Mikhail A. Grachev

Abrupt increase in precipitation and weathering of soils in East Siberia coincident with the end of the last glaciation (15 cal kyr BP)

Abstract An abrupt increase in the temperature in Greenland in the wake of the initiation of the Bolling–Allerod warm phase at ca. 15 cal kyr BP was followed after a few decades by a dramatic increase in the concentration of methane in the atmosphere of the Earth resulting from an increase in humidity in the tropics [J.P. Severinghaus, E.J. Brook, Science 286 (1999) 930–934]. Analysis of a sediment core from Lake Baikal (East Siberia), spanning the end of the last glacial period and the Holocene, revealed an abrupt, stepwise, 1.3–3.4-fold decrease in the concentration of several ‘soluble’ elements such as Na, K, Mg, Ca and Si in hot nitric acid extracts of small intervals (3 cm). This chemical change appears to have occurred over the same time span, based on similarities in the profiles of silica and diatoms found in other 14 C-dated cores. This suggests that the calcium-rich ‘mammoth steppe’ landscape [R.D. Guthrie, Quat. Sci. Rev. 20 (2001) 549–573] of Siberia created during the last glaciation underwent a dramatic transformation at the end of this period (at the beginning of the Bolling–Allerod warm phase) due to an increase in precipitation within a time interval of less than 300 yr.

Silicon nanotechnologies of pigmented heterokonts

Many pigmented heterokonts are able to synthesize elements of their cell walls (the frustules) of dense biogenic silica. These include diatom algae, which occupy a significant place in the biosphere. The siliceous frustules of diatoms have species‐specific patterns of surface structures between 10 and a few hundred nanometers. The present review considers possible mechanisms of uptake of silicic acid from the aquatic environment, its transport across the plasmalemma, and intracellular transport and deposition of silica inside the specialized Silica Deposition Vesicle (SDV) where elements of the new frustule are formed. It is proposed that a complex of silicic acid with positively charged proteins silaffins and polypropylamines remains a homogeneous solution during the intracellular transport to SDV, where biogenic silica precipitates. The high density of the deposited biogenic silica may be due to removal of water from the SDV by aquaporins followed by syneresis—a process during which pore water is expelled from the network of the contracting gel. The pattern of aquaporins in the silicalemma, the membrane embracing the SDV, can determine the pattern of species‐specific siliceous nanostructures. BioEssays 30:328–337, 2008.

Oil in the lake of world heritage

Lake Baikal is the oldest and deepest lake in the world. It contains approximately 20% (23 · 10 3 km 3 ) of the world’s surface reserves. Since the community of diverse endemic organisms of the lake has not suffered from human impact at its recent stage of development [1], it is included into the UNESCO world heritage list. Unique features of Lake Baikal include natural oil seeps in its shelf zone, which have been known since the 18th century [2]. At oil shows in the middle and south sections of Lake Baikal, oil occurs as bitumen in shore cliffs or rises from the lake bottom as floating spherules of viscous hydrocarbons that make up spills (up to 1.5 m across) in an area of approximately 1 km 2 in summer. In winter, the floating oil is accumulated under ice as bituminous films and inclusions in narrow fissures. The oil composition corresponds to the biodegraded type. Its origin and age were debatable until recently [3]. In 2005, a new natural oil occurrence was discovered in deep-water settings of Lake Baikal that differs from the previously known ones. The discovery poses a problem concerning the role of natural oil occurrences in the ecosystem of the unique basin and its petroleum potential. The new oil occurrence was discovered in Middle Baikal (Cape Gorevoi Utes) owing to satellite observations of a dark spot (~1km across) on the lake surface in the spring of 2003. Observations of 2004 and 2005 showed that such a spot appears in this area every spring. In July 2005, numerous oil spots (up to 1 m in diameter) were recorded on the lake surface in an area of approximately 1 km 2 . Echo sounding revealed an underwater acoustic anomaly in the form of a gas flare ~500 m high. The oil sampled from the lake surface was studied using the gas chromatography/mass spectrometry method (Fig. 1). The samples contained n- alkanes, acyclic isoprenides, and polycyclic aromatic hydrocarbons. Based on the database including characteristics of molecular indicators for 76 genetically different oil fields [4], the ratios of molecular indicators (pristane/phytane 6.7; dibenzothiophene/phenathrene <0/1), and the low sulfur content (<0.08%), we concluded that the samples correspond to oils formed in sediments of deep freshwater basins during the Oligocene‐Early Miocene. This age estimate obtained for the Baikal oil based on molecular indicators is consistent with one hypothesis, according to which the Baikal oil is not older than the Cretaceous and it originates from organic matter buried in a freshwater basin [5]. The bottom sediments were sampled at the center of the gas flare and at its periphery (at a distance of 200 m). The core taken in the central part (0‐40 cm) is composed of dark gray reduced massive clayey‐silty sediment. The Holocene diatomaceous ooze layer typical of Baikal is missing at the surface. The sediment was mixed with oil and saturated with gas. The oil content exceeds 10% of the dry sediment. The second core demonstrates distinct bedding along its entire length. According to biostratigraphic data ( Cyclotella minuta, Aulacoseira baicalensis , and others), the sediment represents the Holocene diatomaceous ooze. The surface sediment (upper 4 cm with a brown color) is oxidized, while the remainder of the core is reduced (gray in color). The interval of 10‐40 cm hosts lenses and interbeds of silt and fine- to medium-grained sand with small brown oil droplets (up to 3 mm across) fringed by small gas bubbles. The oil content in this core interval is approximately 1% of dry sediment. The difference between two sampled cores in terms of oil-and-gas occurrence and lithology is probably explained by different intensities of their influx. The central part of the gas flare is characterized by permanent fluxes of gas, oil, and groundwater, which provide

