Monoclonal antibodies to the species-specific and group antigens of Rickettsia prowazekii]

A number of hybridomas to different R. prowazekii determinants were obtained by the hybridization of spleen cells of BALB/c mice immunized with R. prowazekii corpuscular and soluble antigens. Some of the monoclonal antibodies (McAb) reacted with R. prowazekii thermolabile species-specific protein and did not react with R. typhi antigens (McAb of batches B4/4 and A-D3). McAb C5/2 and A3/2 reacted with the group thermostable antigen, common for R. prowazekii and R. typhi. McAb to the species-specific thermolabile antigen belonged to IgG2a. The McAb thus obtained permit the identification of R. prowazekii and R. typhi and the solution of the problem of the intragroup differentiation of rickettsiae belonging to the typhus group.     

Effect of real and simulated weightlessness on the characteristics of the static otolith reflex

To determine the role of the support-proprioceptive factor in functioning of the vestibular system, in particular, the role of static torsional otolith-cervical-ocular reflex (OCOR), the latter was studied in 16 subjects after a seven-day “dry” horizontal immersion and in 14 cosmonauts after a prolonged exposure to weightlessness (for 126–195 days). OCOR was studied by the videooculography method during alternately tilting the head towards the right or left shoulder by an angle of 30° in the frontal plane before the flight and before immersion, as well as on days 1, 3, and 7 after the completion of the immersion experiment and on days 1 (2), 4 (5), and 8 (9) after the spaceflight. For the first time it was demonstrated that elimination of the support and minimizing the proprioceptive afferentation may lead to the absence or inversion of the static torsional OCOR, as well as to a positional nystagmus against the background of the inverted reflex. Comparison of OCOR in cosmonauts after prolonged exposure to weightlessness and in the subjects examined after immersion revealed similarity in this reaction. However, changes in OCOR after immersion were encountered only in 60% of the subjects, whereas after the spaceflight, in 90% of the cosmonauts examined. The post-flight changes in OCOR were more pronounced and long-lasting.     

Antimicrobials,Stress and Mutagenesis

Cationic antimicrobial peptides are ancient and ubiquitous immune effectors that multicellular organisms use to kill and police microbes whereas antibiotics are mostly employed by microorganisms. As antimicrobial peptides (AMPs) mostly target the cell wall, a microbial ‘Achilles heel’, it has been proposed that bacterial resistance evolution is very unlikely and hence AMPs are ancient ‘weapons’ of multicellular organisms. Here we provide a new hypothesis to explain the widespread distribution of AMPs amongst multicellular organism. Studying five antimicrobial peptides from vertebrates and insects, we show, using a classic Luria-Delbrück fluctuation assay, that cationic antimicrobial peptides (AMPs) do not increase bacterial mutation rates. Moreover, using rtPCR and disc diffusion assays we find that AMPs do not elicit SOS or rpoS bacterial stress pathways. This is in contrast to the main classes of antibiotics that elevate mutagenesis via eliciting the SOS and rpoS pathways. The notion of the ‘Achilles heel’ has been challenged by experimental selection for AMP-resistance, but our findings offer a new perspective on the evolutionary success of AMPs. Employing AMPs seems advantageous for multicellular organisms, as it does not fuel the adaptation of bacteria to their immune defenses. This has important consequences for our understanding of host-microbe interactions, the evolution of innate immune defenses, and also sheds new light on antimicrobial resistance evolution and the use of AMPs as drugs.     

A review of gamasid mites (Parasitiformes,Mesostigmata) dwelling in the taiga of the Pechoro-Ilychskii Nature Reserve (northern Cis-Ural Region) with analysis of their assemblages in spruce forests

