1. Colorless Sulfur Bacteria Blanca Pérez Hopkins Microbiology Course 2010

2. Colorless Sulfur Bacteria Comprises a very heterogeneous group of chemoautotrophic bacteria Use of reduced forms of S as e- source Most of them require O 2 as e- acceptor, but a few are able to grow anaerobically using nitrogen oxides Sulfur cycle, Robertson and Keuenen (2006)

3. Colorless Sulfur Bacteria Thiobacillus Thiomicrospira Thiosphaera Sulfolobus Acidianus Thermothrix Thiovulum Beggiatoa Thiothrix Thioploca Thiodendron Thiobacterium Macromonas Achromatium Thiospira Will

4. Gradient tubes H2SH2S O2O2 Interface between opposing oxygen and sulfide gradients H 2 S + 2O 2  SO 4 2- + 2H +

5. Gradient tubes Kosh

6. Gradient tubes Hyansoo Spirocheta sp. symbiotic relationships between Spirochaeta plicatilis with Beggiatoa

7. Thiosulfate plates Use of thiosulfate as e- donor (with O 2 or NO 3 - as e- acceptor) Production of sulfuric acid (bromothymol blue) Aerobic incubation (w/o NO 3 - ) Anaerobic incubation (w NO 3 - )

8. Thiosulfate plates: aerobic conditions 2 days Na 2 S 2 O 3 + 2O 2 + H 2 O  Na 2 SO 4 + H 2 SO 4 Sulfuric acid

9. Thiosulfate plates: anaerobic conditions Aerobic incubation ~2 weeks Sulfuric acid Elemental sulfur

10. Thiosulfate plates

11. Colorless Sulfur Bacteria Blanca Pérez Hopkins Microbiology Course 2010

12. Desulfovibrio sulfodismutans can grow anaerobically by the disproportionation of thiosulfate to sulfate and sulfide Sulfate Reducing Bacteria: disproportionation of thiosulfate