Reclassification of some species of Thiobacillus to the newly designated genera Acidithiobacillus gen. nov., Halothiobacillus gen. nov. and Thermithiobacillus gen. nov.

Abstract

NOTEReclassification of some species of Thiobacillus to the newly designated genera Acidithiobacillus gen. nov., Halothiobacillus gen. nov. and Thermithiobacillus gen. nov.

Influence of salts and pH on growth and activity of a novel facultatively alkaliphilic, extremely salt-tolerant, obligately chemolithoautotrophic sufur-oxidizing Gammaproteobacterium Thioalkalibacter halophilus gen. nov., sp. nov. from South-Western Siberian soda lakes

“…Until recently, lithoautotrophic sulfur-oxidizing bacteria (SOB) were studied mostly in neutral and acidic environments such as fresh and marine waters, wastewater treatment plants (Robertson and Kuenen 1992a, b;Kuenen et al 1992;Kelly and Wood 2000) and acidic mine drainage (Hallberg and Johnson 2001). During the last decade, oxidation of inorganic sulfur has also been reported for chemolithoautotrophic bacteria in the saline alkaline environments such as soda lakes.…”

Isolation, Characterization, and In Situ Detection of a Novel Chemolithoautotrophic Sulfur-Oxidizing Bacterium in Wastewater Biofilms Growing under Microaerophilic Conditions

“…One of the difficulties in establishing the enrichment culture of SO07 was that the population became unstable in liquid medium with thiosulfate as the electron donor, in which SO07 was outcompeted by other sulfur-oxidizing bacteria. The use of elemental sulfur instead of thiosulfate was effective in recovering the SO07 population and making it dominant, probably because strain SO07 grows faster on elemental sulfur than other sulfur-oxidizing bacteria, though the specific growth rate of strain SO07 on thiosulfate was lower than those of sulfuroxidizing bacteria (11,22). In general, thiosulfate has been used as the electron donor for isolation of sulfur-oxidizing bacteria because it is more readily soluble in water than elemental sulfur.…”

“…The 16S rRNA gene sequences of strain SO07 and previously identified Halothiobacillus species were, however, 89% similar at most. The most notable difference between the genus Halothiobacillus and strain SO07 is that strain SO07 cannot grow under high NaCl concentrations (no growth above 150 mM NaCl), while the genus Halothiobacillus requires 400 to 1,000 mM NaCl and can tolerate up to 4,000 mM NaCl (22,36). Therefore, it seems inappropriate to class strain SO07 as a species of Halothiobacillus.…”

“…The physiological characteristics of strain SO07 were compared with the characteristics of other sulfur-oxidizing bacteria belonging to the ␣-, ␤-, and ␥-Proteobacteria: Starkeya novella (21) in the ␣-Proteobacteria; Thiobacillus thioparus (20) in the ␤-Proteobacteria; and Halothiobacillus neapolitanus (22), Halothiobacillus hydrothermalis (11), Halothiobacillus halophilus (22), and Acidithiobacillus thiooxidans (22) in the ␥-Proteobacteria. It should be noted that all these bacteria had originally been classified as Thiobacillus but were recently reclassified by Kelly et al (21) and Kelly and Wood (22).…”

“…Recently, novel sulfur-oxidizing bacteria belonging to the ␥ and ε subclasses of the Proteobacteria have been discovered and isolated from various habitats, e.g., marine mud (7,8), oil field waters (12,23), and a hydrothermal vent system (36). Moreover, sulfur-oxidizing bacteria originally classified as Thiobacillus species were reclassified into the ␣, ␤, and ␥ subclasses of the Proteobacteria based on their phylogenetic relatedness and their physiological similarities (14,19,21,22,29). These reports clearly indicate that the phylogenetic and physiological diversity of sulfur-oxidizing bacteria is greater than has been expected.…”