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79 Cards in this Set
- Front
- Back
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Opportunistic pathogen
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microorganism that does not cause disease in a healthy host but only in individuals where normal defense mechanisms have been compromised
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virulence
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quantitative measure of pathogenesis
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virulence factor
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components of pathogen responsible for its ability to cause an infection
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obligate pathogen
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cannot be found anywhere but in assocation with its host
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facultative
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one that can grow/survive in environment or in host
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What is the building block of peptidoglycan?
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glycan tetrapeptide
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Gram positive cell surface
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composed of 25 layers of peptidoglycan, teichoic acid, lipoteichoic acid
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Gram negative cell surface
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composed of lipopolysaccharide (LPS), lipid A, core polysaccharide, and O-antigen
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Endotoxin
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toxin that affects eukaryotes and is basically the lipid A component of LPS.
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Lipid A
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fatty acids + N-acetylglucosamine phosphate
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fastidious organisms
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require special additions to media
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prototroph
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bacterial strain with no unusual nutritional requirements
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auxotroph
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strain that carries a mutation that causes a nutritional requirement
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# of colonies x dilution factor =
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colony forming units (cfu) per mL of original sample
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Koch's postulates
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1. Bacteria should be found in all diseased animals but not healthy ones.
2. Bacteria should be isolated and grown in pure culture 3. Bacteria from culture should cause disease in a healthy animal 4. The same bacteria should be re-isolated from diseased animals |
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aerobes
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bacteria that grown in the presence of oxygen and use oxygen for respiration
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obligate aerobes
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require oxygen for growth
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facultative aerobes
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do not require oxygen for growth but grow better with it
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microaerophillic
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likes a little bit of oxygen
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obligate anaerobes
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low to no tolerance for oxygen
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aerotolerant anaerobes
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tolerate oxygen but don't require it for growth
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RNA polymerase
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core enzyme that carries out polymerization of RNA
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sigma factor
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initiation of transcription
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promoter
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site on DNA where RNA polyermase and sigma factor bind. Starts at -35 sequence and ends at the -10 (TATA) box
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terminator
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sequence that promotes termination
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operon
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complete unit of transcription greater than or equal to 1 gene in length
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regulon
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co-regulated operons in response to environmental changes
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polar effect
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genetic phenomenon that arises when a mutation in an upstream gene in an operon can stop transcription of downstream genes
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global control systems
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regulate many operons all at the same time
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Two-component systems
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consist of a sensor kinase and a response regulator
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Differences in the general secretory pathway between gram negatives and gram positives
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Gram positive: proteins are secreted to cytoplasmic membrane on the outside
Gram negative: proteins are secreted to membrane or periplasm |
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Sec. B and SRP
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recognize SS
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Sec A
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thread protein through pore
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Sec Y, G, C
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transmembrane pores
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MIC
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minimal inhibitory concentration; amount needed to stop growth
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selective toxicity
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relative toxicity to bacteria compared to the host
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Phagocytosis
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process for cellular eating
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chemotaxis
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directed movement that is controlled by a gradient of chemical attractant
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chemokines
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call ino ther cells to infected/wounded area
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fMLP
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strong chemoattractant
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Polarization
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controlled by Cdc42; neutrophils sense chemical gradient and turn towards it
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protrusion
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controlled by rac; cell pushes itself forwards (lampellipodium)
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adhesion
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controlled by Rho; sites of contact between bottom of cell and "glass" where it is crawling
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translocation
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controlled by Rho; body moving towards middle of cell
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de-adhesion
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neutrophil moves forwards
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elongation
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force for movement that is inhibited by cytochelasin
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integrins
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transmembrane molecules
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Steps in phagocytosis
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1. Recognition and binding
2. Internalization 3. Phagosome maturation |
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Features of plasmids
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replication, fertility, antibiotic resistance, heavy metal resistance, virulence genes, bacteriocins, alternate iron acquisition
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Conjugation
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transfer of plasmid DNA to another bacteria by tra genes; code for F-pilus and conjugation is regulated -> pili act as phage receptors
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Transposons
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jumping genes; transposase is own gene with own promoter and has to be regulated
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conservative transposons
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copy number does not increase upon transposition
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specialized transduction
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bacteriophage carries a virulence gene or genes
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Pathogenicity islands
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virulence genes are often located on these; often have different G + C content than chromosomal DNA
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Features of transposon mutagenesis
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generate random or semi-random insertion
tag mutated gene allowing isolation and characterization of that and surrounding genes generate polar mutations and affect expression of downstream genes |
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transposon library
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collection of bacteria that contains multiple individuals each with a single transposon insertion
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Reporter
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used in biological system to quantitate gene or protein expression; usually an enzyme with properties that make it easy to remember such as lac Z encoding beta-galactosidase, pho A encoding alkaline phosphatase, GFP, CAT
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transcriptional fusions
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rely on the promoter of a target gene but contain their own ribosome binding site and start codon
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translational fusions
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in-fram fusions between two proteins so that the promoter, ribosome binding site, start codon and some or all of the coding sequence are fused in frame with another protein
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DNA microarrays
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used to study gene expression
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forward genetics
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unbiased; randomly mutate and look for phenotype (phenotype to genotype)
use transposon library in bacteria, select for mutants affecting phenotype, identify site of insertion |
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reverse genetics
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start with known gene and ask what the phenotype of a mutant would be (genotype to phenotype); biased
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PAMP's
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pathogen associated molecular patterns
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Prr's
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pattern recognition receptors; examples are TLR's, NLRs Nal ps, Nai ps, Ipat
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inflammasome
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activates a protease called caspase 1 which cleaves pro-il-1 to il-1
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Functions of complements
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1. opsinization
2. membrane attack 3. chemotaxis |
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Alternative pathway
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C3 is hydrolyzed by C3 convertase into C3a and C3b. C3b is chemically reactive and can attach to any molecule or bacterial surface. this creates a binding site for other proteins which leads to the binding of more proteins and the making of more C3 convertase.
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antigen
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any molecule that can be recognized by the immune system
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AB Isoyptes
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different flavors of antibodies: the constant Fc portion is switched out for a different constant part (types: IgA, IgM, IgG, IgE, IgD
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IgM
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good at activating complement
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IgA
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easy to secrete across epithelial barriers and mucosal surfaces
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IgG
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promotes phagocytosis
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Functions of antibiotics
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1. neutralize
2. opsinize 3. activate complement |
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MHC
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major histocompatibility complex
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MHC Class 1
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presents CD8 T-cells and expresses peptides from cytosol
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MHC Class II
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presents CD4 T-cells and presents peptides from phagosome
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Which type of T-cells make cytokines?
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CD4 T-cells make IFN gamma and TNF alpha
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IFN gamma
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potent activator of macrophages
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Which type of T-cells become killers?
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CD8 T-cells
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