End of chapter questions Flashcards
Exam 1
Differentiate the role of pili from the role of flagella?
Pili, made up of pilin protein, aid in bacterial attachment to solid surfaces such as mucous membranes. Flagella, consisting of flagellin protein, are responsible for motility
What is the role of the capsule in the pathogenesis of infectious disease?
Capsules help microorganisms resist phagocytosis. Phagocytic cells are less able to bind to the capsular polysaccharide than they are to surface proteins. In addition, capsules hide antigens on the surface of bacteria, preventing them from interacting with antibodies produced by an animal in response to an infection
Why is lipopolysaccharide a significant outer-membrane structure in gram-negative bacteria?
LPS is also known as an endotoxin. This molecule is toxic to animals, inducing nonspecific effects such as fever, inflammation, hypotension, and shock. LPS contains three regions: an antigenic O-specific polysaccharide, a core polysaccharide, and an inner lipid A. The lipid A moiety is responsible for producing fever and shock conditions in patients infected with gram-negative bacteria.
A bacterium that grows only on plates incubated in the absence of oxygen would be categorized as an
obligate anaerobe
Fimbriae present on the outer surface of bacteria are used for
Adherence to surfaces
All of the following are characteristic of fermentation except:
It begins with the breakdown of pyruvic acid
It follows glycolysis and produces reduced nicotinamide adenine dinucleotide (NADH)
It produces acids, alcohols, and gases
It can occur in the presence of oxygen
It follows glycolysis and produces reduced nicotinamide adenine dinucleotide (NADH)
Why are older bacterial cells more easily decolorized than cells from younger colonies?
Older bacterial cells are decolorized more easily than younger cells, because as cells age their cell walls become “leaky” and allow molecules to pass more readily out of the cell. In the Gram stain, the crystal violet-iodine complex is more readily lost during the decolorization step
Why are spore-forming organisms more resistant than non-spore-forming species?
Bacterial spores have a thick protein coat that makes them highly resistant to chemical agents, temperature changes, dehydration, ultraviolet and gamma radiation, and desiccation. They are also metabolically inactive and can therefore survive periods of startvation
Explain the three ways in which genetic material can be transferred from one bacterium to another
The three ways in which genetic material may be transferred from one bacterium to another are transformation, transduction, and conjugation. Transformation is the uptake and incorporation of naked or free DNA into a bacterial cell. Transduction is the transfer of bacterial genes by a bacteriophage from one cell to another. Conjugation is the transfer of genetic material from a donor bacterial strain to a recipient strain. Conjugation requires close contact between the two cells
For the following DNA, write the complementary sequence. Include labeling the 3’ and 5’ end. 3’TTACGGACAAC 5’
3’ TTACGGACAAC 5’
5’ AATGCCTGTTG 3’
In RNA, thymine is replaced by
Uracil
In bacteriophage, how does lysogeny differ from the lytic cycle?
During lysigeny, phage DNA is inserted into the bacterial genome, but virus particles are not produced. When the bacterial cell replicates, the viral genome is copied along with the bacterial chromosome. During the lytic cycle, bacteriophages are produced until the bacterial cell dies and is lysed.
What is the difference between sterilization and disinfection?
Sterilization is a chemical or physical process resulting in the destruction of all living organisms. Disinfection can be either a physical or chemical method that reduces the number of viable cells
Explain situations in which you would use a disinfectant and an antiseptic
Disinfectant:
Clean surfaces
Antiseptics:
Hand washing
Describe the difference between physical and chemical methods of disinfection and sterilization
Physical methods involve heat (boiling water, autoclaving, pasteurization, dry heat). radiation (ionizing, nonionizing), and filtration (liquid, air). Chemical methods involve disinfectants and antiseptics. They include chemicals such as alcohols, aldehydes, halogens, chlorine, quaternary ammonium compounds, phenolics, heavy metals, and gases.
What method is required to kill endospores effectively
High-level disinfectants
List and describe factors that influence the degree of killing during disinfection and sterilization
Type of organisms
number of organisms
concentration of the disinfecting agent
presence of organic material
contact time
temperature
pH
biofilms
Explain EPA regulations on chemical surface disinfectants and FDA regulations on chemical skin antiseptics
Antimicrobial Division of the Environmental Protection Agency (EPA):
regulates the registration of use, sale, and distribution of antimicrobial pesticide products for certain surfaces or pesticide products incorporated into substances under the pesticide law.
The US Food and Drug Administration (FDA):
approves antiseptics through two processes-
new drug application (NDA)
over-the-counter (OTC) drug review
