High-pressure-temperature gradient instrument: use for determining the temperature and pressure limits of bacterial growth

Evolutional and ecological implications of the properties of deep-sea barophilic bacteria

The rate of reproduction of deep-sea bacteria from six different capture depths between 1957 and 10,476 meters was studied as a function of temperature and pressure. The results showed the following: the true deep-sea bacteria of different depths have several characteristics, presumably evolutionally derived, distinguishing them from each other and from bacteria of atmospheric-pressure environments; pressure plays a significant role in determining the distribution of oceanic life; and pressure-adapted bacteria are easily recovered from and ubiquitous in the deep ocean. Organisms evolving in habitats of different temperatures and pressures need to be studied to understand the physical limits of life, the distribution of life within the earth and its oceans, the role of organisms in organic diagenesis and petroleum formation, and the possible existence of life on and within other planets.

A high-pressure thermal gradient block for investigating microbial activity in multiple deep-sea samples

Details about the construction and use of a high-pressure thermal gradient block for the simultaneous incubation of multiple samples are presented. Most parts used are moderately priced off-the-shelf components that easily obtainable. In order to keep the pressure independent of thermal expansion of the sample vessels, a back-pressure system with a constant leak rate was installed. Pressure is applied through high-pressure liquid chromatography (HPLC) pumps that run in constant pressure mode with variable flow rate, thereby regulating any pressure fluctuations. The device allows incubations along a wide range of temperatures and pressures and can easily be modified to accommodate different experiments, either biological or chemical. As an application, we present measurements of bacterial sulfate reduction rates in hydrothermal sediments from Guyamas Basin over a wide range of temperatures and pressures. Sulfate reduction rates increase with increasing pressure and show maximum values at pressures higher than in situ.

Proteins under pressure. The influence of high hydrostatic pressure on structure, function and assembly of proteins and protein complexes

Oceans not only cover the major part of the earth's surface but also reach into depths exceeding the height of the Mt Everest. They are populated down to the deepest levels (approximately 11,800 m), which means that a significant proportion of the global biosphere is exposed to pressures of up to 120 MPa. Although this fact has been known for more than a century, the ecology of the 'abyss' is still in its infancy. Only recently, barophilic adaptation, i.e. the requirement of elevated pressure for viability, has been firmly established. In non-adapted organisms, increased pressure leads to morphological anomalies or growth inhibition, and ultimately to cell death. The detailed molecular mechanism of the underlying 'metabolic dislocation' is unresolved. Effects of pressure as a variable in microbiology, biochemistry and biotechnology allow the structure/function relationship of proteins conjugates to be analyzed. In this context, stabilization by cofactors or accessory proteins has been observed. High-pressure equipment available today allows the comprehensive characterization of the behaviour of proteins under pressure. Single-chain proteins undergo pressure-induced denaturation in the 100-MPa range, which, in the case of oligomeric proteins or protein assemblies, is preceded by dissociation at lower pressure. The effects may be ascribed to the positive reaction volumes connected with the formation of hydrophobic and ionic interactions. In addition, the possibility of conformational effects exerted by moderate, non-denaturing pressures, and related to the intrinsic compressibility of proteins, is discussed. Crystallization may serve as a model reaction of protein self-organization. Kinetic aspects of its pressure-induced inhibition can be described by a model based on the Oosawa theory of molecular association. Barosensitivity is known to be correlated with the pressure-induced inhibition of protein biosynthesis. Attempts to track down the ultimate cause in the dissociation of ribosomes have revealed remarkable stabilization of functional complexes under pseudo-physiological conditions, with the post-translational complex as the most pressure-sensitive species. Apart from the key issue of barosensitivity and barophilic adaptation, high-pressure biochemistry may provide means to develop new approaches to nonthermic industrial processes, especially in the field of food technology.

High-pressure, high-temperature bioreactor for comparing effects of hyperbaric and hydrostatic pressure on bacterial growth

We describe a high-pressure reactor system suitable for simultaneous hyperbaric and hydrostatic pressurization of bacterial cultures at elevated temperatures. For the deep-sea thermophile ES4, the growth rate at 500 atm (1 atm = 101.29 kPa) and 95 degrees C under hydrostatic pressure was ca. three times the growth rate under hyperbaric pressure and ca. 40% higher than the growth rate at 35 atm.

Engineering considerations for the application of extremophiles in biotechnology

Biotechnology may soon take greater advantage of extremophiles--microorganisms that grow in high salt or heavy metal concentrations, or at extremes of temperature, pressure, or pH. These organisms and their cellular components are attractive because they permit process operation over a wider range of conditions than their traditional counterparts. However, extremophiles also present a number of challenges for the development of bioprocesses, such as slow growth, low cell yield, and high shear sensitivity. Difficulties inherent in designing equipment suitable for extreme conditions are also encountered. This review describes both the advantages and disadvantages of extremophiles, as well as the specialized equipment required for their study and application in biotechnology.

High-Pressure Equipment for Growing Methanogenic Microorganisms on Gaseous Substrates at High Temperature

High-pressure, high-temperature investigations on thermophilic microorganisms that grow on hydrogen or other gaseous substrates require instrumentation which provides sufficient substrate for cell proliferation up to 2 × 10 8 to 3 × 10 8 cells per ml under isothermal and isobaric conditions. To minimize H 2 leakage and to optimize reproducibility at high pressure and high temperature, 10-ml nickel tubes with a liquid/gas ratio of 1:2 were used in a set of autoclaves connected in series. By applying a hydraulic pump and a 2.5-kW heating device, fast changes in temperature (up to 400°C) and pressure (up to 400 MPa) can be accomplished within less than 10 min. To quantify bacterial growth, determinations of cell numbers per unit volume yielded optimum accuracy. Preliminary experiments with the thermophilic, methanogenic archaebacterium Methanococcus thermolithotrophicus showed that bacterial growth depends on both temperature and pressure. At the optimum temperature, increased hydrostatic pressure up to 50 MPa enhanced the growth yield; at a pressure of >75 MPa, cell lysis dominated. Changes in cell proliferation were accompanied by changes in morphology.