introduction concepts lectures 1-2 Flashcards
microbiology
study of microorganisms
include: bacteria, viruses, fungi, parasites
viruses
minuscule, accelular infectious agents
have either DNA or RNA
obligate intracellular parasites
no cytoplasmic membrane, cytosol, organelles
not alive (cannot carry out any metabolic pathway, neither grow or respond to environment, cannot reproduce independently)
fungi
chemo-heterotrophic (cannot fi carbon - no photosynthesis)
cell wall composed of chitin
unicellular or multicellular
closely related to animals
functions = decompose dead organisms and recycle their nutrients, help plants absorb water and minerals, used for food and in manufacture of foods and beverages, produces antibiotics
protozoa
eukaryotic, unicellular, lack a cell wall
motile by cilia, flagella, and or pseudopodia
distribution = requires moist environments, live in ponds, streams, lakes, critical in plankton
prokaryotes
small in size but can be seen with light microscope, bigger than most viruses
DNA - single, circular DNA chromosomes, no membrane to enclose DNA, nucleoid region for DNA
plasmids encode specialized genetic information
gram positive bacterial cell wall
thick layer of peptidoglycan
lipoteichoic acids - anchor peptidoglycan cell membrane and give cell negative charge
appear purple following gram staining procedures
gram negative bacterial cell wall
thin layer of peptidoglycan
bilayer membrane outside peptidoglycan containing phospholipids, proteins and LPS
may be impediment to the treatment of disease
appears pink following gram staining procedures
teichoic acid and lipoteichoic acid
only found in gram positive bacteria
can be used to determine serotypes
lipopolysaccharide (LPS)
found only in gram negative bacteria
can be used to distinguish bacteria
gram stain
fixation –> crystal violet –> iodine treatment –> decolorization –> counter stain safranin
acid-fast stain
used to stain cells that have unusual cell walls
ex. impermeable to mycolic acid - waxy or resistant to water-based stains
bacterial spores
endospore
unique structures produced by some bacteria that are defensive strategy against unfavorable conditions
formation cycle
1. vegetative cell
2. chromosome is duplicated and separated
3. cell is septated into a sporangium and forespore
4. sporangium engulfs forespore for further development
5. sporangium begins to actively synthesize spore layers around forespore
6. cortex and outer coat layers are deposited
7. mature endospore
8. free spore is released with the loss of the sporangium
9. germination spore swells and released vegetative cell
criteria for bacterial classification
growth on media, microscopy, biochemical tests, immunologic tests
non-selective media for growth
supports the growth of many different bacteria; intended to cultivate as many different species as possible
blood agar for bacteria or fungi - 2 components = nutrient medium and blood
buffered peptone water - bacteria and balanced pH with peptone
bolton’s broth - anaerobic bacteria, horse blood, nutrient medium
selective media for growth
used to eliminate or reduce large numbers of irrelevant bacteria in specimens; incorporates inhibitory agents that prevents growth of irrelevant bacteria
differential media for growth
makes use of bacteria’s ability to produce pigments or produce secreted enzymes
allows differentiation between two colonies of bacteria growing on the same plate
bacterial microscopy criteria
used in conjunction with staining methods
lot of different microscopy methods *see lecture 1 slides 43-55
biochemical tests criteria
lot of different tests
*see lecture 1 slides 56-65
immunologic tests criteria
typically involves determining the serotype
sero = use of antibodies
add cells to media with antibodies to specific microorganisms
clumping = positive result
eubacteria
classic bacteira
no true nucleus
gram positive, gram negative, and cell-wall lacking eubacteria
archaebacteria
do not have classic peptidoglycan cell wall; may have characteristic similar to eukaryotic cells
bacterial metabolic requirements
carbon, nitrogen, energy source, water, various ions
oxygen is not required by all bacteria
obligate aerobes
must have O2
obligate anaerobes
cannot live with O2
facultative anaerobes
like O2, but okay without it
aerotolerant anaerobes
do not need O2, but okay with it
microaerophiles
need a little bit of O2
DNA replication is tied to bacterial replication
coordinated process where two equivalent daughter cells are produced
binary fission
need sufficient metabolites to support synthesis of bacterial components - particularly nucleotides for DNA synthesis
bacterial transcription location difference than eukaryotes
occurs in nucleoid of prokaryotes
transfer of DNA: conjugation
transfer of genetic material - usually plasmid - between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells
transfer of DNA: trandsuction
DNA is transferred from one bacterium to another by a virus
transfer of DNA: transformation
occurs when a host organism takes in foreign DNA
trp operon
repressible
always inactive/turned off
unless an inducer - lactose - is available form environment
immunology slides
*see lecture 2 slides 39-end