In the plain taiga of the Pechoro-Ilychskii Nature Reserve, 91 species of gamasid mites have been revealed. Cheiroseius (7 species), Veigaia (6), Arctoseius (5), Dendrolaelaps (5), and Dinychus (4) are the most diverse genera. European (29%), Palaearctic (27%), and Holarctic species (30%) are represented in the fauna by somewhat equal fractions, whereas cosmopolitan and semicosmopolitan species constitute about 14%. Comparison of gamasid assemblages populating certain habitats allowed revealing two distinct groupings, namely, forest and floodplain ones. Forest assemblages are characterized by high population density (220–760 ind./dm²) and by predominance of Parazercon radiatus, Zercon forsslundi, Veigaia nemorensis, Gamasellus montanus, and Trachytes spp. Floodplain assemblages are less abundant (80–130 ind./dm²) and comprise mainly meadow and hydrophilic species (A. cetratus, Cheiroseius spp. Gaeolaelaps spp., and Gamasellodes bicolor). Low diversity of the family Parasitidae (4 species) and structural peculiarities of assemblages dwelling in coniferous forests (namely, the absence of Pergamasinae and significant fractions of Veigaia, Gamesellus, Trachytes, and also of representatives of the family Zerconidae) demonstrate similarities between the mesostigmatan population of this northern European region and that of the Siberian taiga. Solitary records of such Arctic species as Arctoseius ornatus and Zerconopsis labradorensis, and of the hypoarcto-montane species Iphidinychus gaieri within the taiga belt, seem to reflect the instability of range margin. Taking into account the literary data, we recognize a complex of boreal and borealmountain species (Trachytes edleri, Dinychus septentrionalis. D. crassus, Caurozercon duplex, Neozercon smirnovi, Zercon forsslundi, and Z. zelawaiensis) in the Palaearctic fauna. Their habitats, however, are not restricted only to dark coniferous forest along. The structure of gamasid mite assemblages in mesophytic spruce forests of the Palaearctic varies strongly. By contrast to vascular plants, where many species accompany the dark coniferous taiga everywhere, there is not a single mesostigmatic mite species common to all the spruce forests analyzed, ranging from Romania in the west to Sakhalin Island in the east. On the whole, changes in gamasid mite assemblages across the spruce forest belt seem to follow a succession of meridional changes in gamasid faunas regardless of an edificatory spruce species.     

Error-prone Replication Bypass of the Primary Aflatoxin B1 DNA Adduct,AFB1-N7-Gua

Hepatocellular carcinomas (HCCs) are the third leading cause of cancer deaths worldwide. The highest rates of early onset HCCs occur in geographical regions with high aflatoxin B₁ (AFB₁) exposure, concomitant with hepatitis B infection. Although the carcinogenic basis of AFB₁ has been ascribed to its mutagenic effects, the mutagenic property of the primary AFB₁-DNA adduct, AFB₁-N7-Gua, in mammalian cells has not been studied extensively. Taking advantage of the ability to create vectors containing a site-specific DNA adduct, the mutagenic potential was determined in primate cells. This adduct was highly mutagenic following replication in COS-7 cells, with a mutation frequency of 45%. The spectrum of mutations was predominantly G to T base substitutions, a result that is consistent with previous mutation data derived from aflatoxin-associated HCCs. To assess which DNA polymerases (pol) might contribute to the mutational outcome, in vitro replication studies were performed. Unexpectedly, replicative pol δ and the error-prone translesion synthesis pol ζ were able to accurately bypass AFB₁-N7-Gua. In contrast, replication bypass using pol κ was shown to occur with low fidelity and could account for the commonly detected G to T transversions.     

Ground beetles (coleoptera,carabidae) of the Ola Plateau highlands,Kolyma Uplands

The ground beetle fauna was studied in 12 biotopes of the tundra belt on Ola Plateau, 130 km NW of Magadan. In all, 16 species were found above timber line (900–1220 m), which is comparable with the diversity in the mountain tundras of the upper reaches of the Kolyma (Berman et al., 1984; Bukhkalo, 1997), but the faunistic similarity of these regions is low (Jaccard’s coefficient 22–29%). Besides the widespread species, a group of ground beetles with limited ranges is present; it includes Carabus kolymensis Lafer, 1989 occurring in the East Siberian mountain tundras, the Siberian-Nearctic, mainly arctic Pterostichus agonus G. Horn, 1880, and the East Siberian Pterostichus eximius A. Mor., 1862. The use of the term “arctic species” in arealogical and ecological studies is discussed.     

Phylogeny of Cas9 determines functional exchangeability of dual-RNA and Cas9 among orthologous type II CRISPR-Cas systems

The CRISPR-Cas-derived RNA-guided Cas9 endonuclease is the key element of an emerging promising technology for genome engineering in a broad range of cells and organisms. The DNA-targeting mechanism of the type II CRISPR-Cas system involves maturation of tracrRNA:crRNA duplex (dual-RNA), which directs Cas9 to cleave invading DNA in a sequence-specific manner, dependent on the presence of a Protospacer Adjacent Motif (PAM) on the target. We show that evolution of dual-RNA and Cas9 in bacteria produced remarkable sequence diversity. We selected eight representatives of phylogenetically defined type II CRISPR-Cas groups to analyze possible coevolution of Cas9 and dual-RNA. We demonstrate that these two components are interchangeable only between closely related type II systems when the PAM sequence is adjusted to the investigated Cas9 protein. Comparison of the taxonomy of bacterial species that harbor type II CRISPR-Cas systems with the Cas9 phylogeny corroborates horizontal transfer of the CRISPR-Cas loci. The reported collection of dual-RNA:Cas9 with associated PAMs expands the possibilities for multiplex genome editing and could provide means to improve the specificity of the RNA-programmable Cas9 tool.