Phenotypic characterization of the archaebacterial genus Sulfolobus: comparison of five wild-type strains

Abstract

Though amenable to routine manipulation and a popular subject of molecular genetic and biochemical studies on archaebacteria, the genus Sulfolobus has remained poorly described in phenotypic terms. To delineate their physiological capabilities and diversity, five laboratory strains, including type strains of the described species Sulfolobus acidocaldanius and S. solfataricus, were compared with respect to a variety of growth and biochemical parameters, including component profile of the surface-layer cell wall, inhibitors of growth, growth rate as a function of temperature and pH, and compounds used as sole sources of carbon or nitrogen. Motility and photoregulated production of an orange pigment were detected in all five strains tested.The results provide new criteria for distinguishing Sulfolobus strains as well as potential tools for the physiological and genetic manipulation of these extreme thermophiles.Since their description as sulfur-oxidizing inhabitants of geothermal springs (2), Sulfolobus spp. and related bacteria have proven to be of much more than geochemical interest. This group includes the most thermophilic aerobes known and has provided the first evidence of molecular phenomena previously unknown in procaryotes or, in several cases, in any organism. These phenomena include cell membranespanning isoprenoid tetraether lipids containing cyclopentane rings (8), sulfur-containing quinones (22), introns in procaryotic tRNA genes (15), a "reverse DNA-gyrase" (16), production of positively supercoiled DNA in vivo (26), and bacterial promoters homologous to eucaryotic polymerase II promoters (30). Comparison of macromolecular sequences and biochemical properties indicates that these and other novel features reflect a long evolutionary history distinct from those of eubacteria and eucaryotes rather than adaptation of Sulfolobus spp. to their specialized habitat per se. Specifically, Sulfolobus spp. seem to have originated within a diverse branch of the archaebacteria dominated by extremely thermophilic, nonmethanogenic anaerobes (17). Most representatives of this sulfur-dependent branch have been isolated and characterized only within the past decade and have provided much new information about such fundamental questions as the extent of biological diversity, its evolutionary basis, and the upper temperature limit for life (32). Additional motivation for study stems from the potential for technological applications of the stable enzymes found in these organisms (10).Much of the scientific significance of the genus Sulfolobus derives from the fact that it is the most readily studied representative of this diverse group of extreme thermophiles. Two species have been validly described to date, Sulfolobus acidocaldarius (2) and S. solfataricus (35), both of which grow optimally at high temperature (80 to 85°C) and low pH (2 to 4) and display an irregular coccoid shape.

Genetic fidelity under harsh conditions: Analysis of spontaneous mutation in the thermoacidophilic archaeon Sulfolobus acidocaldarius

“…Our data predict that S. acidocaldarius should accumulate neutral mutations (mainly synonymous substitutions) at about half the rate per generation as does E. coli. Furthermore, S. acidocaldarius reproduces only about one-eighth as quickly as E. coli under optimal conditions (doubling time of 2.9 h at about 80°C) (6), although the relative numbers of microbial generations per year in nature cannot be inferred solely from this fact.…”

“…S. acidocaldarius, obtained from the American Type Culture Collection (ATCC 33909), was clonally purified by streaking on solid medium and was confirmed to yield a pattern of genomic EcoRI restriction fragments identical to that of S. acidocaldarius strain DG6 (6). The laboratory designation for the resulting strain is DG185.…”

“…Unless otherwise noted, growth media (pH 3.5) consisted of a mineral mixture supplemented with xylose, tryptone, and uracil; plates contained gellan gum for solidification (7). Incubation was at 75°C, which is near the midpoint of the temperature range for growth for this species (6).…”

The non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPN) of Sulfolobus solfataricus: a key-enzyme of the semi-phosphorylative branch of the Entner–Doudoroff pathway

“…starch, glucose, arabinose, fructose ;Grogan 1989) and relies on the modified branched ED pathway for glucose catabolism (Ahmed et al 2005). In the common shunt of the branched ED pathway, glucose dehydrogenase first oxidizes glucose to glucono-lactone (Giardina et al 1986;Lamble et al 2003), which is subsequently converted to gluconate either via a spontaneous reaction or via an enzymatic conversion by glucono-lactonase.…”

A broadly applicable gene knockout system for the thermoacidophilic archaeon Sulfolobus islandicus based on simvastatin selection

“…The lacS gene can be used as selection marker in these strains when grown on minimal medium, utilizing lactose as the sole carbon and energy source (Albers & Driessen, 2008;Maezato et al, 2011a;Schelert et al, 2004). Unfortunately, lactose selection is limited to S. solfataricus and a few S. islandicus strains such as S. islandicus REN1H1, because many strains of Sulfolobus cannot be grown efficiently in medium using lactose as the sole carbon and energy source (Berkner & Lipps, 2008;Grogan, 1989). Maltose selection has also been established in S. solfataricus, in which the malA gene was used as a marker (Maezato et al, 2011b).…”