Dynamic biofilm architecture conferring viral protection
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Transcript of Dynamic biofilm architecture conferring viral protection
Presented by
NISHANTH. S
2016601106II M.Sc.(Ag.) in Microbiology*
Department of Agricultural MicrobiologyTNAU CBE - 3
TAMIL NADU AGRICULTURAL UNIVERSITY
The Bacterium or a Bacteria
Bacterial biofilm
Extracellular matrix (ECM)
Bacterial cells
A cause for infection !!!
What are biofilms?
Biofilms are defined as highly structured communities of
microorganisms that are either surface associated or attached to one
another and are enclosed within a self-produced protective extracellular
matrix (ECM)
What does ECM comprises !!!
Polysaccharides
Proteins
Lipids
e- DNA
High cell densiy
10 8 to 10 11 cells g-1 wet weight
(Ramage et al. 2009)
Cont…
Planktonic bacteria vs biofilms???
1. The intercellular signaling system (QS) - regulationBhardwaj et al (2013)
2. Cyclic nucleotide second messengers – cyclic GMPHengge et al (2015)
3. bap protein – assembles matrix scaffold proteins & builds the
biofilm matrix Taglialegna et al (2016)
Cont…
(Fleming et al. 2016)
Why microbes form biofilms???
Prevention of biofilms
How to overcome biofilm effect???
(Zhao et al. 2017)
Phage therapy
Why Phages not antibiotics !!!
Lytic cycle – A key to phage therapy
Multiple defence strategies – an overview
Surface modification
(Kimberley D. Seed 2015)
Pre-infection strategy
Prevention of phage adsorption
1. Blocking of phage receptors
2. Production of extracellular matrix
3. Production of competitive inhibitors
Three categories(Labrie et al. 2010)
Pre-infection strategy
Prevention of phage adsorption
1. Blocking of phage receptors
2. Production of extracellular matrix
3. Production of competitive inhibitors
Three categories(Labrie et al. 2010)
Pre-infection strategy
Prevention of phage adsorption
1. Blocking of phage receptors
2. Production of extracellular matrix
3. Production of competitive inhibitors
Three categories
E. coli
FhuAAn iron transporter
Entry of coliphages (T5)
No Compete with Microcin J25 (an antibiotic)
(Labrie et al. 2010)
NUTRIENT RICH ENVIRONMENT
Pre-infection strategy
Prevention of phage adsorption
1. Blocking of phage receptors
2. Production of extracellular matrix
3. Production of competitive inhibitors
Three categories
E. coli
FhuAAn iron transporter
NUTRIENT LESS ENVIRONMENT
Entry of coliphages (T5)
Compete with Microcin J25
(Labrie et al. 2010)
Infection strategy
Prevention phage DNA entry
Sie (superinfection exclusion) – proteins that blocks the entry of phage DNA
Rapid inhibition of DNA injection into the cells
Imm – changes the conformation of the injection sites
Sp – inhibits the activity of T4 lysozyme (gp5)
(Labrie et al. 2010)
Cutting phage nucleic acid
Defence island system associated with restriction modification
DISARM allows phage adsorption but prevents phage
replication.
Composed of five genes1. DNA methylase
2. Helicase domain
3. Phospholipase D (PLD) domain
4. DUF1998 domain and
5. A gene of unknown function
R/M system (3 activities)
1. Restriction endonuclease activity
2. DNA modification activity
3. Target recognition activity
DISARM
(Ofir et al. 2017)
Cont…
(Labrie et al. 2010)
Cont…
(Labrie et al. 2010)
Cutting phage nucleic acid
Clustered Regularly Interspaced Short Palindromic Repeats
CRISPR Cas system
Lysogeny dependent inhibition of biofilm formation
(Labrie et al. 2010)
Abortive infection system
Rex system found in phage λ – lysogenic E. coli strains
(Labrie et al. 2010)
State of phage and host !!!
Phage lives Phage dies
Bact
eri
um
liv
esB
act
eri
um
die
s
Adsorption resistance
Blocking of phage receptors
Production of ECM
Production of competitive inhibitors
Superinfection exclusion
DISARM
CRISPR CAS
Absence of resistance
Abortive infection
Transcription blocks
Translation blocks
Replication blocks
Newly discovered defence systems
Prokaryotic argonaute
BREX system
(Swarts et al. 2017)
Key protein in RNA interference system
pAgos – NA guided host defence against
invading NAs
Complete phage resistance
Involves DNA methylation of the host cell
Methylation on non-palindromic TAGGAG
motifs (bacterial genome)
Case study
Engineering the Bacillus paralicheniformis 9945a DISARM system into Bacillus subtilis has
rendered the engineered bacteria protected against phages from all three major families of
tailed double-stranded DNA phages
phi3T
Three core genes - drmA, drmB, drmC
Methyltransferase – drmMI or drmMII
Additional gene - drmD or drmE
Conclusion
Department of Agricultural MicrobiologyTNAU CBE - 3
To understand the interactions between phages and their
bacterial hosts:
i. in order to fully exploit their antimicrobial potential and
ii. to effectively control their populations in bio-industries.
Future thrust
Department of Agricultural MicrobiologyTNAU CBE - 3
1. The efficacy of phage resistance mechanisms against
genetically diverse phages – need to be measured.
2. Multiple anti-phage barriers.
3. Systems targeting phages with ss DNA, ss RNA and ds RNA.