micro first exam Flashcards
Describe the observations by Hooke (1665) and van Leeuwenhoek (1684) that lead to the discovery of microorganisms and the experiments Needham (1745) and Pasteur (1864) conducted that refuted the theory of spontaneous generation.
Hooke discovered living things are made of cells, first to use microscope to observe living things
Lee discovered where microbes are- found bacteria/protists in his microsope,
Needham found microbes could arise spontaneously,
Pasteur proved swan necks could be used to stop the airborne microbes from contaminating broth, showing it wasnt a random life force (spont gen) as needham said, but airborne microbes/ proved endospores exist
Explain the significance of endospores in Needham’s work. Explain how Lister (1867) used phenolics to introduce aseptic technique to surgery.
the endospores were still alive after boiling because the heat was insufficient, microbes could have also still been alive through leaving the flask open. lister used phenolic to make his surgery antiseptic, and ensure there was a cleaner process for operating on open wounds.
Discuss limitations of Koch’s postulates in relation to normal microflora and opportunistic infections.
**Some organisms cannot be grown in laboratory medium, like pathogens
**Infected individuals do not always have symptoms
**Some diseases are polymicrobial
**Suitable animal hosts not always available for testing
Discuss evidence that the microbiome relates to host health, including antibiotics/AAD and disinfectants/obesity (Tun 2018).
change in microbiome occurs with diet change, imbalance in microbiota can cause metabolic diseases, also leading to obesity. environmental factors can also impact microbiome, to enable obesity. a study in mice was obzerved, transfering their microbiota, and thus the metabolism/obesity of one mice was transfered to the other. similarly, antiobiotics can reduce diversity in the microbiome, leading to more proneness to infection.
Estimate the age of the earth and when life and oxygenic photosynthesis first appeared.
Earth formed ~4.6 bil yrs ago, life began after earth cooled ~3.8 bil yrs ago
Explain the importance of oxygenic photosynthesis in terms of free energy.
this process converts sunlight into chemical free energy. use of light energy to synthesize ATP and NADPH.
bacteria took water and split into O, protons, and e- creating an oxygen rich environment and the rise of multicellular orgs.
Contrast the domains in terms of cell walls (chitin, cellulose, peptidoglycan and pseudomurein), ribosome size, extremophiles, cellular size, reproduction (binary fission / budding / meiosis), membrane-bound organelles , cytoskeleton, chromosome (linear/circular; single/multiple), motility (flagellum…cilia), membrane lipids, and hopanoids.
fungi- chitin cell wall
plant- cellulose cell wall
bacteria- peptidoglycan cell wall
archaea- psuedomurein
euk- no cell wall
Fungi, protist, and plant are E
Methanogen are A
Protochloron- B
ribosome size:
70s for bacteria and archaea, 55s for mitochondria, 80s for eukarya
Extremophiles:
usually A or B- thermophiles, psychrophiles, halophiles(high salt), acidophiles(low pH)
Cell size
B- 1-2 microns
A- usually 1, but up to 4 microns
E- 10 to 100 microns
Reproduction:
E can reproduce sexually (meiosis), A and B cannot
A and B use horizontal gene transfer
Membrane bound organelles:
E: nucleus and organelles yes
B- no
A- no
Cytoskeleton:
E- filament cyto
B- yes, similar to E
A- yes
Chromosome:
A and B- circular
E- linear
Motility:
B- flagella, A- pili
E- cilia and flagella
membranes:
A- unique lipids, some have monolayer some have bilayer, branched fatty acids
E- lipid bilayers
Hopanoids:
bacterial membrane lipids
Sketch concentration versus flux for passive and facilitated diffusion across a membrane.
-draw-
Carl Woese proposed a universal tree that separated life into three domains. Sketch this tree showing the domains, branches for fungi, cyanobacteria and extreme halophiles. Discuss if this tree makes sense.
-draw-
Explain the significance of bacterial size in terms of surface-to-volume ratio and nutritional requirement for phosphate.
as length inc, surface vol decreases.
-large surface to vol ratio
-direct consequence of aspect-ratio homeostasis at the single-cell level
-allows them to rely on oxygen and material diffusing into the cell
bacteria require anions like phosphate for storage and energy metabolism
Provide five bacterial morphologies and explain the clinical significance of pleomorphism, with reference to Legionella (James 1995).
rod shape(bacili), cocci (sphere), vibrial, and spirochetes, filamentous
legionella is a rod shaped pathogenic gram negative bacteria
Contrast spirilla and spirochetes.
spirillum being rigid with external flagella
spirochetes being with internal flagella
Contrast Mycoplasmas, Gram positives and negatives in terms of cell wall thickness, outer membrane, teichoic acid, LPS, and endospores. Discuss how these structures relate to sensitivity to penicillin and lysozyme.
mycoplasmas- lack cell wall, smallest cell capable of replicating outside of host, most are pathogens that thrive in isotonic conditions, no techoic acid, no LPS, endospores, gram negative
Gram positives
thick cell wall, mostly contains peptidoglycan, no outer membrane, will make endospores, no LPS, have techoic acid
Gram negatives
thin cell wall, contain outer membrane, lipid bilayer, LPS (lipopolysaccharides) will stabilize OM, dont make endospores, no techoic acid
sensitivity to penicillin and lysozyme:
penicilin inhibits cell wall synth (gram pos)
lysozyme inactive against most gram-negative bacteria, but can penetrate gram pos
Label these functional groups - methyl, carboxyl, carbonyl, and amine - and the formation of polypeptides by dehydration synthesis.
methyl ch3
carboxyl o=c-oh
carbonyl o=c
amine- a nitrogen atom having a lone pair. Amines resemble ammonia structurally where nitrogen can bond up to 3 hydrogen atoms
-the chemical reactions in which a water molecule is eliminated from the reactant molecule. The resulting linkage between the two amino acids creates a dipeptide, and this process can be repeated to form polypeptides and proteins
-Amino acids have two functional groups; amino -NH2 and carboxylic group (-COOH). They react to form an amide linkage (-CO-NH-) with the elimination of water molecules.
