Self - Evaluation Quesitons

Streptococcus mutans is a common component of dental plaque. However, the bacteria is not found on the tongue of a person if its present on their teeth. What type of molecule is most likely is most likely responsible for this specificity?

Fimbria

Based on the graph below, what external feature has most likely been affected in the mutant bacterial stain?

Flagella (?)

How does substrate level phosphorylation differ from oxidative phosphorylation?

For substrate-level phosphorylation, the energy needed to make ATP comes directly from hydrolyzing energy-rich bonds of a substrate. For oxidative phosphorylation the energy needed to make ATP is produce indirectly through the movement of electrons between electron donors and acceptors that result in the generation of a proton motive force.

In this figure of a dividing cell, what is the name of the protein forming the ring (indicated by the arrow)

FtsZ

Select all reasons for the onset of stationary phase in a batch culture

accumulation of toxic water products nutrient limitation

When performing a Gram stain, it is important to properly decolarize; decolorizing with alcohol for too short or too long can lead to improper Gram stain and false results. Match the following scenarios with their most likely outcomes

decolorization is too long -> both gram positive and gram negative bacteria appear gram negative (pink) decolorization is too short -> both gram positive and gram negative bacteria appear gram positive (purple/blue)

This image shows two strains of a pathogenic bacterium stained with india ink. Bac A is the wild type and Bac B has a single mutation that inhibits the production of a extracellular structure A) which strains you would expect to be fully about to cause disease (virulent)? Justify your answer using data from figure and what you learned in class B) Which show stains you would expect to not be fully able to cause disease (avirulent or attenuated virulence)? Justify your answer using data from figure and what you learned in class

Bac A would be able to cause disease and Bac B would not be able to cause disease Bacterium A is expected to be more pathogenic as the halo around cells stained with indicates the presence of a capsule. Conversely, Bacterium B lacks halo and, therefore, also lacks a capsule. Capsules protect the bacterial cell against the immune system and thus the bacterium a capsule would be more virulent.

Label the cell morphology of this bacterium

Bacillus

Which of the following is not a product of glycolysis ?

glucose

Some prokaryotic cells have external layers known as capsules or slime layers. Choose all options that are functions of these external layers

physically protects the cell from desiccation promotes cell aggregation promotes adhesion of the cell to surfaces

Match the cellular activities with their corresponding energy sources

transport of maltose into cell using an ABC transporter -> ATP movement of nutrients via a uniport -> PMF flagella rotation_> ? glucose uptake of E.coli through a group translocation -> ?

Type IV pili can be used for movement by some kinds of bacterial cells. This movement is called ______ motility

twitching

The following image is an example of a bacterium with what type of flagellar arrangement

Lophotrichous (?)

rank the following primary metabolic pathways in order that a bacterial species would prefer to use them, assuming it was capable of all of them. The rank of one would be more preferred.

1) Aerobic respiration 2) anaerobic respiration 3) fermentation

What is the correct order of the phases of a batch culture when graphed on a semi-log plot?

1) lag 2) exponential 3) stationary 4) death

Please order the flagellar assembly from the first component ro the final component

1) mot proteins 2) MS/C rings 3)hook proteins 4) filament proteins (?)

What is the generation time of the bacteria whose growth is shown in the graph?

2 hours

In an optical microscope with a 10X ocular lens and 3 different objective lenses, 4x, 10x, and 40x, what is the highest possible magnification that a slide can be observed at?

400x

A chemical compound (compound X) is being evaluated for its potential use as an antibiotic. A series of experiments are performed to determine what biological effects compound X has on a bacterial cell. Figure 1 shows the experimental data measuring the concentration of ATP, phosphoenolpyruvate (PEP), and sodium ions (Na+) inside the cells during the experiment. Figure 2 illustrates experimental data measuring the proton motive force (PMF) of the bacterial cells. Assume all other biological conditions not shown in the above graphs remain the same between the two conditions. Transportation of which molecule is being inhibited by the compound X? What general mechanism of membrane transport was inhibited by compound X? Briefly, explain your reasoning for ruling in or out each of the three types of active transport when deciding your answer for part A. Use data from both of the above graphs in your answer.

A) Na, Simple transport (Symport was also accepted as the H+ and Na+ would be both entering the cell) B) Sodium ions are charged and would need to be actively transported into the cell. The ATP levels remain the same between the two conditions. This fact rules out the use of an ABC transporter. The PEP levels remain the same between the two conditions. This fact rules out the use of group translocation. PMF decreases with treatment of compound X. PMF powers simple transport. Therefore, simple transport is responsible for the movement of sodium ions across the plasma membrane.

The figure shows a population of bacterial cells stained with india ink. What is causing the visible halo that the arrow is pointing to?

Capsule

Which compound is an important component of the endospore core that combines with calcium to protect the spore contents?

