Microbio Exam 1
Whether a molecule is oxidized or reduced in a redox reaction depends on its reduction potential relative to the available electron donors and acceptors present that the organism can utilize. Given the following reduction potentials for various redox half reactions, in a lithotrophcapable of utilizing ammonia as an energy source, which substances would be potential terminal electron acceptors for respiration? NO2-/NH3+0.34 V NO3-/NO2-+0.43 V O2/H2O +0.82 V A.Both O2 and NO3- are possible electron acceptors B.O2 C.NO3- D.NO2-
A.Both O2 and NO3- are possible electron acceptors
An organism oxidizes H2and reduces nitrate (NO3−) to nitrite (NO2−). Which serves as the electron donor? A.H2 B.nitrate C.Nitrite D.O−
A.H2 ***
How do cocci and rods differ in morphology?
Cocci are more rounded like dots and rod are longer
Recognize the different morphologies of prokaryotic cells and their possible arrangements.
Cocci: spherical or ovoid Rod/bacillus: cylindrical Spirillum: flexible spiral Spirochete: rigid spiral Appendaged bacteria irregular/ asymmetrical
What is the purpose of gas vesicles in prokaryotes? What are gas vesicles made of and what is inside them?
Confer buoyancy Conical-shaped, gas-filled structures made of two proteins Impermeable to water and solutes
Why is peptidoglycan such a strong molecule
Cross-linking between amino acids in the layer of peptidoglycan forms a strongmesh-like structure that provides structure to the cell
Why were cyanobacteria so important in the evolution of life on Earth?
Cyanobacteria began the process of oxygenating the earth atmosphere
How do microbes contribute to the nutrition of animals such as humans and cows?
Cycling of key plant nutrients by microorganisms, microbes in the rumen of animals such as cattle and sheep, complex carbs digested by gut microbes on humans
What structures are universal to all type of cells?
Cytoplasmic membrane, cytoplasm, macromolecules, small organic molecules, inorganic ions, ribosomes, and DNA genome
During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction? A.+20 kcal/mol B.-10 kcal/mol C.-40 kcal/mol D.-20 kcal/mol
D.-20 kcal/mol
Which of the following statements is FALSE? A.The peptidoglycan layer consists of alternating NAG-NAM sugars linked via peptides B.Crosslinks in gram-negative organisms often link diaminopimelic acid (DAP) directly to an adjacent tetrapeptide C.Gram-negative organisms do not utilize peptide interbridgesfor crosslinking D.All bacteria have cell walls E.All of the above statements are false
D.All bacteria have cell walls
Which of the following circumstances is/are of concern in an attempt to fulfill Koch's postulates? A.Infected animals do not show the same symptoms as infected humans. B.The suspected pathogen is present in healthy humans. C.An axenic (or "pure") culture cannot be obtained. D.All of the above are of concern.
D.All of the above are of concern.
Which of the following is true regarding the diversity of life? A.Domain Archaeadoes not contain any disease-causing organisms. B.Bacteria can vary greatly in size and range up to 700 μmin length. C.Microbial Eukarya may have first arisen two billion years ago, well before fungi, plants, or animals. D.All of the above are true.
D.All of the above are true.
If the citric acid cycle was interrupted after the reaction that forms citrate, predict how this would affect the total amount of ATP generated per glucose molecule. A.The amount of ATP would be reduced from a total of 38 ATP to 22 ATP. B.The amount of ATP would be reduced from a total of 38 ATP to 14 ATP. C.The amount of ATP would be reduced from a total of 38 ATP to 30 ATP. D.The amount of ATP would be reduced from a total of 38 ATP to 8 ATP.
D.The amount of ATP would be reduced from a total of 38 ATP to 8 ATP.
Which of the following bacterial structures serves a similar function as adipose tissue in animals? A.polyphosphate granules B.gas vesicles C.magnetosomes D.polyhydroxyalkanoate granules
D.polyhydroxyalkanoate granules
Using phase contrast microscopy on a wet mount of live cells, you observe motile bacilli moving rapidly and randomly through the field of view, changing directions after a brief tumble and taking off in a different direction. These cells are exhibiting ________ motility. A.Twitching B.Gliding C.twitching or gliding D.swimming
D.swimming
How is DNA arranged in the chromosomes of eukaryotes?
DNA is wound around histones forming nucleosomes which are then organized into chromosomes
Describe the typical growth curve for a bacterial population. Be able to identify each growth phase on a growth curve plot and describe what are the characteristics/features of each phase.
Lag phase: interval between inoculation of a culture and beginning of growth Exponential phase (balanced growth): doubling at regular intervals Stationary phase: growth rate of population is zero (metabolism continues) Decline phase:total number decreases due to cell death Cryptic growth occurs here (subpopulations adapt to cannibalize and reuse resources released from dying cells)
What component of the gram-negative cell has endotoxin properties?
Lipid A portion of LPS (lipopolysaccharide layer)
Explain whether you expect the enzyme lysozyme to be equally effective against Bacteria and Archaea.
