Biology Now, 2e

Navel Gazing ■ 275

species on himself known solely for eating pesti-

cides. Why it was on his skin remains a mystery.

Amazingly, the team found more than just

bacteria. On one particularly fragrant individ-

ual, who said he had not washed in years, they

detected two species of archaeans. Although some

bacteria thrive in unusual environments, the

domain Archaea is well known for the extreme

lifestyles of its members (Figure 15.8). Some are

extreme thermophiles that live in geysers, hot

springs, and hydrothermal vents—cracks in the

seafloor that spew boiling water. The cells of most

organisms cannot function at such high tempera-

tures, but thermophiles have come up with evolu-

tionary innovations that enable them to succeed

where others cannot. Other archaeans, classified

as halophiles, thrive in very salty, high-sodium

environments where nothing else can live.

Yet archaeans have also been found in less exotic

locations. In another citizen science project from

Dunn and Fierer, students analyzed the micro-

bial DNA swabs from home surfaces—kitchen

They had discovered new species of bacte-

ria playing house in our navels. Still, Dunn was

most interested in finding patterns hiding in the

data. The first pattern they found was that the

microbes in belly buttons are somewhat predict-

able. Six species showed up in about 80 percent of

people, and when present, those species tended to

be most widespread. “If I go to a cocktail party, I

can tell you which species will be most abundant

in the room,” says Menninger with a laugh. That

distribution pattern reminded Dunn of rainforest

ecology: in any given forest, the types of plants

might vary, but an ecologist can depend on a

certain few tree types dominating the landscape.

Likewise, infrequent species tended to be

present only in small quantities in belly buttons.

Some were familiar: Bacillus subtilis, known to

cause foot odor, also lives in some belly buttons

(where it likely causes the same smell). Others

were quite rare: one participant hosted a species

previously found only in the soil of Japan, yet

the man had never been to Japan. Dunn found a

Archaea found in mineral hot

springs are able to withstand

extreme acidity and high

temperatures.

Hydrogen-eating, methane-

producing archaeans have

been found in deep-sea

thermal vents.

A new archaean species was

recently found in an abandoned

copper mine. Others have been

found living in acidic drainage

from mines.

Q1: Which shape in Figure 15.7 corresponds to the archaeans from deep-sea thermal vents?

Q2: Why are many archaeans referred to as “extremophiles”?

Q3: Is there anywhere you think archaeans could not survive? Justify your answer.

Figure 15.8

Archaeans are everywhere

Archaeans, and bacteria to a lesser extent, thrive in environments that humans are incapable of surviving in.