Predicted bacteriorhodopsin from Exiguobacterium sibiricum is a functional proton pump

The predicted Exigobacterium sibiricum bacterirhodopsin gene was amplified from an ancient Siberian permafrost sample. The protein bacteriorhodopsin from Exiguobacterium sibiricum (ESR) encoded by this gene was expressed in Escherichia coli membrane. ESR bound all-trans-retinal and displayed an absorbance maximum at 534nm without dark adaptation. The ESR photocycle is characterized by fast formation of an M intermediate and the presence of a significant amount of an O intermediate. Proteoliposomes with ESR incorporated transport protons in an outward direction leading to medium acidification. Proton uptake at the cytoplasmic surface of these organelles precedes proton release and coincides with M decay/O rise of the ESR.

Microbial populations in Antarctic permafrost: biodiversity, state, age, and implication for astrobiology

Antarctic permafrost soils have not received as much geocryological and biological study as has been devoted to the ice sheet, though the permafrost is more stable and older and inhabited by more microbes. This makes these soils potentially more informative and a more significant microbial repository than ice sheets. Due to the stability of the subsurface physicochemical regime, Antarctic permafrost is not an extreme environment but a balanced natural one. Up to 10(4) viable cells/g, whose age presumably corresponds to the longevity of the permanently frozen state of the sediments, have been isolated from Antarctic permafrost. Along with the microbes, metabolic by-products are preserved. This presumed natural cryopreservation makes it possible to observe what may be the oldest microbial communities on Earth. Here, we describe the Antarctic permafrost habitat and biodiversity and provide a model for martian ecosystems.

[Spectral properties of the green alga Trebouxia--a phycobiont of cryptoendolithic lichens in the high-latitude polar regions of Antarctica]

An algologically pure culture of the green alga Trebouxia, a phycobiont of cryptoendolithic lichens, was isolated from the sandstone samples collected in the high-altitude polar regions of Antarctica. The absorption and the second-derivative absorption spectra of the acetone extract of the Antarctic phycobiont cells were studied in comparison with those of the Trebouxia phycobiont isolated recently from the Parmeliaceae lichen in the Mid-European climatic zone. The cells of the Antarctic phycobiont were characterized by a lower content of chlorophyll a and a higher ratio of chlorophyll b and carotenoids to chlorophyll a as compared to the Mid-European phycobiont. Furthermore, the carotenoids of the Antarctic phycobiont were more diverse. The low-temperature fluorescence spectra of the Antarctic phycobiont were characterized by an increased intensity of the short-wavelength fluorescence peak of chlorophyll a and a diminished intensity of fluorescence in the long-wavelength spectral region.

[The absorption and fluorescence spectra of the cyanobacterial phycobilins of cryptoendolithic lichens in the high-polar region of Antarctica]

The algologically pure cultures of the green-brown cyanobacterium Chroococcidiopsis sp. and three cyanobacteria of the genus Gloeocapsa, the blue-green Gloeocapsa sp.1, the brown Gloeocapsa sp.2, and the red-orange Gloeocapsa sp.3, were isolated from sandstones and rock fissures in the high-polar regions of Antarctica. These cyanobacteria are the most widespread phycobionts of cryptoendolithic lichens in these regions. The comparative analysis of the absorption and the second-derivative absorption spectra of the cyanobacteria revealed considerable differences in the content of chlorophyll a and in the content and composition of carotenoids and phycobiliproteins. In addition to phycocyanin, allophycocyanin, and allophycocyanin B, which were present in all of the cyanobacteria studied, Gloeocapsa sp.2 also contained phycoerythrocyanin and Gloeocapsa sp.3 phycoerythrocyanin and C-phycoerythrin (the latter pigment is typical of nitrogen-fixing cyanobacteria). The fluorescence spectra of Gloeocapsa sp.2 and Gloeocapsa sp.3 considerably differed from the fluorescence spectra of the other cyanobacteria as well. The data obtained suggest that various zones of the lichens may be dominated either by photoheterotrophic or photoautotrophic cyanobacterial phycobionts, which differ in the content and composition of photosynthetic pigments.

