The effect of pressure on the bilayer phase transitions of two kinds of asymmetric phospholipids, phosphatidylcholines (PCs) with different saturated acyl chains in the sn-1 and sn-2 positions on the glycerol backbone and mixed-chain PCs with an unsaturated acyl chain in the sn-1 or sn-2 position, is described. The alignment of the sn-1 and sn-2 acyl chains at the therminal methyl ends and the mismatch of the effective chain length between the sn-1 and sn-2 acyl chains produce a significant influence on their bilayer properties. The correlation between molecular asymmetry of PC molecules and phase stabilities of the bilayer membranes is discussed.
Whale carcasses support unique biological assemblages in deep sea. The carcasses release reducing chemicals such as hydrogen sulfide and nourish chemosynthesis-based biological communities. Two “stepping-stone” hypotheses regarding whale-fall ecosystems have been proposed. One explains a dispersal pathway for hydrothermal vent/hydrocarbon seep faunae in the deep sea and another an evolutionary process of vent/seep specialists. Here we summarize the whale-fall ecosystems, especially in Japanese waters and our attempts to verify the hypotheses.
Fungi are one of the most important components in ecosystems and they occupy a wide variety of environments by virtue of their highly versatile physiology function. Recently, the presence of fungi in one of the extreme environments, deep-sea, has started to be recognized. In this article, recent scientific findings through the investigation of fungal diversity in deep-sea sediments collected from several deep-sea environments, including water depths of 10,000 m and methane cold-seep sites were described. PCR-mediated analysis revealed the presence of diverse highly novel fungal phylotypes, including new taxonomic groups placed in deep branches within the phylum of Chytridiomycota with Rozella spp. as the closest related organisms, which may provide key insights into the early evolution of fungi.
In this article, recompression induced resuscitation and atmospheric pressure acclimation of deep-sea multicellular organisms were investigated. Despite captured deep-sea organisms at depths between 910 m and 1,300 m sustain serious damage on decompression and exposure to high temperature of surface seawater, the organisms recovered by immediate re-compression until 5 MPa within 30 minutes after submersible bring back to mother ship. The re-pressurized deep-sea organisms can acclimatize at atmospheric pressure condition for a few months after slow decompression at a rate of −0.025 MPa/h. Furthermore, negative potential application induced antirust effect of pressure-stat aquarium system, which composed of stainless steel, was also described.
Deep-sea fish distributes to abyssal depths of several thousand meters, the pressures of which shallower-living fish cannot tolerate. Tolerance to abyssal pressures by deep-sea fish is likely to depend at least in part on adaptive modifications of proteins. However, structural modifications that allow proteins to function at high pressures have not been well understood. To elucidate the mechanisms of protein adaptation to high pressures, we cloned α-actin and myosin heavy chain cDNAs from skeletal muscles of two deep-sea fishes, Coryphaenoides yaquinae and C. armatus, and two non deep-sea fishes, C. acrolepis and C. cinereus. The comparison of the α-actins from deep-sea fishes with those of non deep-sea fishes identified three amino acid substitutions, which would make the deep-sea fish actin function even at 60 MPa. The myosin heavy chains from deep-sea fishes have a Pro residue in the loop-1 region and have a shorter loop-2 region than non deep-sea fishes. Additionally, the myosin heavy chains from deep-sea fishes have the biased amino acid substitutions at core positions in the coiled-coil structure of the rod region. The roles of these characteristic sequences in myosin heavy chain from deep-sea fish, however, have remained unclear.
Yeast is promising microbe to applying for brewing, bread-making, and some fermented foods, and to development recently for producing bio-ethanol. Yeast exists also in the deep-sea and the many species have been described from the deep-sea in previous reports. Most of the deep-sea yeasts are “non-conventional yeasts” including approximately 1000 species excepting well-known Saccharomyces cerevisiae and Schizosaccharomyces pombe, in the best of our knowledge. Yeast isolated from the deep-sea often possesses unique metabolic properties. We recently focused on a biosurfactant producing yeast, strain SY62, which was isolated from at a depth of 1,156 m in Sagami Bay in Japan. Although the yeast indicated little difference from conventional Pseudozyma hubeiensis on taxonomy, the secreted glycolipid-type biosurfactant, mannosylerythritol lipids (MEL), indicated structurally differences from those of conventional strains. The structural differences on MEL produced by SY62 resulted in the good hydrophilicity compared to those produced by conventional strains. The results indicated that the deep-sea bio-resources have great potential for exploring novel useful microorganisms and metabolites. The difference of metabolites seemed to be caused by evolution under high-pressure stress in the deep-sea.
Deep-sea microorganisms have a wide variety of useful and undiscovered enzymes for their survival in extreme environment. In this article, recent advances in the fundamental and applied researches on several recalcitrant seaweed polysaccharide degrading enzymes, which are newly obtained from the deep-sea bacteria, were described. The enzymes hydrolyze the backbone of the polysaccharides such as agarose and carrageenans to produce various oligosaccharides with great potentials for our health promotion. Furthermore, owing to the unique and profitable properties of the enzymes, they are used as powerful tools for researches in molecular biology and food analysis.
To date, together with rapidly developed culture-independent molecular techniques, knowledge in biomass, phylogenetic diversity and biogeography of microbial components has been extensively characterized in various terrestrial and oceanic habitats of deep biosphere. However, the general sketch of phenotypic and physiological diversity of subsurface microorganisms has remained poorly understood as most of the indigenous subsurface microbial components still escape from the laboratory cultivations. In this article, the physiological properties of the microorganisms that have been cultivated from various subsurface environments are overviewed.
We describe a simple setup to observe H2O ice VI single crystals under high pressure by using transparent Bridgman anvils with a compact hydraulic oil cylinder. It is confirmed that growth and melting of the ice VI single crystal was clearly observed as reported in diamond anvil cell experiments. Furthermore, this setup allows students starting to learn high pressure experiments to understand the opposed anvil technique because the anvils are not only easy to manipulate but also visible even when pressure is generated.