-Hence, peptide formation is an example of a dehydration synthesis reaction.
Sketch saturated and unsaturated fats and identify which is more fluid. Identify the hydrophilic and –phobic poles of a phospholipid.
-draw-
Explain the role of hopanoids and saturation in membrane stabilization and fluidity.
similar to sterols, helps stabilize bacteria membrane
Describe the role of membranes and ATP in homeostasis, using the terms hypertonic and hypotonic, as well as diffusion, facilitated diffusion and active transport.
diffusion follows gradient non charged and low MW only, random process
facilitated diffusion is a specific carrier proteins for particular molecules
active transport requires energy, powered by ATP, goes against gradient
microbes can adapt to hyper/hypotonic by using certain solutes to keep osmotic conc of their cytoplasm compatible with the habitat.
ATP level based on metabolic demand
for homeostasis must regulate metabolism
Sketch concentration vs flux plot for facilitated and passive diffusion.
-draw-
Identify these structures found in some bacteria – PHA, volutin, ribosomes, and magnetosomes – as organic or inorganic and explain their function.
magnetosomes- used by some bacteria to orient themselves in magnetic fields. both organic and inorganic
ribosomes- protein synthesis
volutin- polymerized phosphate and represents a storage form for inorganic phosphate and energy. Inorganic
PHA- polyesters produced in nature through bacterial fermentation of sugars or lipid, storage for carbon and energy
Contrast these cytoskeleton structures: microtubules, microfilaments and intermediate filaments.
microtubules- protofilaments assembled from heterodimers of bacterial tubulin A (BtubA) and bacterial tubulin B (BtubB), hollow, transport and motility
microfilaments- double-stranded molecules of polymerized fibrous (F) actin, form 3d network, cell movement
intermediate filaments.- several intertwined strands of fibrous proteins. Intermediate filaments have no role in cell movement.
Contrast pili, fimbriae, flagellum, cilia and undulipodium.
Flagella are long, rope-like organelles used primarily for cellular motility, hook and hollow
cilia- used for either motility or as a sensory organelle, cell may have one primary cilium or multiple cilia. Neither bacteria nor archaea possess cilia.
pili- bacterial sexual reproduction (also known as conjugation) and facilitate attachment and DNA transfer, short and thin
fimbriae- adhesion , short hair-like, found on most Gram-negative bacteria and on some Gram-positive bacteria
undulipodium- motile filamentous extracellular projection of eukaryotic cells
Discuss the dual roles of pili in HGT and electron transfer.
HGT- pili transfer DNA from one cell to the other
electron transfer- pili facilitate electron transfer to insoluble Fe(III) oxides and biofilms
Contrast these glycocalyx types: capsule, slime layer and biofilm.
slime layer- diffuse, unorganized material thats removed easily, usually made of polysac
capsule- organized, not easily washed off, helps resist phagocytosis
biofilm- complex, slimey communities of microbes, can cause serious illness
Explain the clinical significance of capsules and biofilms.
biofilm can form on medical devices and create illness
capsules have ability to resist biotic or abiotic aggressions, like the immune system
Describe the great plate anomaly in terms of cultivation efficiency and nutrient availability, using the terms copiotroph and oligotroph.
most of the microbes seen in the microscope cannot currently be grown under laboratory conditions, some may actually be nonviable, others are viable but nonculturable
copiotroph- organism found in environments rich in nutrients
oligotroph- can live in an environment that offers very low levels of nutrients
^ will grow slower
in low nutrient environment, oligotrophic bacteria have greater growth efficiency compared to copiotrophs and outcompete them
Discuss the four phases of bacterial growth in batch culture and contrast batch with chemostat systems.
the lag phase, ribosome manufacture
the exponential or log phase, balanced growth
the stationary phase, nutrient limitation
the death or decline phase
chemostat system: used for continuous culture
bioreactors where growing cells reach a steady state condition at which specific growth rate, as well as biomass, substrate and the product concentrations remain constant
Explain the role of quorum sensing in batch culture and biofilm formation.
qs helps bacteria anticipate and adjust to changes in the environment. homoserine lactone is the qs molecule. HSL controls biofilm formation. biofilm is a virulence factor induced by qs.
Compare estimates of microbial biomass by CFU, MPN, direct counts (microscopy) and turbidity (A600).
CFU- colonies that are viable, able to multiply
MPN- estimate population density based on the presence or absence of microbial cells, number of coliform-group organisms per unit volume of sample WATER,
uses several dilutions
microscopy- population size must be large and dispersed
turbidity/A600/spectrophotometry- scattering of light is proportional to biomass
Differentiate selective from differential media and defined from complex media
differential media- permit ID of microbes based on characteristics (blood agar)
selective media- promote growth of certain microbes while inhibiting the growth of others, for example gram pos and neg
defined media- each ingredient can be defined w a chemical formula
complex media- some ingredients of an unknown composition