[Myasthenia onset in elderly patients]

Possibility of myasthenia debut at old age is shown. 5 cases of 73-87 year-olds with the diagnosis-generalized form of myasthenia are reported. Peculiarities of clinical manifestations in this age group are described. Polymorbidity in the individuals of old age is noted. It is recommended to include vasoactive preparations in the scheme of therapy.

Long-term preservation of microbial ecosystems in permafrost

It has been established that significant numbers (up to 10 million cells per gram of sample) of living microorganisms of various ecological and morphological groups have been preserved under permafrost conditions, at temperatures ranging from -9 to -13 degrees C and depths of up to 100 m, for thousands and sometimes millions of years. Preserved since the formation of permafrost in sand-clay sediments of the Pliocene-Quaternary period and in paleosols and peats buried among them, these cells art the only living organisms that have survived for a geologically significant period of time. The complexity of the microbial community preserved varies with the age of the permafrost. Eukaryotes are found only in Holocene sediments; while prokaryotes are found to greater ages, i.e., Pliocene and Pleistocene. The diversity of microorganisms decreases with increasing age of sediments, and as a result cocci and corynebacteria are predominant. Enzyme activity (catalase and hydrolytic enzymes) and photosynthetic pigments (chlorophyll and pheophytin have also been detected in permafrost sediments. These results permit us to outline some approaches to the search for traces of life in the permafrost of Martian sediments by borehole core sampling. It is in the deep horizons (and not on the planet surface), isolated by permafrost from the external conditions, that results similar to those obtained on Earth can be expected.

[Diagnosis of hemorrhages in the brain with rupturing of blood into the ventricular system]

Clinical observations of 424 patients with intracerebral hemorrhages (314 with parenchymatous-ventricular and 110 with parenchymatous) verified at autopsy are reviewed. An analysis of the observations allowed the differentiation of the very acute, acute and subacute forms of parenchymatous-ventricular hemorrhages. The incidence of some "classical" symptoms of parenchymatous-ventricular bleeding was shown to change. The erroneous diagnosis of the ischemic nature of the stroke in 7.7% of observations was analyzed. The accuracy of computing differential diagnosis (using Bies's procedure in postulating the independence of the signs) was 75-79% depending on the type and localization of cerebral hemorrhages.

[Formation of free radicals at photoreduction of allophycocyanin B]

A photoinduced ESR signal is detected in the presence of 10(-2) M of dithionine in phycobilisomes and in fractions enriched in allophycocyanin B. The signal is characterized by the line width of 12G and g-factor of 2.004. It is demonstrated that the appearance of the free radicals is related to photoreduction of allophycocyanin B.

[Modelling of acute liver failure in rabbits]

A study was made of experimental acute liver failure induced in rabbits by administering D-galactosamine. Thirty-three rabbits were examined with the use of a set of the clinical, biochemical, electrophysiological and histomorphological methods. The results attest to the adequacy of the model studied to the tasks set up, since it provides for the reversibility of liver injuries, high reproducibility of the pathological process, death of the animal from the growing liver failure, large size of the experimental animal, the minimal risk for the laboratory staff and maximal approximation to the pathogenesis of viral hepatitis B in man. The evidence derived may be used for further development of the correcting pathogenetic therapy.

[A study of the interaction between the peripheral motor neurons of muscle antagonists by the H-reflex method under normal conditions and in spastic hemiparesis]

With the aid of the reflex method the authors studied the functional condition and interconnection of peripheral motoneurons of the muscles-antogonists in normal conditions and in spastic hemiparesis. In patients with spastic hemiparesis there was an increase in the inhibition latent period of the H-reflex following a conditioning stimula of the fibular nerve and a nonmonotonous restitution in the amplitude of the H-reflex during the periods of "late inhibition". These data permit to assume that in patients with pyramidal insufficiency the changes in the system of reciprocal inhibitive interaction of muscles-antagonists are fixed and are not subjected to a supraspinal control. This may determine the spastic character of the muscle tone in such patients.