Lysozome would not be affective in archaea because archaea lack peptidoglycan in their cell walls
Explain how magnetosomes contribute to the motility of magnetotactic bacteria.
Magnetotactic bacteria use magnetosomes to align with magnetic fields and swim toward or away from O2at surfaces
How are magnetosomes and the Gloeomargarita inclusions similar and how do they differ?
Mangetosomes allow bacteria to orient within magnetic field Gloeomargarita form intracellular granules of bentonite which is formed through biomineralization which yields intracellular inclusions
What traits have allowed the bacteria Epulopiscium and Thiomargarita to have such large cells?
May have larger size to allow more storage of sulfur used as an energy source
Describe several ways in which microorganisms are important in the food and agricultural industries.
Microbial fermentation of dairy products and fermentation for bread and alcohol
What is the oldest form of life?
Microorganisms
What does the Germ Theory of Disease establish?
Microorganisms (pathogens) can lead to disease
Briefly describe how do microbes contribute to the global biomass.
Microorganisms comprise 20% of the carbon and 80% of the nitrogen and phosphorus in the biomass of all organisms of earth
How can you determine total cell count in a culture or a sample?
Microscopic cell count: observing and enumerating cells present
What are the evolutionary advantages of being small?
More surface to are relative to cell volume support greater nutrient and waste product exchange per unit cell volume more efficient
Which electron carriers described in section 3.10 accept 2e- + 2H+? Which accept electrons only?
NADH dehydrogenases, quinones and flavoproteins accept 2e- and 2H+ Cytochromes and iron-sulfur proteins carry electrons only.
Why do bacterial cells need cell walls? Do all bacteria have cell walls?
Needed to withstand osmotic/turgor pressure to prevent cell lysis and maintains cell shape and rigidity. Majority (90%) of bacteria have cell walls
Which one is a better electron donor: nitrate (NO3-) or fumarate? How do you know?
Nitrate because the standard reduction potential of nitrate is more positive than fumarate.
Can you see the "natural" colors of specimens using electron microscopy?
No
Could a bacterial cell dispense with a cell wall if it had a capsule? Why or why not?
No because a capsule doesn't provide structural support that the cell wall does
Describe the structure and components of the outer membrane in gram-negative cell walls. What are the functions of the outer membrane?
Outer membrane contains polysaccharides covalently bound to lipids: lipopolysaccharide layer (L P S) Facilitates surface recognition, important virulence factors, and add strengthbarrier against antibiotics and other harmful agents Contains porins(transmembrane transport proteins) Contains polysaccaharidemade of core polysaccharide and O-polysaccharide
Briefly describe the general steps of the citric acid cycle.
Pathway by which pyruvate is oxidized to CO2 1. Pyruvate from glycolysis is decarboxylated, producing CO2, NADH, energy rich acetyl-coA(which enters CAC) 2.Acetyl-CoA + intermediate oxaloacetate forms citric acid.
What do the enzyme lysozyme and the antibiotic penicillin have in common?
Peptidoglycan can be destroyed by lysosomes and penicillin blocks the formation of peptide cross links which also destroys peptidoglycan
Contrast the motility of a peritrichously flagellated bacterium such as Escherichia coli with that of a polarly flagellated bacterium such as a species of Pseudomonas.
Peritrichous: Forward motion is imparted by all flagella forming into a bundle and rotating counterclockwise (C C W). Clockwise (C W) rotation causes the bundle to break apart and the cell to tumble. A return to counterclockwise rotation leads the cell off in a new direction. Polar: Cells change direction by reversing flagellar rotation (thus pulling instead of pushing the cell) or, with unidirectional flagella, by stopping periodically to reorient and then moving forward by clockwise rotation of its flagella.
Compare planktonic growth vs sessile growth.
Planktonic growth: growth in suspension of free-floating/free-swimming cells Sessile growth: attached to surface
What is the function of porins and where are they located in a gram-negative cell wall?
Porins: transmembrane protein channels for entrance and exit of solutes located in the outer membrane of the cell wall
Does glucose formation from the elements release or require energy?
Releases free energy; it is exergonic
Know who were Robert Hooke and Antoni van Leeuwenhoek and their contributions to the field of microscopy.
Robert Hooke was a micropist who illustrated microscopic images such as molds (first know depiction of microorganisms) Antoni van Leeuwenhoek constructen simple microscope to find microorganisms (discovered bacteria in 1676)
Describe the major functions of the cytoplasmic membrane.
Separates cell from its environment , surrounds cytoplasm, selective permeability
How would you expect the flagellar basal body to differ between gram-negative and gram-positive bacteria?
The flagellar structure has two rings in the basal body of gram-positive bacteria, while gram-negative flagellar structure contains four rings in the basal body
Compare the leading causes of death in the US in the 1900 vs today. What do you think are the main reasons for the changes observed?
The leading cause of death were infectious diseases caused by pathogens today the leading cause of death is heart disease. The main reasons were advances in understanding disease processes, sanitary and public health measures, vaccines, and antibiotics
Compare and contrast the nucleus vs. the nucleoid.
