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Expression of biosynthetic gene cluster in sponge associated bacterium during co-cultivation experiment: Chemical warfare between bacterial neighbors
pcaQ pcaD/C pcaH pcaG pcaI pcaJ pcaF pcaB peptidase
0 1 2 3 4 5 6 7 8 9kbkb10
Narsinh L. ThakurNational Institute of Oceanography, Goa
Vladislav A. Grebenjuk and Werner E. G. Müller, UNI - Mainz, Germany
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Agenda
Sponge-associated bacteria
Biosynthetic gene cluster
PKS gene pathway
Co-cultivation experiment
PCA gene pathway
Summary
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Sponge – bacteria association
Sponge-bacteria association: a fascinating research topic
In some sponge species 40% of the animal‘s biomass is attributed tobacteria
Elicited considerable interest as sponges are rich in bioactivemetabolites
Thakur and Müller Symbiosis, 2005, 39: 1- 8
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Sponge
Classification:Phylum: PoriferaClass: DemospongiaeOrder: HadromeridaFamily: SuberitidaeGenus: SuberitesSpecies: domuncula
Sponge Suberites domuncula
Species: domuncula
Collected from Rovinj, Croatia
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Isolation of bacteria
Suberites domuncula
Bacterial colonies
SB1RFLP pattern
alphaalpha--proteobacteriumproteobacterium MBICMBIC 33683368
Antibacterial and anticancer activity
SB1SB2SB3SB4SB5SB6
Thakur et al. Aquatic Microbial Ecology, 2003, 31: 77-83
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SB2 bacterium
SB2 strain (α- Proteobacterium MBIC 3368) has beenisolated from different sponges irrespective of theirtaxonomic identity or geographical location.
Bacterial strain SB2 showed antibacterial and cytotoxicpotential.
The genome of bacterial strain SB2 contains gene clusterfor polyketide synthases.
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Biosynthetic gene pathways
Natural genetic machinery involved in the production ofcompounds and energy in the living organisms.
Polyketides and Non-ribosomal peptides are the mostimportant biosynthetic pathways.important biosynthetic pathways.
Polyketides and Nonribosomal Peptides arepharmacologically important as antibacterial, cholesterolcontrol, anticancer, immunosuppressant drugs as well aspigments, toxins, nitrogen storage polymers etc.
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Biosynthetic gene pathwaysPKS I (Modular Polyketide Synthases)
Module I Module II Module III Module IV
Extender Moduleloading module
ketosynthase (KS) domain
Acyl transferase (AT) domain
acyl carrier protein (ACP)
thioester domain
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Detection of PKS gene pathway
DNA
isolation
Primer design and
PCR
SB2
Detection of KS-3 gene on gel
KS-1KRKS AT DH ER
14 16 18 20 22 24 26 28 30 32kbkb
34 36 38
KS-2 KS-3 KS-4TE
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Cloning
Restriction
digestion
DNA
isolationDNA fragement
Vector
Restriction
digestionCosmidVector
SB2
Müller et al., Applied & Environmental Microbiology, 2004, 70: 2332-2341
Recombinant Plasmid
Transformation in bacterial hostclones
E. coli
Selected clones with PKS cluster
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Chemical warfare
SB2 SB6alphaalpha--proteobacteriumproteobacterium gamagama--proteobacteriumproteobacterium
Growth inhibition
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Co-cultivation experiment
Filter paper 0.22 µm
SB6
MediumSB2
SB6
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Co-cultivation experiment
After 72 h incubation
SB2 bacterium
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Real-time PCR analysis
After 24 h, 48 h, 72 h incubation
RNA
extraction cDNA synthesis
Real-time Q-PCR analysis
Detection of KS-3 gene expression
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Gene expression
KS-3 gene
150
200
ssio
n (%
) 5 - fold dilution of cDNA
25- fold dilution of cDNA
Up-regulation after 24 h incubation
SB2 SB2 + SB6 SB2 + SB10
50
100
Rel
ativ
e ex
pres
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Gene expression and growth curve
SB2
1
2
3
4
5
OD
600
Highest up-regulation during late exponential phase and early stationary phase, which is reported to be a peak period of secondary metabolite production in bacteria.
0
1
3h 6h 9h 12h 15h 18h 21h 24h 27h 30h 33h 36h 48h 54h 72h
time interval
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PCA Gene cluster
SB2 showed very slow growth in normal Zobell medium
While exploring pks gene cluster Protocatechuate gene cluster
(pca) was detected
PCA gene cluster was cloned and sequenced
PCA gene cluster comprises all the genes coding for enzymesg p g g y
involved in the conversion of protocatechuate to acetyl coenzyme A.
pcaQ pcaD/C pcaH pcaG pcaI pcaJ pcaF pcaB peptidase
Protocatechuate pathway
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Growth study
Growth of SB2 in M9 medium supplemented with
Glucose
Sodium benzoate
Protocatechuate 0.25
SOBPCAGlucose
3 6 9 12 24 27 30 33 36 48
0.05
0.10
0.15
0.20
OD
600
Time (hrs)SB2
Müller et al., Applied & Environmental Microbiology, 2004, 70: 2332-2341
(Concentration 4 mM)
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Summary
Association of alpha-proteobacterium (MBIC 3368) withsponges
Role of biosynthetic gene cluster in the chemical warfarebetween bacterial neighborsbetween bacterial neighbors
Gene up-regulation during late exponential phase andearly stationary phase, which is reported to be a peakperiod of secondary metabolite production
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Thank you