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25 Cards in this Set

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  • Back
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Quorum sensing
-ability to sense density
-coordinated behavior between bacteria
Operon
- multiple genes / products expressed from a single RNA
- unique to bacteria
Regulon
- multiple genes or operons controlled by the same regulator
Common sites of biofilm formation
- catheter contamination
- gum disease
- implant contamination
- cells or clusters that detach acn cause bloodstream infection, emboli, spread
How can microbes quickly adapt to their environment?
- integrating distinct signaling circuits
- can turn on / off genes
- on / off virulence
- switch between cell types
What do biofilms shield pathogens from?
- phagocytes
- antibodies
- complement
- antibiotics
Bacteria in biofilm are protected!
How are some biofilms treated?
surgery
What mobile genetic elements can spread among bacterial populations?
- bacteriophage (bacterial virus)
- plasmid
- pathogenicity islands
- transposons
- antibiotic resistance genes
What is a lytic bacteriophage?
- A bacterial virus that can lyse and kill cells
What is a lysogenic / temperate / prophage?
- Bacterial viruses that do not immediately lyse cells
- phage DNA can be incorporated into baterial chromosome
What can be encoded on phage genome?
- toxins!!
- diptheria, shiga, streptococcal, cholera
- toxin genes can be transcribed even if phage lysis genes are not transcribed
What is transduction?
- phage-mediated gene transfer
1) transducing phage containing donor genomic DNA leads to
2) cell lysis and release of phage and then
3) phage infects recipient cells and
4) donor DNA integrates into recipient DNA
What are insertion sequences?
- "jumping genes"
- transposable elements WITHOUT recognizable phenotype (like antibiotic resistance)
- contain transposase gene and inverted DNA sequences at ends
- are able to inactive target genes depending on where they insert
What are transposons?
- Insertion sequences with EXTRA genes
- may encode antibiotic resistance
- may lead to emergence of new, more virulent strains
What are pathogenicity islands?
- large transposons
- important in horizontal gene transfer (cell --> cell spread)
- can confer advantageous traits (for example: type III secretion systems)
What is the general secretion system of all bacteria?
"sec" pathway
What is the sec pathway?
- secretion system that allows for translocation of proteins from the cytoplasm (across inner membrane) to the periplasm
Koch's postulates
1) same pathogen needs to be there in every case of the disease
2) pathogen needs to be isolated from diseased host and purified
3) pure pathogen needs to cause disease in healthy animal
4) pathogen needs to be isolated from the second animal that you inoculated and needs to be identical to original pathogen
- basically you need to be able to isolate the same pathogen to name the pathogen associated with the disease of interest
What is selective media?
- allows SOME microbes to grow but NOT others
(selects for certain microbe growth)
What is differential media?
You can visibly see the difference between different microbes
(maybe a color change etc.)
(can DIFFERENTIATE between two microbes)
What are the three growth phases of bacterial culture?
1) lag phase
- bacteria are adjusting their physiology to the media
2) exponential growth
- binary fission / rapid cell division
3) stationary phase
- nutrients become limiting so cells cease dividing / slow down dividing
What are the characteristics of growth in bacterial populations?
Bacteria grow exponentially (1-2-4-8-16 etc)
= N(0) x 2^g
What factors influence bacterial growth?
- nutrients
- temperature
- pH
- osmotic pressure
- oxygen requirements
What is the difference between gram-positive and gram-negative bacteria?
+ : have one membrane, stain purple
- : have two membranes, stain pink
Thicker peptidoglycan in gram+ bacteria will retain the purple dye
What are some differences between bacteria and eukaryotes?
- bacteria have circular DNA
- bacteria have plasmids
- bacteria replicate by binary fission