. At the same time, conversion of an avirulent Pstr mutant to pesticin sensitivity restored some degree of virulence.

[The ability of fleas of synanthropic rodents and small gerbils to feed on human blood]. / Sposobnost' blokh sinantropnykh gryzunov i melkikh peschanok pitat'sia krov'iu cheloveka.

Experimental study of the ability of Ceratophyllus (Nosopsyllis) mokrzeckyi, C. (G.) laeviceps, X. conformis fleas, Norway rats' parasites from the northern and northwestern Caspian Sea coasts, and the specific Norway rats' flea C. (N.) fasciatus, to feed on human blood, demonstrated that all these species may be of epidemiological significance due to their active attacks on man and human blood sucking. The murine rodent fleas C. (N.) mokrzeckyi are, though, less active human blood suckers (29.9%) than the other species under study.