Thiobacillus ferrooxidans is a bacteria that plays a role in the bioleaching of metals, specifically in the oxidation of iron and sulfur compounds. It doesn't directly convert lime (calcium hydroxide) to gypsum (calcium sulfate).

Here's how the process works:

1. Iron Oxidation: Thiobacillus ferrooxidans oxidizes ferrous iron (Fe2+) to ferric iron (Fe3+). This process releases protons (H+), which acidify the environment.

2. Acidification: The acidic environment created by the bacteria dissolves the lime (calcium hydroxide).

3. Sulfate Formation: Thiobacillus ferrooxidans can also oxidize sulfide minerals (like pyrite) into sulfate (SO4^2-).

4. Gypsum Formation: The dissolved calcium from the lime reacts with the sulfate ions, forming calcium sulfate (gypsum).

Therefore, Thiobacillus ferrooxidans plays a crucial role in the acidification of the environment, which ultimately allows for the formation of gypsum from lime.

Note: This process is usually observed in mining operations, where Thiobacillus ferrooxidans is used to extract metals from sulfide ores. The bacteria's ability to oxidize iron and sulfur creates an acidic environment that dissolves metals and forms gypsum as a byproduct.