Hibernation as a Stage of Ribosome Functioning.

In response to stress, eubacteria reduce the level of protein synthesis and either disassemble ribosomes into the 30S and 50S subunits or turn them into translationally inactive 70S and 100S complexes. This helps the cell to solve two principal tasks: (i) to reduce the cost of protein biosynthesis under unfavorable conditions, and (ii) to preserve functional ribosomes for rapid recovery of protein synthesis until favorable conditions are restored. All known genes for ribosome silencing factors and hibernation proteins are located in the operons associated with the response to starvation as one of the stress factors, which helps the cells to coordinate the slowdown of protein synthesis with the overall stress response. It is possible that hibernation systems work as regulators that coordinate the intensity of protein synthesis with the energy state of bacterial cell. Taking into account the limited amount of nutrients in natural conditions and constant pressure of other stress factors, bacterial ribosome should remain most of time in a complex with the silencing/hibernation proteins. Therefore, hibernation is an additional stage between the ribosome recycling and translation initiation, at which the ribosome is maintained in a "preserved" state in the form of separate subunits, non-translating 70S particles, or 100S dimers. The evolution of the ribosome hibernation has occurred within a very long period of time; ribosome hibernation is a conserved mechanism that is essential for maintaining the energy- and resource-consuming process of protein biosynthesis in organisms living in changing environment under stress conditions.

In vitro Reconstitution of the S. aureus 30S Ribosomal Subunit and RbfA Factor Complex for Structural Studies.

Ribosome-binding factor A (RbfA) from Staphylococcus aureus is a cold adaptation protein that is required for the growth of pathogenic cells at low temperatures (10-15°C). RbfA is involved in the processing of 16S rRNA, as well as in the assembly and stabilization of the small 30S ribosomal subunit. Structural studies of the 30S-RbfA complex will help to better understand their interaction, the mechanism of such complexes, and the fundamental process such as 30S subunit assembly that determines and controls the overall level of protein biosynthesis. This article describes protocols for preparation of RbfA and the small 30S ribosomal subunits and reconstitution and optimization of the 30S-RbfA complex to obtain samples suitable for cryo-electron microscopy studies.

[Elongation Factor P: New Mechanisms of Function and an Evolutionary Diversity of Translation Regulation].

The protein synthesis in cells occurs in ribosomes, with the involvement of protein translational factors. One of these translational factors is the elongation factor P (EF-P). EF-P is a three-domain protein that binds between the P and E sites of the ribosome, near the P-tRNA, the peptidyl transferase center, and E-site codon of the mRNA. The majority of studies showed that the EF-P helps the ribosome to synthesize stalling amino acid motifs, such as polyprolines. In the first part of this review, we inspect the general evolutionary variety of the EF-P in different organisms, the problems of the regulation provided by the EF-P, and its role in the sustainability of the protein balance in the cell in different physiological states. Although the functions of the EF-P have been well studied, there are still some problems that remain to be solved. The data from recent studies contradict the previous theories. Consequently, in the second part, we discuss the recent data that suggest the involvement of the EF-P in each translocation event, not only in those related to poly-proline synthesis. This activity contradicts some aspects of the known pathway of the removal of the E-tRNA during the translocation event. In addition, in the third part of this review, we tried to partly shift the interest from the antistalling activity of domain I of the EF-P to the action of domain III, the functions of which has not been closely studied. We expand on the idea about the involvement of domain III of the EF-P in preventing the frameshift and debate the EF-P's evolutionary history.

[Modeling of lactic acid fermentation of leguminous plant juices].

