Investigation of the catabolism of acetate and peptides in the new anaerobic thermophilic bacterium Caldithrix abyssi

This work is concerned with the metabolism of Caldithrix abyssi—an anaerobic, moderately thermophilic bacterium isolated from deep-sea hydrothermal vents of the Mid-Atlantic Ridge and representing a new, deeply deviated branch within the domain Bacteria. Cells of C. abyssi grown on acetate and nitrate, which was reduced to ammonium, possessed nitrate reductase activity and contained cytochromes of the b and c types. Utilization of acetate occurred as a result of the operation of the TCA and glyoxylate cycles. During growth of C. abyssi on yeast extract, fermentation with the formation of acetate, propionate, hydrogen, and CO₂ occurred. In extracts of cells grown on yeast extract, acetate was produced from pyruvate with the involvement of the following enzymes: pyruvate: ferredoxin oxidoreductase (2.6 μmol/(min mg protein)), phosphate acetyltransferase (0.46 μmol/(min mg protein)), and acetate kinase (0.3 μmol/(min mg protein)). The activity of fumarate reductase (0.14 μmol/(min mg protein)), malate dehydrogenase (0.17 μmol/(min mg protein)), and fumarate hydratase (1.2 μmol/(min mg protein)), as well as the presence of cytochrome b, points to the formation of propionate via the methyl-malonyl-CoA pathway. The activity of antioxidant enzymes (catalase and superoxide dismutase) was detected. Thus, enzymatic mechanisms have been elucidated that allow C. abyssi to switch from fermentation to anaerobic respiration and to exist in the gradient of redox conditions characteristic of deep-sea hydrothermal vents.     

Metabolism of the thermophilic bacterium Oceanithermus profundus

The metabolism of the novel facultatively anaerobic thermophilic bacterium Oceanithermus profundus was studied during growth on maltose, acetate, pyruvate, and hydrogen. The utilization of carbohydrates was shown to proceed via the glycolytic pathway. Under microaerobic growth conditions, the metabolism of O. profundus grown on maltose depended on the substrate concentration. At an initial maltose concentration of 1.4 mM, O. profundus carried out oxygen respiration, and in the presence of 3.5 mM maltose, facilitated fermentation occurred, with the formation of acetate and ethanol and limited involvement of oxygen. The use of pyruvate and acetate occurs via the TCA cycle. In cells grown on acetate, the activity of glyoxylate pathway enzymes was revealed. Depending on the energy-yielding process providing for growth (oxygen respiration or nitrate reduction), cells contained cytochromes a and c or b, respectively. The results obtained demonstrate the plasticity of the metabolism of O. profundus, which thus appears to be well-adjusted to the rapidly changing conditions in deep-sea hydrothermal vents.     

Recent developments in the thermophilic microbiology of deep-sea hydrothermal vents

The diversity of thermophilic prokaryotes inhabiting deep-sea hot vents was actively studied over the last two decades. The ever growing interest is reflected in the exponentially increasing number of novel thermophilic genera described. The goal of this paper is to survey the progress in this field made in the years 2000–2005. In this period, representatives of several new taxa of hyperthermophilic archaea were obtained from deep-sea environments. Two of these isolates had phenotypic features new for this group of organisms: the presence of an outer cell membrane (the genus Ignicoccus) and the ability to grow anaerobically with acetate and ferric iron (the genus Geoglobus). Also, our knowledge on the diversity of thermophilic bacteria from deep-sea thermal environments extended significantly. The new bacterial isolates represented diverse bacterial divisions: the phylum Aquificae, the subclass Epsilonproteobacteria, the order Thermotogales, the families Thermodesulfobacteriaceae, Deferribacteraceae, and Thermaceae, and a novel bacterial phylum represented by the genus Caldithrix. Most of these isolates are obligate or facultative lithotrophs, oxidizing molecular hydrogen in the course of different types of anaerobic respiration or microaerobic growth. The existence and significant ecological role of some of new bacterial thermophilic isolates was initially established by molecular methods.     

