Posted 12/12/2006

Biofilms, a new frontier in microbiology, is the focus of scientists at the Decho laboratory

Life on the cutting edge can be lonely.

Dr. Alan Decho remembers when he arrived at the University of South Carolina12 years ago, eager to study something called biofilms.

"At the time it was not very well known. It fact, most of my grant proposals were not funded because people didn't believe (biofilms) existed," Decho said.

It's a different story today. Decho has research money and biofilm research under way that reaches from his high-end lab at USC to the tropical waters of the Bahamas.

Decho explained that while relatively new to scientific inquiry, biofilm formation is a common microbial process that has been around about as long as the earliest life forms on earth.

"We think of most bacteria as free cells just floating around," Decho says from his fifth floor office in the Arnold School's new research center.

A biofilm forms, he says, when bacteria attach to a surface and form a slimy protective mucous layer. Behind the layer, the bacteria begin to act as a single entity - much like an army -- using chemical signals to direct their activities.

By organizing into a biofilm, a group of bacteria can become up to 1,000 times more resistant to antibiotics and able to resist chlorination, radiation, high heat and other conditions that would destroy individual cells.
 
THREATS TO HEALTH

Biofilms are all around as well as inside of us, says Decho. They are a leading cause of hospital-acquired infections that kill upwards of 90,000 persons per year. Scientists also say chronic urinary tract infections and many cases of bronchitis are the result of persistent biofilms that linger in the body.

Biofilms are a problem with medical implants when they attach to the surface of a device and produce infections that can be deadly.

In the environment biofilms attach to the surfaces of industrial equipment, ship hulls, and water pipes. A biofilm in an air conditioning system was the source for the 1976 outbreak of Legionnaire's Disease.

Scientists estimate the biofilm formation results in an annual $100-plus billion in economic, industrial and health-care costs.

As harmful as they can be, biofilms also play an important role in human health, Decho said. Biofilms that line the esophagus and the intestines form a line of defense against other bacteria that could cause illness.

With three ongoing grants from the National Science Foundation, and funding from the National Oceanic and Atmospheric Administration, Decho and his lab team are studying biofilms to learn how bacteria communicate within a biofilm.

QUORUM SENSING

Understanding how biofilms communicate - scientists call it quorum sensing - is critical to developing a way to interfere with that activity, Decho said.

"Some people feel that antibiotics may soon be outdated because bacteria can develop resistance to them. But if we can disrupt the communications, these bacteria become a bunch of uncoordinated cells that are unaware of each other. Under those circumstances we can more easily kill them," he said.

Like a general planning a military operation, Decho says he's searching for compound, called analogs, that resemble the communications signals used by biofilms. The difference, however, is that the analog would have no meaning for the bacteria and confound their communication, so they could be easily destroyed by antibiotics.

The Arnold School lab has identified one compound that has potential and is working to analyze its structure.

Decho says the Department of Health and Environmental Sciences and the USC Chemistry Department are collaborating in a joint study of quorum sensing that has "far-reaching practical applications.

The process relates to the spread of disease in public health, the resistance of infections in medicine and recently discovered high-diversity of bacteria within certain natural environments."

NEW EQUIPMENT

The joint project is supported by a $2 million NSF grant. Decho plans to use part of the money to upgrade his lab with equipment that can better examine bacteria and identify their chemical activities.

Decho speaks enthusiastically of another NSF research project involving USC and several other universities at a remote subtropical island named Highborne Cay, part of the Bahamas.

The study involves studying the interaction of biofilms as they create structures called stromatolites, layered deposits of calcium carbonate.

Stromatolites are the oldest macroscopic evidence of life on earth dating back more than three billion years ago, with an incredibly high diversity of bacterial species that communicate and work together to form these rock structures. They were widespread in ancient seas and are still forming in existing environments such as the Bahamas. They will teach us some fundamental rules about how bacteria interact with each other.

Among other ongoing projects Decho's lab is:

•  Studying how biofilms change the optical quality (e.g. reflectance, scattering, absorbance, fluorescence) of the undersea environment. The project, sponsored by the Navy, is aimed at understanding how light acts under water. The technology is important to the Navy because it can be used to detect objects, such as mines, hidden under sediment.

•  Studying how biofilms help bacteria survive environmental extremes. On San Salvador, another Bahamian island, bacterial grow in hypersaline pools that virtually dry up at times. Decho wants to know why these bacteria can be revived from a dry, hardened state to an actively-metabolizing state within hours after exposure to rainwater.

•  Studying how biofilms can transfer contaminants to a variety of small coastal marine animals.

•  Studying biofilms in the proximity of human colon cancers to see if specific types of bacteria may either help initiate and/or stimulate early colon cancer.

Many of these projects involve collaborations with the USC Chemistry Department. “We’re at the tip of an iceberg that may provide some interesting science and perhaps real solutions to some costly practical problems”

For more information about biofilms:

• Decho laboratory