Chapter 5, Problem 1DAA

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 do the dashed lines in the graphs signify?

Summary Introduction

To determine: What do the dashed lines in the graphs signify.

Concept introduction: Enzymes are the protein molecules that enhance the rate of the reactions without being changed by them. It acts as a biocatalyst. Each enzyme works the best within a certain range of environmental conditions that include temperature, pH, and salt concentration.

Explanation of Solution

The isolated bacteria Ferroplasma acidarmanus grow well at acidic environment (pH zero) of copper mine where the water temperature is about 40 ºC and heavily laden with arsenic and other toxic metals.

The F. acidarmanus has an ancient energy harvesting pathway. It uses the electrons from iron-sulfur compounds in the mineral such as pyrite. Removing electrons from these compounds dissolve the minerals that lead to the high concentration of metal ions such as copper, zinc, cadmium, and arsenic in groundwater. This also produces sulfuric acid which lowers the pH of the water around the cells to zero.

Despite the surrounding environment the internal pH of the bacteria is 5.0. However, most of the enzymes in bacteria functions best at much lower pH. This causes a thinking of presence of the unknown type of internal environment in the bacteria that keeps their enzymes in a highly acidic environment.

Refer to Fig. 5.13 “pH anomaly of Ferroplasma acidarmanus”, there are four different enzymes carboxylesterase, α-glucosidase, GlyFa1, and GlyFa2 which works best around pH 1.5, 3, 1.8, and 3.8 respectively. The dashed line shows the optimum activity for each enzyme.

Conclusion

The dashed line indicates the optimum enzyme activity for each enzyme.