Isolation, Phenotypic Characterization, and Phylogenetic Position of a Novel, Facultatively Autotrophic, Moderately Thermophilic Bacterium, Thiobacillus thermosulfatus sp. nov.

Abstract

Thiobacillus thermusulfatus ATCC 51520T (T = type strain) was isolated from sewage sludge samples enriched with elemental sulfur. The cells of this organism were gram negative, rod shaped, motile, facultatively autotrophic, and strictly aerobic and contained polyphosphate inclusions and polyhedral bodies. During growth on thiosulfate, the following intermediates were produced: tetrathionate, trithionate, and sulfate, and the pH was lowered from neutrality to around 2.5. Autotrophic growth was observed at pH values between 4.3 and 7.8 and at temperatures of 34 to 65°C; optimum growth occurred at pH 5.2 to 5.6 and 50 to 52.5"C. Ubiquinone QS was present in the respiratory chain. The DNA contained 61 f 1 mol% G+C. No denitrification was observed under autotrophic and heterotrophic conditions. The cells produced a glycocalyx during growth in the presence of So. As determined by a 16s rRNA gene sequence analysis, T. thermosulfatus is a distinct species that belongs to the beta subdivision of the Proteubacteria and is closely related phylogenetically to Thiobacillus perumetabulis. The GenBank accession number for the complete 16s rRNA gene sequence of T. thermosulfatus is U27839.According to Kelly and Harrison (17) in Bergey's Manual of Systematic Bacteriology, the only criterion for grouping all of the Thiobacillus species in one genus is that all of these organisms are rod-shaped eubacteria that obtain energy for autotrophic growth from oxidizing inorganic sulfur-containing substrates. Consequently, this genus comprises species that have different pH, temperature, and nutrient requirements. In fact, it includes organisms that are acidophilic, organisms that are neutrophilic, organisms that are thermophilic, denitrifiers, and facultative heterotrophs (19). When temperature requirements are considered, the following three Thiobacillus species are recognized as moderately thermophilic organisms: Thiobacillus tepidarius, Thiobacillus aquaesulis, and Thiobacillus caldus (33)(34)(35). A Thiobacillus-like moderately thermophilic bacterium was also partially characterized by Williams and Hoare (32).The great phenotypic diversity of the thiobacilli is supported by the results of genetic analyses. The first phylogenetic study of sulfur-and iron-oxidizing eubacteria placed members of the genus Thiobacillus in three of the four subdivisions of the Proteobacteria (21, 27). A phylogenetic analysis of 16s rRNA gene sequences revealed that most members of the genus Thiobacillus belonged to the beta subdivision, but some strains were more closely related to other genera that are not iron or sulfur oxidizers (21). In fact, this study revealed that Thiobacillus acidophilus and Thiobacillus versutus were members of the alpha subdivision. Moreover, Thiobacillus acidophilus was closely linked to the genus Acidiphilium, suggesting that this organism should not be included in the genus Thiobacillus. The species Thiobacillus versutus and two other hydrothermal vent isolates were described as members of a new genus, and Thiobacillus ferroox...

Reassessment of the phylogenetic relationships of Thiomonas cuprina

“…The type species is Thiomonas (5NBRC 102094 T ); 2, Thiomonas delicata NBRC 14566 T ; 3, 'Thiomonas arsenivorans' DSM 16361; 4, Thiomonas intermedia ATCC 15466 T (type species of the genus); 5, Thiomonas perometabolis ATCC 23370 T ; 6, Thiomonas thermosulfata ATCC 51520 T . Data were obtained in the present study and from London (1963), London & Rittenberg (1967), Mizoguchi et al (1976), Huber & Stetter (1990), , Katayama-Fujimura et al (1984), Kelly & Harrison (1989), Shooner et al (1996), , , Battaglia-Brunet et al (2006) and Katayama et al (2006) …”

Thiobacter subterraneus gen. nov., sp. nov., an obligately chemolithoautotrophic, thermophilic, sulfur-oxidizing bacterium from a subsurface hot aquifer

“…A number of thermophilic, hydrogen-and/or sulfuroxidizing members of the b-Proteobacteria have been described, including genera such as Hydrogenophilus (Hayashi et al, 1999;Stöhr et al, 2001), Thiomonas (Shooner et al, 1996), Thermothrix (Caldwell et al, 1976;Odintsova et al, 1996), Tepidimonas (Moreira et al, 2000) and Thiobacillus (Wood & Kelly, 1988). These organisms have been isolated from terrestrial hot-spring environments or wastewater-treatment plants, and most of them are facultatively autotrophic or strictly heterotrophic organisms.…”

Tepidiphilus margaritifer gen. nov., sp. nov., isolated from a thermophilic aerobic digester

“…Within the b-subclass of the Proteobacteria, eight species of thermophilic organisms, included in five genera, have been described to date. The species Thiomonas thermosulfata (Shooner et al, 1996), Thermothrix azorensis (Odintsova et al, 1996), Thermothrix thiopara (Caldwell et al, 1976) and Tepidimonas ignava (Moreira et al, 2000) represent thermophilic organisms, characterized by their ability to use sulfur or sulfur compounds as an energy source. Tepidimonas ignava, isolated from a Portuguese hot spring, is the only strictly heterotrophic organism among these sulfur bacteria.…”