organisation - the Instituto Gulbenkian de Ciência

BACTERIAL
SIGNALLING
Karina B. Xavier Principal Investigator
PhD in Biochemistry, Universidade Nova de Lisboa, 1999
Research Scientist, Princeton University, USA
Principal Investigator at the IGC since 2006
Bacteria use small molecules called autoinducers to communicate with one another
by a process called quorum sensing. This process enables bacteria to regulate
behaviours which are only productive when many bacteria act as a group,
similarly to multi-cellular organisms. Behaviours regulated by quorum sensing
are often crucial for successful bacterial-host relationships whether symbiotic
or pathogenic. We use an integrative approach, from molecules to circuits, to
understand the role of quorum sensing in bacterial behaviours. Our research
involves elucidation of the molecules used as signals, the network components
involved in detecting the signals and processing information inside individual
cells, and characterisation of the behaviour of the bacterial community in multispecies
bacterial consortia. We aim to determine the role of cell-cell communication
in multispecies consortia such as the microbiota of the mammalian gut, a
community of great importance to human health.
INTER-SPECIES CELL-CELL SIGNALLING:
ITS ROLE IN BACTERIA CONSORTIA
This project will start in 2012.
GROUP MEMBERS
Jessica Thompson (Post-doc, started in April)
Pol Nadal (Post-Doc, started in February)
Catarina S. Pereira (PhD student)
Rita Valente (PhD student)
Paulo J. Correia (Trainee)
COLLABORATORS
Isabel Gordo (IGC Portugal)
Jocelyne Demengeot (IGC, Portugal)
Stephan Miller (Swarthmore College, USA)
Rita Ventura (ITQB, Portugal)
FUNDING
Howard Hughes Medical Institute (HHMI), USA
Fundação para a Ciência e a Tecnologia (FCT), Portugal
PUBLIC ENGAGEMENT IN SCIENCE
TV interview for science & technology series
In this project we will use an integrated approach towards the characterisation
of the molecular mechanisms involved in inter-species cell-cell communication
and its role in bacterial-host interactions. Our approach is composed of three
specific aims:
1. Characterisation of the molecular mechanisms involved in the regulation of
sensing and response to AI-2, the best studied interspecies signal, in the
model bacteria Escherichia coli;
2. Identification of novel inter-species signals. There is substantial evidence
of additional signals mediating interspecies quorum sensing in
γ-proteobacteria but the molecules remain unidentified;
3. Study of AI-2 signalling directly in vivo. We propose to extend our approaches
to study interspecies interactions directly in the gut of mice.
This work can lead to the rational development of novel therapies that specifically
target inter-species quorum sensing to control complex bacterial communities.
INHIBITION OF BACTERIAL PLANT VIRULENCE BY INTERFERENCE
WITH INTERSPECIES CELL-CELL COMMUNICATION.
In Erwinia carotovora virulence is regulated by non-species specific signal that
foster interspecies communication. In this project we aim to identify receptor
protein(s) and the molecular components of signal transduction involved in recognition
and response to interspecies signals. We will study how these mechanisms
influence gene expression in Erwinia carotovora to determine its impact
in virulence using the potato tuber infectious assay. These bacteria can persist
in the Drosophila gut and induce inflammation. We are studying the effect of
mutants impaired in interspecies communication in Erwinia-Drosophila interactions
in the presence or absence of other bacterial species. We hypothesise that
Erwinia uses Drosophila as a vector for infection and that interspecies communication
has an important role in this process.
We have performed a genetic screen for mutants impaired in regulation of virulence
factors mediated by interspecies signals. We are analysing these mutants
to identify a new signal involved in interspecies communication and also to
determine the impact of these mutants in the production of virulence factors
involved in the pathogenesis of Erwinia towards fruits and legumes but also
during the interaction between Erwinia and Drosophila.
COLONIES OF XENORHABDUS SPP. A PROTEOBACTERIA.
This bacteria undergoes a complex life cycle that involves a symbiotic stage, in
which the bacteria are carried in the gut of the nematodes, and a pathogenic
stage, in which susceptible insect prey are killed by the combined action of the
nematode and the bacteria.
IGC ANNUAL REPORT ‘11
RESEARCH GROUPS
67