Divergence of the polytene chromosome banding sequences as a reflection of evolutionary rearrangements of the genome linear structure

Banding sequences of five chromosomal arms (A, C, D, E, and F), accounting for about 70% of the total genome size in 63 Chironomus species, were used as markers to analyze divergence patterns of the linear genome structure during the evolution. The number of chromosomal breakpoints between the pairs of banding sequences compared served as a measure of divergence. It was demonstrated that the greater the divergence between the species compared, the higher the number of chromosomal breakpoints and the smaller the size of the conserved chromosomal segments. A banding sequences comparison in sibling species demonstrated a lower number of chromosomal breakpoints; the breakpoint number was maximum in a comparison of the banding sequences in the subgenera Chironomus and Camptochironomus. The use of the number of chromosomal breakpoints as a genome divergence measure provided establishment of phylogenetic relationships between 63 Chironomus species and discrimination of sibling species groups and cytocomplexes on a phylogenetic tree.Translated from Genetika, Vol. 41, No. 2, 2005, pp. 187–195.Original Russian Text Copyright © 2005 by Gunderina, Kiknadze, Istomina, Gusev, Miroshnichenko.     

Spectral characteristics of electrical activity of the respiratory center in brain processes in fetus and newborn rats in vitro

Power spectral analysis of inspiratory discharges of C3-C5 ventral roots in brainstem-spinal cord preparation from foetal (18 and 20 gestation days) and newborn (0-1 and 2-3 postnatal days) rats was performed. The respiratory centre perinatal development manifests itself by decreasing of respiratory rhythm variability and increasing of inspiratory burst duration. In foetal inspiratory bursts, low-frequency oscillations (1-10 Hz) dominate. In early postnatal stage, the relative power of low-frequency oscillations begin to decrease, and medium frequency oscillations (10-50 Hz) start to dominate over the inspiratory discharge. The data obtained suggests, that perinatal maturation of respiratory centre is characterised by stabilisation of the respiratory rhythm generation and developmental alteration of inspiratory activity's spectral and temporary parameters.     

Dynamics of accelerated ions in coronal loops and model of a gamma-ray source

The dynamics of ions accelerated to energies of 10–100 MeV/nucleon in an electric field of ～0.01–0.1 V/cm, which has a component directed along the magnetic field of solar coronal loops with a characteristic size of ～100000 km, is considered. The motion of fast ions trapped in a current-carrying magnetic loop that has a magnetic mirror at its base (the mirror trap model) is analyzed. The applicability of the obtained theoretical results to interpret gamma-ray bursts that, according to the data of the RHESSI space observatory, occurred on July 23, 2002 and October 28, 2003, is discussed. In those two bursts, a single and a pair gamma source displaced relative to the hard X-ray sources were localized in the 2.223-MeV neutron-capture line. On the basis of complex analysis of multi-wavelength (X-ray, gamma-ray, and optical) observations and the data on fast solar protons, a new topological model of the source of accelerated particles (of the mirror trap type) and a new scenario of the event that occurred on July 23, 2002 are proposed. Evidence of the possibility of particle acceleration by the electric field in coronal mass-ejection loops during large solar flares is obtained. The simulation results indicate that the gamma-ray source in the excitation lines (4.1–6.7 MeV) should coincide with the region where the accelerated ions interact with the background plasma of the solar atmosphere above the spot of the flare active region.     

Investigation of structure and antigenic capacities of Thermococcales cell envelopes and reclassification of "Caldococcus litoralis" Z-1301 as Thermococcus litoralis Z-1301

Fourteen strains of hyperthermophilic organotrophic anaerobic marine Archaea were isolated from shallow water and deep-sea hot vents, and four of them were characterized. These isolates, eight previously published strains, and six type strains of species of the order Thermococcales were selected for the study of cell wall components by means of thin sectioning or freeze-etching electron microscopy. The cell envelopes of most isolates were shown to consist of regularly arrayed surface protein layers, either single or double, with hexagonal lattice (p6) symmetry, as the exclusive constituents outside the cytoplasmic membrane. The S-layers studied differed in center-to-center spacing and molecular mass of the constituent protein subunits. Polyclonal antisera raised against the cells of 10 species were found to be species-specific and allowed 12 new isolates from shallow water hot vents to be identified as representatives of the species Thermococcus litoralis, Thermococcus stetteri, Thermococcus chitonophagus, and Thermococcus pacificus. Of the 7 deep-sea isolates, only 1 was identified as a T. litoralis strain. Thus, hyperthermophilic marine organotrophic isolates obtained from deep-sea hot vents showed greater diversity with regard to their S-layer proteins than shallow water isolates.