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Viruses gain good reputation in bacteria treatment

A man turns to face the camera while sitting at his desk.

Zhiqiang Hu, an associate professor of civil and environmental engineering, worked with then-doctoral student Yanyan Zhang to examine the uses of bacteriophages against biofilms.

In recent years, the notion of “good bacteria” having an impact on people’s health has sparked a trend in the food and nutritional supplement industry. Products containing probiotics, for instance, are marketed to aid in digestive health.

In the middle of cold and flu season, amid sniffles, sneezes and coughs, a team from the College of Engineering’s Civil and Environmental Engineering Department has published a paper that suggests there could be some “good viruses” too.

In their recently published paper, Associate Professor Zhiqiang Hu, working with then-doctoral student Yanyan Zhang, looked at the effects of bacteriophages in water and wastewater treatment, particularly when paired with chlorine.

Derived from the Greek word phagein, meaning, “to eat,” a bacteriophage, simply known as a phage, is a virus that replicates inside bacteria.

Phages attach themselves to bacteria, a parasitic behavior that ultimately destroys the bacteria once the phage begins propagating. Eventually, so many new phages are created the bacterial cell bursts.

The research served as the basis for Zhang’s doctoral dissertation examining the effects of phages on the bacteria Pseudomonas aeruginosa alone and when paired with chlorine . For control purposes, researchers also examined chlorine-only treated bacteria and maintained an untreated sample.

A woman in a lab coat looks at the camera while opening a container.

Yanyan Zhang conducted the phage research while a doctoral student at MU. Now a post-doctoral researcher at the University of Alberta, she and Hu published their findings in the January 2013 issue of Biotechnology and Bioengineering.

P. aeruginosa is a common type of bacteria that thrives in both normal and low-oxygen environments. The bacteria can cause infections in humans and, in extreme cases, can lead to fatal infections if allowed to colonize in a major organ. It is the bacteria implicated in “hot tub rash,” an infection of the hair follicle often caused by bacteria found in hot tubs and in water slides.

Bacteria are capable of grouping together to form a biofilm, which produces an outer surface layer, making the bacteria harder to kill.

The amount of time it take phages to fully destroy a biofilm depends on the number of phages and the biofilms’ size.

“If this biofilm is a basketball court, the virus would be something the size of a pingpong ball,” Hu said.

Now a post-doctoral researcher at the University of Alberta, Zhang collected samples from a Columbia wastewater treatment facility. The phages were isolated and collected from these samples. Microplate wells containing biofilms of P. aeruginosa were treated with chlorine, phages or a “cocktail” of phages followed by chlorine disinfection.

Four close up slides of bacteria.

Above are four transmission electron microscopic images showing the biofilm subcellular structures after the phage and chlorine treatment. Image A (top left) is the control. Image B (top right) is a chlorine-only treated biofilm. Image C is phage-only treated, and image D is the phage and chlorine-treated biofilm.

“The replication of phages is very fast, 20 or 30 minutes, but because a biofilm is so thick, it can take a couple of days to destroy the biofilm. It took us five days to completely remove biofilms,” Hu said.

Particular phages only bind on the receptors of certain bacteria, making it easier to target a specific type of bacteria. Because of this, Hu said this viral growth wouldn’t harm beyond the intended target.

“Only if you’re the bacteria,” he said.

“Phages have a specific host,” Zhang added.

Slides of biofilms.

Images of the biofilm wells show the comparison of the effects of chlorine, phage and a phage-chlorine treatment to wastewater samples over the course of five days.

Over the course of five days, Hu and Zhang noticed a greater reduction of biofilms in the phage-treated samples. Samples treated with the phage and chlorine showed the greatest reduction of biofilms.

Zhang’s interest in phage research started early in her doctoral studies.

“In the beginning, Dr. Hu asked me to read about nanotoxicity on bacteriophages,” she said. “That’s where I learned phages can be used to control bacteria.”

It’s a field of study that’s always ongoing, according to Hu.

“As water specialists, we are always doing a lot of research for water and wastewater treatment,” Hu said. “You’re always looking at organisms that we can use to treat water.”

The next step is taking the approach to a larger scale.

“It’s most difficult to convince people to use this treatment approach,” Hu said.

“The best way to inform people about the benefits of viruses is through education,” Zhang added. “People will learn some viruses pose no harm to human cells.”

The paper, “Combined Treatment of Pseudomonas aeruginosa Biofilms with Bacteriophages and Chlorine,” was published in the January 2013 issue of Biotechnology and Bioengineering.