Ken Nealson leads a group of 10 young science writers through his expansive microbiology laboratory, eagerly pointing out all of the chemostats, deep freezers, genetic sequencers, and other scientific equipment that his research team uses to probe the bacterial world. 

“My graduate students don’t know how good they have it here, until they leave,” Nealson said. 

But the expensive equipment isn’t for the graduate student’s sake, rather, the entire lab is dedicated to a single bacterium that Nealson fondly calls “Shewie.”
   
Shewanella is a type of bacteria that uses chunks of metal for respiration.  Biochemists describe respiration as the extraction of electrons from food, which are then passed through several proteins and enzymes to generate energy.  Humans and most other animals use oxygen, rather than metal, to finally get rid of the electrons. 

So while humans breathe air, “the bugs are breathing rocks,” Nealson joked at his lab on the University of Southern California campus. 

However, it’s not the rock breathing per se that’s so remarkable. 

Nealson, the Wrigley Professor of Geobiology at the University of Southern California, has been studying this unusual organism for the past 20 years. 

Unlike most other bacteria, shewanella engages in respiration while the minerals are outside of its cell wall - a discovery that has revolutionized what microbiologists know about bacteria.
 
It was once thought that all bacteria performed respiration inside of the cell, as it’s convenient to simply transport a small molecule like oxygen through the cell wall. 

But because Shewanella lives in oxygen poor environments – such as the sediment of lakes – it has evolved the capacity to respire with chromium and manganese oxide rather than air.

Chunks of minerals are too large to be taken up by bacteria. And Shewie doesn’t break down the rocks to then absorb the smaller components.  Instead, and against the conventional wisdom of microbiology, Shewie simply congregates on the rocks and starts breathing.
   
“Bacteria don’t do things outside of the cell. They take everything in and do it inside the cell,” Nealson’s critics would tell him. That a bacterium could do otherwise “was a very difficult thing to get the world to believe.”

However, he persisted with his experiments and mounted evidence supporting his discovery.

“When someone says it can’t be right, then you know you’re on to something,” he said.

Nealson showed that he could put Shewie in a test tube with manganese oxide and sugar, and after several days, the ink black manganese oxide would transform into the electron-saturated form of manganese, leaving the test tube clear. 

This was a smoking gun for respiration. But he still had to take a closer look.

Using high-powered microscopes and biochemical analysis, Nealson demonstrated that shewanella has the proteins necessary to respire metallic compounds. 

What’s more, these compounds were indeed on the outer membrane of the bacteria. The external proteins would allow the bacteria to transfer electrons to the chromium and manganese oxide without having to absorb large chunks of rock.  But the evidence still didn’t convince, who Nealson refers to as, “the e. coli gang.”

Virtually all microbiologists are trained with the model bacteria e. coli, and e. coli don’t have enzymes and proteins on the outside of their cell wall. It’s been roughly 20 years since his initial experiments, and Shewie’s unique physiology is just now getting into the textbooks.

Nealson recalled his battle with the old guard of bacteriologists in a gleeful tone. He has spent an industrious 20 years of his career investigating shewanella, and has earned considerable esteem in the process. 

And he still has more work ahead.
   
Nealson’s lab is manufacturing bacterial fuel cells using shewanella that will convert pollutants – such as chromium and other industrial waste – into water and electricity. 

These bacterial batteries should produce enough electricity to power themselves, which could provide a revolutionary self-sustained waste disposal system.

“You get rid of your waste, you make distilled water, and you get paid for,” Nealson said. “This is a good deal.” 

He’ll just have to see if environmental scientists are easier to persuade than microbiologists.