microbiology (guest lec) Flashcards
eukaryote cell wall:
- cellulose
- chitin
bacterial cell wall:
peptidoglycan
- network of sugar polymers cross-linked by polypeptides
archeal cell walls:
polysaccharides and proteins
- no peptidoglycan
Gram staining: features
- bacterial groups classified based on cell wall composition
- gram negative: less peptidoglycan, outer membrane (pink/ red- red safranin dye)
- gram positive: thick cell wall of peptidoglycan (purple- crystal violet)
Gram staining: process
- stained with crystal violet and iodine
- rinsed in alcohol
- stained with red dye (safranin)
capsule:
- some prokaryotes make polysaccharide or protein layer
fimbriae:
hair like appendages for adherence or motility
sex pili:
longer than fimbriae
- allow prokaryotes to exchange DNA
motility: and taxis
- most commonly use flagella
- taxis: ability to move toward/ away from certain stimuli
reproduction:
- binary fission
- divide every 1-3 hrs
endospores:
most prokaryotes form metabolically inactive endospores which remain viable in harsh conditions for centuries
factors contributing to genetic diversity:
- rapid reproduction
- mutation
- genetic recombonitation
prokaryotes: rapid reproduction
via binary fission
- although generally identical
prokaryotes: mutation rates
- low due to binary fission
- however rapid reproduction (short generation times) accumulate mutations rapidly in population
prokaryotes: high diversity
- from mutations allows for rapid evolution
prokaryotes: genetic recombination and eg.
- transformation
- transduction
- conjugation
transformation:
prokaryotic cell take up foreign DNA from surrounding environment
transduction:
movement of genes btw bacteria by bacteriophages (viruses which infect bacteria)
conjugation: and eg.
transfer of DNA btw cells from direct cell-to-cell contact (sex pili)
- eg. F plasmid of E.coli
R plasmid:
carry genes for antibiotic resistance
phototrophs:
obtain energy from light
chemotrophs:
obtain energy from chemicals
autotrophs:
require CO2 as carbon source
heterotrophs:
require organic nutrient to make organic compounds
obligate aerobes:
- prokaryotes which require O2 for cellular respiration
obligate anaerobes:
- prokaryotes which are poisoned byO2 and use fermentation or anaerobic respiration
facultative anaerobes:
- prokaryotes which can survive with or without O2
nitrogen fixation:
- some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3)
- they can make nitrogen available to plants
metabolic cooperation: and eg
- cooperation btw prokaryotes allows them to use environmental resources they could not use as individual cells
- eg. biofilm of dental plaque made of numerous bacterial species
chemical recycling:
- chemoheterotrophs (decomposers)
- nitrogen-fixing prokaryotes add usable nitrogen to environment
mutualism:
both organisms benefit
commensalism:
one organism benefits, while neither harming/helping other significantly
parasitism:
parasite harms but does not kill host
pathogens:
parasites that cause disease
- only bacteria
- produce toxins (exotoxins/ endotoxins)
