Bio 221 Microbiology Exam 2 Name _______________________ Matching Match the following metabolic pathway with the key diagnostic enzyme for the presence of the pathway. (1 point each) ___ ___ ___ ___ ___ ___ Entner-Duodoroff Pathway Calvin Cycle Wood-Ljungdahl Pathway Reverse TCA cycle Hexose monophosphate shunt (Pentose phosphate pathway) Glyoxylate shunt A. B. C. D. E. F. CO dehydrogenase Fumarate reductase Ribulose bisphosphate carboxylase 6-Phosphogluconate dehydrogenase KDPG aldolase Isocitrate lyase Match the following types of plasmid vectors and their characteristics. (2 points each) ___ ___ ___ ___ broad host range vector suicide vector shuttle vector cloning vector A. Contains origins of replication that enable the plasmid to replicate in bacteria and human cells. B. Contains an origin of replication this is very specific and the plasmid will not replicate in the recipient cell. C. Contains special features for inserting new genes and/or expressing their gene products. D. Contains an origin of replication that is able to replicate in more than one species of bacteria. Multiple Choice (1 point each) ____ Which of the following is NOT a source of electrons for anoxygenic photophosphorylation? A. B. C. D. E. Hydrogen sulfide Thiosulfate Succinate Water Hydrogen gas ____ Which of the following sequences of types of organisms accurately reflect the order in which these types of organisms are found in a microbial mat (from top to bottom) A. Cyanobacteria, purple non-sulfur bacteria, purple sulfur bacteria, green sulfur bacteria B. Green sulfur bacteria, purple sulfur bacteria, purple non-sulfur bacteria, cyanobacteria C. Cyanobacteria, green sulfur bacteria, purple non-sulfur bacteria, purple nonsulfur bacteria D. Purple non-sulfur bacteria, purple sulfur bacteria, green sulfur bacteria, cyanobacteria ____ Why is it necessary for phototrophs to make NAD(P)H? A. B. C. D. for for for for biosynthesis electron transfer phosphorylation fermentation the Krebs cycle ____ Which of the following key biosynthetic precursors is NOT generated either through the Embden-Myerhoff-Parnas Pathway or the Entner-Duodoroff pathway? A. B. C. D. E. Glucose 6-phosphate Phosphoenolpyruvate Pyruvate 3-Phosphoglycerate -Ketoglutarate ____ What is an anapleurotic reaction? A. A reaction that occurs in more than one pathway. B. A reaction that can proceed in either the forward or reverse direction? C. A reaction that is exactly the opposite of a reaction catalyzed by a different enzyme. D. A “replenishing” reaction that provides an alternative mechanism to generate key intermediates “lost” due to biosynthetic reactions. ____ Which of the following families of amino acids require -Ketoglutarate as a precursor? A. B. C. D. E. Glu, Pro, Gln, Arg Asp, Lys, Asn, Met, Thr, Ile Ala, Val, Leu Ser, Gly, Cys Trp, Tyr, Phe ____ What is the function of chaperone proteins? A. Assisting protein secretion by keeping polypeptides from folding prematurely. B. Binding to signal peptides and guiding them to their target in the cell membrane. C. Cleaving the signal peptide after secretion of the polypeptide through the cell membrane. D. Guiding mRNAs to the appropriate ribosomes. ____ Why is cellulose a poor nutrient source for humans and most non-ruminant animals? A. B. C. D. It’s bonds are difficult to break. It is only made from one sugar. It is inaccessible through cell wall It is complexed with membrane. ____ Why are biodegradable plastics biodegradable? A. B. C. D. Made thinner. Made from biological material. Special bacteria break them down. Made of water soluble material. ____ If you wanted to cleave a protein into smaller, specific polypeptides for analysis, which type of enzyme should you use. A. B. C. D. peptidase endopeptidase carboxypeptidase aminopeptidase ____ Which of the following enzymes is involved in the break down of starch? A. B. C. D. Starchase. Gluconase Acetase. Amylase. ____ When studying gene expression, Why do investigators typically use reporter gene fusions in which the promoter for their gene of interest is linked to a gene encoding an enzyme such as beta-galactosidase or a protein such as green fluorescent protein. A. the reporter gene is smaller than the original gene so it is easier to control than the original gene. B. the reporter gene codes for an enzyme that is easier to detect (using a simple assay) than the original gene product. C. the reporter