The nucleus contains linear DNA molecules in eukaryotes. The genomes of bacteria and archaea are closed circular chromosomes in the nucleoid
Describe the major features of the nucleus.
The nucleus contains the chromosomes Enclosed by two membranes that interact with nucleoplasm (inner membrane) and cytoplasm (outer membrane) Within the nucleus is the nucleolus
Which reactions in glycolysis are redox steps?
The oxidation of glucose to form pyruvate
Why is the glyoxylate cycle necessary for growth on acetate but not on succinate?
These reactions occur in conjunction with the citric acid cycle when cells grow on two-carbon electron donors, such as acetate
In what ways are microorganisms important to humans?
They provide oxygen and inhabit every environment that supports life
Why might a photosynthetic cell benefit from controlling its buoyancy?
To position itself properly in a water column.
Compare total cell count with viable cell count in a culture.
Total cell count: -Use a microscope to count cells In squares -Cant distinguish between live and dead cells -precision difficult to achieve -needs staining -motile cells need to be immobilized -debris can be mistaken for cells Viable cell count: -Measure living reproducing population -Spread plate method and put plate method -30-300 colonies -colony forming unites instead of viable cell # -accounts for clumps
For testing a bacterium's response to a toxic substance, why would g be useful information?
Toxic substances can change the homeostasis of the bacteria, which can effect their growth and reproduction.
Differentiate between trace metals and growth factors. How are these used by the cell?
Trace metals are required in small amounts and are used as cofactors for catalysis of iron Growth factors are organic micronutrients which function as coenzymes
How can type IV pili facilitate pathogenesis
Type IV pili adhere to host tissues and support twitching motility
What is a microbial colony and how is one formed?
When a single microbial cell multiplies
Using a microscope, could you differentiate a coccus from a spirillum? A pathogen from a nonpathogen?
Yes you can identify different morphologies but you CANNOT identify a pathogen from a nonpathogenic
What are biofuels?
a fuel derived directly from microorganisms
Describe redox reactions and the relationship between an electron donor and an electron acceptor.
ability to donate electrons during electron transfer reactions (redox reactions) Redox reactions include two half reactions. Electron donor:transfers electrons (oxidized) Electron acceptor:adds electrons (reduced)
Where on an enzyme does the substrate bind?
active site: region of enzyme that binds substrate
How are viruses different from Bacteria, Archaea, and Eukarya? Compare and contrast the basic general characteristics of each group.
bacteria and archaea are prokaryotes, undifferentiated, and small Archaea are associated with extreme environments but THEY ARE NOT ALL EXTREMOPHILES Eukarya include plants, animal, and fungi and they vary in size, shape, and physiology Viruses ARE NOT CELLS they are parasites that only replicate within hosts, they don't carry out metabolism, and are very diverse
Describe how bacteria use a biased random walk to move toward an attractant.
biased random walk occurs in presence of attractant
Describe the process of binary fission.
cell division following enlargement of a cell to twice original size 1. circular DNA replication 2. cell elongation 3. septum formation 4. cell separation
What are SASPs and what is their function?
core of endospore contains small acid-soluble spore proteins (SASPs), which bind and protect DNA and function as carbon and energy source for outgrowth.
Why is a viable count more sensitive than a microscopic count? What major assumption is made in relating plate count results to cell number?
different organisms may have vastly different requirments for growth.
What is free energy?
energy available to do work
How many electrons and how much ATP are required to fix one molecule of N2 into two of NH3?
for fixing one mole of N2, 16 ATPs are used.
What is a semilogarithmic plot and what information can we derive from it?
graphical representation of a time series. The duration of exponential growth (t) and the number of generations during the period of exponential growth (n),
Why do cells enter stationary phase?
growth-limiting factor such as the depletion of an essential nutrient, and/or the formation of an inhibitory product
How do Koch's postulates ensure that cause and effect of a given disease are clearly differentiated?
he took the pure culture, and put it into a lab animal that didn't have the disease originally, and then he compared the disease that made the animal sick with the original
How can cells be made to fluoresce?
illuminating them from above with light of a single color. They fluoresce because they contain natural fluorescent (chlorophyll) or they were stained with dye
Describe the major features of enzymes. What molecules interact with enzymes?
in reaction, enzyme combines with reactant (substrate), forming enzyme-substrate complex, releasing productand enzyme
Why is aseptic technique necessary for successful maintenance of pure cultures in the laboratory?
in streaking a plate, the microbial cells are separated by the streaking process to yield widely separated single cells that then grow and divide to form colonies. uses pure cultures containing a single microbe usually require streak plate technique with inoculating loop
Explain the concept of growth in the context of microbiology.
increase in the number of cells
What are potential issues when estimating growth using turbidimetric methods?
microbes that form clumps or biofilms in liquid medium)
Describe the structural elements that comprise the cytoskeleton.
microtubules: hollow tubes; composed of α-and β-tubulin microfilaments: polymers of actin protein maintain intermediate filaments: fibrous keratin proteins
What is activation energy?
minimum energy required for chemical reaction to begin
What key reactions occur in the mitochondrion and in the chloroplast, and what key products are made in each?
mitochondria: respiration and oxidative phosphorylation for aerobic eukaryotes chloroplast: site of photosynthesis
Which two classes of macromolecules contain most of a cell's nitrogen?
mostly proteins, ammonia (NH3), nitrate (NO3−), or nitrogen gas (N2). Nearly all microbes can use NH3. many use nitrate (NO3−)
Do pure cultures have to be used in a chemostat?
no
What traits are shared between oxidative phosphorylation and photophosphorylation?
oxidative phosphorylation: from respiratory electrons photophosphorylation: from light energy Similarities a membrane associated electron transport chain. creation of a proton gradient. harvesting energy of the proton gradient by making ATP with the help of an ATP synthase.
