The Scientist - USA (2020-11)

11.2020 | THE SCIENTIST 15

And [we’ve] always known that there’s

a microbial component to corrosion.”

So this time, Richards was drilling for

microbes to see if he and his students

could shed light on the Pappy Lane’s par-

ticularly rapid deterioration.

Along with ECU microbiologist Erin

Field, Richards and his students drilled a

total of six core samples of the ship’s steel

hull—containing both the metal structure

itself and the concrete-like layer of bacteria

and their secretions on either side—from

the bow to the stern. The team also collected

pieces of loose debris from the ship, as well

as seawater and sediment samples, all of

which were placed into a cooler for the trip

back to the lab for genetic analysis.

The data revealed pronounced dif-

ferences in microbial communities—in

terms of both the species makeup and the

metabolic functionalities—on the differ-

ent materials of the shipwreck and in the

surrounding water and sediment (Front

Microbiol, 11:1897, 2020). “I often think

about it in terms of the human micro-

biome,” Field says. “We have microbes

that live all over and in our bodies, but

you won’t find the same microbes in your

gut that you will on your skin because the

environments are different.”

Field was particularly interested in

how iron-oxidizing bacteria, which eat

iron from the ship’s metal and produce

rust as a waste product, were contribut-

ing to the Pappy Lane’s deterioration. In

the lab, Field and her team cultured bac-

teria from the debris and core samples

and found that iron-oxidizing bacteria

such as Zetaproteobacteria were present

in every sample, and particularly abun-

dant in samples with visible rust. “It’s

possible that their presence could indi-

cate early detection for future corrosion,”

Field says. She also notes that Zetapro-

teobacteria, as some of the first to settle

on shipwrecks, may make the environ-

ment more hospitable to other microbes.

For example, they deplete the immediate

surroundings of oxygen, possibly inviting

sulfate bacteria that grow well in anoxic

conditions to further corrode the ship’s

steel, Field speculates.

The findings could have implica-

tions for preservation strategies not just

for shipwrecks, but for any aquatic steel

structure, she notes. “Most [current]

preservation methods are not account-

ing for the microbial role... so we’re

still missing that piece of the puzzle. And

we’re finding that microbes are definitely

affecting the deterioration or preserva-

tion of these wrecks.”

The University of Southern Mis-

sissippi’s Leila Hamdan, who has been

studying the microbiomes of deep-sea

wrecks for a decade but was not involved

in the Pappy Lane work, says that it’s

exciting that the team was able to take

core samples to search for microbial life

on the shipwreck itself. “In that w ay, you

can ask those really specific questions of:

How does microbial life exist on these

human-made surfaces?” She adds that

she was not surprised that the micro-

bial communities varied in and around

the wreck. “We definitely see parallels

there,” she says of her work on deep-

sea wrecks. Analyzing samples of the

surrounding sediment, her team recently

found an increasing abundance of cel-

lulose- and hemicellulose-degrading

bacteria with proximity to two newly

We’ve always known that

there’s a microbial component

to corrosion.

—Nathan Richards, East Carolina University

A B OAT FULL OF BUGS: The Pappy Lane was

intentionally run aground in the 1960s off the

coast of North Carolina. Now it’s home to a

diverse community of microbes.

JOHN MCCORD, UNC COASTA L

STUDIES INSTITUTE