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Bobtail squids light the way for infection investigation at NMSU

Each night when the moon brightens the shallow warm waters of Sydney, Australia, a burrowed squid rises from the sand to hunt. Hunting for shrimp, the tiny predator, who is now exposed in the moonlight, suddenly becomes the prey.



New Mexico State University doctoral student Alba Chavez stands next to the Sydney Opera House. Chavez worked on collaboration with the Center of Marine Bio-innovation in Sydney, Australia, where researchers discovered that vibrio bacteria produce chemical components that kill other organisms. (Courtesy photo)

Using innate survival skills, the nocturnal squid quickly releases a beam of light to counter the moon's ray, making it virtually invisible to the hungry predators lurking beneath.

"They're kind of like stealth squid swimming around," said New Mexico State University Biologist Michele Nishiguchi.

The squid's survival skill comes from a bioluminescent bacterium, a bacterium that glows in the dark. The counter illumination effect, or silhouette reduction, removes the squid's shadow from the water, making it to appear to disappear.

"They have an ink sac that wraps around the light organ like a diaphragm on a camera, and they open it up," Nishiguchi said. "So all the bacteria is exposed, and there's full light production."

Nishiguchi and a team of researchers in her lab have been studying the symbiotic relationship between bobtail squid and bioluminescent bacteria. They use the squid as live models to examine human infection and pathogens, like cholera.

Twice a year, Nishiguchi travels to Sydney where she collaborates with the Center of Marine Bio-innovation (CMB). During a recent trip down under, researchers discovered that vibrio bacteria produce chemical components that kill other organisms.

"My findings indicate that vibrio are kind of a selfish bacteria," said Alba Chavez, a microbiology doctoral student in the College of Arts and Sciences at NMSU. "They don't like to interact with other organisms. So similar to the antibiotics, such as penicillin produced in fungi is used to kill other fungi, vibrio is doing the same. So, that was really interesting for me and for Dr. Diane McDougald's laboratory at the University of New South Wales-CMB as well."

Chavez, who received a bachelor's from the Universidad Autónoma de Chihuahua in 2004, flew to the University of New South Wales in November where she spent a month collecting specimens and using the marine center equipment to study the bacteria in the planktonic community.

"By using the different facilities, I was able to see how the different organisms respond to each other, what kind of components they need to interact with one other, and if they don't like each other, what type of toxicity they produce," Chavez said.

Chavez presented her preliminary findings at the CMB in Sydney. Later in the year, she plans to present her results at The American Society for Microbiology national conference.

Nishiguchi began working with the squid and the bioluminescent bacteria as a postdoctoral student in the mid 90s at the University of Southern California, and her research focuses on two areas - environmental factor changes and biomedical aspects.

She looks at changes in water temperatures, salinity and nutrients in ocean systems.

"We're finding a lot of that is changing, and this goes back to seasonal changes and possibly global climate change," Nishiguchi said. "If there's climate changes going on, it may effect the dynamics of this relationship, so that's one thing I think is really important."

She also seeks to understand more about how the bacteria find the squid before infecting it.

"Why is it only these squids that have these bacteria that produce light?" Nishiguchi said. "Why don't they take the other millions of bacteria in the sea water? There are lots of different biochemical and molecular mechanisms that are responsible for adhering inside the squid light organ."

Nishiguchi said she was surprised to find ecological divisions with the bacteria during the course of her research. She said there were strains that liked warmer temperatures while others preferred the southern hemisphere, which has colder water.

"They're all the same species of vibrio, so I thought they would all be really different genetically, and that's not the case," Nishiguchi said. "They're really similar, they just have a very good ability to adapt very quickly. We call them plastic."

Nishiguchi said future research in the field involves examining the human microbiome, which involves the beneficial bacteria living within our bodies.

"What happens when you wipe out the natural fauna, like with antibiotics?" Nishiguchi said. "Does it allow pathogens to come in more readily?

Nishiguchi believes people might be doing themselves a disservice by using antibacterial soaps.

"Get in the dirt and get dirty," Nishiguchi said. "I think it enhances your immune system, and you're going to be better prepared when there is an attack by a foreign pathogen. Bacteria are not bad, they're actually really good for our own human health and managing the ecosystems, because they're great at degrading things and processing things, and we need them."