02 Oct 2012
A recently discovered `killing system’ employed by bacteria could offer valuable insights into how to combat diseases including antibiotic-resistant hospital-acquired infections.
A new research project at the University of Dundee is to study how the system is used by some bacteria to kill others and how important it is in causing infection. Diseases caused by bacteria continue to represent a great threat to human health, particularly as multi-antibiotic resistance rises inexorably.
Dr Sarah Coulthurst, in the College of Life Sciences at Dundee, has been awarded a Medical Research Council grant of £330,000 to carry out research on the bacterium Serratia marcescens, which is known to cause serious hospital-acquired infections, especially in neonatal units.
“If we study and understand the mechanisms by which harmful bacteria survive, grow, overcome the normal defences of humans and cause disease, then we can develop new ways to combat them. Such new ways might be new drugs, vaccines or more efficient diagnostic tools,” said Dr Coulthurst.
She said that the bacteria themselves can offer clues as to how best they can be killed.
“This is a case of ‘learning from the experts’ – the bacteria themselves,” she said. “They have excellent systems for killing off other bacteria. If we can work out how they do that then it can potentially inspire future work to develop new anti-bacterial drugs. We will also know more about an important class of hospital infection-causing bacteria. Ultimately our work may contribute towards the search for novel antibiotics and other therapeutic strategies to combat bacterial disease.”
Serratia marcescens belong to a class of bacteria called ‘opportunistic Enterobacteria’, which frequently cause antibiotic-resistant hospital-acquired infections.
“This bacteria is relatively easy to study in the laboratory, so we can use it as a model to understand how all these related bacteria cause disease,” said Dr Coulthurst.
A process called ‘protein secretion’ plays a key role in the ability of many different types of pathogenic bacteria to survive and cause disease. Protein secretion is a process in which bacteria move a specific set of their proteins out of the bacterial cell and into their surroundings, sometimes even injecting them directly into human cells. These secreted proteins can then attack and destroy or hijack the cells of the infected host, causing disease.
Dr Coulthurst’s research project will look at a recently discovered type of secretion system, to try and learn how bacteria can use it as a weapon to become successful pathogens. Little is known about this new secretion system, called ‘Type VI Secretion’.
“It is important that we find out how this system works and what it does, since it is clear that many pathogenic bacteria use this system to help them successfully infect a host organism and cause disease,” said Dr Coulthurst.
“Some types of bacteria use the system to directly attack the cells of the infected host, whereas some types of bacteria use the system to efficiently kill other bacteria. The use of Type VI secretion systems to attack other bacteria is important for the success of pathogenic bacteria, since killing their rival bacteria, for example harmless or ‘good’ bacteria normally found in the body, leaves the way clear for the pathogen to cause a harmful infection.
“Our research will greatly improve our understanding of how this new secretion system is used by pathogenic bacteria to enable them to out-compete their rivals and thus prosper and cause disease in humans.”