Dipicolinic acid

Choose all of the following that describes a function or feature of gas vesicles

Give photosynthetic bacteria buoyancy to position them in the photic zone of aquatic environments. composed of glycogen (?)

Labeling the staining status of each bacterium

Gram negative

Labeling the staining status of this bacterium

Gram positive

Explain how a symporter uses the proton motive force to move a substance into the cell against a concentration gradient

In the case of using the PMF, the molecule that are transported with the proton through the channel. The energy is generated from using the high concentration of protons on the outside of the cell to drive import of a molecule across the membrane against the concentration gradient.

Mannitol salt sugar (MSA) is laboratory medium that is pink in color and contains 7.5% NaCl, along with other complex organic molecules, Only Staphylococcal species can grow on this medium. Colonies of Staphylococcal species that ferment mannitol, such as Staphylococcus aureus, turn the medium yellow. Colonie of species that cannot ferment mannitol, such as Staphylococcus epidermidis, cause no color change in the medium. Which statement best describe MSA?

MSA is selective for Staphylococcus species and differential for S. aureus (?)

Which of the following reactions would generate the most energy for a bacterial cell? Use the redox tower provided

Oxidation of glucose using nitrate

Which of these is a direct inhibitor of transpeptidase function?

Penicillin

What is the name of this carbon storage polymer?

Polyphosphate (?)

Rivers that people swim in are often monitored for bacterial contamination. Assuming you took a sample of river water at 8AM and needed to know how many bacteria were in the sample by 9AM what would be the technique to use?

Pour-plate technique (?)

A small sample of bacterial cells are transferred into two media: 1) rich medium, and 2) a minimal medium. Match the length of a lag phase with the type of growth medium .

Rich growth medium -> short lag phase Minimal growth medium -> long lag phase

Two identical bacterial cultures of wild type cells are grown in the same liquid medium. One culture is grown in an aerobic environment and the other culture is grown in an anaerobic environment devoid of any terminal electron acceptors. The figure above shows the motility of the cells grown in their respective environments. The cells in both cultures are viable and express normal flagella. A) Name a compound you could add to the anaerobic culture to increase the motility of cells in the anaerobic culture while maintaining an anaerobic environment? B) Why would this work? Please label your answer part A and B.

Student names electron acceptor other than oxygen (A.KA a alternative electron acceptor such as sulfate, nitrate, or sulfur). This would allow for increase in PMF to power the flagellar rotation under anaerobic conditions.

The antibiotic telavancin (see above) inhibits bacterial growth by binding to alanine (D-Ala) residues in peptidoglycan. Telavancin binding impedes synthesis of new peptidoglycan, restricting the capacity of bacteria cells to grow and divide. Gram positive bacterial cells are sensitive to telavancin while Gram negative bacterial cells insensitive to this antibiotic. Based on your knowledge of the cellular structure of Gram negative and Gram positive bacteria, provide a molecular explanation for the insensitivity demonstrated by Gram negative bacteria.

Telavancin is a very large molecule and cannot cross a membrane. Gram negative bacteria contain two membranes, the outer membrane (OM) protects Gram negative bacteria because telavancin is not able to cross the OM to gain access to the peptidoglycan

When transferring bacteria growing in batch culture in an enriched medium to a new tube containing defined medium, there is often a long lag phase. Which of the following explains the lag phase>

The bacteria need to synthesize the proper enzymes for metablosim

In the Limulus amebocyte lysate (LAL) test, the LAL reagent interacts with bacterial endotoxin and lipopolysaccharide (LPS) to form a clot. The LAL test provides a simple positive (clot forms) or negative (no clot forms) result. Imagine you are provided a culture and perform the LAL test. If a clot forms, what does that tell you about the culture you have been given?

The culture contains spores from gram positive bacteria (?)

Daptomycin is an antibiotic that binds to the bacterial membrane and allows ions to freely flow through the membrane. How would this kill a cell?

The influx of ions would stimulate the production of autolysin, which eventually destroys the cell. (?)

The graph shows a bacterial nutrient transport experiment. Cells were grown in growth media cultures containing increasing concentrations of Na+ and the rate of entry of the nutrient moving into the cells. From this graph, which of these interpretations is correct?

These cells have a sodium-dependent succinate symporter

In order to generative energy, some bacteria use environmental nitrate (NO3) as a terminal electron acceptor and generate nitrite (NO2). This is an example of what type of primary metabolic pathway

anaerobic respiration

In the diagram below, which arrow represents the energy required for the reactants to achieve a transition state in the presence of an enzyme catalyst?

b

An antibiotic was discovered that inhibits growth of Gram-negative bacteria and does not inhibit Gram-positive bacteria. From the list below, select the cell process that this antibiotic would most likely inhibit

lipopolysaccharide synthesis

endoflagella are useful to some bacteria because they provide ?

motility

Label the cell morphology of each bacterium

staphylococci