Microbiology: Mastering Chapter 4

A student from one of the research labs is having trouble preparing a slide for examination and photographing. The bacterial slide that he has brought to you was prepared using a commercially purchased stain. He has asked for your help in determining what he is doing wrong so that he can change the lab protocols and continue on with his project. After examining the slide under oil immersion, you determine that no bacteria are present even though the student is able to show you the culture he used to make that slide that has visible growth in the liquid medium. Which of the following statements does NOT explain the fact that there are no bacteria present on the student's slide? -Overheating during the fixation step boiled the water within the bacterial cells and resulted in the cells bursting. -Insufficient heating of the slide did not drive out the thin layer of water and this resulted in minimal bonding between the bacteria and the glass slide. -Rinsing with alcohol during the washing step stripped the bacteria off the glass slide. -By not allowing a glass slide to completely air dry before heat fixation, the flame will cause the surrounding water to boil and this will damage the bacterial cell.

You volunteer to help the student with his fixation technique and in choosing a proper stain for the project he is working on. After watching and helping the student correct any problems with his fixation technique, you now need to determine which stains to use. The single criterion for the project is to be able to determine cell shape and size in a pure broth culture after some treatments. No differentiation between cell types is required (i.e., Gram-positive or Gram-negative), so you want to convince the student that a simple stain would be his best option. The charged dyes used in simple staining will penetrate the bacterial cell and will be retained after rinsing the slide with water to remove surplus dye. Which staining procedure would be best to use to stain the slides required for this student's project? Why? -An acidic stain such as nigrosin will stain the cells a dark black coloration for easier viewing under the microscope. -The positively charged methylene blue will be attracted to the negatively charged components of the cell wall and will be retained. -Using crystal violet followed by a rinse and Gram's iodine will stain the cells a dark blue with large crystals. -Malachite green and heat will colorize the cell for easier visualization and is a simple process.

Put the following descriptions in order for the staining reactions in the cells of a bacterial smear during the Gram staining procedure. 1. Clear cells are stained a red or pink whereas the color of other cells remains unchanged. 2. All cells are stained purple. 3. Cell wall of Gram-negative cells is broken down; Gram-positive cells remain intact. 4. Dye molecules are rendered insoluble in presence of mordant; dye is rinsed away.

Which of the following statements is INCORRECT regarding prokaryotic cells? -Their DNA is not enclosed within a membrane. -They lack a plasma membrane. -They lack membrane-enclosed organelles. -They reproduce by binary fission. -They typically have a circular chromosome

You have been asked to lead a demonstration for the undergraduate microbiology lab course about the uses of negative staining when studying bacteria. A "negative" stain does not stain the bacterial cell itself but stains the space between cells. Under magnification, the acidic (negatively charged) nature of the stain will be repelled by the negatively charged bacterial cell wall and will leave the cell colorless in a stained background. Negative stains are used primarily to reveal the presence of negatively charged bacterial capsules; therefore, they are also called capsule stains. Encapsulated cells appear to have a halo surrounding them. The negative stain procedure does not require heat fixation, which limits any chances of alteration in bacterial cell shape and size. The bacterial suspension is added to a drop of stain, such as nigrosin or eosin, and drawn across the glass slide using a coverslip. Nigrosin staining-not safranin staining-of Klebsiella pneumoniae will allow for the visualization of the cell shape and the determination of the presence of a capsule. False True

A gram-positive bacterium suddenly acquires resistance to the antibiotic methicillin. This trait most likely occurred due to acquisition of new genetic information through =meisosis. -binary fission. -conjugation. -transformation. -transduction.

Functions of the glycocalyx include all of the following EXCEPT -increased virulence. -binary fission. -source of nutrition. -protection against dehydration. -biofilm formation.

Which structure acts like an "invisibility cloak" and protects bacteria from being phagocytized? -slime layer -fimbriae -cell wall -capsule -cell membrane

The terms "run" and "tumble" are generally associated with -cell wall fluidity. -clustering properties of certain rod-shaped bacteria. -cell membrane synthesis. -taxic movements of the cell in response to attractants or repellents

Fimbriae and pili differ in that -pili are used for attachment to surfaces. -pili are used for motility. -pili are used for transfer of DNA and motility. -there are only one or two pili per cell. -pili are used to transfer DNA.

