VL14: Biofilms Flashcards
Define biofilm
Surface attached microbial communities composed of microorganisms and a matrix of extra-polymeric substances (exopolysaccharides, proteins, and nucleic acids)
Why do bacteria form biofilms?
- self defence (resist physical forces that sweep away unattached cells, resist phagosytosis by immune system cells and resist penetration of toxins (antibiotics))
- allows cells to remin in a favorable niche (help trap nutrients and prevent detachment in flowing systems)
- co-operative interactions
Where can biofilms form?
- solid substrates in contact with moisture
- soft tissue surfaces in living organisms
- liquid air interfaces
What are the steps in biofilm formation?
- Planctonic stage
- Attachment (reversible, then irreversible)
- Microcolony formation
- Macrocolony/ cells form extracellular matrix
(5. Dispersal)
Explain how to figure out if your bacteria have formed a biofilm + simple was of characterization
crystal violet assay for biofilm
(grow cells, wash to remove planktonic B, stain remaining cells to visualize attachment pattern
can be used for semi-quantitative assessment)
describe morphology, microscopy
How is biofilm formation regulated? Describe 1 vibrio cholerae mutant, and name one Name one (or three) of the structures (genes) important for biofilm formation (in vibrio cholerae)
many genes/ reg pathway/ environmental sensing neccesary for biofilm formation, integrated in other aspects of the lifestyle
type 4 pili, if you knock out mshA growth is significantly reduced)
(spo0A is master regulator of sporulation) deletion of spo0A inhibits biofilm formation
sigF = sigma factor, forms different kind of biofilm
How do biofilms impact human health?
biofilms are THE major bacterial lifestyles
medical/ dental conditions chronic infections antibiotic resistances treatments are expensive and inefrfective infections in indwelling medical devices
What about showercurtains?
good place for biofilms, potential pathogen source
What about dental plaques?
1 acidic film of glycoproteins on teeth
2 colonization by streptococcus
3 bacteria of different species stick to early colonizers
4 multispecies biofilm
and kidney stones?
15-20% involve UTI
bacterial infection, biofilm, mineralization
produce urease -> crystal formation
and cystic fibrosis? how become biofilm bacteria tolerant?
in CF pseudomonas infections often result in ab resistant biofilms, p.aeruginosa makes extrac/ polysaccarides alignate Pel and Psl
B in biofilms may be tolerant to antimicrobial agents (don’t grow but survive)
-restricted antimicrobial diffusion, differential physiological activity and induction of specific tolerance mechanisms contribute to tolerance
What’s the problem with pseudomonas biofilms and antibiotic therapy?
some ab kill only metabolically active cells
colistin interferes with membrane structre/function
only combined treatment gets rid of most bacteria
What about biofilms and hearts?
biofilms can develop on heart valves and surrounding tissue = prosthetic valve endocarditis
Whats the simple most important medical problem with biofilms?
urinary catheters
can result in bacteremia
Which different areas of life are affected by biofilms?
cooling water in power plants food processing medical implants paper manufacturing drinkng water oil recovery teeth
pipe plugging, corrosion, water contamination
biofilms help degraide soil bound contaminants, help cycle nutrients (increase agricultural productivity)
What are the key components of the biofilm extracellular matrix?
polysaccharides
proteins
dead cells
dna
What does rugose mean?
runzelig (wild type surface of v.cholerae biofilm)
what are important matrix proteins (v.cholerae)? What happens if you knock them out?
RbmA RbmC Bap1
if you knock one of them out, biofilm can still form but differently,
if you knock them all out no biofilm forms
Which molecule is important for biofilm regulation? How is it made? How degraded? With what receptors does it interact and what are the results?
c-di-GMP (cyclic-di-GMP) remember name!
made by Diguanylate cyclase (contain a GGDEF domain)from 2GTPs
degraded by phosphodiesterases, sensed by receptor proteins
level of c-di-GMP determines if biofilm is formed
it interacts with transcription factors, riboswithches, PilZ domains, Degenerate GGDEF and EAL domains
and what are the outputs?
biofilm +, motility -, virulence -, cell cycle +
major regulator of biofilm formation AND a major global regulator
What determines how much c-di-GMP is present?
affected by many different environmental factors
light, oxygen, surface, arginine, nitiric oxide ect
most importantly QS
cell density via QS -> cyclic di-GMP -> Phenotypic changes
describe 3 requirements of biofilm growth
attachment (help of adhesin or VPS (vibrio polysaccharide)
requires cell-cell communication (QS)
Requires coordinated gene regulation (cyclic di GMP, regulates polysaccharide formation and switch between motile and biofilm growth)
1 example of preventing biofilm infections
seaweed produces furanones and remains slime free
Summary of Biofilms
Biofilms are a community of microorganisms embedded in an organic polymer matrix consisting of polysaccharide, proteins and DNA
Biofilms are prevalent in medical, industrial, environmental, agricultural settings
-C-di-GMO, a nucleotide-based intracellular signaling molecule is critical for planktonic to biofilm life-style switch
3 important characteristics of biofilms
- usually highly resistant to antibiotics ( high or long term doses are needed to fight biofilms)
- help horizontal gene transfer (closely interacting communities of bacteria including extracellular DNA and dead cells)
- Protect bacteria from phagocytosis (by extracellular matrix, causes phagocytes to release proinflammatory enzymes and cytokines -> inflammation and tissue destruction)
