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19 Cards in this Set
- Front
- Back
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What are biofilms?
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• Biofilms are defined as surface-attached microbial communities that are composed of microorganisms and a matrix of extrapolymeric substances (exopolysaccharides, proteins, and nucleic acids)
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Bacteria form biofilms for several reasons(name 3)
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1) Self Defense
2) Keep them in favorable nitch 3) allows them to live close together |
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How do Biofilms cause medical problems?
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• Resistant to antibiotics and host immune cells
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How do biofilms form on teeth?
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thing layers of Glycoproteins form on tooth. Glycoproteins biofilm gets attached my streptococcus bacteria. Different species attach to early colonizes. Results in a multilayer biofilm.
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What are the 5 stages Gram negative bacteria go through making a multicellular organization?
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(i)planktonic
(ii) attachment (iii) microcolony formation (iv)macrocolony (v) dispersal. |
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What is a Biofilm Matrix? What three things does it consist of?
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A biofilm is a structured consortium of bacteria,
embedded in a self-produced polymer matrix consisting of 1. Polysaccharide 2. Proteins 3. DNA |
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How is cyclic-Di-GMP formed?
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– c-diGMP is produced by diguanylate cyclase (DGC) proteins containing the GGDEF domain
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How does planktonic switch to biofilm life style?
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C-di-GMP nucleotide-based intracellular signaling molecule is critical for planktonic to biofilm life-style switch.
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how is c-di-GMP degraded?
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c-diGMP is degraded by phosphodiesterase (PDE) proteins bearing the EAL or HD-GYP domains
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How is c-di-GMP sensed by the cell?
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c-diGMP is sensed by receptor proteins and receptor proteins then interact with a downstream protein to affect a particular cellular function.
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What are
Aerobes: Anaerobes: Facultative organisms: Aerotolerant anaerobes: Microaerophiles: |
• Aerobes: require oxygen to live
• Anaerobes: do not require oxygen and may even be killed by exposure • Facultative organisms: can live with or without oxygen • Aerotolerant anaerobes: can tolerate oxygen and grow in its presence even though they cannot use it • Microaerophiles: can use oxygen only when it is present at levels reduced from that in air |
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What is oxidative stress?
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Oxidative stress is an unavoidable by-product of the aerobic lifestyle, because O2 and H2 O2 are formed when molecular oxygen chemically oxidizes electron carriers.
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What protective enzymes can Remove damaging oxidants
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1) catalase
2) peroxidase 3) superoxide dimutase 4) superoxide reductase |
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All microorganisms require water. why is it critical and what is water activity (Aw)
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Water availability is critical. If there is a high concentration of solutes, water may be unavailable to cells—e.g. in honey or saturated salt solutions.
Water availability is expressed as water activity (aw)—the vapor pressure of air over a substance divided by the vapor pressure over pure water |
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What are
Halophiles Extreme halophiles Nonhalophiles Halotolerant |
Halophiles live in moderately salty habitats such as seawater (0.4M NaCl). Many are obligate halophiles.
Extreme halophiles grow at higher salt concentrations, approaching saturation. Nonhalophiles cannot tolerate moderate salt concentrations. Halotolerant species can live in a range of conditions from no salt to moderate levels. |
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What is Osmo-regulation?
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to counter an efflux/influx of water
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• Microorganisms can be classified into groups by their growth temperature optima.
• Psychrophiles • Mesophiles • Thermophiles • Hyperthermophiles |
• Psychrophiles – growth below 20°C
• Mesophiles – growth at 20 to 44°C • Thermophiles – growth at 44 to 70°C • Hyperthermophiles – growth above 70°C |
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How does fermentation effect the pH
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Fermentation results in acidic intermediates that
decrease pH; growth on proteins can result in ammonia production and increase in pH. |
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What are
Acidophiles Neutralophile Alkaliphiles |
Acidophiles – microbes that grow at low pH (below pH 3).
Neutralophile (pH 5-8)– most human pathogens Alkaliphiles – grow at high pH (above pH 9 |
