High pressure (1 to 10 kbars, i.e. 100-1000 MPa) affects biological constituents and systems. Several physicochemical properties of water are modified, such as the density, the ionic dissociation (...

Review : High-pressure, microbial inactivation and food preservation:

Ultrahigh Pressure (UHP) offers interesting possibilities for food processing ranging from extraction of plant compounds, restructuring foods and rapid formation of small ice crystals. Pressures between 300 and 600 MPa can inactivate yeasts, moulds and most vegetative bacteria including most infectious food-borne pathogens. Thus, pressure is a potential alternative to heat pasteurization as pressure leaves small molecules such as many flavour compounds and vitamins intact. In general, bacterial spores can only be killed by very high pressures (>1000 MPa). Bacterial spores, however, can often be stimulated to germinate by pressures of 50–300 MPa. Germinated spores can then be killed by relatively mild heat treatments or mild pressure treatments. However, in most cases a small fraction of spores can survive this treatment. Consequently, there is still no practical application of UHP treatment as a sterilization process, but it is still an interesting area for further exploration.

Recent advances in the microbiology of high pressure processing

Towards a phylogeny of gastropod molluscs: an analysis using morphological characters

Preface Principles of Photosynthesis Mechanisms of Photosynthetic Oxygen Evolution and the Fundamental Hypotheses of Photosynthesis (Yuzeir Zeinalov) Thermoluminescence as a Tool in the study of Photosynthesis (Anil S. Bhagwat and Swapan K. Bhattachrjee) Biochemistry of Photosynthesis Chlorophyll Biosynthesis - A review (Benoit Schoefs and Martine Bertrand) Chloroplast Biogenesis 90, Probing the Relationship between Chlorophyll Biosynthetic Routes and the Topography of Chloroplast Biogenesis by Resonance Excitation Energy Transfer Determinations (Constantin A. Rebeiz, Karen J. Kopetz, and Vladimir L. Kolossov, USA) Protochlorophyllide Photoreduction - A review (Martine Bertrand and Benoit Schoefs) Formation and Demolition of Chloroplast during Leaf Ontogeny (Basanti Biswal) Role of Phosphorus in Photosynthetic Carbon Metabolism (Anna M. Rychter and I.M. Rao) Inhibition on Inactivation of Higher Plant Chloroplast Electron Transport (Rita Barr and Frederick L. Crane) Molecular Aspects of Photosynthesis: Photosystems, Photosynthetic Enzymes and Genes Photosystem I Structures and Functions (Teisuo Hiyama) Covalent Modification of Photosystem II Reaction-Center Polypeptides (Julian P. Whitelegge) Reactive Oxygen Species as Signaling Molecules Controlling Stress Adaptation in Plants (Tsanko Gechev, Ilya Gadjev, Stefan Dukiandjiev, and Ivan Minkov) Plastid Morphogenesis (Jan Hudak, Eliska Galova, and Lenka Zemanova) Plastid Proteases (Dennis E. Buetow) Supramolecular Organization of Water-Soluble Photosynthetic Enzymes Along the Thylakoid Membranes in Chloroplasts (Jayashree K. Sainis and Michael Melzer) Cytochrome C6 Genes in Cyanobacteria and Higher Plants (Kwok Ki Ho) Atmospheric and Environmental Factors Affecting Photosynthesis External and Internal Factors Responsible for Midday Depression of Photosynthesis (Da-Quan Xu and Yun-Kang Shen) Root Oxygen Depravation and the Reduction of Leaf Stomatal Aperture and Gas Exchange Effects on Photosynthesis (R.E. Sojka, H.D. Scott, and D.M. Oosterhuis) Rising Atmospheric CO2 and C4 Photosynthesis (Joseph C.V. Vu) Influence of High Light Intensity on Photosynthesis: Photoinhibition and Energy Dissipation (Robert Carpentier) Development of Functional Thylakoid Membranes: Regulation by Light and Hormones (Peter Nyitrai) Photosynthetic Pathways in Various Crop Plants Photosynthetic Carbon Assimilation of C3, C4 and CAM Pathways (Anil S. Bhagwat) Photosynthesis in Non-Typical C4 Species (Maria Valeria Lara and Carlos Santiago Andreo) Photosynthesis in Lower and Monocellular Plants Regulation of Phycobilisome Biosynthesis and Degradation in Cyanobacteria (Johannes Geiselmann, Jean Houmard, and Benoit Schoefs) Photosynthesis in Higher Plants Short-Term and Long-Term Regulation of Photosynthesis During Leaf Development (Dan Stessman, Martin Spalding, and Steven Rodermel) Recent Advances in Chloroplast Development in Higher Plants (Ilia D. Denev, Galina T. Yahubian, and Ivan N. Minkov) Photosynthesis in Different Plant Parts Photosynthesis in Leaf, Stem, Flower, and Fruit (Abdul Wahid, and Ejaz Rasul) Photosynthesis and Plant/Crop Productivity and Photosynthetic Products Photosynthetic Plant Productivity (Lubomir Natr and David W. Lawlor) Photosynthates Formation and Partitioning in Crop Plants (Alberto A. Iglesias and F.E. Podesta) Photosynthesis and Plant Genetics Crop Radiation Use Efficiency - Avenue for Genetic Improvement (G.V. Subbarao, O. Ito, and W.L. Berry) Physiological Perspectives on Improving Crop Adaptation to Drought - Justification for a Systemic Compnent-Based Approach (G.V. Subbarao, O. Ito, R. Serraj, J.H. Crouch, S. Tobita, K. Okada, C.T. Hash, R. Ortiz, and W.L. Berry) Photosynthetic Activity Measurements and Analysis of Photosynthetic Pigments Whole-Plant CO2 Exchange as a Non-Invasive Tool for Measuring Growth (Evangelos D. Leonardos, and Bernard Grodzinski) Approaches to Measuring Plant Photosynthetic Activity (Elena Masarovicova and Katarina Kralova) Analysis of Photosynthetic Pigments: An Update (Martine Bertrand, Jose L. Garrido, and Benoit Schoefs) Photosynthesis and Its Relationship with other Plant Physiological Processes Photosynthesis, Respiration, and the Limits to Growth (Bruce N. Smith, Heidi A. Summers, Emily A. Keller, and Tonya Thygerson) Nitrogen Assimilation and Carbon Metabolism (Alberto A. Iglesias, Maria J. Estrella, and Fernando Pieckenstain) Leaf Senescence (Agnieszka Mostowska) Photosynthesis Under Environmental Stress Conditions Photosynthesis in Plants under Stressful Conditions (Rama Shanker Dubey) Photosynthetic Response of Green Plants to Environmental Stress: Inhibition of Photosynthesis and Adaptational Mechanisms (Basanti Biswal) Salt and Drought Stress Effects on Photosynthesis, Enzyme Cohesion and High Turn Over Metabolite Shuttling, Essential for Functioning of Pathways, Is Impaired by Changes in Cytosolic Water Potential (B, Huchzermeyer and H.W. Koyro) Photosynthetic Carbon Metabolism of Crops under Salt Stress (Bruria Heuer) Photosynthesis under Drought Stress (Habib-ur-Rahman Athar and Muhammad Ashraf) Role of Plant Growth Regulators in Stomatal Limitation to Photosynthesis During Water Stress (Jana Pospisilova and Ian C. Dodd) Adverse Effects of UV-B Light on the Structure and Function of the Photosynthetic Apparatus (Imre Vass, Andras Szilard, and Cosmin Sicora) Heavy Metal Toxicity Induced Alterations in Photosynthetic Metabolism in Plants (Shruti Mishra and R.S, Dubey) Effects of Heavy Metals on Chlorophyll-Protein Complexes in Higher Plants: Causes and Consequences (Eva Sarvari) Photosynthesis in the Past, Present, and Future The Origin and Evolution of C4 Photosynthesis (Bruce N. Smith)

