Lecture 2 Flashcards
gram positive cell walls contain a thick peptidoglycan layer along with one or both of the following structures that provide elasticity and stability
- wall teichoic acids (WTA)
- anchored to peptidoglycan
- lipoteichoic acids (LTA)
- anchored to cell membrane
wall teichoic acids (WTA) and lipoteichoic acids (LTA) are anchored to what
- WTA: peptidoglycan
- LTA: cell membrane
WTA and LTA have what two main functions that increase the virulence of gram positive organisms
-
adhesins
- adherence to host cells is the first step in the invasion process
- inititate endotoxin-like activites when released
acid fast cells contain what structure that keeps the immune system from recognizing them?
mycolic acid layer
- gives organism a waxy coat
acid fast cells contain what structure that are embedded in the mycolic acid layer and allow passage of small hydrophilic molecules
tetrameric porins
acid fast organisms should be stained using?
- acid fast stain
- uses carbol fuchsin (primary stain)
- methylene blue (counterstain)
what are the clinically important acid fast organisms?
- mycobacterium
- nocardia
flagellum have what three major components?
- filament
- hook
- basal body
filament portion of flagellum contains what antigen?
H antigen
function of basal body of flagellum
anchors flagellum in the cell wall and cell membrane
function of bacterial pili
- have adhesins that promote adherence to other bacteria or to host cells
what are the two main types of pili
- common pili = fimbriae
- sex pili
common pili (fimbriae) are composed of subunits. The tips of these subunits contain adhesins, and many of these adhesins are ?
- pilin subunits
- adhesins are lectins
function of lectins?
adhesins that bind to sugars
what is the polysaccharide layer outside the bacterial cell wall called? What antigen is in this structure?
- Glycocalyx
- K antigen
glycocalyx comes in what two forms?
- capsule: rigid, closely surrounds cell
- slime layer: loose, more diffuse
nucelar region (Nucleoid) of a bacteria contain what structures?
- NO nuclear membrane
- contains primarily DNA but also RNA and protein
- most bacteria have one single, circular chromosome
- some bacteria have plasmids
plasmids encode for information
- ancillary (non-essential)
- genes that encode Abx resistance, heavy metal resistance, toxins
- increase virulence
bacteria ribosomes are what? and contain what subunits?
- 70S
- 30S + 50S
what are inclusions/inclusion bodies?
collective term for various granules, vesicles, and vacuoles within cytoplasm
- function as storage depots
what do volutin granules store
storage form of polymers of inorganic polyphosphate
what do glycogen granules store
polymers of a-D-glucose
what do PHB granules store
chains of B-hydrobutyric acid
describe endospores
- resting stage allowing an organism to survive harsh environmental conditions; often triggered due to nutrient depletion
- NOT a reproductive function for bacteria
endospores contain what that keep it hidden from immune system
- calcium bound to dipicolinic acid
- keratin spore coat
what are clinically relevant genera that produce endospores
- bacillus
- clostridrium
- both are gram positive
sex pili are present on which types of bacteria
gram negative only
bacteria replicate via what mechanism
binary fission
- produces two genetically identical cells
in a liquid culture, most bacteria have a typical growth curve with what 4 phases
- Lag phase
- exponential phase
- stationary phase
- decline
describe measuing bacterial growth using optical density
- more cells in culture -> more absorbance of light
- measures all cells in culture (viable and non-viable)
describe measuring bacterial growth using colony-forming unit
- dilute culture and plate -> each colony from 1 cell
- measures viable cells
lag phase
- no cell division
- increase in biomass
- length depends on nutrients available and condition of inoculum
log phase (exponential phase)
- exponential growth
- rapid cell division
- primary metabolites
- pathogens produce virulence factors
stationary phase
- supplies of energy and nutrients exhausted
- resources renewed by cell death
- death = division
- zero population growth
death, decline phase
- insufficient resources for growth
- exponential cell death
first step to determining what an organism is?
isolate an organism in pure culture
- streaking plates with a wire loop
differentiate between defined and complex media
- defined media: known quantities of each component, narrower range of growth
- complex media: some components not chemically defined, broader range of growth
enriched media
- complex + growth factors
- used for growing fastidious organisms
selective media
select against unwanted organisms
differential media
- differentiates between organisms
- contains components that result in a visible change (color of colony, formation of precipitate)
MacConkey agar contains what
- Lactose
- bile salts and crystal violet inhibit gram +
- differential and selective
chocolate agar contains what?
lysed red blood cells (enriched medium)
Haemophilus and Neisseria are fastidious organisms and require what to be added to medium
Hemin and NAD
differentiate between obligate and facultative bacteria
- obligate: limited to a narrow range of a given environmental parameter
- facultative: capable of surviving in different conditions
most pathogenic bacteria survive in what temperature?
- Mesophiles: range 12-42 C, optimum 30-37 C
most pathogens exist in what pH
- Neutrophile 5.5-8.5 pH
why do obligate/strict anaerobes not survive in oxygenated environments
do not have enzymes for ROS produced during metabolism
list enzymes that aerobic and facultative bacteria have to counteract ROS
- superoxide dismutase
- catalase
- peroxidase
capnophiles
require high CO2 levels
halophiles
need high salt
osmophiles
need high osmolarity/sugar
