Lecture 1 Flashcards
what did people first believe bacteria was generated?`
through putrefaction (spoilage)
what is Spallanzani known for?
Challenging the theory of spontaneous generation when sealed flasks after sterilizing broth
What did Pasteur suggest and what else came from his suggestion?
Suggested the Germ Theory- specific bacterial organism were capable of causing an infectious disease. From that came asepsis, antisepsis, and disinfection techniques
what is Robert Koch most known for?
Showing which bacteria caused particular diseases
what are Koch’s postulates? (try describing it in your own words!)
- the microorganism must be found in abundance in all organisms suffering from the disease, but not be found in healthy organisms
- the microorganism must be isolated from a diseased organism and grown in pure culture
- the cultured microorganism should cause disease when introduced into a healthy organism
- the microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent
what are the structures essential for all prokaryotic cells?
cell membrane, cytoplasm, ribosomes, and one or a few chromosomes
what are some things you would find in the cytoplasm of a prokaryotic cell?
DNA/chromosome, ribosome, and actin filaments
name the 3 layers of prokaryotic cell starting from most inner to most outer
cytoplasmic membrane, then cell wall, then capsule
what makes up the cell envelope, where is it and what does it do?
it is the external covering outside the cytoplasm, made up of cell wall and cell membrane and it maintains cell integrity
what is the cover for a gram positive bacteria?
thick cell wall composed of peptidoglycan and cell membrane (2 layers)
what is the cover for a gram negative bacteria?
outer cell membrane, thin peptidoglycan layer, and a cell membrane (3 layers)
what are the functions of the cell walls?
determines cell shape, prevents lysis (bursting) or collapsing due to changing osmotic pressures.
what is the primary component of the cell wall?
peptidoglycan
What are some characteristics of a gram positive cell wall?
thick (20-80 nm), homogenous sheath of peptidoglycan, contains both lipoteichoic acid and teichoic acid
What the functions of the gram positive cell wall?
cell wall maintenance, enlargement during cell division, move cations across the envelope, and stimulate a specific immune response
Where would you find LPS, lipoproteins, and porin proteins?
In the outermost layer of a gram negative cell wall
what do porins do?
regulate molecules entering and leaving the cell through passive diffusion
what are the 3 parts of LPS?
Lipid A (toxic part), core polysaccharide (helps solubilise lipid A), and O sidechain (somatic antigen)
what happens to a gram positive bacteria when stained?
retains crystal violet and stains purple
what happens to a gram negative bacteria when stained?
lose crystal violet and stain red from safranin counterstain
what are the 4 steps to staining?
- crystal violet (primary dye)
- gram’s iodine (mordant)
- alcohol (decolorizer)
- safranin (red dye counterstain)
what are the external surfaces on a prokaryote?
appendages and glycocalyx
What are the two major groups of appendages and examples of them?
- motility- flagella and axial filaments
2. attachment or channels-fimbriae and pili
True or False: all prokaryotes have flagella
False!!!! not all prokaryotes have flagella
what are the parts to a bacterial flagella?
filament, hook, and basal body
which gram stained bacteria have the most protein rings in their flagella
gram (+) have 2 and gram (-) have 4
what are the two kinds of proteins in a bacterial flagella
flagellin protein (filament) and integral proteins in the basal body
what are the two types of external stimulus?
chemical stimuli- chemotaxis and light sitmuli phototaxis
what are some aspects of runs?
single direction, counterclockwise,smooth linear direction, increase with positive stimulus
what are some aspects of tumbles?
abrupt, random, clockwise, increase with negative stimulus
how fimbriae and flagella different?
fimbriae are fine and small, flagella are long and thick
what is the function of fimbriae?
big in adhesion to other cells and surfaces
what are the two types of glycocalyx?
slime layer-loosely organized and attached
capsule-highly organized and attached
what is the function of the glycocalyx?
protects cell from dehydration and nutrient loss, inhibit phagocytosis and killing white blood cells, and attachment-formation of biofilms
what are the functions of the capsule?
