The Language of Bacteria... and Just About Everything Else
Secrets to immune and endocrine function may lie in interkingdom
communication
By Kendra Rumbaugh

Courtesy of Kendra Rumbaugh

Mammals possess sophisticated endocrine networks in which hormonal signals
modulate hundreds of biological effects such as cell differentiation,
reproduction, and immune responses. Disrupting these pathways often leads to
dire consequences such as birth defects and cancer. Though bacteria are
unicellular, they also possess signaling pathways that can be likened to
tiny endocrine systems.
Bacterial quorum sensing (QS) pathways allow bacteria to sense their cell
density and respond by coordinating protein expression. Thus bacteria
communicate and can coordinate their efforts in diverse activities such as
building biofilms, transferring DNA, or causing infections. QS has forced
microbiologists to view bacteria not as single entities but as interactive
and heterogeneous communities that must be studied within this context. This
interactivity and communication extends beyond microbes at
prokaryote-eukaryote interfaces such as the host-pathogen relationship.
Thus, much of what we are learning may extend beyond the microbial world.

During the last decade, the quorum sensing field has exploded. Breakthroughs
have been made in identifying bacteria that possess QS systems, elucidating
their cell-signaling pathways, identifying the genes controlled by QS, and
in purifying their signaling compounds. Many Gram-negative bacteria produce
acylated homoserine lactones (AHLs) for cell-to-cell communication. AHLs are
small lipid-based chemicals, which mainly diffuse through bacterial
membranes and may be specific for one species of bacteria or shared between
many species. A second, extremely important signaling molecule, aptly named
Autoinducer-2 (AI-2), is proposed to be a so-called universal autoinducer,
which is synthesized by dozens of bacteria and may be sensed by hundreds
more.

Full Text at TheScientist
http://www.the-scientist.com/yr2004/sep/research2_040913.html

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