Describe the structure of S-layers. What are the functions of S-layers?
paracrystalline structure consisting of protein or glycoprotein (outermost layer) functions include strength, protection from lysis, conferring shape, creating periplasmic-like space, facilitating cell surface interactions, promoting adhesion, protecting cell from host defenses
How does the biofilm growth mode differ from that of planktonic cells? Which growth mode better protects the bacterial cells from harm?
planktonic cells are suspended while biofilms occur when the cells are attached and form a polysaccharide matrix making it nearly impenetrable intensely interwoven prevents harmful chemicals and grazing
What is a pure culture?
population of cells derived from a single cell
List two advantages of using turbidity as a measure of cell growth.
quick and easy to perform typically do not require destruction or significant disturbance of sample Same sample can be checked repeatedly.
In what major way do quinones differ from other electron carriers in the membrane?
quinones: non-protein electron carriers
What is the role of NAD+/NADH in glycolysis?
reducing NAD+ to NADH
Describe the major function of the nucleolus?
site of ribosomal RNA synthesis
What are some of the problems that can arise when unstained preparations are enumerated in microscopic counts?
small cells can be overlooked, cannot distinguish between live and dead cells, precision is difficult to achieve
Describe the structure and function of a bacterial flagellum.
structure that assists in swimming long, thin appendages anchored in cell at one end
Under what nutritional conditions would you expect PHAs or glycogen to be produced?
synthesized when carbon in excess
Which major characteristic of ABC transport systems makes them ideal for organisms living in nutrient-poor environments?
the periplasmic binding proteins used in abc transport systems have high substrate affinity and can bind even in super low concentrations
Define the term generation. What is meant by the term generation time?
time required for microbial cells to double in number
What features differentiate an endospore from a vegetative cell?
vegetative cell differentiates to nongrowing, heat-resistant, light-refractive structure (SASPs absent in vegetative cells)
What is wastewater treatment and why is it important?
wastewater treatment is essential to sanitation and human health it relies on microbes to treat water contaminated with human waste so it can be reused
Under what conditions would a lag phase not occur?
when an exponentially growing culture or stationary culture is transferred into fresh medium
What is coenzyme A and why is it important?
Involved in fermentation; Coenzyme A derivatives have energy-rich thioester bonds
What major fermentation product is present in fermented milk products?
Lactic acid
What is the function of a catalyst? What are enzymes made of?
A catalyst (facilitates reaction without being consumed) is usually required to overcome activation energy barrier. Catalysts lower activation energy, increasing reaction rate Enzymes: major cellular catalysts; typically proteins (some RNAs)
Why is biofilm formation such a major problem in human medicine?
-Implicated in joint infections, implanted medical devices -Responsible for cavities and cause gum disease
What are the stages and events that occur during biofilm formation?
-Planktonic cells attach (flagella, fimbriae, pili) -Colonization: growth and extracellular polysaccharide (EPS) production -Development: metabolic changes -Dispersal: colonize new sites
What are the possible sources of error in plate counting? Explain the "great plate count anomaly."
-depends on inoculum size, viability, culture medium, incubation conditions -Mixed cultures grow at different rates. -plating inconsistencies -clumps. The great plate count anomaly": Direct microscopic counts of natural samples reveal far more organisms than those recoverable on plates.
Describe two ways in which N2-fixing organisms can protect their nitrogenase from O2.
-removal by respiration. -production of oxygen-retarding slime layers -localization of nitrogenasein differentiated heterocyst
What is the limit of resolution for a light microscope? What defines this limit?
0.2 um the limit is defined by the ability to distinguish two adjacent objects as distinct and separate
How many molecules of CO2, NADH, and FADH2 are released per pyruvate oxidized in the citric acid cycle?
2 CO2, 3 NADH, 1 FADH2, 1 ATP formed per oxidized pyruvate
What is considered a countable colony number?
30-300 colonies
Which statement best illustrates the importance of a high surface-to-volume ratio that is found in microorganisms? A.If a cell has a high surface-to-volume ratio, there will be enough surface area to get the needed nutrients in to support cellular metabolism and the accumulated waste out. B.If a cell has a high surface-to-volume ratio, the volume of the cell will be much larger than the surface area. There would be enough surface area to get the needed nutrients in and the accumulated waste out. C.If a cell has a high surface-to-volume ratio, there will NOT be enough surface area to get the needed nutrients in to support cellular metabolism and the accumulated waste out. D.If a cell has a high surface-to-volume ratio, the volume of the cell will be much larger than the surface area. There would NOT be enough surface area to get the needed nutrients in and the accumulated waste out.