Lactic acid fermentation of leguminous plant juices was modeled to provide a comparative efficiency assessment of the previously selected strains of lactic acid bacteria as potential components of starter cultures. Juices of the legumes fodder galega, red clover, and alfalfa were subjected to lactic acid fermentation in 27 variants of experiment. Local strains (Lactobacillus sp. RS 2, Lactobacillus sp. RS 3, and Lactobacillus sp. RS 4) and the collection strain Lactobacillus plantarum BS 933 appeared the most efficient (with reference to the rate and degree of acidogenesis, ratio of lactic and acetic acids, and dynamics of microflora) in fermenting fodder galega juice; Lactobacillus sp. RS 1, Lactobacillus sp. RS 2, Lactobacillus sp. RS 3, Lactobacillus sp. RS 4, and L. plantarum BS 933 were the most efficient for red clover juice. Correction of alfalfa juice fermentation using the tested lactic acid bacterial strains appeared inefficient, which is explainable by its increased protein content and a low level of the acids produced during fermentation.

[Fermentation of a high-protein plant biomass by introduction of lactic acid bacteria].

Lactic acid bacteria displaying increased ability to produce lactic acid, medium proteolytic activity, and tolerance to osmotic stress were isolated under selective conditions from phyllosphere and rhizosphere of registered and raised cultivars of legumes. Lactic fermentation of poorly ensilable leguminous plants (red clover and Caucasian goat's rue) was performed by introduction of rifampin-resistant homofermenting representatives of the genus Lactobacillus (selected according to a set of technologically important characteristics). The results demonstrate that introduction of active local strains of lactobacteria, as well as the collection strain Lactobacillus plantarum BS 933, enhances activation of ensiling and increases the quality of fodder, as assessed according to the standard criteria (a decrease in pH of the medium, the ratio of lactic acid to fatty acid homologues, and the composition of silage microflora).

[Effect of natural and genetically modified rhizospheric Pseudomonas aureofaciens bacteria on accumulation of arsenic by plants]. / Vliianie prirodnykh i geneticheski modifitsirovannykh rizosfernykh bakterii Pseudomonas aureofaciens na nakoplenie mysh'iaka rasteniiami.

Gene constructions rendering bacteria resistant to arsenic and capable of dissolving phosphates and/or arsenates were created by cloning ars operon and the gene of citrate synthase from a chromosome of the strain Pseudomonas aeruginosa PAO1. Genetically modified variants of the strain Pseudomonas aureofaciens BS1393 have been constructed, which are resistant to high concentrations of arsenic and dissolve poorly soluble phosphates and/or arsenates. Recombinant strains P. aureofaciens BS1393(pUCP22::arsRBC) and P. aureofaciens BS1393(pUCP22::gltA) exerted positive effects on the survival of sorgo (Sorghum saccharatum L.) and its ability to accumulate arsenic.

[The production of phenazine antibiotics by the Pseudomonas aureofaciens strain with plasmid-controlled resistance to cobalt and nickel]. / Produktsiia fenazinovykh antibiotikov u shtamma Pseudomonas aureofaciens, soderzhashchego plazmidu rezistentnosti k kobal'tu i nikeliu.

Plasmid pBS501 responsible for the resistance of the wild-type Pseudomonas sp. BS501 (pBS501) to cobalt and nickel ions was conjugatively transferred to the rhizosphere Pseudomonas aureofaciens strain BS1393, which is able to synthesize phenazine antibiotics and to suppress a wide range of phytopathogenic microorganisms. The transconjugant P. aureofaciens BS1393 (pBS501) turned out to be resistant to cobalt and nickel with an MIC of 8 mM. When grown in a synthetic medium with 0.25 mM cobalt, the transconjugant accumulated 6 times more cobalt than the wild-type strain BS501 (pBS501) (1.2 and 0.2 microgram Co/mg protein). Electron microscopic studies showed that cobalt accumulates on the surface of transconjugant cells in the form of electron-opaque granules. In a culture medium with 2 mM cobalt or nickel, strain BS1393 produced phenazine-1-carboxylic acid in trace amounts. The transconjugant P. aureofaciens BS1393 (pBS501) produced this antibiotic in still smaller amounts. Unlike the parent strain BS1393, the transconjugant P. aureofaciens BS1393 (pBS501) was able to suppress in vitro the growth of the phytopathogenic fungus Gaeumannomyces graminis var. tritici 1818 in a medium containing 0.5 mM cobalt or nickel.