A University of Wisconsin professor and four other medical scientists from around the country recently discovered a toxic molecule that causes disease in humans and simultaneously allows survival in small Pacific Ocean squid.

The toxin, known as tracheal cytotoxin (TCT), was found in the laboratory of UW professor of medical microbiology Margaret McFall-Ngai. It is considered a critical catalyst for the development of the self-defense organ in squid.

The toxin was discovered to spur the development of a structure, which is a light-producing organ that can mimic starlight to confuse predators of squid, according to a UW release. When the squid are born, they must acquire the toxin-producing bacteria from their ocean environment.

In humans, this same kind of toxin, produced by different species of bacteria, is known as the cause of whooping cough, gonorrhea and tremendous tissue damage, McFall-Ngai said.

“Depending on the biological context, the molecule does different things, either good or bad,” UW spokesperson Terry Devitt said.

McFall-Ngai noted that just because something is harmful to one animal does not mean it cannot benefit another.

“The communication between bacteria and their hosts determines whether or not the relationship is beneficial or harmful,” McFall-Ngai said, adding all 2,300 different kinds of bacteria in human body are potentially valuable.

This discovery has raised a problem in the use of conventional antibiotics.

McFall-Ngai said antibiotics that we consume today destroy bacteria indiscriminately, killing both the good and bad bacteria when only the pathogenic ones are targeted. Since some of the destroyed bacteria are critical in human digestion, people sometimes have digestion problems after taking antibiotics.

“It is like killing all the black-haired people in my lab because there is [one] black-haired person whom I want to destroy,” she said. “We need to be more specific, such as by categorizing into the black-haired person with the blue eyes.”

The finding gives new insight for medical scientists to design a new kind of antibiotics targeting specific bacteria that is the main agent of diseases.

“The fact that similar molecules are used by both beneficial and pathogenic bacteria should be an important consideration for the design of antibiotics,” McFall-Ngai said. “It is a beginning of an [improvement] in the field of medical science.”

Michael Clay, a UW junior assisting McFall-Ngai in the squid research, said he did not know many details about the research, but added there was a lot of excitement around the lab.

“[McFall-Ngai and the graduate students] were very happy about the finding. It was big news in the lab,” Clay, whose job is to maintain chemical levels in the squid’s tanks and ensure their health, said. “But I feel honored to work with them in this important discovery. They are nice people and they worked hard in the research.”

McFall-Ngai’s next research project will attempt to discover the molecule that receives information and responds to tracheal cytotoxin in squid.