Example BI445 Exam Questions by Topic



Example BI445 Exam Questions by Topic

Review Questions

How do relatively small molecules (4 bonds in peptidoglycan.

15.______________________________

Either type of chemical that affects the movement of bacteria.

Acid-fast

Teichoic acid

Mollicutes

Hopanes

Mesosomes

Diaminopimelic acid

Lipoteichoic acid

M-Protein

Protoplasts

Keto-Deoxooctanoic acid

O-Antigen

Endotoxin

Lysozyme

S-layer

Zones of Adhesion

Murein Sacculus

Periseptal Annuli

Spheroplasts

Membrane-derived Oligosaccharides

Mycolic acid

Peritrichous

Filament

Hook/Basal Body

Flagellin

Swimming (Runs)

Tumbles

Attractants

Repellents

Chemotaxis

Polysomes

Poly-Hydroybutyrate

Glycogen

Polyphosphate

Sulfur Granules

Ribozymes

Isoelectric focusing

SDS Gel Electrophoresis

Agarose Gel Electrophoresis

Plasmids

Nucleoid

Sex pili

Type I pili

Techniques

Answer the following questions about the two 2D gels represented above. The one on the left contains proteins that are from cells grown on complete medium, and the one on the right contains proteins from cells that were grown in media containing very little Nitrogen.

1. On each gel indicate the protein is the most acidic with an A.

3. Which protein is most likely involved in binding NH3 at very low concentrations?

5. Proteins vary greatly in their ionic charge. What substance is the protein exposed to so that all polypeptides have similar charge:mass ratios?

Macromolecule Calculations

(5 points) The internal pH of a bacterial cell is typically 7.0. Given that the volume of the cell is about 10-12 ml, how many free protons (or more precisely hydronium ions H3+) present in the cytoplasm of a cell? First determine the H+ ion concentration.

(5 points) How much broth should you inoculate to produce 1 μg of viral DNA from an E. coli lysogen carrying lambda virus? Assume a burst size of 100 Lambda virus particles from a bacterial culture containing 5 x 109 bacterial cells per ml. The molecular weight of the Lambda genome is approximately 3 x 10 7 grams per mole.

(10 points) Assuming RNA makes up 20% of the dry cell weight, and 80% of the RNA is ribosomal RNA, how many ribosomes are there per cell? Assume the cell weighs 2.84 x 10-13 g and the molecular weight of the 23S rRNA is 106 g per mol. Don’t forget that the 23S rRNA makes up 2/3 the mass of rRNA in the cell!

(10 points) A cytochrome c molecule is isolated from E. coli grown under anaerobic conditions. The apoprotein (without the heme prosthetic group) has an apparent MW of 9,300 Daltons, and appears to make up 0.2% of the protein of the cell. How many copies of the protein are present in the cell? How many amino acids does it likely contain?

(10 points) Lipopolysaccharide makes up 3.4% of the dry weight of the cell. There are about 1.43 x 106 copies per cell. What is the average molecular weight of LPS? Assume the dry weight of the cell is 2.84 x 10-13 g.

(5 points) Lipopolysaccharide makes up 5% of the dry weight of the cell. There are about 4,300 copies per cell. What is the average molecular weight of LPS?

(5 points) How much broth should you inoculate to produce 1 mg of plasmid DNA from an E. coli clone carrying a high copy number (20 per cell) plasmid of 5000 base pairs?

Filter Binding Assay

(10 points) In a filter-binding assay, 10 (g of an unknown bacterium’s chromosomal DNA is bound to a nitrocellulose filter. The size of the chromosome is 2 x 106 base pairs. Assuming there is a single copy of each tRNA gene, or 60 total tRNA genes, how much tRNA will bind to the filter? Assume a typical tRNA has 80 nucleotides.

(10 points) Consider the tRNA molecule shown here. What is its approximate molecular weight based on the number of nucleotides? If tRNA makes up 3.07 % of the dry cell mass, how many tRNA molecules are there in a cell? Assuming 60 different tRNA, how many copies of each are present?

(10 points) In a filter-binding assay, 10 (g of an unknown bacterium’s chromosomal DNA is bound to a nitrocellulose filter. The size of the chromosome is 2 x 106 base pairs. If 3.85 ng of 16S rRNA binds the filter, how many copies of the ribosomal RNA operon are present? First calculate the MW of the chromosome. Then calculate the fraction of the DNA that codes for 16S rRNA. Multiply that fraction times the MW of the chromosome, and divide the result by the MW of the 16S rRNA.

Batch Culture Growth

Given the following data set for the growth of a bacterial culture,

|Time, hours |OD | | |

| | | | |

|0 |0.12 | | |

|0.67 |0.23 | | |

|1.25 |0.51 | | |

|1.83 |0.73 | | |

|2.41 |0.88 | | |

|3.08 |0.95 | | |

(6) A. Make a graph of log10OD as a function of time.

(8) B. Calculate (, g, and k.

(2) C. Indicate in which parts of the graph where primary and secondary metabolism are occurring.

(1) Which of the following phases of growth of a batch culture of microorganisms is characterized by endogenous respiration?

a. lag b. exponential c. stationary d. death

Which of the following inocula would show the longest lag period when transferred to glucose minimal media?

a. a stationary-phase culture grown on TSB

b. a stationary-phase culture grown on glucose minimal media

c. an exponential-phase culture grown on TSB

d. a exponential-phase culture grown on glucose minimal media

(1) Which of the following inoculums would show the shortest lag period when transferred to glucose minimal media?

a. a stationary-phase culture grown on TSB

b. a stationary-phase culture grown on glucose minimal media

c. an exponential-phase culture grown on TSB

d. a exponential-phase culture grown on glucose minimal media

(1) Which of the following would be major cell activities during secondary metabolism

a. competence

b. aerobic respration

c. anaerobic respiration

d. all of the above

e. none of the above

Batch Culture Growth Rates 16 points

A. Given that a typical bacterial culture contains 3 x 109 cfu/ml/OD, and that the sensitivty of a spectrophotometer is about 0.05, what is the smallest bacterial population that can be studied with a spectrophotometer?

B. Prepare graphs of OD as a function of time and log OD as a function of time from the growth data below. Indicate lag, exponential, stationary, and death phases if present.

C. Calculate k, g, and μ from the growth data below. Use hours, rather than minutes as the time scale.

| |Time |minutes |hours |OD |logOD |

|E. coli |10:00 |0 |0.00 |0.050 | |

|37 oC |10:30 |30 |0.50 |0.070 | |

|  |11:00 |60 |1.00 |0.100 | |

|  |11:30 |90 |1.50 |0.160 | |

|  |12:00 |120 |2.00 |0.375 | |

|  |12:30 |150 |2.50 |0.485 | |

|  |2:15 |255 |4.25 |0.660 | |

|  |2:45 |285 |4.75 |0.740 | |

|  |3:15 |315 |5.25 |0.750 | |

-----------------------

64 kD

64 kD

10 kD

10 kD

PI=10

PI=4

PI=10

PI=4

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