A.If a cell has a high surface-to-volume ratio, there will be enough surface area to get the needed nutrients in to support cellular metabolism and the accumulated waste out.
Arrange the following types of microorganisms in the order in which they evolved on Earth. A.anaerobes, anoxygenic phototrophs, oxygenic PT, aerobes, multicellular org B.anaerobes, anoxygenic phototrophs, aerobes, oxygenic PT, multicellular org C.anaerobes, multicellular organisms, aerobes D.aerobes, oxygenic phototrophs, anoxygenicPT, anaerobes, multicellular org
A.anaerobes, anoxygenic phototrophs, oxygenic PT, aerobes, multicellular org
What structure in the cell links the proton motive force to ATP synthesis? How does it function?
ATP synthase The proton motive force creates torque in the membrane protein complex. The formation of ATP from respiratory electron flow is called oxidative phosphorylation.
What is the function of ATPases in fermentative bacteria?
ATPases in strict fermenters generate pmf for motility and transport by hydrolyzing ATP from substrate-level phosphorylation
What four bacterial phyla contain the most well-characterized species?
Actinobacteria, Firmicutes, Proteobacteria, and Bacteroidetes
Contrast the overall energy yield for aerobic respiration in bacteria with that of fermentation.
Aerobic respiration of 1 mole glucose produces 38 moles ATP Fermentation of 1 mole of glucose produces 2 moles ATP
How does pseudomurein resemble peptidoglycan? How do the two molecules differ?
Alternating N-acetylglucasomine (also in peptidoglycan) and N-acetyltalosaminuronic acid (in peptidoglycan its N-acetylmuramic acid) B-1,3 glycosidic bonds (peptidoglycan has B-1,4) Amino acids are all L-stereoisomer Cannot be destroyed by lysosomes and penicillin
What are hami?
Archaea "grappling hooks" assist in surface attachment, forming biofilms. Attaches cells to surfaces or each other
Describe the principle of the aseptic technique.
Aseptic technique (transfer without contamination)
Why do organisms growing by anaerobic respiration generate less ATP than organisms growing by aerobic respiration? A.They don't use electron transport to generate proton motive force. B. O2 has the most positive reduction potential and thus is a better electron acceptor. C.Much less NADH is produced to be used as an electron donor. D.They don't generate ATP by oxidative phosphorylation.
B. O2 has the most positive reduction potential and thus is a better electron acceptor.
Which of the following is NOT an example of how microorganisms are beneficial? A.fermentation of dairy products B.biofilm formation in fuel tanks, pipes, and drains C.production of ethyl alcohol for biofuel D.cycling of nutrients like nitrogen and phosphorus
B.biofilm formation in fuel tanks, pipes, and drains ****
Distinguish which list of structural properties and activities are true for ALL cells. A.cytoplasmic membrane, ribosomes, metabolism, motility B.cytoplasmic membrane, ribosomes, metabolism, evolution C.cytoplasmic membrane, ribosomes, growth, differentiation D.cytoplasmic membrane, ribosomes, growth, genetic exchange
B.cytoplasmic membrane, ribosomes, metabolism, evolution
Fermentation occurs when there is no usable external electron acceptor (like O2) available for respiration. Fermentation products are made following glycolysis as a result of reactions that __________. A.generate more ATP energy from the substrate B.oxidize NADH so that NAD+ can be reused again in glycolysis C.get rid of toxic waste products generated during glycolysis D.synthesize more NAD+ from substrate molecules
B.oxidize NADH so that NAD+ can be reused again in glycolysis
In organisms growing by respiration, NADH and FADH2 produced during glycolysis and the CAC are reoxidizedby A.fermentation of pyruvate. B.the electron transport chain. C.fermentation of citric acid. D.gluconeogenesis.
B.the electron transport chain
Name the three domains of life. Which of these contain eukaryotic life forms?
Bacteria, archaeologists, and eukarya Eukarya contain eukaryotic life forms
What is the major difference between bacterial and archaeal cell walls?
Bacterial: -Peptidoglycan -Outer membrane -Polysaccharide wall Archaea: -Lack peptidoglycan -Lack outer membrane
What are the major differences between bacterial and archaeal cytoplasmic membranes?
Bacterial: phospholipid bilayer, ester linkages, fatty acid lipids Archae: can be lipid bilayer or a monolayer, ether linkages, isoprene lipids
What is a batch culture? How do its characteristics and conditions compare to a continuous culture?
Batch culture: a closed-system microbial culture of fixed volume Batch culture: -Closed system -fixed volume -lag phase, exponential phase, stationary phase, death phase Continuous culture: -open system -known volume added while spent medium is removed at same rate -controls growth rate (k) and yield (biomass/ml)
What is reverse electron transport, and why is it unnecessary for chemoorganotrophs?
