Which bacterium is involved in the sulfur cycle?

-✅Explanation: Thiobacillus is a genus of bacteria that plays a crucial role in the sulfur cycle. These bacteria can oxidize various sulfur compounds, including hydrogen sulfide (H₂S) and elemental sulfur (S₈), transforming them into usable forms for other organisms.
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📌Other Options Explanations:
-(a) Rhizobium: Rhizobium forms a symbiotic relationship with legumes for nitrogen fixation.
-(b) Azotobacter: Azotobacter is a free-living nitrogen-fixing bacterium.
-(d) Pseudomonas: Pseudomonas is a diverse genus with many species, some involved in various processes.

🔑Key Points:
-Dinitrogen gas (N2) is the final end product of denitrification.
-It is carried out by a diverse group of prokaryotes, as well as some eukaryotes.
-Denitrification is carried by bacteria such as Pseudomonas and Thiobacillus.
-It is an important phenomenon as it removes fixed nitrogen i.e., nitrate from the ecosystem and returns it to the atmosphere in a biologically inert form (N2).