Handbook of Photosynthesis

Cubic phases and isotropic structures formed by membrane lipids — possible biological relevance

The structural damage to and leakage of internal substances from Saccharomyces cerevisiae 0–39 cells induced by hydrostatic pressure were investigated. By scanning electron microscopy, yeast cells treated at room temperature with pressuresbellw 400 MPa for 10 min showed a slight alteration in outer shape. Transmission electron microscopy, however, showed that the inner structure of the cell began to be affected, especially the nuclear membrane, when treated with hydrostatic pressure around 100 MPa at room temperature for 10 min; at more than 400–600 MPa, further alterations appeared in the mitochondria and cytoplasm. Furthermore, when high pressure treatment was carried out at — 20° C, the inner structure of the cells was severely damaged even at 200 MPa, and almost all of the nuclear membrane disappeared, although the fluorescent nucleus in the cytoplasm was visible by 4,6-diamidino-2-phenylindole (DAPI) staining. The structural damage of pressure-treated cells was accompanied by the leakage of internal substances. The efflux of UV-absorbing substances including amino acid pools, peptides, and metal ions increased with increase in pressure up to 600 MPa. In particular, amounts of individual metal ion release varied with the magnitude of hydrostatic pressures over 300 MPa, which suggests that the ions can be removed from the yeast cells separately by hydrostatic pressure treatment.

