Revealing the weapons by which bacteria fight each other

April 4, 2013

A new study which was performed jointly at Umea University and the University of Washington in Seattle, USA, discovered that bacteria can degrade the cell membrane of bacterial competitors with enzymes that do not harm their own membrane. This exciting finding opens the way for the development of new antibacterial drugs to fight bacteria using their own weapons.

During the infection of a , can excrete toxins that cause damage to host cells and tissue. Interestingly, bacteria also use similar mechanisms in competition with one another. Notably, they can use secretion systems with syringe-like structures to inject the toxins into other cells. Among the different secretion systems that are known in bacteria, the type VI secretion system is of particular importance to interbacterial competition, and is found in many different . The collaborating Swedish-American research teams now found that certain enzymes, phospholipases, are secreted by the type VI system and that they are only effective against the competitor but not the producer's own cell membrane.

Sun Nyunt Wai, professor at the Laboratory for Molecular Infection Medicine Sweden (MIMS) and the department of Molecular Biology in Umeå, Sweden, and Joseph D. Mougous, professor at the University of Washington, Seattle, USA, studied together with their students and post-docs the genes and proteins that are behind this selective . They studied the type VI secretion systems in Pseudomonas aeruginosa, causing severe infections of intestines, blood and lungs, and in , a pathogen causing the life-threatening cholera diarrhea.

"Bacteria have evolved many strategies for defence against predators and competitors in the environment. In this study we found that the bacteria possess phospholipases, that degrade a major phospholipid component in the cell membranes," Sun Nyunt Wai, said. And we found that the bacteria producing the antibacterial effector at the same time produced an immunity protein that protects them against their own toxin. Her student Krisztina Hathazi and postdoctoral fellow Takahiko Ishikawa participated in the studies and are co-authors of the report in Nature.

When the team tested their hypothesis with mutants lacking the genes for immunity, they found that membrane integrity was greatly impaired, as the bacterial cells were now harmed by self-intoxication.

"The finding that bacterial phospholipases, classically considered potent mediators of virulence, can also serve as offensive weapons against competing bacteria was really quite surprising and challenges basic assumptions made concerning these enzymes," commented PhD student Alistair B. Russell, the first author of the report. Both Alistair and the second author, Michele LeRoux, are graduate students in the laboratory of Joseph D. Mougous, the corresponding author of this study. Joseph and his students are members of the Department of Microbiology and Molecular and Cellular Biology Program at the University of Washington in Seattle, and an additional author of the study, professor Paul A. Wiggins, is a member of the Departments of Physics and Bioengineering at the University of Washington in Seattle.

Explore further: Pseudomonas deploys a toxin delivery machine to breach cell walls of rivals without hurting itself

Related Stories

Decoding the molecular machine behind E. coli and cholera

February 9, 2012

Scientists from Queen Mary, University of London have discovered the workings behind some of the bacteria that kill hundreds of thousands every year, possibly paving the way for new antibiotics that could treat infections ...

Structure mediating spread of antibiotic resistance identified

January 8, 2009

Scientists have identified the structure of a key component of the bacteria behind such diseases as whooping cough, peptic stomach ulcers and Legionnaires' disease. The research, funded by the Wellcome Trust and the Biotechnology ...

Researchers discover energy supply for protein secretion

May 10, 2012

In order to interact with the environment, bacteria secrete a whole arsenal of proteins. Researchers have now found how one of the transportation systems used for this purpose – the type VI secretion system – works ...

X-rays reveal the self-defence mechanisms of bacteria

September 14, 2012

A research group at Aarhus University has gained unique insight into how bacteria control the amount of toxin in their cells. The new findings can eventually lead to the development of novel forms of treatment for bacterial ...

Recommended for you

Genome study offers clues about history of big cats

July 21, 2017

(Phys.org)—A large international team of researchers has conducted a genetic analysis and comparison of the world's biggest cats to learn more about their history. In their paper published on the open source site Science ...

Researchers discover mice speak similarly to humans

July 21, 2017

Grasshopper mice (genus Onychomys), rodents known for their remarkably loud call, produce audible vocalizations in the same way that humans speak and wolves howl, according to new research published in Proceedings of the ...

Good fighters are bad runners

July 21, 2017

For mice and men, a strength in one area of Darwinian fitness may mean a deficiency in another. A look at Olympic athletes shows that a wrestler is built much differently than a marathoner. It's long been supposed that strength ...

Researchers discover biological hydraulic system in tuna fins

July 20, 2017

Cutting through the ocean like a jet through the sky, giant bluefin tuna are built for performance, endurance and speed. Just as the fastest planes have carefully positioned wings and tail flaps to ensure precision maneuverability ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.