Sulfolobus Species

The high temperature, low pH, and aerobic growth of the Sulfolobales make them attractive candidates for industrial use, as there is little risk of contamination and no need to purchase specialized equipment for anaerobic manipulation. 

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A large number of hyperthermophilic Archaebacteria, especially the deep sea Thermococcale and Sulfolobus species elaborate a-amylases.79-82 Many have been cloned and sequenced.78 Pyrococcus furiosus,83,84 Thermococcus profundus,85 Thermococcus hydrothermalis,78 Sulfolobus solfataricus and Sulfolobus acidocaldar-iusS6 secrete thermophilic a-amylases. The a-amylases of all of these organisms have optimal enzyme activity at 90°C or higher and often only begin to show activity at 40°C or 50°C. Pyrococcus furiosus secretes an a-amylase with an optimum temperature of 100°C and a maximum temperature of 140°C.87 The optimum pH values vary between 5 and 9. Table 7.1 summarizes the names of the organisms, the optimum temperature, and optimum pH values for several of these enzymes. 

Finally, the need for further investigations into the metabolism of glucose in thermophilic archaebacteria should be stressed. Firstly, the fate of glyceraldehyde in Sulfolobus species needs to be established, and there is still eontroversy coneeming the pathways in Tp. acidophilum. That is, Searcy and Whatley [15] have provided evidence from respiratory studies for the operation of glycolysis in Tp. acidophilum but we have been unable to detect many of the enzymes of this pathway [14]. Secondly, there is a... 

Compared with the investigations in the extreme halophiles, there is very little information on the operation of a pentose-phosphate pathway in other archaebacteria. The radiorespirometric analyses of glucose metabolism in Sulfolobus species [13], which established the Entner-Doudoroff type pathway (section 2.2), were also consistent with a non-cyclic pentose-phosphate pathway in S. brierleyi and a conventional oxidation cycle in Sulfolobus strain LM. Similarly, respiratory studies [15] provide evidence for a pentose phosphate cycle capable of glucose oxidation in Tp. acidophilum. No data are available for the methanogens. 

Within the sulphur-dependent thermophilic branch of the archaebacteria, the situation is less clear. Sulfolobus species are facultatively autotrophic [13] and many of the citric acid cycle enzymes have been reported (reviewed in ref. [1]). Thus, when growing heterotrophically in the presence of oxygen, an oxidative cycle may be operative, although respirometric analyses suggest that its use may be limited [13]. 

Sulfolobus species are archaebacteria, distinct from other leaching bacteria, which are eubacteria. They are usually found in acidic environments with temperatures in the range 50-80°C. Archaebacteria lack muramic acid, a constituent of the eubacterial cell wall. Sulfolobus cells are typically small and spherical (0.7-1.0 pm in diameter). They lack true cell walls, being surrounded by a plasma membrane... 

Sulfolobus species also appear to contain more than one DNA polymerase. The enzyme reported by Rossi et al. [167] from S. solfataricus was the major component of two chromatographically separable DNA polymerase activities, and showed a preference for Mg for activity. Loss of activity of the enzyme above 75 °C in short assay periods was probably due to DNA template melting rather than thermostability problems. Three discreet DNA polymerases, designated A, B and C, were at least partially purified from S. aciddcaldarius [168], an organism also used as a source of DNA polymerase by Klimczak et al. [169]. The A and B enzymes were unaffected by aphidicolin and were relatively thermostable. 

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