Med Micro 10 - Biofilm Flashcards
Definition of biofilm
A microbial (bacterial, fungal, algal) community, enveloped by the extracellular biopolymer which these microbial cells produce, that adheres to the interface of a liquid and a surface. Typically on something solid, but also on surface of lakes,
Tower
work more like a city. different bacteria expressing different genes at different times. towers can form in biofilms hundreds of micrometers high
Main points of biofilm production
Change form from planktonic to biofilm - essentially enter, bind initially based on nutrient availability via cationic interaction (epitopes, pili), then bind irreversibly via polysaccharide, more bind (cell division and recruitment)… fragments or planktonic bacteria are released from biofilm to bind elsewhere.
Acute vs chronic
acute caused by planktonic (and some biofilm), Chronic caused by biofilm
Advantages that biofilm provides to the bacteria
Difficult to eradicate, extracellular material produced which acts as defense, change form - collaborate, antibiotics kill rapidly dividing cells but biofilm grow slow, antibiotic resistance; some that bind to biofilm cannot normally bind. Neutrophils release lots of chemicals, can cause damage which releases more nutrients,
Mechanical debridement
Removal of biofilm and dead tissue. Remove from open wounds or ulcers by scrapping.
Biofilm formation (compare above)
Initial binding reversibly, then polysaccharides bind irreversibly, allow. Mature biofilm often have pores to allow liquid and nutrients to flow in.
Examples of gene regulation
Polysaccharide regulation and pores; regulated by quorum sensing
Phagocytes and biofilms
release of pro-inflammatory enzymes and cytokines leading to inflammation and subsequent tissue destruction resulting in increase in nutrients. Our immune system selects for pathogens that can hide…
Microbial communication
constantly secreting molecules
What type of molecules do types of bacteria release in quorum sensing?
Gram +: typically oligopeptides, bound by extracellular receptors. Gram -: small lipid soluble molecules or AHL, enters via transporter
Vibrio fisheri and symbiosis
Concentrated in light organ of hawaiian squid. Lots of nutrients in there for the bacteria. At high concentration they release autoinducers which cause them to make them create light. Squid can control the amount of light so it forms no shadow at night when moon shines on it. Release extra bacteria during the day, grow during the day,
Quorum sensing
The regulation of gene expression in response to fluctuations in cell population density. Produce and release signal molecules into the environment called autoinducers
Another word for autoinducer
Self-stimulation
Possible Ecological Roles for Quorum Sensing
Chemotaxis; Coordination of gene expression (up or down) in initial population; Coordination of gene expression and bacterial behaviour among multiple populations; Avoidance of host defence responses; Direct communication between the bacterium and the host
Why does initial population need to regulate its genes?
It’s vulnerable, doesn’t want to express some virulence factors initially. It will want to bind first (pili)
Direct communication between the bacterium and the host
Example: nodules of bacteria (essentially biofilm surrounded by plant) which provide nitrogen fixation
Interspecies, intraspecies, inter kingdom
Interspecies: 2 species of bacteria. intraspecies: self. inter kingdom: bacteria and plant
Process of quorum sensing
- Bacteria leak a chemical into their surroundings. 2. As bacteria increase, chemical increases until there’s enough to generate a response. 3. Independent, solitary bacterial cells can become part of a much larger, multicellular organism known as a biofilm, when the amount of a certain chemical reaches a particular level
Why is quorum sensing “all or nothing”?
Don’t want to waste energy if it won’t be effective, and don’t want to generate infectious disease until there are enough bacteria.
Process when hiding with coagulase
Hide from immune system by forming clots, then once it reaches quorum, it wants to escape
Why is a biofilm called a multicellular organism?
Like city. Different cells have different roles with different genes expressed.
Population changes
The bacteria appear relatively innocuous as they quietly grow in number. When their population reaches a certain level, instant changes occur in their behaviour, appearance and metabolism. Changes can overwhelm immune system, include binding, reproduction, releasing toxins and/or invasion, causing disease (virulence)
AHL
Acyl homoserine lactone. An autoinducer family
Autoinducers,,,
Signalling molecules must be small, and move across membranes passively or actively, They must be recognized and alter the behaviour patterns and gene expression of the recipient. There are similar to pheromones
Quorum sensing and evolution
S. mutans. Regulate genes which are involved with attacking other bacteria and have ability to uptake and integrate DNA - evolution! Naturally competent. . . . . numerous bacteriocins and genetic competence, resulting in killing of other species, DNA release, and gene exchange
Bacteriocin
chemicals that attack other bacteria
Biofilm treatment?
New treatments - prevent binding; anti quorum sensing chemicals?
What might be a good way to take advantage of what we know about quorum sensing and biofilm formation in the development of new antimicrobials?
Inhibit the AHL and autoinducers to block their function; convince bacteria that it has quorum early so it can be taken care of by immune system. Both of these can block biofilm.
Other than AHL in quorum sensing, how might the environment regulate gene expression, especially during infectious disease?
Temperature, pH, nutrient availability esp. iron, bile (lysteria)
Using diagram compare the genetics of quorum sensing and another form of gene regulation
Quorum: secrete molecule, affects self and neighbours, result.
