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Bacterial inter-species communication mediated by the autoinducer-2 signal
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During the last few decades, scientists have come to appreciate the
immense complexity in bacterial signaling interactions that sustain microbial
communities. Quorum-sensing (QS) is a cell-cell communication process
whereby single cell bacteria regulate gene expression synchronously in a
population in response to self-produced extracellular signal molecules, called
autoinducers. Autoinducer-2 (AI-2), the synthase of which, LuxS, is present
in both Gram-negative and Gram-positive bacteria, was proposed to represent
a non-species-specific signal that mediates inter-species communication. In
enteric bacteria, extracellular AI-2 levels peak in late exponential phase and
rapidly decline as bacteria continue to grow. This depletion occurs because
AI-2 activates the expression of an operon, lsr (for LuxS Regulated), encoding
the Lsr transporter and enzymes that degrade the signal. As the Lsr system
imports self and non-self AI-2, lsr-containing bacteria can interfere with AI-2
signaling of other species and shut off group behaviors regulated by this
molecule: this system represents the first example of interference with a
bacterial inter-species QS signal.(...)
Descrição
Dissertation presented to obtain the
Ph.D degree in Biology by Universidade Nova de Lisboa, Instituto de Tecnologia Química e
Biológica, Instituto Gulbenkian de Ciência.
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Universidade Nova de Lisboa. Instituto de Tecnologia Química e Biológica