Chemolithotrophs typically use CO2 as carbon source (autotrophs); Use reverse electron transport to form reducing power
Why would a complex culture medium for a given microorganism be easier to prepare than a chemically defined medium?
Because it would consume a lot of time to create a defined medium vs just using a complex medium which already has a bunch of nutrients for the bacteria to grow on.
Why can it be said that the proton motive force is a unifying theme in most of bacterial metabolism?
Because no matter the electron source, energy conservation is the result of electron transport reactions and the formation of the proton motive force. The pmf is then tapped by ATPase to form ATP.
Why would it be impossible for gram-positive bacteria to store sulfur as gram-negative sulfur-oxidizing bacteria can?
Because the elemental sulfur is oxidized to sulfate, which is stored in the periplasm. This would be impossible in gram-positive bacteria because they do not possess a periplasm.
Why is it that eukaryotic cells are typically larger than prokaryotic cells?
Because they have to house more things
Compare the main microbial metabolic strategies hypothesized to have been present on the planet before and after cyanobacteria appeared.
Before cyanobacteria (3.8 bya) the earth was sterile. Early phototrophs lived in microbial mats that formed at the sediment surface
What is a biofilm? How does it compare to a microbial mat?
Biofilm: cells enmeshed polysaccharide matrix attached to surface Biofilms cover solid surfaces, while mats cover sediments.
Which chemical elements make up the bulk of a cell's dry weight?
C, O, N, H, P, S are ~96% of dry weight of bacterial cell
Which group is NOT a domain in the tree of life? A.Bacteria B.Archaea C.Viruses D.Eukarya
C. Viruses ****
In Bacillus subtilis, which of the following is a possible outcome of a mutation that prevents the cell from synthesizing dipicolinicacid? A.The mutant will remain viable under optimal conditions as well as high heat and radiation B.The mutant will have the same viability as the wild type under all conditions C.The mutant will remain viable under optimal conditions only D.The mutant will not be viable under any condition
C.The mutant will remain viable under optimal conditions only
Two capillary tubes were immersed in a suspension of motile bacteria. After 10 minutes, the capillary tubes were removed and the number of bacteria in the capillary was counted. Tube A contained 105bacteria/ml, whereas Tube B contained 1000 bacteria/ml (the same concentration as the original suspension of bacteria). Which of the following statements best describes these results? A.Tube A contained a buffer control and Tube B contained an attractant. B.Tube A contained a buffer control and Tube B contained a repellent. C.Tube A contained a repellent and Tube B contained a buffer control. D.Tube A contained an attractant and Tube B contained a buffer control.
C.Tube A contained a repellent and Tube B contained a buffer control.
A defined culture medium is designed to meet the needs of a particular type of organism, supplying all of the nutrients the organism needs, including essential biochemicalsthat the cell cannot synthesize. Based on the following recipe, this defined medium would best support the growth of certain members of what group?Recipe: 7 g of K2HPO4and 2 g of KH2PO4 (buffers); 1g of (NH4)2SO4 (nitrogen source for nucleotide and amino acid biosynthesis); 0.1g of MgSO4and 0.02g of CaCl2; 10g of glucose; trace elements mix; 1000 mL of distilled water; adjust to pH 7. A.autotroph B.phototroph C.chemoorganotroph D.chemolithotroph
C.chemoorganotroph
While examining cellular material, you find that organelle DNA is present. What organelle(s) must be within the sample? A.rough or smooth endoplasmic reticulum B.Golgi complex C.chloroplasts or mitochondria D.lysosomes
C.chloroplasts or mitochondria
Be able to calculate cells per mL of original sample (colony forming units, CFU) if you have number of colonies grown, dilution factor, and volume plated.
CFU= #colonies (DF)/volume
Functionally speaking, what are the different types of inclusions found in prokaryotic cells?
Carbon storage polymers Polyphosphate, Sulfur, and Carbonate Minerals Gas Vesicles Magnetosomes
What is the effect of a catalyst on the activation energy of a reaction? On the ΔG0′?
Catalysts lower activation energy, increasing reaction rate Overall reaction has negative or zero free-energy change
What are some alternate arrangements of cell envelope structure?
Cell envelope structures including cytoplasmic membranes (CM), cell walls (CW), outer membranes (OM), and S-layers (SL) can be found in both bacterial and archaeal species.
What are the approximate limits to how small a cell can be? Why should this be so?
Cell size is limited by a cell's surface area to volume ratio; the cell needs enough volume to house essential genes, sufficient ribosomes, and a minimum number of metabolic, structural, and transport proteins
What is the carbon source for autotrophic organisms?
Chemolithotrophs typically use CO2 as carbon source (autotrophs)
Explain why Paracoccus denitrificans would outcompete Escherichia coli if both organisms were competing for glucose in the presence of O2.
