JW - Biofilms and Bacteriophage II Flashcards
(16 cards)
What role do phages play in bacterial communities? (3)
- Phages are key ecological drivers
- Influence bacterial diversity, evolution, and ecological balance
- Can directly alter community composition through killing, lysogeny, and gene transfer
How can biofilms be broken down using enzymes?(2)
- Nucleases can degrade extracellular DNA
- This disrupts the biofilm structure
What evidence suggests lysis occurs in Pseudomonas biofilms? (2)
- Red staining shows cell lysis
- Run-off from lysed biofilms causes lysis on fresh Pseudomonas lawns
What is likely causing lysis in Pseudomonas microcolonies? (2)
- Phage activity (bacteriophage)
- Plaques indicate phage-induced lysis
What phage was isolated and sequenced from the biofilm? (3)
Pf4
- A filamentous bacteriophage of Pseudomonas aeruginosa
- Similar to Pf1 but includes integrase gene allowing genome integration
What are some features of Pf phages? (5)
- Filamentous structure
- Chronic (non-lytic) life cycle
- Repeating protein coat
- 6 nm in diameter, 1 μm in length
- Circular single-stranded DNA
How does the chronic life cycle of Pf phage work? (4)
- ssDNA enters host and converts to dsDNA plasmid
- Host machinery replicates the phage
- Filamentous particles are assembled and secreted
- No host cell lysis
If the phage life cycle is non-lytic, why do lysis zones appear? (3)
- Mutation in the C repressor gene
- Loss of control over phage replication
- Cells lose immunity to reinfection → phage-induced lysis
What does mutation in the C repressor gene suggest about biofilm evolution? (2)
- High mutation frequency in biofilms
- Possible fitness advantage to loss of repression
What happens when the Pf4 phage is deleted from Pseudomonas? (3)
- Biofilm is less stable
- Mice survive longer during infection
- Indicates phage presence increases virulence
How does Pf4 contribute to biofilm resilience? (3)
- Forms liquid crystal arrangements
- Strengthens the matrix
- Increases antibiotic resistance
What is the role of Pf phage in human immunity? (2)
- Suppresses immune response
- Found in chronic lung infections
How is extracellular DNA visualized in the biofilm? (2)
- Staining reveals DNA filaments between cells
- Viral particles in the matrix also contain DNA
What does sequencing of biofilm ecDNA reveal? (2)
- Aligns to the entire Pseudomonas aeruginosa genome
- Suggests eDNA is primarily genomic DNA
What unusual pattern is seen in ecDNA sequencing data? (2)
- Spikes in read frequency in specific regions
- These regions correspond to bacteriophage DNA
What does the presence of naked phage DNA in biofilms suggest? (2)
- Phage DNA exists outside viral particles
- Seen even without proteinase treatment → not all DNA is encapsulated
