General Bacteriology Flashcards
Describe bacteria.
-unicellular
-lack membrane bound organelles & nucleus
Describe eukaryotes VS prokaryotes.
Describe bacteria size, shape, & arrangement.
-1 um in diameter
-smaller size = lg surface to vol ratio
-spherical bacterium = 2um diameter
-eukaryotic = 20um diameter
-pleomorphism (cocci, rods/bacilli, spirals)
Describe bacterial taxonomy & phylogeny.
-polyphasic taxonomy
>phenotypic, genotypes, phylogenetic
-bacterial phylogeny = evolutionary relationship between bacteria
-species = taxonomic unit
Describe bacterial cell wall.
-peptidoglycan = unique to prokaryotes
-function: rigid, protection (mechanical & osmotic lysis)
-differences in structure & chemical composition = pathogenicity & staining properties
Describe bacterial cell wall staining properties.
- Gram staining = differentiates bacteria by chemical & physical properties of cell wall (detecting peptidoglycan)
- Ziehl neelsen (acid fast) = presence of my colic acid in cell wall (mycobacterium)
Describe gram pos, gram neg, & mycobacteria.
- Gram pos (purple) thiccer peptidoglycan
-lipoteichoic acid = antigenic
-resistance to physical disruption & drying - Gram neg (red)
-LPS
-lipid A = endotoxin (activates immune system & harmful effects)
-polysaccharide chain = antigenicity
-low resistance to physical disruption & drying - Mycobacteria = mycolic acid as virulence factor
Describe flagella.
-bacterial surface in gram neg
-locomotion, bacterial motility
-arrangement ID bacteria
-endoflagella in periplasmic space = cork screw motility
Describe pili/fimbriae.
-hair like appendage on bacterial surface
-antigencity
-attachment pili = adherence to host tissue
-conjugation pili = transfer of genetic material
Describe capsule.
-polysaccharide outer layer
-functions:
>nutrient reserve
>protection from adverse environment
>adhere to host cell surface
>evade phagocytosis
Describe endospores.
-cryptobiotic state of dormancy
-durable
-survive in adverse environment (long periods)
-formed intracellularly (free spores)
-made by clostridium & bacillus when exposed to adverse conditions like nutrition depletion
Describe sporulation VS germination.
- Sporulation
-formation of spores from vegetative bacterial cells during unfavorable environmental conditions - Germination
-return of dormant spores to vegetative growth induced by nutrients (non nutrient agents)
Describe exceptions to general bacterial populations.
- Mycoplasma - no cell wall (peptidoglycan)
- Leptospira - 2 circular chromosomes
- Borrelia burgdorferi - linear chromosomes
Describe bacterial metabolism.
-replication by binary fission (asexual)
-growth curve:
>lag = increase cell size, active metabolism (no division)
>exponential phase (log) = cells multiple max rate
>max stationary phase = exhaustion of nutrition or toxic product accumulation, growth stops (balance of growth & death rate)
>decline/death phase
Describe the factors required for bacterial growth.
-different nutrients for species
-source of metabolic energy: fermentation, respiration, photosynthesis
-diff temp (mesophiles mostly) & oxygen
Describe bacterial virulence factors.
-exo & endotoxins
-superantigens
-biofilms
-quorum sensing
Describe exo VS endotoxins.
- Exotoxins = proteinaceous toxins made by bacteria (heat labile)
- Endotoxins = cell wall components that induce inflammation by stim immune system (heat stable)
Describe superantigens.
-exotoxins cause dysfunction of IS
-activation via variable region of B chain of TCR (not antigen specificity) = no immune protection
-T cell prolif & cytokine release
-nausea, vomiting, fever, shock
-ex: staph, strep
Describe biofilms.
-bacterial pop adhere to each other or surface = bi polymer matrix - exchange nutrients & make LPS
Describe quorum sensing.
-bacteria make sm signal molecules (autoinducers) to communicate
-when pop reaches defined density = changes in behavior, appearance & metabolism
Describe transfer of virulence factors.
-between bacteria thru conjugation, transformation, or transduction
-horizontal gene transfer mediated by outer membrane vesicles
-plasmid & bacteriophages carry genes for antibiotic resistance, toxins, capsules, fimbriae
Definitions!
-pathogen = infectious agent (microorganism that can cause disease by colonization of host)
-pathogenesis = biological mech that lead to disease
-pathogenicity = ability of microorganism to damage host
-infection = invasion & multiplication of pathogens in individual or pop
-virulence = capacity of pathogen to damage host
-virulence factors = properties found in isolates that cause disease but aren’t found in isolates of same species that lack ability to cause disease
-predisposition = what predisposes an animal to an infectious disease
-infectious disease = disease caused by microorganisms
infection doesnt mean disease - all communicable diseases are infectious but not vice versa
Describe the diff types of pathogens.
*less than 5% of microbes are pathogenic
-majority extracellular
-obligate intracellular (host cell to replicate)
-facultative intracellular
-opportunistic
Describe the infectious disease triangle.
Describe the seq of events in pathogenesis.
- Host
- Overcome host defense
- Compete w normal microbiota to adhere to host tissue & colonize host systems
- Multiply
- Exert damage to host
Describe the consequence of host pathogen interaction.
-Inflammation
-local tissue damage (toxin or IS)
-toxemia (structural/functional)
-acute or chromic systemic disease
