New discovery shows DNA both protects and harms bacteria

By Jordanna Heller
Posted December 2, 2008

Clockwise from left: Heidi Mulcahy, Study Author; Shawn Lewenza, Principal Investigator; and Laetitia Charron-Mazenod, Lab Technician.: Photo by Chris KindratskyFaculty of Medicine researchers have shown for the first time that DNA acts as a double-edged sword that both protects and harms bacteria. The finding was made in the lab of Shawn Lewenza, PhD, Assistant Professor in the Department of Microbiology & Infectious Diseases at the UCalgary Faculty of Medicine, and published in PLoS Pathogens. Heidi Mulcahy, PhD is the lead author on the paper.

Lewenza and his colleagues have shown that DNA makes cells within a biofilm a thousand times more antibiotic resistant. A biofilm is a community of bacteria that grow on mucous membranes in the body, such as the surface of the lungs, and on devices implanted in the body such as catheters. Bacterial biofilms cause many types of infections and are extremely difficult to treat because of their increased antibiotic resistance. Extracellular DNA is released from dead cells and accumulates in biofilms and in certain infection sites.

Could lead to treatment for people with chronic biofilm infections

This finding explains how specific biofilms in Cystic Fibrosis (CF) patients may survive constant antibiotic treatment and resist the host immune response. The discovery may also help explain the success of DNAse therapy currently used to treat CF patients and suggests that degrading DNA in biofilms might improve antibiotic treatment of other chronic biofilm infections including wounds and sinusitis.

Lewenza and his team have also shown that an excess concentration of DNA is antimicrobial and kills bacteria.

Lewenza is the principal investigator on this study. His research is supported by the Westaim Corporation and the Alberta Science and Research Authority, and he is the Westaim-ASRA Chair in Bacterial Biofilm Research.

About the Faculty of Medicine at the University of Calgary

The U of C's Faculty of Medicine is a national leader in health research with an international reputation for excellence and innovation in health care research, education and delivery. Through its educational programs, the Faculty of Medicine trains the physicians and scientists who will lead the next generation of health practitioners. Through its clinical work, continuing medical education programs, and close relationship with the Calgary Health Region, the Faculty of Medicine moves new treatments and diagnostic techniques from the laboratory bench to the hospital bedside efficiently and effectively, improving patient care.

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