Biofilm structure Flashcards
what percentage of infections are biofilm related?
> 70%
how is industry affected by biofilms?
- Marine fouling.
- Fouling of hydroelectric, water reticulation, heat exchange and food processing pipelines.
- Corrosion of metal surfaces.
- Wastewater treatment (biofilms have a positive effect)
- Trickling filters.
- Activated sludge.
- Fluidised-bed reactors.
- Bioremediation.
what is marine fouling
what are some disadvantages?
Marine fouling occurs when organisms attach themselves to underwater objects like boats, rope, pipes and building structures. Mussels are one of the biggest culprits.
Once attached, they are difficult to remove, leading to operational downtime, increased energy use and damage
what is bioremediation?
Bioremediation is a branch of biotechnology that employs the use of living organisms, like microbes and bacteria to decontaminate affected areas. It is used in the removal of contaminants, pollutants, and toxins from soil, water, and other environments.
what are coliforms and how are they used to measure the safety of drinking water?
Coliform bacteria are defined as either motile or non-motile Gram-negative non-spore forming bacilli that possess β-galactosidase to produce acids and gases under their optimal growth temperature of 35–37 °C. They can be aerobes or facultative aerobes, and are a commonly used indicator of low sanitary quality of foods, milk, and water
Coliform bacteria are organisms present in the environment and in the feces of all warm-blooded animals and humans.
Coliform bacteria will not likely cause illness. However, their presence in drinking water indicates that disease-causing organisms (pathogens) could be in the water system
NGO guidelines suggest that 10–100 CFU per 100 mL is tolerable for short periods of times, but above 100 CFU per 100 mL the risk to life is too great
biocorrosion caused by bacteria results in what?
pitting, crevice corrosion and stress corrosion cracking.
what is pitting?
in biofilms there is an oxygen gradient throughout, you get more anaerobic as you go down, the action of the anaerobic cells will eat into the metal
anaerobic cells can directly extract electrons derived from the oxidation of Fe0 to Fe2+ to support anaerobic respiration.
Typically following aerobic corrosion, anaerobic corrosion involves a redox reaction that reduces hydrogen ions and oxidizes a solid metal.
whats the primary step of wastewater treatment?
Removal of large objects eg stones etc
what are the secondary steps of wastewater treatment?
- Activated sludge (flocs)
- trickling filters
- biofilms
- bacteria convert dissolved or suspended solids to setteable solids
what are the tertiary steps of wastewater treatment?
- Biological or chemical removal of nitrite/ammonia and phosphates
- virus removal
- trace chemicals removed
what are trickling filters
Microorganisms are encouraged to grow on stones/plastic over which the sewage is trickled i.e. to form biofilms. The microorganisms remove dissolved organic carbon through metabolism to CO2 or incorporation as biomass.
Two or more trickling filters may be connected in series so that wastewater can be recirculated for greater treatment efficiency.
aeration is critical
why is aeration critical in trickling filters?
Air moving through the spaces between the filter’s surfaces provides sufficient oxygen to meet the oxygen requirements for microbial metabolism.
how are medical and dental things affected by biofilms?
- dental plaque
- chronic wounds
- cystic fibrosis
- medical implants
what is activated sludge?
Activated sludge refers to a flocculent culture of organisms developed in aeration tanks under controlled conditions, according to WEF.
An activated sludge is an aerated sludge which contains aerobic microorganisms like bacteria and protozoa. It is a part of the wastewater treatment process for treating sewage or industrial wastewater. In this, aeration and a biological floc are used to break down organic matter
what is biological debridment?
Sometimes, the healing process can leave some tissue so damaged that it’s no longer viable.
If you have a significant wound that leads to tissue death, or gangrene, your doctor may need to remove the damaged tissue. Dead tissue can harbor bacteria that may cause more extensive infections. Removing the nonviable tissue promotes healing and reduces the risk of further complications. The process of removing nonviable tissue is called debridement.
Debridement is only necessary when a wound isn’t healing well on its own
give a definition of a biofilm
A biofilm is a microbial, sessile community characterised by cells that are:
* Irreversibly attached to a substratum, interface or to each other.
* Are embedded in a self-produced matrix of extracellular polymeric substances (EPS), and
* In comparison to planktonic cells, they exhibit an altered phenotype with respect to:
– Growth rate
– Gene transcription
Rarely find an individual species, there may be one dominant one but unlikely only one
biofilms refer to many different microbial aggregates which all share what characteristics?
– Organisms are embedded in a hydrogel formed by EPS. (APS can be variable and influenced by the environment)
– Long retention time of cells next to each other = microconsortia.
– Heterogeneity in space and time.
– High biodiversity: strong gradients, high habitat variability, subpopulations.
– Retention of exoenzymes.
– Retention of nucleic acids – large gene pool.
– Increased resistance to biocides, desiccation and other stress.
– Access to degradation of particulate matter.
– Sorption of dissolved and particulate nutrients from environment.
– Physiological differences between planktonic and biofilm cells.
whats the difference between aggregates and a few planktonic cells?
matrix
why are there anaerobic habitats below aerobic colonies in biofilms
due to respiratory oxygen consumption
what is the EPS?
what molecules does it contain
Extracellular polymeric substances
the glue or ‘house’ of biofilm cells
Biofilm cells are embedded in EPS, which fundamentally influence their microenvironment.
Without the EPS there wouldn’t be a biofilm
- Biopolymers of microbial origin
- Polysaccharides
- Proteins
- Glycolipids, phospholipids, LPS
- Nucleic acids
what bacteria produces aliginate in the mucoid strain but not in the non-mucoid strain?
Pseudomonas aeruginosa
Describe how the mucoid and non-mucoid strains of P.aeruginosa were visualised and compared using florescence labels
Aliginate stained with TRITC-ConA (red)
and the cells stained with SYTO9 (green)
how do the structures of the mucoid and non mucoid strains of P.aeruginosa differ?
The mucoid strian has a build up of stacks but the non mucoid strain is relatively flat with cells on top of each other more vulnerable to liquid
no aliginate to hold stakcs togethe rin the non mucoid strain
what is the role of alginate in mucoid and non mucoid biofilm formation?
Biofilm morphology: due to presence of alginate, cells stick together from the beginning and, therefore, form clusters and, later, mushrooms
name three key discoveries in the differentiation of biofilms
- Bacterial biofilm effluents are autotoxic at time of cell death.
- Autotoxic activity is detected in biofilm effluent.
- For some bacteria, the differentiation is quorum sensing regulated.
what is the reason for the autotoxic activity in a single species population?
deliberately cause the cell to die
Theory
to create a nutrient source to enable growth of the whole population/structure
give three conserved autoinducer systems and quorum sensing systems
- Acylated homoserine lactone, AHL (also called AI-1) mediated regulation in Gram negative bacteria.
- AI-2 signalling system (luxS, luxR) in Gram negative and Gram positive bacteria.
- Peptide mediated regulation in Gram positive bacteria (competency, gene transfer, sporulation).
what two ways can dispersal occur?
active and passive