Effects of hydrostatic pressure on the ultrastructure and leakage of internal substances in the yeast Saccharomyces cerevisiae

To clarify the involvement of actin in the formation of the yeast cell wall, reverting protoplasts of Schizosaccharomyces pombe were used as a simple model system. Actin of reverting protoplasts was labeled with rhodamine-conjugated phalloidin and observed by conventional fluorescence microscopy and laser scanning confocal microscopy. A close spatial as well as temporal relationship between actin and cell wall formation was observed in protoplast reversion. That is, the site of actin 'dots' in the reverting protoplasts coincided with the site of new wall formation and the timing of rearrangement of actin coincided with the initiation of cell wall formation and with the timing of cell wall expansion. Treatment of reverting protoplasts with cytochalasin D (CD) further clarified the close relationship between actin and cell wall organization. The effect of CD was dose dependent. A high dose of CD caused the absence of actin as well as the complete inhibition of cell wall formation. A low dose of CD caused weakly stained unlocalized actin, which induced grossly aberrant cell wall deposition as well as substantial changes in the morphology of the reverting protoplasts. These results demonstrated that actin is associated with initiation of cell wall formation, the proper deposition of cell wall materials, and maintaining the normal morphology of reverting protoplasts. Scanning electron microscopy revealed the presence of a fibrillar net structure on the surface of non-treated control reverting protoplasts. However, the absence of a fibrillar network on the surface of reverting protoplasts was observed in the presence of a high concentration of CD. Lack of localization of microfibrils as well as poor development of the fibrillar network were also observed in the presence of a low concentration of CD. Recovery experiments confirmed the close relationship between actin and cell wall formation.

Actin is associated with the formation of the cell wall in reverting protoplasts of the fission yeast Schizosaccharomyces pombe.

The ultrastructure of regenerating cell wall in Schizosaccharomyces pombe protoplasts was studied with a high resolution, low voltage scanning electron microscope (LVSEM). In contrast to the transmission electron microscopy, the LVSEM images give three-dimensional information on the cell wall regeneration in yeast protoplasts. We found that, after only a few minutes of incubation, the protoplasts began to show protuberances in a unipolar manner, and a fibrilar network was formed asymmetrically which covered the whole surface of the protoplasts after 5 hr. The network consisted of microfibrils about 8 to 10 nm wide, forming flat and wavy bundles of various widths and lengths, up to about 200 nm wide and 1 micron long, mainly made of yeast glucan. Free ends of microfibrils were seldom found. Interfibrillar spaces were progressively filled with granular particles and finally the complete cell wall was formed after 12 hr. The fibrillar network was destroyed by the digestion with beta (1----3)-glucanase. When protoplasts were regenerating in the presence of aculeacin A, the fibrillar networks were not formed, resulting in incomplete cell wall formation. These observations suggest that beta-glucan is the main component of the microfibrils and that it plays an important role in the formation of the cell wall in S. pombe.

Cell Wall Formation in Regenerating Protoplasts of Schizosaccharomyces pombe: Study by High Resolution, Low Voltage Scanning Electron Microscopy

High resolution scanning electron microscopy revealed that the basic unit of the paracrystalline network in squash prolamellar body is a tetrapodal structure, which has four short tubular arms meeting at one point with equal angle. Fractured faces of the prolamellar bodies displayed three lattice forms; hexagonal, square and zigzag (distorted hexagonal) lattices. Tilting observations of the ultrathin sections, together with scanning electron microscope observations, showed that the paracrystalline tubular network in the squash prolamellar body is of zincblende-type. A pentagonal configuration of the network was sometimes observed. Many prolamellar bodies were also very often observed, which displayed two or three different lattice forms in a single prolamellar body. It became evident from these observations that most, if not all, of the prolamellar bodies in the squash etioplasts are paracrystalline network of spinel-type twin which is composed of two or more domains of zincblende-type. We propose a three dimensional model of the squash prolamellar body in which five paracrystal domains of zincblende-type are assembled around a pentagonal column at the center and connected by boundary lattice layers of wurtzite-type.

Naoko Yamada

Papers

Effects of hydrostatic pressure on the ultrastructure and leakage of internal substances in the yeast Saccharomyces cerevisiae

Actin is associated with the formation of the cell wall in reverting protoplasts of the fission yeast Schizosaccharomyces pombe.

Cell Wall Formation in Regenerating Protoplasts of Schizosaccharomyces pombe: Study by High Resolution, Low Voltage Scanning Electron Microscopy

Three-dimensional structure of the prolamellar body in squash etioplasts

High Resolution, Low Voltage Scanning Electron Microscopy of Uncoated Yeast Cells Fixed by the Freeze-Substitution Method