Chapter 3 Micro Lecture Test 1 (Part 2)

Explain the difference in which bacteria produce and release endotoxins, as opposed to way in which they produce and release exotoxins.

*Endotoxins*: toxins that are part of the cell wall of gram negative bacteria *(lipid A)* and are released only *when the cell dies* and *the cell wall breaks apart*. Form structural components of cell wall of Gram Negative Bacteria and liberated only on cell lysis or death of bacteria. *Exotoxins*: toxins that are actively secreted by bacterial cells. Secreted by certain species of bacteria which diffuse into the surrounding medium

Describe what infectious dose is and relate it to pathogenicity.

*Infectious dose (ID)*: minimum number of organisms required to establish an infection

Describe what virulent factors are.

*Virulence factors*: parts, components, or secretions of microorganisms that allow them to progress towards and establish an infectious disease

List and describe the four sequential steps that lead to an infectious disease.

1)*Entry or introduction*- into the body or tissues of the host 2)*Attachment*- to the tissues of the host 3) *Colonization (contamination)*-accomplished by defeating phagocytosis and other defenses of the immune system 4) *Disease* caused generally *by destroying* the body cells, tissues, or organs

List the three cellular shapes that bacteria can have.

1)Coccus 2)Bacillus 3)Spiral

Give the functions of the following bacterial structures: a) bacterial chromosome, b) plasmid, c) ribosomes, and d) endospores. Which of these bacterial structures should be considered virulent factors? Why or why not?

1. *Bacterial chromosomes*: most bacteria have *a single circular chromosome*. *It contains the hereditary (genetic)* information of bacteria. 2. *Plasmids*: non essential circular pieces of DNA. 3. *Ribosomes*: sites of protein synthesis. 4. *Endospores* (an extremely resistant stage). •Endospores (spores) are dormant bodies produced by gram positive bacteria in the genera Bacillus and Clostridium. •Spores are dehydrated, have a very thick cell wall, and are extremely hard to destroy •They can resist adverse conditions for *extremely long* periods of time (34 years), boiling, alcohol, bleach, 400 rad, and hydrogen peroxide *won't* kill them.

Give the function of the following structures: a) flagella b) fimbriae and c) pili.

1. *Flagella* (propellers) •Their function is to *confer motility*; it is used to propel the organisms in liquid environments at a speed of 60 body lengths per second. They can be present in different numbers and arrangements. 2. *Fimbriae* • *Fimbriae* are sticky, bristle-like projections sprouting off some bacterial cells. Bacteria use fimbriae for *attachment*. Neisseria gonorrhoeae is the organism that causes the STD gonorrhea. In males it starts infecting the body by *colonizing the urethra* by means of fimbriae. 3. *Pili* • *Pili* are tubular structures composed of pilin. Also known as *conjugation pili*, they are present only in gram *negative bacteria*. They function mainly in the *transfer of DNA* from one bacterium to another through a process of DNA transfer called: **Conjugation**

List the functions of the cytoplasmic membrane. Is the cytoplasmic membrane a virulent factor? Why or why not?

1. It *regulates transport* in and out of the cell. •Like eukaryotic cells, it contains channels and carriers that make it *selectively permeable*. 2. *Secretion* of metabolic products. 3. It's the *site for energy reactions* (cellular or anaerobic respiration).

CH.3 Multiple choice questions: 8, 10, 12, and 13

8. Which of the following is NOT a function of a glycocalyx? A. It forms pseudopods for faster mobility of an organisms. B. It can protect a bacterial cell from drying out. C. It hides a bacterial cell from the other cells. D. It allows a bacterium to stick a host. Correct answer: A 10. Which cellular structure is important in classifying a bacterial species as Gram positive or Gram negative? A. Flagella B. Cell Wall C. Cilia D. Glycocalyx Correct Answer: B 12. Gram-positive bacteria _________________________. A. Have a thick cell wall, which retains crystal violet dye. B. Contain teichoic acids in their cell walls. C. Appear purple after Gram staining. D. all of the above. Correct Answer: D 13. Endospores ________________________. A. Are reproductive structures of some bacteria. B. Occur in some archea. C. Can cause shock, fever, and inflammation. D. Are dormant, resistant cells. Correct Answer: D

Give the main differences between the two types of bacterial cell walls. Which component of the cell wall is responsible for the way in which the two types of cell walls stain during the gram stain procedure?

A. *Gram Positive Cell Walls* 1) They have a relatively *thicker layer of peptidoglycan*(20-80 nm) in thickness 2) They contain teichoic acids but *lack an outer membrane*. 3) Stain violet due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with. B. *Gram Negative Cell Walls* 1) They have a *thinner* layer of peptidoglycan (1-3 nm) 2) They have an *outer membrane* that consists mainly of lipopolysaccharides

On each of the bacterial organelles from points 1 and 2 above (capsules, slime layers, flagella, fimbriae, and pili) state whether they should be considered virulent factors or not, and explain why or why not.

Capsules are virulent factors because they allow bacteria to colonize by preventing bacteria from being phagocytized , flagella are virulent factors because their propelling of bacteria into the environment allow entry into the body or tissue of the host , slime layers are virulent factors because their sticky surface allow bacteria to colonize , fimbriae are classified as virulent factors because their sticky bristle like projections allow bacteria to attach, and pili does not classify as a virulent factors because they transfer dna, a step not involved in leading to an infectious disease.

Give the main function of the bacterial cell wall.

Function: Cell walls give bacteria their characteristic *shape* and provide strong *structural support* keeping them from bursting or collapsing by osmotic pressure.

Explain the importance of lipid A as a virulent factor.

The lipid (Lipid A) is a component of the outer membrane that is toxic and is referred to as an endotoxin

List the two bacterial enzymes discussed in class as examples of virulent factors and describe the effects that they have in the body of the host.

a) *Collagenase*: digests collagen b) *Hyaluronidase*: digests hyaluronic acid -Collagenase and hyaluronidase are also termed: "spreading factors"

List the three categories or types of exotoxins discussed in class and give their main effects on cells.

a) *Enterotoxins*: affects cell lining of the GI tract causing diarrhea (Food poisoning) b) *Neurotoxins*: interfere with normal nerve impulses (Botulism, Tetanus) c) *Cytotoxins*: toxins that kill cells -hemolysins (destroy red blood cells) or leukocidins (kill white blood cells) Shiga toxins (kill epithelial cells lining the L.I.)

Describe the two types of glycocalyces (capsule and slime layer) and give their main function.

a) The capsule: a glycocalyx is formed of components organized as repeating units firmly attached to the cell surface. The capsule is known as an *antiphagocytic factor* because its main function is to *protect bacteria from being phagocytized* by white blood cells, which is accomplished in the following way: 1) It prevents recognition of bacteria by the phagocytes (WBC's) due to its chemical composition. b) *The Slime Layer*: a loose water-soluble glycocalyx that is viscous (sticky), providing one means by which bacteria can *attach* to surfaces

List examples of the symptoms caused by endotoxins.

a)Fever b)Inflammation c) Blood clotting d) Septic schock

Define normal (resident) flora. What would lead to normal flora causing a disease?

•*Normal (resident) flora*: the organisms that live in the skin and mucous membranes without causing harm to the host •It shouldn't gain access to sterile areas of the body