The Influence of Hydrostatic Pressure on the Growth and Viability of Terrestrial and Marine Bacteria.

Although there is abundant evidence that a rich microflora exists at the bottom of the ocean, in deep oil well brines, and in other habitats characterized by high pressure (cf. ZoBell, 1946), no clear understanding has been reached concerning the influence of pressure on the growth, viability, and metabolism of the organisms in such environments. The results of older (Certes, 1884a,b,c; Regnard, 1884; Certes and Cochin, 1884; Roger, 1895; Krause, 1902; Chlopin and Tammann, 1903; Hite, Giddings, and Weakley, 1914; Larson, Hartzell, and Diehl, 1918), as well as more recent, studies (cf. reviews by Macheboeuf and Basset, 1934; Cattell, 1936; Bridgman, 1946) with respect to the effects of presure on microbial processes in general are not only inadequate but in some cases apparently inconsistent. Furthermore, before the advent of the theory of absolute reaction rates in 1935 (Eyring, 1935; Glasstone, Laidler, and Eyring, 1941) no rational basis was available for the interpretation of the action of pressure on chemical reaction rates, and it has been only within the past several years that this theory has been applied to biological reactions in living cells (cf. reviews by Johnson, 1947; Johnson and Eyring, 1948.) The latter studies have shown that, in all cases, the observed effects of pressure may be profoundly modified by temperature; a fundamental relationship that had previously remained almost unnoticed. In view of these circumstances, we have undertaken to reinvestigate the prob. lem, with special reference to the relation between temperature and the effects of hydrostatic pressure, as well as the relation of the natural habitat of the organism to the effects observed. The present report is in the nature of a survey of the influence of pressures up to 9,000 pounds per square inch (about 600 atmospheres), at different constant temperatures, on the growth and viability of representative species of both marine and terrestrial bacteria in pure culture, initially in the logarithmic growth phase. Extensive quantitative data are necessary for kinetic analyses of the pressure effects and will be made the subject of later investigations, as will, likewise, the significance of certain biological and other factors, such as the specific physiology of the organism, growth phase, composition of the medium, and so forth.