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Communication is everything – studying the interactions of bacteria (and the host) in oral pathogenesis

Principal Supervisor: Dr Sarah Kuehne - School of Dentistry

Co-supervisor: Prof Paul Cooper

PhD project title: Communication is everything – studying the interactions of bacteria (and the host) in oral pathogenesis

University of Registration: University of Birmingham

Project outline:

Background: Our mouth provides home to a complex ecosystem where hundreds of bacterial species coexist, compete, synergize and interact with each other and with the host. A delicate symbiotic balance ensures oral health, but dysbiosis can develop and lead to periodontitis, which is the most common human inflammatory disease. Treatment can be difficult, lengthy and costly which is in part due to the fact that oral bacteria mostly live in communities known as biofilms which can be extremely resistant to standard antibacterial interventions. These biofilms are often formed of multiple species, which might cooperate or compete with each other and also interact with the host. In order to study those communities, which vary between healthy and pathological states, an in vitro biofilm model has recently been developed [1].

Living as a biofilm means that bacteria need to have ways of communicating with each other to coordinate its formation and persistence. It has been shown in the past that Porphyromonas gingivalis is capable of producing a molecule known as autoinducer 2 (AI-2), which regulates the expression of genes in a population density-dependent manner [2]. Another well-known oral pathogen, Fusobacterium nucleatum, has also been shown to produce a similar molecule [3]. Such signaling molecules and their roles in virulence have been comprehensively studied in other pathogens like, for example, Vibrio cholera. However, there is limited data on oral pathogens.

Better understanding of inter-bacterial communication, also called quorum sensing (QS), within a biofilm community will lead to novel treatment avenues for diseases such as periodontitis. Small molecules, which will inhibit QS, could be designed in the future as non-antibiotic, anti-virulence drugs, circumventing the threat of antimicrobial resistance and leading the way to novel therapies.

Objectives: There are two main aims within the PhD project:

  • Firstly, establishing a multispecies biofilm based on oral bacteria.
  • Secondly, exploring cell-cell communication within the biofilm (intra and inter-bacterial species communication and communication with the host).

Secondary objective:

  • Establishing genetic tools to be used in P. gingivalis and F. nucleatum to study communication, interaction, virulence and pathogenesis and to develop novel countermeasures.

Methods/techniques: Anaerobic microbiology, growth of bacteria in planktonic cultures and biofilms, Biosensor assays, molecular biology, DNA transfer, CRISPR-Cas, qPCR, advanced microscopy, cell biology (including measurements of reactive oxygen species and cytokine production)

References: 

  1. Development of an in vitro periodontal biofilm model for assessing antimicrobial and host modulatory effects of bioactive molecules. Millhouse E, Jose A, Sherry L, Lappin DF, Patel N, Middleton AM, Pratten J, Culshaw S, Ramage G. BMC Oral Health. 2014 Jun 28;14:80. doi: 10.1186/1472-6831-14-80.
  2. LuxS-dependent quorum sensing in Porphyromonas gingivalis modulates protease and haemagglutinin activities but is not essential for virulence. Burgess NA, Kirke DF, Williams P, Winzer K, Hardie KR, Meyers NL, Aduse-Opoku J, Curtis MA, Cámara M. Microbiology. 2002 Mar;148(Pt 3):763-72.
  3. Autoinducer 2 of Fusobacterium nucleatum as a target molecule to inhibit biofilm formation of periodontopathogens. Jang YJ, Choi YJ, Lee SH, Jun HK, Choi BK. Arch Oral Biol. 2013 Jan;58(1):17-27.

BBSRC Strategic Research Priority: Molecules, cells and systems

Techniques that will be undertaken during the project:

Anaerobic microbiology, growth of bacteria in planktonic cultures and biofilms, development of an in vitro biofilm model, Biosensor assays, molecular biology, DNA transfer, CRISPR-Cas, qPCR, advanced microscopy, cell biology (including measurements of reactive oxygen species and cytokine production),

In addition to wet skills the student will be trained in necessary in silico skills, including basic bioinformatics for sequence analysis and plasmid construction.

Contact: Dr Sarah Kuehne, University of Birmingham