Midterm 1 Flashcards
“the father of microbiology”
observed in detail the first microorganisms
Antoni van Leeuwenhoek
what are the two prevailing hypotheses of where do microbes come from?
- “spontaneous generation” - life arose from inanimate chemicals
- “life from life”: microbes already present become detectable
how did they test “spontaneous generation” versus “microbes from air” hypotheses? what are the objections to this experiment.
experiment: heat serilized medium and then closed lid. no growth seen.
1. heating destroys “life-generating substances”
2. oxygen may be necessary for spontaneous generation
what was louis pasteur’s experiment?
- pasteur sterilized broth with a swan neck flask
- pasteur left broth exposed to air
- when broth was exposed to air, microorganisms grew
- “founder of modern microbiology”
- settled spontaneous generation controversy
- fermentation = microbial process
- pasteurization
- gernm theory of disease with robert kock
Louis Pasteur
what is the “germ theory of disease”?
some diseases are caused by microbes that may be present in air, water, or food and. may be passed from one diseased individual to another
Koch’s postulates
- microbe must be present in diseased animals and absent from healthy ones
- isolate the microbe in pure culture
- when inoculated into a healthy, suceptible animal disease results
- able to re-isolate organism and will be the same as the original
gram positive
- gram positive bacteria have thick peptidoglycan cell walls
- stains purple from gram stain
gram negative
- gram negative bacteria have thin peptidoglycan cell walls and an inner and outer membrane
- stains light pink from gram stain
what is the structure of the flagella
- filament - long, thin, helical structure composed of flagellin
- hook - curved sheath
- basal body - stack of rings firmly anchored in cell wall
what are the different types of bacteria with flagellum?
- monotrichous - single flagellum
- lophotrichous - multiple flagellum on one end
- amphitrichous - multiple flagellum on either end of bacteria
- peritrichous - multiple flagellum all over bacteria
what is the function of flagella?
- motility in response to external stimulus: chemotaxis (chemical stimuli) and phototaxis (light stimuli)
- flagella runs if it turns counterclockwise
- flagella tumbles runs if it turns clockwise
what is endoflagella?
- internal flagella enclosed between cell wall and cell membrane
- produce cellular motility by contracting and imparting a twisting motion
what is fimbriae?
- bristles from the cell surface - fine and hairlike
- function in adhesion to other cells
what is pili?
- found only in gram negative cells
- F+ bacteria extend pili to F- bacteria and partially transfer DNA through conjugation
what is the slime layer?
- made of glycocalyx
- loosely organized; thus, easily washed off
- protects from dehydration and nutrient loss
what is the capsule?
- made of glycocalyx
- tightly attached
- capsule causes resistance to antibiotics
- formation of biofilms
- forms shiny colonies
what is the cell envelope?
- covers the cytoplasm
- composed of two layers: cell wall and cell membrane
- maintains cell shape and regulates flow of molecules
what is the cell wall?
- determines cell shape and prevents lysis
- made of peptidoglycan
what are bacteria that have mycolic acid cell walls instead of peptidoglycan?
mycobacterium and nocardia
these use acid-fast technique for identification
what are plasmids?
- small circular DNA
- free in cytoplasm or integrated into the chromosome
- duplicated and passed on offspring
- not essential to bacterial growth and metabolism
- encodes antibiotic resistance and tolerance to toxic metals
what are endospores?
store duplicated chromosomes inside bacteria and lay dormant until harsh conditions cause cell to die
types of bacteria: clostridium, bacillus, sporosarcina
how do endospores from?
chromosomal duplication -> forespore and sporangium -> sporangium englufts forespore -> sporangium begins to actively synthesize spore layers around forespore -> outer layer forms around early spore
what are the four types of bacterial shapes?
- coccus - spherical
- bacillus - rod (basic form), cocobacillus (short and plump), vibrio (comma shaped)
- helical form - spirochete (flexible with axial filaments), spirillum (rigid with flagella)
- pleomorphic - no defined shape (example: mycoplasmas and h.pylori)
what are the types of bacillus shaped bacterial arrangements?
- single
- diplo
- strepto
- palisades (lined up next to each other)
what are the types of coccus shaped bacterial arrangements?
- single
- diplo (two)
- strepto (chain of cocci)
- staphylo (irregular cluster)
- tetrades (four pack of cocci)
- cubical
what is the basic type of population growth in bacteria?
- binary fission
- duplicated chromosomes (basically cloning)
- happens about every 20 minutes
- exponential growth pattern
what is the bacteria growth curve? what happens at each stage
- lag phase - newly inoculated
- exponential growth phase - maximum rate of cell division, adequate space and nutrients, phase that bacteria are most likely to be killed in
- stationary growth phase - cell death and duplication rate balance out, depleating nutrients and oxygen
- death phase - cells begin to die at an exponential rate
how do you measure bacterial growth?
serial dilutions: succesive 0.1 dilutions of liquid culture of bacteria and count coloies that aise
types of temperature dependent bacteria
- psychrophile: optimum temperature is below 15 C. true psychrophiles are obligate and can’t grow above 20 C. psychotrophs are facultative.
