Revealing the weapons by which bacteria fight each other

Apr 04, 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: Scientists create mouse model to accelerate research on Ebola vaccines, treatments

add to favorites email to friend print save as pdf

Related Stories

Decoding the molecular machine behind E. coli and cholera

Feb 09, 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

Jan 08, 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

Sep 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 ...

Recommended for you

Researchers capture picture of microRNA in action

Oct 30, 2014

Biologists at The Scripps Research Institute (TSRI) have described the atomic-level workings of "microRNA" molecules, which control the expression of genes in all animals and plants.

Blocking a fork in the road to DNA replication

Oct 30, 2014

A team of Whitehead Institute scientists has discovered the surprising manner in which an enigmatic protein known as SUUR acts to control gene copy number during DNA replication. It's a finding that could shed new light on ...

Cell division, minus the cells

Oct 30, 2014

(Phys.org) —The process of cell division is central to life. The last stage, when two daughter cells split from each other, has fascinated scientists since the dawn of cell biology in the Victorian era. ...

A new method simplifies the analysis of RNA structure

Oct 30, 2014

To understand the function of an RNA molecule, similar to the better-known DNA and vital for cell metabolism, we need to know its three-dimensional structure. Unfortunately, establishing the shape of an RNA ...

User comments : 0

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.