Chapter 5, Problem 3DAA

One Tough Bug The genus Ferroplasma consists of a few species of acid-loving archaea. One species, Ferroplasma acidarmanus, was discovered in one of the most contaminated sites in the United States: Iron Mountain Mine in California. F. acidarmamus is the main constituent of .slime streamers (a type of biofilm) growing in water draining from this abandoned copper mine (right). The water is hot (about 40°C, or 104°F), heavily laden with arsenic and other toxic metals, and has a pH of zero.

F. acidarmanus cells have an ancient energy-harvesting pathway that uses electrons pulled from iron-sulfur compounds in minerals such as pyrite. Removing electrons from these compounds dissolves the minerals, so groundwater in the mine ends up with extremely high concentrations of solutes, including metal ions such as copper, zinc, cadmium, and arsenic. The pathway also produces .sulfuric acid, which lowers the pH of the water around the cell to zero.

F. acidarmanus cells keep their internal pH at a cozy 5.0 despite Living in an environment similar to hot battery acid. However, most of the cell’s enzymes function best al much lower pH (FIGURE 5.13). Thus, researchers think F. acidarmanus may have an unknown type of internal compartment that keeps their enzymes in a highly acidic environmental.

FIGURE 5.13 pH anomaly of Ferroplasma acidarmanus.

Left graphs showing pH activity profile of four enzymes isolated from Ferraplasma acidarmanus Researchers had expected all of these enzymes to function best at the calls’ cytoplasmic pH (5.0).

What is the optimal pH for the carboxylesterase?