- mesophile: intermediate temperatures at 20 C to 30 C. this includes most human pathogens which have optimal temp at 30 C and 40 C
- thermophile: optimal temperature greater than 45 C and hyperthermophiles grow between 80 C 120 C
example: serratia marcenscens is pink at 25 C but beige at 38 C
types of oxygen dependent bacteria
- aerobe: uses oxygen in its metabolism
- obligate aerobe: can’t grow without oxygen
- facultative anaerobe: aerobe that doesn’t need oxygen to metabolize and can grow without it
- microaerophile: doesn’t grow at normal atmospheric O2 concentration but requires a small amount
- obligate anaerobe: cannot tolerate any free O2 and will die under exposure
- aerotolerant anaerobes: do not utilize oxygen but can survive and grow to a limited extent in its presence
type of carbon dioxide dependent bacteria
canophiles grow best a higher CO2 than normally in atmospher
types of pH dependent bacteria
- neutrophiles - live or grow in pH 6 and 8
- obligate acidophiles - must grow in low pH (example: euglena mutabilis or thermoplasma)
- alkaliphiles - live or grow in habitats between pH 7 and 12
types of osmotic pressure bacteria
- osmophiles - live in habitats with a high solute concentration
- halophiles - prefer high concentrations of salt
- obligate halophiles - grow optimally in solutions of 25% NaCl but require at least 9% NaCl for growth (staphylococcus aureus)
types of bacteria in other environmental factors
- non-photosynthetic - damaged when in contact with light
- barophiles - survive at high atm pressure
three types of symbiosis
- mutualism: when organisms live in an obligatory but mutually beneficial relationship
- commensalism: the member called the commensal recieves benefits but coinhabitant remains neutral
- parasitism: host microbe is harmed by the growth of parasitic microbe
two types of non-symbiotic relationships
- synergism - two or more free-living organisms benefit off of nearby interactions
- antagonism - association of free-living species leads to competition in the community
types of nutrition
- macronutrients - large quantities needed for principal cell structure and metabolism (carbon, hydrogen, nitrogen, phosphorus, sulfur)
- micronutriends - present in smaller amounts and needed for protein maintenance (metals)
fastidious - bacteria with special nutrition needs (N. meningitius)
what is a growth factor
an organic compound such as amino acid, nitrogenous base, or vitamin that can’t be synthesized by organism but must be provided as nutrient
types of carbon sourced bacteria
- heterotroph - must obtain C in organic form (must eat other things that have carbon)
- autotroph - uses inorganic CO2 as its carbon source (make their own carbon sugars like plants)
two types of autotrophs
- photoautotroph - sunlight (plants, cyanobacteria)
- chemoautotroph- simple inorganic chemicals (methanogens)
four types of heterotrophs
- chemoheterotroph - protozoa, fungi, bacteria, animals
- saprobe - metabolize the organic matter from dead organisms (decomposers)
- symbiotic microbes - obtain organic matter from living organisms (parasites, commensals, mutualistic microbes)
- photoheterotroph - sunlight or organic matter (purple and green photosynthetic bacteria)
types of metabolism
- anabolism - synthesis of cell molecules and structures
- catabolism - breakdown of bonds of larger molecules (generates ATP)
enzymes
- decrease activation energy
- catalyst - increases reaction rate
- sensitive to pH, temperature, and oxmotic pressure
- competitive inhibition - binds to active site
- non-competitive inhibition - binds to allosteric site
what are the enzyme locations?
