Comparative genomics of the lactic acid bacteria

Lactic acid-producing bacteria are associated with various plant and animal niches and play a key role in the production of fermented foods and beverages. We report nine genome sequences representing the phylogenetic and functional diversity of these bacteria. The small genomes of lactic acid bacteria encode a broad repertoire of transporters for efficient carbon and nitrogen acquisition from the nutritionally rich environments they inhabit and reflect a limited range of biosynthetic capabilities that indicate both prototrophic and auxotrophic strains. Phylogenetic analyses, comparison of gene content across the group, and reconstruction of ancestral gene sets indicate a combination of extensive gene loss and key gene acquisitions via horizontal gene transfer during the coevolution of lactic acid bacteria with their habitats.

Phosphodiesterase production in an aqueous two-phase system by Nicotiana tabacum 1507

Studies were conducted on the production of phosphodiesterases by Nicotiana tabacum 1507 cell suspension in an aqueous two-phase system formed by adding 4% polyethylene glycol (mol wt 20,000) and 7.5% dextran (mol wt 70,000) to the medium. The time course of growth, biosynthesis, secretion, and partitioning of phosphodiesterases was followed in comparison with N. tabacum 1507 cultivation as a free suspension. Partitioning of phosphodiesterases took place mainly in the bottom dextran phase, and a possibility was revealed for obtaining an enzyme preparation with high phosphodiesterase activity.

Influence of carbon dioxide clouds on early martian climate

Recent studies have shown that clouds made of carbon dioxide ice may have warmed the surface of early Mars by reflecting not only incoming solar radiation but upwelling IR radiation as well. However, these studies have not treated scattering self-consistently in the thermal IR. Our own calculations, which treat IR scattering properly, confirm these earlier calculations but show that CO2 clouds can also cool the surface, especially if they are low and optically thick. Estimating the actual effect of CO2 clouds on early martian climate will require three-dimensional models in which cloud location, height, and optical depth, as well as surface temperature and pressure, are determined self-consistently. Our calculations further confirm that CO2 clouds should extend the outer boundary of the habitable zone around a star but that there is still a finite limit beyond which above-freezing surface temperatures cannot be maintained by a CO2-H2O atmosphere. For our own Solar System, the absolute outer edge of the habitable zone is at approximately 2.4 AU.

In situ measurements of optical parameters in Lake Baikal with the help of a Neutrino telescope

We present results of an experiment performed in Lake Baikal at a depth of approximately 1 km. The photomultipliers of an underwater neutrino telescope under construction at this site were illuminated by a distant laser. The experiment not only provided a useful cross-check of the time calibration of the detector but also allowed us to determine inherent optical parameters of the water in a way that was complementary to standard methods. In 1997 we measured an absorption length of 22 m and an asymptotic attenuation length of 18 m. The effective scattering length was measured as 480 m. By use of (cos theta) = 0.95 (0.90) for the average scattering angle, this length corresponds to a geometric scattering length of 24 (48) m.

Evolution of RNA-binding specificity in T4 DNA polymerase

DNA polymerase of phage T4 (T4 gp43), an essential component of the T4 DNA replicase, is a multifunctional single-chained (898-amino acid) protein that catalyzes the highly accurate synthesis of DNA in phage replication. The enzyme functions both as a DNA-binding replication protein and as a sequence-specific RNA-binding autogenous translational repressor. We have utilized a phylogenetic approach to study the relationships between the two nucleic acid-binding functions of the protein. We found that autogenous translational control of gp43 biosynthesis has been conserved in phage RB69, a distant relative of T4, although we also found that the RB69 system differs from its T4 counterpart in two regards: (a) nucleotide sequence and predicted secondary structure of the RNA target (translational operator), and (b) RNA specificity of the protein. T4 gp43 is specific to the RNA operator sequence of the T4 genome whereas RB69 gp43 can bind and repress operator RNA from both phages equally well. In studies with T4-RB69 gp43 chimeras, we mapped T4 gp43 RNA-binding specificity to a protein segment that also harbors important determinants for DNA binding and the polymerase catalytic function. Our results suggest that RNA functions as a regulator of both the dosage and activity of this DNA replication enzyme.

Methods for permanent conservation of biological objects and anatomic preparations in synthetic resins

Two methods for preparing packets of synthetic resin for permanent preservation of biological objects and anatomical tissue have been developed. The first method is applied when adding corrosive preparations to epoxide resin. The corrosive preparation is soaked in a mixture of epoxide resin and hardener in a ratio, experimentally determined. The induration proceed at room temperature for 12 h. The second method has two options and is applied for the conservation of biological objects and anatomical preparations in polymethylmethacrylate by a successive immersing of the object in a system of dehydrating mixtures: 50%, 70%, 90% and 96% water solution of methanol and ethanol and in a mixture of acetone and ethanol (1:1) and in acetone or in methylene chloride. The object, thus prepared, is impregnated in vacuum with polymer of methylmethacrylate, benzoyl peroxide and stearic acid or in a composition containing: methylmethacrylate, benzoyl peroxide, dibutylphthalate and tertiary aromatic amine, in optimum correlations of the components, experimentally determined. The induration proceed by heating in a water bath (37 + 3 degrees C) for 3 h and at 30 degrees C temperature in the course of 6-8 h in the first option or at room temperature for about 3 days in the second option. The advantages of the proposed methods are: the use of cheap and available materials for the production of a simplified technological scheme of strongly transparent packages, preserved over a long period; preserving the sizes, the form and natural colour of the objects and preparations as well as a possibility for selective tinting of the separate tissues and systems in the preserved biological objects and anatomical preparations; a possibility for stereomicroscopic observation of the objects and preparations preserved.