E. coli is a versatile chemoorganotroph with electron transport similar but not identical to Paracoccus denitrificans E.coli: Grows by aerobic respiration (O2), fermentation (no external electron acceptors), or anaerobic respiration (with nitrate) Can optimize under multiple conditions Conserves less energy than P.denitrificans if no O2 and nitrate present, E. coli uses nitrate reductase as terminal reductase
If a mutation causes a particular strain of pathogenic bacteria to lose its capsule, what would be the potential consequence? A.Capsules are essential for bacterial survival and cells lacking them would not survive B.Cells without capsules would lose their ability to invade and colonize new hosts C.Cells without capsules would be susceptible to antimicrobials that were previously ineffective D.A and B are correct E.B and C are correct
E.B and C are correct
In which medium shown in Table 4.2, defined or complex, do you think Escherichia coli would grow the fastest? Why?
E.coli would grow faster on the complex media than on the defined media because a ready-made nutrition source is available in the complex media
Describe the major functions of the endoplasmic reticulum, the Golgi complex (also known as Golgi apparatus), the lysosomes
ER: Smooth ER participates in the synthesis of lipids and carbohydrate metabolism. Rough ER produces glycoproteins and new membrane material. Golgi: modifying ER products Lysosomes: containing digestive enzymes and recycling cell components
How many electrons and how much ATP are required to make one hexose molecule by the Calvin cycle?
Easiest to consider cycle as six molecules of CO2 required to make one hexose
What is an electron micrograph? Why do electron micrographs have greater resolution than light micrographs?
Electron micrograph: electron microscope fitted with cameras to allow photograph (electron micrograph) to be taken Electron microscopes use electrons instead of light to image cells and cell structures
What is the proton motive force (pmf) and how is it formed?
Electron movements are exergonic, providing free energy to pump protons to outer surface of membrane: Generates proton motive force
What structures can be used to distinguish between prokaryotic cells and eukaryotic cells?
Eukaryotic cells contain organelles (nucleus, mitochondria, and chloroplast) while prokaryotic cells lack a nucleus and organelles
How does a chemoorganotroph differ from a chemolithotroph? A chemotroph from a phototroph?
Eukaryotic flagella are long appendages that propel through whiplikemotion.Bundle of nine pairs of microtubules surrounding a central pair of microtubules.Dynein is attached and uses A T P to drive motility
What processes are universal to all types of cells?
Evolution, metabolism, and growth
Compare and contrast exergonic and endergonic reactions, including their overall ΔG0′.
Exergonic: Reactions with −ΔG0′ ;release free energy. Endergonic: Reactions with +ΔG0′ ;require energy.
What are extremophiles? In what types of environments can they be found?
Extremophiles are microorganisms that can survive harsh environments they can be found in volcanic hot springs, glaciers, high salinity places, extreme acidic or alkaline habitats, or deep in the sea/ earth at high pressure
How do fimbriae differ from pili, both structurally and functionally?
Fimbriae: -short pili mediating attachment -facilitate genetic exchange between cells (conjugation) -Produced by all gram-negatives and many gram-positives Pili: -Enable organisms to stick to surfaces -thin filamentous protein structures
Compare and contrast defined vs complex media, selective vs differential media.
In defined media the exact chemical composition is known Complex media is composed of digests of microbial, animal, or plant products Selective medium contains compounds that selectively inhibit growth of some microbes but not others Differential media contains an indicator, usually a dye, that detects particular metabolic reactions during growth
Discuss the consequences of exponential growth.
Initial increase is slow but it quickly speeds up, resulting in huge increase in cell numbers (e.g., lactic acid bacteria spoiling milk).
Compare flagella and archaella in terms of their structure, function, and energy source.
Flagella: -rigid and helical -consists of several components: Filament (main part) composed of flagellin protein, Hook, Basal body (motor) -increase or decrease rotational speed relative to strength of proton motive force Archaella: -Smaller than bacterial flagella -Move by rotation driven by ATP hydrolysis
Describe how you could use a turbidity measurement to tell how many colonies you would expect from plating a culture of a given OD.
For unicellular organisms, OD is proportional to cell number within limits.
What is dipicolinic acid and the DPA complex, and where is it found?
Found in endospores dipicolinicacid, enriched in Ca2+ -together they bind free water and help dehydrate the endospore, also inserts between bases to help stabilize DNA
How do we determine generation time for a bacterial population?
Generation time (g) of an exponentially growing population g= t/n g= generation time t= duration of exponential growth n= number of generations during the period of exponential growth
What properties of the cell change as it gets smaller?
Genomes are highly streamlined, missing functions that must be supplied by other microbes or hosts (basically not enough space in cell to house non-essential genes)
How does gliding motility differ from swimming motility in both mechanism and requirements?
Gliding motion occurs at lower speed and in a smooth manner, while swimming motion is faster and it does not occur at a constant rate.
What two major roles do the citric acid cycle and glycolysis have in common?
Glycolysis and the CAC can oxidize several C4-C6 compounds (e.g.,glucose, citrate, malate, fumarate, succinate)
What color will a gram-negative cell be after Gram staining by the conventional method? And a gram-positive? What causes the different results observed in Gram staining?
Gram positive will be purple while Gram negative will be pink. The color difference is due to the differences in the structure of the cell wall
Summarize the differences in structure between gram-positive and gram-negative cell walls.