Which of the following is NOT characteristic of the glycocalyx found in bacteria? View Available Hint(s) -a viscous coating surrounding the cell made of polysaccharide, polypeptide, or both -a structure that can be visualized using an acidic negative stain and a basic counterstain -creates a slimy, slippery coating that prevents bacteria from attaching to surfaces -if firmly attached, contributes to bacterial virulence

Each of the following statements concerning the gram-positive cell wall is true EXCEPT -it protects the cell in a hypertonic environment. -it maintains the shape of the cell. -it is sensitive to lysozyme. -it is sensitive to penicillin. -it contains teichoic acids

Which of the following statements about gram-negative cell walls is FALSE? -They have an extra outer layer composed of lipoproteins, lipopolysaccharides, and phospholipids. -Their Gram reaction is due to the outer membrane. -They are toxic to humans. -They protect the cell in a hypotonic environment. -They are sensitive to penicillin

You have isolated a motile, gram-positive cell with no visible nucleus. You can safely assume that the cell -has a cell wall. -has a mitochondrion. -has cilia. -has 9 pairs + 2 flagella. -lives in an extreme environment.

In the figure, which diagram of a cell wall has a structure that protects against osmotic lysis? (A= Gram positive & B= Gram negative) -a -b -both a and b -neither a nor b -The answer cannot be determined based on the information provided.

In the figure, which diagram of a cell wall is decolorized by alcohol? (A= Gram positive & B= Gram negative) -a -b -both a and b -neither a nor b -The answer cannot be determined based on the information provided.

In the figure, which diagram of a cell wall is resistant to many antibiotics (e.g., penicillin)? (A= Gram positive & B= Gram negative) -a -b -both a and b -neither a nor b -The answer cannot be determined based on the information provided

In the figure, which diagram of a cell wall contains teichoic acids? (A= Gram positive & B= Gram negative) -a -b -both a and b -neither a nor b -The answer cannot be determined based on the information provided.

In the figure, which diagram of a cell wall contains porins? (A= Gram positive & B= Gram negative) -a -b -both a and b -neither a nor b -The answer cannot be determined based on the information provided.

Antibiotics that target the cell wall are an effective treatment against many pathogenic bacteria. True False

Spheroplasts, protoplasts, and mycoplasms are bacterial cells without cell walls. True False

The number of organelles such as chloroplasts, mitochondria, and rough endoplasmic reticulum is the same in all eukaryotic cells. True False

If you observe rod-shaped red cells after the Gram stain, you can assume their cell walls contain endotoxin. True False

Which of the following statements best describes what happens when a bacterial cell is placed in a solution containing 5% NaCl? -Water will move into the cell. -Sucrose will move into the cell from a higher to a lower concentration. -Water will move out of the cell. -The cell will undergo osmotic lysis. -No change will result; the solution is isotonic.

By which of the following mechanisms can a cell transport a substance from a lower to a higher concentration? -extracellular enzymes -facilitated diffusion -aquaporins -simple diffusion -active transport

Which of the following is NOT a typical characteristic of most bacterial plasma membranes? -is selectively permeable -contains proteins -contains cholesterol -site of energy production -composed of a phospholipid bilayer

Which of the following statements is TRUE? -A cell can produce many endospores. -Endospores are for reproduction. -Endospores are easily stained in a Gram stain. -Endospores allow a cell to survive environmental changes by producing a dormant period with no growth. -A cell produces one endospore and keeps growing.

Antibiotics that target cell wall synthesis ultimately cause bacterial cell death as a result of -osmotic lysis. -cell shrinkage. -inhibition of molecular transport. -plasmolysis. -decreased synthesis of plasma membrane.

Where are phospholipids most likely found in a prokaryotic cell? -the plasma membrane -the plasma membrane and around organelles -flagella -ribosomes -around organelles

Where are phospholipids most likely found in a eukaryotic cell? -around organelles -ribosomes -surrounding flagella -the plasma membrane, around organelles, and -surrounding flagella -the plasma membrane

In a hypertonic solution, a bacterial cell will typically -burst. -plasmolyze. -lyse. -stay the same. -osmolyze.

