Analysis of proteins regulating polar flagellum localisation and number in Vibrio cholerae
Lead Research Organisation:
University of Cambridge
Department Name: Pathology
Abstract
The bacterium Vibrio cholerae causes worldwide epidemics and pandemics of the severe diarrhoeal disease cholera. V. cholerae swims through liquids by rotating a long corkscrew-like propeller, called a flagellum, which is an important factor in the ability of the bacterium to colonise the human host and cause disease. The flagellum is positioned at one end, or pole, of the cell, as is the machinery that exports the major virulence factor cholera toxin. To ensure that each V. cholerae cell has a single flagellum at one pole, the cell must carefully regulate when and where this structure is built. I aim to establish a project that will address two questions: How is the flagellum specifically targeted to one cell pole? How is the number of flagella per cell regulated? I will build on preliminary work to determine the functions of two proteins, FlhF and FlhG, that target the flagellum to the right place in the cell and regulate flagellar number, respectively. Through our studies, we will build up a picture of the molecular networks that link flagellum biogenesis, cell asymmetry (or polarity), and cell division.
Technical Summary
Flagellum-based motility is a key virulence factor of the pathogenic bacterium Vibrio cholerae. The flagellum is located at the old cell division pole, a specialised microenvironment that also houses the type II secretion apparatus that exports cholera toxin, other virulence proteins, and the CTXphi phage carrying the cholera toxin genes. V. cholerae builds only one flagellum per cell, suggesting that flagellum biogenesis must be closely coordinated with cell division. I aim to establish a project investigating the factors controlling polar localisation and flagellar number. The proposed work focuses on two V. cholerae flagellar proteins, FlhF and FlhG, that control flagellum localisation or couple flagellum biogenesis and cell division to ensure that each cell has a single polar flagellum. The flhF and flhG genes are conserved in several polar-flagellate pathogens, including Pseudomonas aeruginosa and Helicobacter pylori, and encode proteins with similarity to key effectors of membrane protein targeting (FtsY) and cell division (MinD), respectively. We will build on preliminary data using biochemical and molecular genetic techniques to establish the functions of these proteins and to identify interacting partners, thus mapping out the protein networks that coordinate flagellum biogenesis, polar targeting and cell division.
Organisations
People |
ORCID iD |
| Gillian Fraser (Principal Investigator) |
Publications
Green JC
(2009)
Recruitment of the earliest component of the bacterial flagellum to the old cell division pole by a membrane-associated signal recognition particle family GTP-binding protein.
in Journal of molecular biology
| Description | The bacterium Vibrio cholerae causes worldwide epidemics and pandemics of the severe diarrhoeal disease cholera. V. cholerae swims through liquids by rotating a long corkscrew-like propeller, called a flagellum, which is an important factor in the ability of the bacterium to colonise the human host and cause disease. The flagellum is positioned at one end, or pole, of the cell, as is the machinery that exports the major virulence factor cholera toxin. To ensure that each V. cholerae cell has a single flagellum at one pole, the cell must carefully regulate when and where this structure is built. We have addressed two questions: How is the flagellum specifically targeted to one cell pole? How is the number of flagella per cell regulated? We have found that one protein, called FlhF, has a central role in positioning the flagellum at one cell pole. When cells do not have FlhF, their ability to build flagella is greatly reduced, and any flagella that are constructed are in the wrong position on the cell surface. We have shown that FlhF itself is targeted to one cell pole, even in the absence of all other flagellar proteins, and we have identified the specific region of FlhF that is required for its polar targeting. For FlhF to function properly, we have shown that it must first bind to a small molecule called GTP. Finally, we have shown that FlhF establishes polar localization of the flagellum by recruiting the first flagellar building block to a single cell pole. A second protein, called FlhG, regulates the number of flagella that are built per cell. We found that cells which do not produce FlhG build too many flagella (8-10 per cell), and cells that produce too much FlhG do not build any flagella. FlhG was found to bind to a regulatory protein, called FlrA, which binds to DNA and switches on the genes required for flagella biogenesis. We found that FlhG could stop FlrA switching on flagella genes, and to do this FlhG also needed to bind a small molecule called ATP. Our data indicate that FlhG regulates flagellar number by controlling the activity of the FlrA regulator. |
| Exploitation Route | These findings might be taken forward by scientists working in the field of bacterial flagellum biogenesis. This might include future studies to identify new antibacterial drugs that might target flagella biogenesis and function. |
| Sectors | Other |
| Description | Our findings have been used by other scientists working in the field of bacterial flagella biogenesis. |
| First Year Of Impact | 2009 |
| Sector | Other |
| Impact Types | Societal |