gene is larger than the original gene and therefore more stable than the original gene. D. the reporter gene codes for a product that is safer than the original gene product. E. All of the above ____ Mobilizable plasmids require a self-transmissible “helper” plasmid because they lack which of the following? A. B. C. D. oriT broad host range origin of replication genes that encode the mating bridge antibiotic resistance genes ____ A small portion of a 1 liter flask culture of an ampicillin sensitive strain of E. coli (approximately 108 bacteria) is spread on an agar plate containing ampicillin. After a 24 hour incubation, 50 ampicillin resistant colonies are observed. When did these ampicillin bacteria arise? A. in the 1 liter flask, during incubation in the absence of ampicillin B. on the agar plate, during incubation in the presence of ampicillin C. E. coli cannot spontaneously become resistant to ampicillin ____ Why do linear DNA fragments only integrate into the chromosome but plasmids can exist free in the cytoplasm? A. B. C. D. Fragments Fragments Fragments Fragments lack lack lack lack a promoter. an origin of replication. a resistance gene. a reporter gene. ____ Which of the following is not a mechanism for horizontal gene transfer in nature? A. B. C. D. conjugation electroporation transduction transformation ____ Max Delbrueck and his colleagues designed an experiment to demonstrate that mutations arise before an organism is exposed to a selective agent. This type of test was called the ____. A. B. C. D. E. variability test. fluctuation test. fermentation test. induction test. Ames test ____ In the figure to the right, which diagram best represents the arrangement of components at time 0? Short answer (variable points) Why is the redox potential of the reaction center chlorophyll of the oxygenic phototroph, Anabaena sphericus, greater than +1.0 V? Why do anoxygenic phototrophs contain reaction center bacteriochlorophylls that absorb light at wavelengths that are very different than the chlorophylls of the cyanobacteria? Complete the following table (2 points). What will happen to lac operon expression in an E. coli cell containing the following mutation(s) Use a (+) if the lac operon will be expressed and a (-) if the lac operon will not be expressed. (Assume there is no glucose in the medium). + Lactose lacIS - Lactose (super repressor) lacIq (constitutive repressor) lacOC (constitutive operator) lacIs and lacOC In the previous question, why was it important to state that there is no glucose in the medium? Why are polychlorinated biphenyls (PCBs) do difficult to degrade in the environment? Why do bacteria often secrete a wide assortment of extracellular enzymes? Name 2 things have we learned from sequencing 16S rRNA genes? Describe one advantage and one disadvantage for bacteria to organize certain genes in operons. Explain why Deinococcus radiodurans is resistant to such high levels of radiation. When calculating evolutionary distances by sequence analysis you count then number of differences in the nucleotide sequences of two different organisms and multiply by a correction factor. Why is this correction factor necessary? How does the tree of life, based upon 16S rRNA gene sequences support the theory that some of the first life forms were able to thrive at the high temperatures of the early earth? What is the Ames test used for? VERY briefly explain how the Ames test works. (in other words, not a description of the procedure, just what is being measured) Short essay (6 points each) Please answer 3 of the 4. 6 bonus points possible for answering all 4. Describe the basic steps in peptidoglycan synthesis and explain how penicillin affects cell wall synthesis by actively growing cells. Describe three mechanisms of transcriptional and three methods of translational control of gene expression. Describe the three major mechanisms for horizontal gene transfer. Include a brief description of the mechanism(s) for DNA transfer for each. Many of us are taught that respiration is the consumption of molecular oxygen and photosynthesis is the generation of molecular oxygen. Now that you know how these processes function in the microbial world, explain why this is not necessarily the case. Perhaps it might be better to describe them as “complementary” process. Give some examples of how respiration and photosynthesis complement each other.