JW - Biofilm dispersal

Question 1

What is Biofilm Dispersal? (2)

Answer 1

• A critical stage in the biofilm life cycle where cells detach and spread to new locations
• Important for bacterial survival, colonization, and infection spread

Question 2

What are Mixed-Community Wastewater Treatment Granules? (2)

Answer 2

• Small granules used in wastewater treatment to process mixed waste (residential, industrial, commercial)
• Microbes form biofilms within pores and surfaces of the granules, aiding pollutant removal

Question 3

Why is it important to study the Genetics and Physiology of Biofilm Dispersal? (2)

Answer 3

• Identifying gene systems involved in dispersal may suggest targets for control
• Possible to manipulate biofilm physiology to enhance or inhibit dispersal

Question 4

What is Pseudoalteromonas tunicata (D2)? (3)

Answer 4

• Obligate marine bacterium that colonizes living surfaces (e.g., Ulva lactuca)
• Produces bioactive compounds to prevent marine fouling organisms
• Forms microcolony-based biofilms in lab and in vivo

Question 5

How does P. tunicata disperse its biofilms? (3)

Answer 5

• Uses cell death, lysis, and detachment (seeding dispersal)
• Autolytic protein AlpP generates hydrogen peroxide, leading to localized cell death
• Some cells remain viable

Question 6

What is the function of AlpP? (3)

Answer 6

• 190 kDa autolytic protein detected in biofilms ≥ 3 days old
• Produces hydrogen peroxide from L-lysine, mediating biofilm dispersal
  L-lysine + O2 + H2O → 6-amino-2-oxo-hexanoate + NH3 + H2O2
• Present in several Gram-negative bacteria

Studied with amplex red which reacts with H2O2 to give red fluorescent oxidation product resuforin

Question 7

How does Pseudomonas aeruginosa regulate microcolony differentiation? (2)

Answer 7

• Linked to production of reactive oxygen species (ROS)
• Uses peroxynitrite (ONOO-) and nitric oxide (NO) to trigger dispersal

Question 8

What role does Nitric Oxide (NO) play in P. aeruginosa dispersal? (2)

Answer 8

• NO (nM range) upregulate motility genes and downregulate adhesion/biofilm genes
• NO reduces c-di-GMP levels, turning off biofilm traits and triggering dispersal

Question 9

How does Cyclic-di-GMP (c-di-GMP) turnover control biofilm formation? (3)

Answer 9

• PAS/H-NOX domains → Sense environmental cues (e.g., NO) and regulate c-di-GMP levels
• GGDEF domain (guanylate cyclase) → Synthesizes c-di-GMP (“on switch”)
• EAL domain → Breaks down c-di-GMP (“off switch”)

When you add nitric oxide you see an increase in the EAL (phosphodiesterase) activity.

Question 10

What is Cystic Fibrosis (CF) and its link to biofilms? (3)

Answer 10

• Autosomal recessive mutation in CFTR gene
• Increased mucus & poor ciliary clearance create an ideal environment for P. aeruginosa biofilms
• Chronic bacterial infections contribute to morbidity and mortality

Question 11

How might Nitric Oxide (NO) help in CF treatment? (2)

Answer 11

• Low-dose NO may reduce P. aeruginosa biofilms, enhancing antibiotic effectiveness (esp ceftazidime, tobramycin)
• Could improve respiratory function and quality of life for CF patients

Question 12

What is the RATNO (Reducing Antibiotic Tolerance with Nitric Oxide) study?

Answer 12

• Phase 2 pilot study investigating whether NO enhances antibiotic therapy
• Focuses on disrupting P. aeruginosa biofilms in CF patients to improve treatment outcomes