firmly attach to cell surface, protects cell from drying out, and may prevent bacteria from being recognized and destroyed by host
describe predation
predator vs prey where predator consumes prey
describe competition
an interaction between two organisms over the same limited resource
what are the two kinds of competition
intraspecific and interspecific
describe symbiosis
relationship where one at least one species relies on another to survive
what are the 3 kinds of symbiosis and describe them
mutualism- both benefit
commensalism-one benefited and the other unaffected
parasitism-one benefit and one hurt
what is an opportunistic pathogen
only cause disease in immunocompromised hosts
what are some examples of those affected by opportunistic pathogens
AIDS, transplant, cancer, and already ill patients
what are frank pathogens
cause disease in either healthy or immunocompromised individuals
facultative pathogens
fall between opportunistic and frank, majority of organisms that cause disease fall into this group
as it pertains to virulence, how are pili used?
pili help connect so that exchange of genetic info can happen which can help produce proteases that chop up IgA
what is pathogenicity?
is the potential to cause disease and is applied to groups or species of organisms
what is virulence?
the degree of pathogenicity within a group or species and is measurable by the LD50 or ID50
what is the difference between LD50 and ID50?
LD50 is the dose of bacteria that can cause 50% to die, ID50 is the dose that causes 50% of infection
What is pathogenesis?
the manner by which the disease develops, including the chain of molecular events that lead to development of disease in microorganisms
what are 4 ways that bacteria alter their genes in response to the environment?
- DNA sequence modification
- transcriptional regulation
- translation regulation
- post translational regulation
what are 3 things bacteria adhere to help avoid immunological and physical removal?
- cell surfaces and extracell. matrix
- solid surfaces
- other bacteria
what are the 3 types of interaction for bacteria?
- direct interaction
- molecular bridging
- manipulation of host cell signaling and cytoskeleton
what is the similarities and differences between adhesion for Gram positive bacteria and gram negative?
similarities: both use fimbriae
differences: (-) bacteria use outer membrane proeins and types III-IV secretion
(+) bacteria use MSCRAMMS aka protein A
what are siderophores used for?
chelate available iron and bring it back to the bacteria
what is genetic recombination?
transfer of DNA from one organism to another. transferred DNA may then be integrated in to the recipients nucleoid by various mechanisms
what is homologous recombination
homologous DNA sequences with nearly the same nucleotide sequences are exchanged by Rec A proteins. involves breakage and reunion of paired DNA segments
what are the natural mechanisms of genetic recombination?
transformation, transduction and conjugation
what is transformation?
genetic recombination in which a DNA fragment from one bacterium enters a competent recipient bacterium and it is exchanged for a piece of the recipients DNA
what is transduction?
genetic recombination in which a DNA fragment is transferred from one bacterium to another by a bacteriophage
what is a bacteriophage?
obligate intracellular parasites aka viruses that infect bacteria
what are some unique features of conjugation?
use pilin protein only found in gram negative cells that are used as bridges for partial DNA transfer. in this case also known as conjugation pili or sex pili
what is a pathogenicity island (PAI’s)
discrete genetic loci that encode for factors which make a microbe more virulent, are very large, 10-100 Kb
what can PAI’s encode for?
secretion systems, adhesins, siderophores, and toxins
what are secretion systems?
different ways to exchange virulence factors
what are 4 different stresses pathogens face?
- acid stress within the stomach
- nutrient limitation
- heat shock during fever
- oxidative stress within phagocytes (release of free radicals)
what are 6 ways pathogens avoid the immune system?
- IgA proteases, 2. immunoglobulin binding proteins
- resist action of complement system, opsonisation
- antigenic mimicry
- antigenic variation
- adopt protective niches
understand slip strand vs flip flop vs cassette sequence
look up youtube videos on each
what are the ways pathogens attack back?
through endo and exotoxins
what do endotoxins do and what mediates them?
pyrogenicity (fever), leucopenia (death of wbc’s) and hypotension and are mediated by TNF (tumour necrosis factor)
what do exotoxins do?
form pores in eukaryotic cell membranes producing oligomeric rings, degrade components of the membrane
In AB toxins, which domains do what?
the A subunit is the toxic part which is delivered to the host cell cytoplams by the B subunit
what are the 3 ways that injecting proteins into host cells alter the cytoskeleton and signal transduction pathways?
- manipulating the cytoskeleton to induce membrane ruffling and bacterial invasion
- preventing being scavenged by phagocytic cells
- once inside the host cell, remaining within the vacuole by manipulating host cell vesicular transport system
where are the 3 places pathogens advance in?
- advance within macrophages
- through blood
- within cells
