microbe microbe interaction could be studied briefly

1. Presented by
NISHANTH S
2016601106

2. What is Quorum sensing?
Quorum sensing allows
populations of bacteria to
collectively control gene
expression, and thus synchronize
group behavior.
Quorum sensing is a
process of bacterial cell-to-cell
communication involving the
production and detection of
extracellular signaling
molecules called autoinducers.

3. Schematic model of QS-related interactions between plants and bacteria.
AHL QS signals
(triangles and
circles) from
bacteria (ovals)
affect QS-
regulated
behaviors in the
bacteria and also
elicit a diversity
of responses in
the plant.
The plant produces and secretes AHL mimic compounds
(circle/square, triangle/square) that disrupt or manipulate QS-
regulated behaviors in the bacteria. Plant responses to bacterial AHLs
might affect the secretion of AHL mimic compounds. AHL mimics
from the plant may also affect synthesis of AHLs in the bacteria

4. Production and release of signaling molecule (Autoinducer)
Diffusion of AI molecule at low cell density leaving the QS
circuit in-active
Activation of QS circuit by AI at higher concentration due to
higher cell density
Transcriptional activation of down regulating genes by AI
receptor complex or other activated signaling molecule
Activation of virulence, biofilm formation, sporulation,
competence and antibiotic production

6.  Gram-negative use acylated homoserine lactones (HSLs) as
autoinducers
 Grampositive bacteria use oligopeptides as autoinducers
Bioluminescence Vibrio species
Biofilm formation Pseudomonas aeruginosa
Virulence Vibrio cholerae
Antibiotic production Photorhabdus luminescences
Competence Bacillus subtilis

7. Canonical quorum-sensing circuits
Gram-negative bacteria
LuxI-type enzymes catalyse the
formation of species-specific
HSLs (orange circles), which are
detected by LuxR-type
transcriptional regulators.
Gram-positive bacteria
Oligopeptides (green bars)
mediate quorum sensing in Gram-
positive bacteria, and two
component phosphorylation
cascades are used for signal
transmission.

8. Canonical quorum-sensing circuits
V. harveyi quorum-sensing circuit.
LuxLM synthesizes AI-1 (blue
diamonds) and LuxS is required
for production of AI-2 (red
triangles).

9. Model for quorum sensing in V. harveyi
• a
V. harveyi regulates light
production using two
parallel quorum-sensing
circuits.
A complex two-component signal transduction system is responsible
for detection of the autoinducers and information relay to the luciferase
structural operon (luxCDABEGH).
H - histidine
D - aspartate
HTH - helix–turn–helix