A new subfamily LIP of the major intrinsic proteins

BackgroundProteins of the major intrinsic protein (MIP) family, or aquaporins, have been detected in almost all organisms. These proteins are important in cells and organisms because they allow for passive transmembrane transport of water and other small, uncharged polar molecules.ResultsWe compared the predicted amino acid sequences of 20 MIPs from several algae species of the phylum Heterokontophyta (Kingdom Chromista) with the sequences of MIPs from other organisms. Multiple sequence alignments revealed motifs that were homologous to functionally important NPA motifs and the so-called ar/R-selective filter of glyceroporins and aquaporins. The MIP sequences of the studied chromists fell into several clusters that belonged to different groups of MIPs from a wide variety of organisms from different Kingdoms. Two of these proteins belong to Plasma membrane intrinsic proteins (PIPs), four of them belong to GlpF-like intrinsic proteins (GIPs), and one of them belongs to a specific MIPE subfamily from green algae. Three proteins belong to the unclassified MIPs, two of which are of bacterial origin. Eight of the studied MIPs contain an NPM-motif in place of the second conserved NPA-motif typical of the majority of MIPs. The MIPs of heterokonts within all detected clusters can differ from other MIPs in the same cluster regarding the structure of the ar/R-selective filter and other generally conserved motifs.ConclusionsWe proposed placing nine MIPs from heterokonts into a new group, which we have named the LIPs (large intrinsic proteins). The possible substrate specificities of the studied MIPs are discussed.

The Origin and Genetic Relationships of the Baikal Seal, Phoca sibirica, by Restriction Analysis of Mitochondrial DNA

Abstract The origin and genetic relationships of the Baikal seal, Phoca sibirica, were studied by restriction fragment length polymorphism analysis of mitochondrial DNA (mtDNA). Using 17 different six-base recognition restriction endonucleases, we examined 98 Baikal seals, and two other related species, the ringed seal, P. hispida, (n=87), and the Caspian seal, P. caspica, (n=94). Analysis revealed the existence of 87 mtDNA haplotypes in the total of 279 specimens. The haplotypes of each species were divided into different clusters on a dendrogram obtained by UPGMA based on haplotype frequency and mtDNA base substitution. No common haplotypes were found among the species examined. The Baikal seal is much more closely related to the ringed seal than the Caspian seal. The amount of divergence suggested that an ancestor of the Baikal seal came down to the lake approximately 0.4 million years ago as was previously indicated by paleontological studies. The seals examined here showed lower variabilities.

Determination of Elemental Sulfur in Bottom Sediments Using High-Performance Liquid Chromatography

A procedure for determining elemental sulfur in bottom sediments by microcolumn reversed-phase high-performance liquid chromatography was developed. The analytical range was 4–1200 μg/g (in terms of the dry weight of a sediment). The procedure is based on the direct injection of acetone extracts of sediments into a chromatographic column. The detection limit was 5 ng/peak (signal-to-noise ratio of 3 : 1); the relative standard deviation was 5.6%. Errors introduced at particular stages of analysis and the total errors were evaluated for different sampling techniques. The results of determining elemental sulfur in the core samples of bottom sediments from Lake Baikal are presented.

Do Oil-Degrading Rhodococci Contribute to the Genesis of Deep-Water Bitumen Mounds in Lake Baikal?

This study sought to understand the origin and fate of one of the bitumen mounds found on the bottom of Lake Baikal. These mounds are located at a depth of 900 m beneath oil spots detected on the surface of Lake Baikal (53° 18′24″, 108° 23′20″). The two mounds were sampled with a manipulator from a “MIR” deep-water manned submersible. Mature mound No. 8 was subjected to chemical and microbiological studies. Mound No. 3 was subjected only to chemical studies; we failed to perform microbiological analyses of this mound for logistic reasons. Oil spots collected from the water surface, samples of mound No. 3 and No. 8, were subjected to GC/MS analysis. The water contained aliphatic hydrocarbons with chains between C8 and C23, with the most abundant chain length being C18. Mound No. 3 with the most abundant chain length being C18 actively released oil droplets into the water. It contained 770 mg/g of C13-C32 n-alkanes, with a maximum at C23 (160 mg/g). Mound No. 8 was inactive and contained 148 mg/g of aliphatic C22-C34 n-alkanes, with a maximum at C25. Mound No. 8 also consisted of 3% inorganic matter, 48% unresolved complex mixture (UCM) and less than 1% other compounds (polyaromatic hydrocarbons, isoprenoids, carotenoids, and hopanes). The core of this sample used as inoculate, yielded Rhodococci when cultivated on oil as the only source of carbon. Cultivation of the sample on agar-containing Raymond inorganic medium with crude West Siberian oil as the only source of carbon revealed colonies of these bacteria, which all appeared identical. PCR was performed with DNA isolated from 5 colonies, using primers for 16S rRNA genes. Comparison of the sequences of the 5 PCR products over a length of 714 bp revealed that they were almost identical. Phylogenetic analysis of these homologous sequences showed that they were similar to the corresponding sequences of the genus Rhodococcus. Substrate demands, the morphology of the colonies, and SEM and TEM data confirmed that the isolates obtained could indeed be Rhodococci. All of the isolates could grow in bulk cultures with inorganic medium supplemented with crude oil. Moreover, all of the isolates degraded aliphatic hydrocarbons with lengths between C11 and C29. C23-C29 hydrocarbons were degraded completely. The isolates could grow at 4–37°C. The most unexpected finding was that of the many microorganisms capable of consuming oil, only Rhodococci exhibited this ability in the inactive bitumen mound. The possible mechanisms of how crude oil is transformed into bitumen mounds and mature bitumen are discussed.