In nature, the vast majority of micro-organisms live in mixed species communities associated with surfaces and surrounded by a protective ‘glue’ made up of sticky polymers. These microbial communities, known as biofilms, are present in almost every environment where there is enough moisture to support microbial growth.
In the human body, biofilms are naturally found on the skin and throughout the gut from the mouth to the lower intestine. Normally these communities are harmless. However, the overgrowth of ‘bad’ (pathogenic) bugs at the expense of ‘good’ (commensal) microorganisms can result in disease.
The Oral Microbiology group is focused on understanding the processes that lead to the establishment of these mixed-species microbial communities on tooth surfaces (dental plaque). Dental plaque is responsible for the two major causes of tooth loss worldwide: dental caries (tooth decay) and periodontitis (gum disease).
We have identified a number of molecular mechanisms that allow microorganisms to stick to teeth. Recently, we have started a number of projects to determine the role of the sticky ‘glue’ (extracellular matrix) that holds microbial communities together in dental plaque and other biofilms.
The extracellular matrix of biofilms is composed largely of long-chain carbohydrates and nucleic acids. Extracellular DNA, released from bacteria when they die, forms a major part of the scaffold of many different biofilm matrices. Our studies have shown that extracellular DNA is an important component of biofilms formed by bugs in the mouth.
In collaboration with Prof. Grant Burgess’ group in Marine Biotechnology, we are developing new enzymes to degrade extracellular DNA and disrupt oral biofilms, breaking them up and stopping them growing on surfaces. We are also investigating the potential of these enzymes to control a variety of other medically important biofilms including those that form in people’s sinuses or on artificial speech valves. It is anticipated that this work will aid the development of new measures for controlling the accumulation of bacteria on surfaces in the human body.
Image: Fungal microcolony on the surface of an artificial speech valve. The growth of fungi such as Candida spp. on speech valves leads to degradation of the valve material and loss of function. Here, fungi were stained with concanavalin A (green), a lectin that cross-reacts with Candida cell walls; DAPI (blue), a DNA stain that enters fungal cells; and propidium iodide (red/orange), a DNA stain that only enters dead or compromised cells.