Effect of hydrogen and carbon dioxide partial pressures on growth and sulfide production of the extremely thermophilic archaebacterium Pyrodictium brockii

Abstract

The effect of hydrogen and carbon dioxide partial pressure on the growth of the extremely thermophilic archaebacterium Pyrodictium brockii at 98 degrees C was investigated. Previous work with this bacterium has been done using an 80:20 hydrogen-carbon dioxide gas phase with a total pressure of 4 atm; no attempt has been made to determine if this mixture is optimal. It was found in this study that reduced hydrogen partial pressures affected cell yield, growth rate, and sulfide production. The effect of hydrogen partial pressure on cell yield and growth rate was less dramatic when compared to the effect on sulfide production, which was not found to be growth-associated. Carbon dioxide was also found to affect growth but only at very low partial pressures. The relationship between growth rate and substrate concentration could be correlated with a Monod-type expression for either carbon dioxide or hydrogen as the limiting substrate. The results from this study indicate that a balance must be struck between cell yields and sulfide production in choosing an optimal hydrogen partial pressure for the growth of P. brockii.

Purification and characterization of the hydrogen uptake hydrogenase from the hyperthermophilic archaebacterium Pyrodictium brockii

“…P. brockii is a disk-shaped organism with an optimal growth temperature of 105°C. It is a strict anaerobe and grows chemolithotrophically with H2 and CO2 (29,39). In the process of oxidizing H2, elemental sulfur is reduced to hydrogen sulfide.…”

“…An 80% H2-20% CO2 mixture was sparged through the culture flask at a rate of 0.1 culture volume per min. P. brockii starter cultures were grown in bottles as previously described (29,31). Cells used in 63Ni labeling experiments were grown in bottles with artificial seawater (31) to which 50 ,Ci of 63NiC12 (New England Nuclear, Boston, Mass.)…”

Hydrogen-oxidizing electron transport components in the hyperthermophilic archaebacterium Pyrodictium brockii

“…To date, most of the work has centered upon trying to elucidate and characterize the various metabolic components that allow bacteria to thrive at high temperatures. The two most intensively studied hyperthermophiles (defined by us [30,31] as organisms that are able to grow at or above 100°C) are the heterotroph Pyrococcus furiosus (2, 5-7, 9-11) and the autotroph Pyrodictium brockii (25,26,(28)(29)(30)(31)(32).…”

“…brockii was originally isolated from the solfatara fields off the coast of Volcano, Italy, by Stetter and his colleagues (35,36). P. brockii has an optimal growth temperature of 105°C (36) and an absolute requirement for H2 and C02, and it couples oxidation of H2 to the reduction of sulfur to sulfide (26,35,36). This form of metabolism has been termed hydrogen-sulfur autotrophy (30,36), a mode of growth that was originally recognized in hyperthermophilic archaebacteria.…”

Hydrogen-Sulfur Autotrophy in the Hyperthermophilic Archaebacterium,Pyrodictium brockii

“…The initial focus was on a hyperthermophilic chemolithotroph, Pyrodictitim brockii (Stetter et al, 1983;Parameswaran et al, 1988; Pihl et al, 1989). This bacterium was chosen for several reasons: it has the reported highest optimum growth temperature (105 0 C) for any organism and it clearly reduces sulfur to sulfide to fulfill some or all of its energetic requirements.…”