If they live in the presence of HCl, they could also make some fun organichlorides. Those products could be simple organic solvents that damage the cell membranes. They could also be more or less toxic compounds, maybe even comparable with chemical weapons. Organic chemistry is full of options.
Add plastic eating bacteria to our gut biomes maybe?
You could make them capable of eating plastic, but what would the byproducts be? You would need to make sure the byproducts aren’t toxic.
Oh, just harmless acetone
If they live in the presence of HCl, they could also make some fun organichlorides. Those products could be simple organic solvents that damage the cell membranes. They could also be more or less toxic compounds, maybe even comparable with chemical weapons. Organic chemistry is full of options.