Gram positive: -Thick peptidoglycan cell wall -No outer lipid membrane -Stain purple -Peptide cross link contains peptide inter bridge -Can form endospore Gram negative: -Mostly composed of outer membrane -Thin peptidoglycan layer -At least 2 layers -Contains lipopolysachridees
Is NADH a better electron donor than H2? Is NAD+ a better electron acceptor than 2H+? Hint: use the redox tower.
H2 is a better electron donor than NADH (it has a more positive reduction potential) NAD+ is a better electron acceptor because of its less negative standard reduction potential.
In the reaction H2 + 1/2O2----> H2O, what is the electron donor and what is the electron acceptor?
H2 is the electron donor and O2 is the electron acceptor
Why might endospore-forming organisms be a problem for human health or the food industry?
Harder to kill
How does an autotroph differ from a heterotroph?
Heterotrophs: obtain carbon from organics Autotrophs: obtain carbon from CO
What happens in a chemostat if the dilution rate exceeds the maximal specific growth rate of the organism?
If a dilution rate is chosen that is higher than max specific growth, the cells cannot grow at a rate as fast as the rate with which they are being removed so the culture will not be able to sustain itself
Why is it useful to stain a sample before studying it with a microscope? Is it always necessary to stain microbial samples?
Improves contrast and visual bacteria. There are other methods such as phase contrast, differential contrast, dark field, and fluorescence
How do binary fission and budding cell division differ?
In budding a new individual is formed which is different from the old individual
In terms of their electron donors, how do chemoorganotrophs differ from chemolithotrophs?
In chemoorganotrophs, from NADH or FADH2 In chemolithotrophs, many different inorganics
Compare and contrast simple transporters, the group system, and ABC transporters in terms of (1) energy source, (2) chemical alterations of the solute during transport, and (3) number of proteins required.
Simple transporter: energy source comes from proton motive force, transport substances without chemically modifying them, only requires a transmembrane protein group system: energy source comes from energy rich organic compounds, transport substances while chemically modifying them, requires 5 proteins ABC transporter: energy source comes from ATP, transport substances without chemically modifying them, requires binding protein, transmembrane transporter, and ATP-hydrolizing protein
How can the small size and haploid genome of Bacteria and Archaea accelerate their evolution?
Small cells can grow faster and evolve more rapidly than larger cells, and mutations are expressed immediately in a haploid genome rather than skipping generations.
Describe the different mechanisms of gliding motility observed in bacteria.
Smooth, continuous motion along long axis without external structures
What advantages do solid media offer for the isolation of microorganisms?
Solid medium is useful for isolating bacteria or for determining the colony characteristics of the isolate.
Compare and contrast the different electron carriers that participate in electron transport.
Soluble electron carriers such as nicotinamide adenine dinucleotide (NAD+/NADH) needed to carry electrons
Compare and contrast generation time (g) versus the instantaneous growth rate constant (k).
Specific growth rate(k) expresses rate of growth at any instant. k= 0.693/g
Compare and contrast the spread-plate with the pour-plate count method.
Spread plate: -uses agar plate -spread evenly on agar -surface colonies seen after incubation Pour plate: -sterile plate with sterile medium used -surface and subsurface colonies seen -needs to be solidified and incubated
Briefly describe the two stages of glycolysis/fermentation.
Stage I: "preparatory," form key intermediates, ATP is "invested" Stage II: redox reactions,energy conserved, 2 pyruvate formed Glycolysis uses 2 ATP in stage I and produces 4 in stage II; net is 2 ATP, 2 NADH, 2 pyruvate per glucose
What major advantage does phase-contrast microscopy have over staining?
Staining often kills cells and can distort their features
In which phase of the growth curve do cells divide in a constant time period?
Stationary phase
Describe the concept of steady-state in a chemostat.
Steady state:cell density and substrate concentration do not change over time Steady-state in chemostat: - controls specific growth rate (k) and yield - growth rate and population density of culture can be controlled independently and simultaneously - Growth yield controlled by concentration of a limiting nutrient.
Briefly describe the general steps of the electron transport chain.
Step 1: Generating a Proton Motive Force. Step Two: ATP Synthesis via Chemiosmosis. Step Three: Reduction of Oxygen.
Describe the structure and functions of bacterial endospores.
Survival structures to endure unfavorable growth conditions many layers: core, inner membrane, cortex, outer membrane, endospore coat, exosporium
E. coli will not grow in the medium described for Thiobacillus thioparus. Why?
T. thioparus is both a chemolithotroph and an autotroph and thushas no organic carbon requirements, which E. coli does.
Describe the procedure for viable counting using serial dilutions.
Ten-fold dilutions commonly used Serial (successive) dilutions needed for dense cultures
What type of electron microscope would be used to view a cluster of cells? What type would be used to observe internal cell structure?
The TEM would be used to observe internal cell structure. The SEM would be used to view a cluster of cells
Why are microbial cells useful for understanding the basis of life?
The ability to grow microorganisms rapidly under a controlled environment makes then useful for experimentation