The lysogeny of Vibrio parahaemolyticus of serovar O4:K12]

Lysogeny has been first established in strains of parahemolytic vibrios of serovar O4:K12. Moderate phages belonged to morphological group IV by home A. S. Tikhonenko's classification and were presented by one serological type. No correlation has been revealed between sensitivity to moderate phages of parahemolytic vibrios and specificity of "O"- or "K"-serotypes.     

Energetic aspects of CO oxidation in desulfovibrio desulfuricans

In cell suspension of Desulfovibrio desulfuricans B-1388, oxidation of CO as the only energy source is associated with reduction of SO42-. After a 2-h incubation of cells in 8% CO, 81% of the gas is converted. Oxidation of 1 mole CO results in formation of 0.23 mole H2S. Intracellular ATP content increases from 2.5 (control) to 8.3 nmoles/mg (during CO conversion). Dinitrophenol inhibits sulfate reduction and CO oxidation. CO dehydrogenase was detected in cytoplasmic and membrane cell fractions (59 and 34%, respectively).     

Respiratory chain supercomplexes in the plant mitochondrial membrane

The intricate, heavily folded inner membrane of mitochondria houses the respiratory chain complexes. These complexes, together with the ATP synthase complex, are responsible for energy production, which is stored as ATP. The structure of the individual membrane-bound protein components has been well characterized. In particular, the use of Blue-native polyacrylamide gel electrophoresis has been instrumental in recent years in providing evidence that these components are organized into supercomplexes. Single particle electron microscopy studies have enabled a structural characterization of some of the mitochondrial supercomplexes. This has provided the opportunity to define a functional role for these supercomplexes for the first time, in particular for the dimeric ATP synthase complex, which appears to be responsible for the folding of the inner mitochondrial membrane.     

Feedback equilibrium control during human standing

Equilibrium maintenance during standing in humans was investigated with a 3-joint (ankle, knee and hip) sagittal model of body movement. The experimental paradigm consisted of sudden perturbations of humans in quiet stance by backward displacements of the support platform. Data analysis was performed using eigenvectors of motion equation. The results supported three conclusions. First, independent feedback control of movements along eigenvectors (eigenmovements) can adequately describe human postural responses to stance perturbations. This conclusion is consistent with previous observations (Alexandrov et al., 2001b) that these same eigenmovements are also independently controlled in a feed-forward manner during voluntary upper-trunk bending. Second, independent feedback control of each eigenmovement is sufficient to provide its stability. Third, the feedback loop in each eigenmovement can be modeled as a linear visco-elastic spring with delay. Visco-elastic parameters and time-delay values result from the combined contribution of passive visco-elastic mechanisms and sensory systems of different modalities     

Structure of dimeric ATP synthase from mitochondria: an angular association of monomers induces the strong curvature of the inner membrane

Respiration in all cells depends upon synthesis of ATP by the ATP synthase complex, a rotary motor enzyme. The structure of the catalytic moiety of ATP synthase, the so-called F(1) headpiece, is well established. F(1) is connected to the membrane-bound and ion translocating F(0) subcomplex by a central stalk. A peripheral stalk, or stator, prevents futile rotation of the headpiece during catalysis. Although the enzyme functions as a monomer, several lines of evidence have recently suggested that monomeric ATP synthase complexes might interact to form a dimeric supercomplex in mitochondria. However, due to its fragility, the structure of ATP synthase dimers has so far not been precisely defined for any organism. Here we report the purification of a stable dimeric ATP synthase supercomplex, using mitochondria of the alga Polytomella. Structural analysis by electron microscopy and single particle analysis revealed that dimer formation is based on specific interaction of the F(0) parts, not the F(1) headpieces which are not at all in close proximity. Remarkably, the angle between the two F(0) part is about 70 degrees, which induces a strong local bending of the membrane. Hence, the function of ATP synthase dimerisation is to control the unique architecture of the mitochondrial inner membrane.     

Structural organization and distribution of symbiotic bacteria Wolbachia in early embryos and ovaries of Drosophila melanogaster and D. simulans

Electron microscopic and morphometric analyses of Wolbachia distribution in early embryos of Drosophila flies have demonstrated that the number of bacteria in the embryo remains constant from fertilization to blastoderm, and that afterwards the symbionts could be observed only in the polar cells. Each bacterium has a three-layer envelope, makes contacts with microtubules and moves through the cytoplasm following the actively dividing nuclei. It has been found for the first time that Wolbachia could produce secretory vacuoles in the cytoplasm of early embryos. The relative volume of Wolbachia was five times as much in the embryos of Drosophila simulans as in those of D. melanogaster (Canton S), while the survival rate of D. simulans was half as much as that of D. melanogaster. It was shown that Wolbachia could form spore-like structures in D. simulans embryos. Ultrastructural investigations of Drosophila ovaries suggest that the bacteria may be present in all ovariol cells, including the oocyte, within whose cytoplasm they are delivered to the host. The highest number of symbionts was observed in germarium cells. In ovariol cells, the bacteria gradually decrease in number as oogenesis progresses. It has been determined for the first time that the symbionts are located closely to membranes of rough endoplasmatic reticulum in follicular and nurse cells of D. melanogaster. The data obtained suggest that Wolbachia may be involved in the regulation of oocyte maturation.     

Enzymatic control of homologous recombination and hyperrecombination in Escherichia coli

The RecA protein is a central homologous recombination enzyme in the bacterial cell. Forming a right-handed filament on ssDNA, RecA provides for a homology search between two DNA molecules and homologous strand exchange. RecA protects the cell from ionizing radiation and UV light and is capable of completing recombination during normal cell growth. Several mutant and natural RecA forms have a higher recombination potential in vitro and in vivo as compared with the wild-type Escherichia coli RecA, causing hyperrecombination. Recombinational hyperactivity of RecA depends to a great extent on the filamentation dynamics and DNA transferase properties, which may depend not only on specific amino acid substitutions in RecA, but also by defects in cell enzymatic machinery, including RecO, RecR, RecF, RecX, DinI, SSB, and PsiB. The functions of these proteins are currently known at the molecular level, while their roles in hyperrecombination are still incompletely understood. An increase in recombination in vivo is not always advantageous for the cell and is therefore limited by various mechanisms. In addition to the limitations imposed by cell enzymatic machinery, genomic rearrangements aimed at inhibiting the expression of hyperactive RecA are fixed through cell generations via selection against hyperrecombination. The mechanisms regulating hyperactive RecA forms in several model systems are considered.     

Carbonic anhydrase subunits form a matrix-exposed domain attached to the membrane arm of mitochondrial complex I in plants

Complex I of Arabidopsis includes five structurally related subunits representing gamma-type carbonic anhydrases termed CA1, CA2, CA3, CAL1, and CAL2. The position of these subunits within complex I was investigated. Direct analysis of isolated subcomplexes of complex I by liquid chromatography linked to tandem mass spectrometry allowed the assignment of the CA subunits to the membrane arm of complex I. Carbonate extraction experiments revealed that CA2 is an integral membrane protein that is protected upon protease treatment of isolated mitoplasts, indicating a location on the matrix-exposed side of the complex. A structural characterization by single particle electron microscopy of complex I from the green alga Polytomella and a previous analysis from Arabidopsis indicate a plant-specific spherical extra-domain of about 60 A in diameter, which is attached to the central part of the membrane arm of complex I on its matrix face. This spherical domain is proposed to contain a heterotrimer of three CA subunits, which are anchored with their C termini to the hydrophobic arm of complex I. Functional implications of the complex I-integrated CA subunits are discussed.