The many holes were apparently done during war time, to extract metal used within the villa's construction.

Two of the bacteria species struggled to extract metals from their basalt samples.

The company extracts metals such as titanium, used in the aerospace and automotive industries, and tantalum, used to make smartphones and other electronic devices, from mined rock.

But mining companies are gearing up for the day in the near future when they will be able to begin extracting metals and minerals from the deep.

The company uses a process called bio-heap leaching, which employs microbes and sulphuric acid to extract metals more cheaply than traditional smelting.