The flagellum and cell fate differentiation

Lead Research Organisation: University of Dundee


How do bacteria fulfill different functions within a large population? Bacteria are single celled organisms that live in the natural environment as part of a complex multicellular community called a biofilm. In a biofilm bacteria adhere to a surface and coat themselves in a protective layer of sugars and proteins. Common examples of where biofilms can be found include teeth, in the form of dental plaque, heart valves in the form of a chronic infection, and in the gut as part of the beneficial bacterial community that helps with food digestion. Life in a biofilm gives individual bacteria advantages that they would not have if they lived in isolation. This makes bacteria living in biofilm communities are difficult to eradicate as they are highly resistant to many antibiotics and antimicrobial agents such as bleach. It appears that bacteria living in a biofilm 'club' together and protect each other. My laboratory is interested in understanding how bacteria coordinate their activity to allow bacteria to communicate and come together to form a biofilm. Information about this process will help us understand the mechanisms that bacteria use to associate together in a biofilm community and therefore may allow the development of novel approaches to treat biofilm related infections. We study the process of biofilm formation using a soil bacterium called Bacillus subtilis. This bacterium is commonly used in the laboratory as a model to understand basic processes regarding gene regulation and expression. The information derived from such studies can be applied to other bacteria associated with human infections. In our study we plan to investigate how the flagellum (the machinery that allows the bacterium to swim) controls the behaviour of the individual bacterial cells.

Technical Summary

Bacteria are single cell organisms that can live as part of a complex community called a 'biofilm'. In a biofilm the bacterial cells are encased in a self-produced polymeric matrix. Biofilms are of strategic importance as they form the basis of chronic infections and bio-remediation processes. In addition biofilms represent one of the most complex examples of bacterial cells displaying different 'cell fates'. For example in a single species Bacillus subtilis biofilm, cells differentiate so that a subpopulation of cells produces the exopolysaccharide which surrounds all of the cells. Other subpopulations of cells differentiate to fulfil other functions. How this occurs within an isogenic population is a challenging scientific problem to understand. The analysis and understanding of the molecular principles underpinning cell fate differentiation is a field of research with relevance to public health, agriculture and industry. My laboratory is interested in defining the molecular mechanisms used at the level of transcription to control these 'multicellular' behavioural processes. Excitingly we have preliminary data that point to a novel role for the flagellum in co-ordinating the transition between a motile cell and a non-motile matrix producing cell during the development of a B. subtilis biofilm. The aim of this proposal is to investigate how this is mediated. We will address this question using a combination of advanced microscopy, software development, and traditional genetic and biochemical techniques.
Description The goal of this project was to investigate whether the bacterial flagellum controlled gene expression. Using a combination of genetic, biochemical and phenotypic experimental approaches we demonstrated that for the Gram-positive bacterium Bacillus subtilis this was indeed the case. Through this work we have shown that the cell is capable of detecting signals from outside the cell and transmitting them to the cytoplasm to control gene expression. In this context the flagellum functions as a mechanosensor. Importantly these data highlight that the bacterial cell has a regulatory system capable of detecting whether or not the flagellum is rotating. Impedance of flagellar rotation could conceivably occur when a cell approaches a surface and starts to form biofilm - a community of microbial cells encase in a self-produced matrix and adherent to a surface. At a surface there would be a physical barrier to impede flagellar rotation. Our data help to address the question of how bacteria are able to sense when they are on a surface and stimulate expression of the genes essential for biofilm matrix production. Given the conserved nature of the flagellum from a wide-range of bacterial species these findings are likely to have implications during biofilm formation in both pathogenic and non-pathogenic settings.
Exploitation Route Understanding the mechanism of signal transduction to inhibit biofilms form forming on surfaces.
Sectors Agriculture, Food and Drink,Healthcare

Description Vacation Scholarship 2009
Amount £1,695 (GBP)
Organisation Society of General Microbiology 
Sector Charity/Non Profit
Country European Union (EU)
Start 05/2009 
End 08/2009
Title Genetically modified bacterial strains 
Description Cell Lines (Bacterial strains in every case): Multiple new bacterial strains have been constructed during this study; many will published in scientific journals and these strains will be made available to the broader scientific community upon request. We will deposit strains, for which we receive multiple requests, with the Bacillus genetic stock centre based in Ohio (USA) which serves as a central repository for the worldwide Bacillus community. The majority of the strains were constructed by the postdoctoral researcher. Some strains allow ground breaking work at the single cell level in bacteria; a field that is becoming rapidly recognised as important to many processes exhibited by bacteria. 
Type Of Material Model of mechanisms or symptoms - in vitro 
Provided To Others? Yes  
Impact Broadening research capability globally. 
Description Outreach Magnificent Microbes 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact The weekend of March 9th and 10th 2012 saw the Division of Molecular Microbiology at the University of Dundee hold "Magnificent Microbes 2" at the Dundee Science Centre. Magnificent Microbes 2 was funded by several sources including the College of Life Sciences, BBSRC, the Society for General Microbiology, the Biochemical Society and the British Mycology Society. The main objectives of the day remained the same and were: to use fun and interesting activities to make children and adults alike aware of how fascinating microbes, such as bacteria and fungi, really are; to train, PhD students and postdoctoral scientists in the art of communicating science to members of the general public; and to refine and develop our bank of resources for future events. Posters, activities, bookmarks

Increased learning and interest in microbiology. Questions were asked by members of the public over a number of subsequent weeks.
Year(s) Of Engagement Activity 2011,2012
Description RSE outreach activity 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach Local
Primary Audience Schools
Results and Impact Schools based outreach activity Outreach activity in hard to reach area in highlands of Scotland

no actual impacts realised to date
Year(s) Of Engagement Activity 2012