- exoenzymes - outside of the cells (gram negatives excreting toxins)
- endoenzymes - inside of cell
three classes of electron donor and acceptors
- organotrophy: organic e- donor and inorganic/organic terminal e- acceptor
- lithotrophy: inorganice e- donor and inorganic/organic terminal e- acceptor (Fe2+ donor -> rust)
- phototrophy: light capture by chlorophyll, split of H2S or H2O or organic molecules
outside of O2, nitrogen and sulfur are also terminal acceptors
what are the oxidized forms of nitrogen
dissimilatory denitrification:
NO3- -> NO2- -> NO -> 1/2N2O -> 1/2N2
nitrates in human urine indicate bacterial growth and is often a UTI indicator
cyanobacteria
- appear green
- oxygenic phototrophs
three types of pathways after glycolysis
- fermentation: use of glycolysis to incompletely oxidize glucose - facultative and aerotolerant anaerobes
- aerobic respiration: reactions that convert glucose to CO2 using O2 - most amount of ATP produced
- anaerobic respiration: doesn’t use O2 as the final e- acceptor
examples of glycolysis in microbes
- escherichia coli - gluconate from mucus secretion in gut
- bacteroides thetaiotaomicron - induce colinic production of mucus
- zymomonas - ferments the blue agave plant
two types of fermentation
- alcoholic: yeast, clostridium bacteria - products are ethanol and CO2
- acidic: K.pneumoniae, clostridium - products CO2 and lactic acid
makes alcoholic beverages, organic acids, dairy products, vitamins, antibiotics
where does ETC and ATP synthase occur in bacteria
- gram negative: occurs in periplasm (between inner and outer membrane)
- gram positive: occurs with between cytoplasmic membrane and cell wall
types of antibiotics
- semisynthetic drugs: chemically modified after being isolated from natural sources
- synthetic drugs: made completely in lab (very pricey)
origins of antimicrobial drugs
- bacteria: streptomyces and bacillus
- molds: penicillium and cephalosporium
antibiotic spectrum of activity
- narrow spectrum: agent attacks on a few or one organisms (good for gram positive)
- broad spectrum: agent attacks many different organisms (general antibiotic) - can lead to antibacterial resistence
Five mechanisms of antibiotic action
- inhibition of cell wall synthesis (penicillins and cephalosporins)
- disruption of cell membrane function
- inhibition of protein synthesis (inhibition of translation)
- action as antimetabolites (sulfonamides and trimethoprim - competitive inhibiton)
- inhibition of nucleic acid synthesis (block synthesis or nucleotides, inhibit replication, stop transcription, inhibit DNA synthesis)
adverse reactions to drugs
- toxicity to organs
- allergy to antibiotics
- broad-spectrum antibiotics can destroy both infectious agents and beneficial species
three types of DNA transfer amongst bacteria
- transformation: free DNA from environment enters bacteria genome
- transduction: DNA transfered by virus (bacteriophage)
- conjugation: F+ extends pili and gives duplicated plasmid to F- (bacteria sex)
mechanisms of acquiring drug resistance
- drug inactivation (penicillin by penicillinase)
- decreased permeability (receptor is altered and drug can’t enter cell)
- activation of drug pumps (membrane protein pump drug out of cell)
- change drug binding site
- use alternative metabolic pathway
ways to minimize drug resistance
- effective drug concentrations
- simultaneous drug administration (synergism - additive effect or antagonism - decreased effect)
- restrict antibiotic use to only necessary
- reduce antibiotics in food
- infection control in hospitals
- proper hygiene
what diseases do these bacteria cause?
1. s. pyrogenes
2. b. pertusis
3. e.coli and k.pneumonia
- strep
- whopping cough
- UTI
how do you choose what antimicrobial drug to use?
- identify the specific microoganism causing the infection
- degree of microorganism susceptibility to various drugs
- overall medical condition of patient
how do you test for drug susceptibility of microorganisms?
- Kirby-Bauer Disc diffusion test: add antibiotics to plate of bacteria and measure zone of inhibition. larger the zone of inhibition -> larger the susceptibility to antibiotic.
- E-test: measure the lowestest concentration of antibiotics (usually only for fungus because it is incredibly expensive)
what is minimum inhibitory concentration (MIC)?
the smallest concentration (highest dilution) of drug that visibly inhibits growth
what is therapeutic index (TI)?
the ratio of drug dose toxic to humans versus minimum effective dose
the higher the TI the better. FDA approved antibiotics has TI of 100/1 or higher
how to microbes communicate?
quorum sensing (only in specific activity) - activates when population density is at a minimum threshold
what are the three criteria for quorum-sensing?
- production of quorum-sensing signal should happen during particular growth phase or in response to specific environmental changes
- signal should be recognized by a specific bacterial receptor in extracellular environment
- a critical threshold concentration must be reached for quorum-sensing signal to begin
what are the six processes regulated by acyl-homoserine lactone mediated quorum sensing?
- disease production in plants
- disease production in animals
- diseaes suppression in plants
- antibiotic production
- biofilm formation
- dna transfer
what is the virbio fischeri symbiotic relationship with hawaiian bobtail squid important in the discovery of quorum sensing?
when it becomes night time, vibrio fisheri is in high cell densitiy and generates bioluminescence to help disguise the squid’s shadow.
what were the two models for why there is luminescence expression in the vibrio fischeri?
- extracellular signal whose concentration is changing as the cells grow
- intracellular signal whose concentration is changing due to differences in cell as they grow
experiment: culture grown to high density and then put into conditioned and fresh medium. conditioned medium had higher induction of light at lower cell density. showing model 1 is correct
what were the two models for the regulation of light production in the virbrio fischeri?
- cells secrete an inducer that had to rech critical concentration before light production
- cells remove an inducer that had to rech critical concentration before light production
experiment: conditioned medium is separated into low, moderate, and high molecule size and added to fresh medium. found it to be an inducer that at high concentrations will activate trancription factor/sensor kinase and trigger production of light.
two types of quorum sensing regulation
- gram negative bacteria: acyl homoserine lactone (diffuses freely into cell membrane)
- gram positive bacteria: quorum sensing peptide (downstream affect)
genes in vibrio fischeri that regulates quorum sensing
- Lux I and Lux R (regulate light production - LuxR-LuxI QS system)
- Lux A (responsible for light production)
what is quorum quenching
using antagonist of induces to minimize quorum sensing as an alternate to antibacterial therapies