Which of the following are NOT energy reserves? -polysaccharide granules -metachromatic granules -carboxysomes -ribosomes -lipid inclusions

The DNA found in most bacterial cells -is found in multiple copies. -is surrounded by a nuclear membrane. -utilizes histones for chromosomal packaging. -is linear in structure. -is circular in structure

Which type of solution would cause a bacterium with a weak or damaged cell wall to burst as water moves into the cell? -an isotonic solution -a hypertonic solution -a hypotonic solution -either a hypotonic or an isotonic solution

Cells placed in a hypotonic solution tend to lose water due to osmotic pressure. True False

Endospores are a reproductive structure. True False

Which of the following structures is NOT found in some prokaryotic cells? -peritrichous flagella -flagellum -pilus -cilium -axial filament

Which of the following is NOT a functionally analogous pair? -nucleus -nucleiod region -cilia - pili -9+2 flagella - bacterial flagella -chloroplasts - thylakoids -mitochondria - prokaryotic plasma membrane

The internal structure of eukaryotic cilia and flagella are the same. True False

Which one of the following organisms has a cell wall? -mycoplasmas -L forms -fungi -protoplasts -animal cells

Which of the following statements accurately describes specific bacterial cell walls? View Available Hint(s) -In gram-negative bacteria, the thin layer of peptidoglycan is surrounded by an outer membrane made of phospholipids, lipopolysaccharides, and proteins. -The cell walls of gram-negative bacteria contain many more layers of peptidoglycan than those of gram-positive bacteria. -Gram-negative bacterial cell walls contain teichoic acids, whereas the cell walls of gram-positive bacteria do not. -In bacteria with acid-fast cell walls, the carboxylic acid in the walls forms a layer outside a thin layer of hydrophilic polypeptides.

Which statement regarding the structure or function of ribosomes is correct? -Ribosomes are found both free-floating and attached to the rough endoplasmic reticulum in eukaryotes and in prokaryotes. -Ribosomes are the sites of lipid biosynthesis in both prokaryotes and eukaryotes. -The ribosomes in the prokaryote are slightly larger than those found in the eukaryotic endoplasmic reticulum. -In eukaryotes, the ribosomes found in chloroplasts and mitochondria are 70S ribosomes, which are similar in size to prokaryotic ribosomes.

Which of the following pairs is mismatched? -mitochondria ATP production -lysosome digestive enzymes -centrosome food storage -Golgi complex secretion -endoplasmic reticulum internal transport

Which of the following organelles most closely resembles a prokaryotic cell? -Golgi complex -nucleus -cell wall -vacuole -mitochondrion

Bacteria are a commonly used organism for studies of genetic material in the research laboratory. The nucleic acids must first be isolated from the cells for these studies. Which of the following would most likely be used to lyse gram-positive bacterial cells for nucleic acid isolation? -alcohol -mycolic acid -polymixins -water -lysozyme

Which of the following is NOT found or observed to occur in both mitochondria and prokaryotes? -ATP-generating mechanism -cell wall -70S ribosomes -binary fission -circular chromosome

Which of the following eukaryotic organelles is correctly matched with its function? -flagellum--protection -mitochondrion--protein synthesis -glycocalyx--transport -vacuole--storage of materials

Which of the following is found in the cytoplasm of prokaryotic cells but is ABSENT from the cytoplasm of eukaryotic cells? -DNA -water -a cytoskeleton -enzymes

Many enzymes in both prokaryotic and eukaryotic cells are compartmentalized within organelles. True False

Which of the following facts does NOT provide evidence for the endosymbiotic theory? View Available Hint(s) -Mitochondria and chloroplasts contain circular DNA, similar to the DNA in prokaryotes. -The ribosomes contained within mitochondria and chloroplasts are very similar to prokaryotic ribosomes. -Prokaryotes contain peptidoglycan in their cell walls. -The same antibiotics that inhibit protein synthesis in prokaryotes also inhibit protein synthesis within mitochondria and chloroplasts