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Microbiology Chapter 16 Objectives and Vocabulary
Terms in this set (81)
Compare and contrast mutualism, commensalism, and parasitism.
Mutualism- Both partners benefit
Commensalism- One partner benefits and the other is unharmed
Parasitism- The parasite benefits at the expense of the other
Describe how the composition of a person's microbiome can change over time.
It can change over time as microbes are encountered in various foods, on pets, on other humans, and in the environment itself.
Describe the importance of the normal microbiota in protecting against infection, promoting oral tolerance, aiding digestion, and in producing substances beneficial to human health.
Protecting against infection- It protects against infection by covering binding sites that may be used for attachment, consuming available nutrients, and producing compounds toxic to other bacteria. It can also stimulate the adaptive immune system
Oral tolerance- Our defenses learn to lessen the immunity response to the many microbes that inhabit the gut which prevents the immune system from overreacting to harmless microbes which is call hygiene hypothesis
Aiding digestion- The microbiome allows the body to extract more energy from foods, body relies on MO to break down most types of dietary fiber
Producing substances important for human health- Bacteria in the intestinal tract produce vitamin K and B that can be used by the host, also bacterial fermentation of dietary fiber produces butyrate which is an important energy source for the epithelial cells that line the large intestine.
Define the terms primary pathogen, opportunistic pathogen and virulence.
Primary Pathogen-MO that causes disease in otherwise healthy individuals
Opportunistic Pathogen- Cause disease only when body's innate or adaptive defenses are compromised
Virulence- Degree of pathogenicity of an organism
Describe the characteristics of infectious diseases, including the course of disease, duration of symptoms, and distribution of the pathogen.
Course of disease- Starts with incubation period, sometimes a prodromal phase (period of feeling sick), then a phase of illness (signs and symptoms), then convalescence (stage of recuperation and recovery)
Duration of Symptoms-
Acute infection- Symptoms that develop quickly but last only a short time ex: strep throat
Chronic infections- Develop slowly and last for months or years ex: tuberculosis
Latent infections- never completely eliminated, microbe continues to exist in host tissues without causing symptoms, can reactivate
Distribution of Pathogen-
Localized infection- Microbe is limited to a small area
Systemic infection- The infectious agent is spread throughout the body
List Koch's postulates and compare to the molecular Koch's postulates
1. MO must be present in every case of disease
2. MO must be grown in pure culture from diseased hosts
3. The same disease must be produced when a pure culture of the MO is introduced into susceptible hosts
4. Mo must be recovered from the experimentally infected hosts
Molecular Koch's Postulates-
1. The virulence factor gene or its product should be found in pathogenic strains of the MO
2. Mutating the virulence gene to disrupt its function should reduce the virulence of the pathogen
3. Reversion of the mutated virulence gene or replacement with a wild-type version should restore virulence to the strain
Describe the requirements for adherence and colonization.
Adherence- bacterias use adhesions to attach to host cells, adhesion attaches to a molecule called a receptor and adhesion-receptor binding is highly specific, dictating the type of cells to which the bacterium can attach
Colonization- To colonize a mucosal surface, the pathogen must deal with the hosts defenses that protect those surfaces, they'll avoid IgA antibodies, must also be able to tolerate any toxic products such as fatty acids
Describe the mechanisms pathogens use to penetrate the skin and mucous membranes.
Penetrate the skin- They rely on skin-damaging injury
Penetrate the Membrane- Mucous membranes are the entry point for most pathogens
a. Directed uptake by cells- Gram-negative bacteria often inject effector proteins that induce engulfment by host cells, this causes actin molecules in the host cell cytoplasm to rearrange resulting in membrane ruffling which encloses the bacterial cells, bringing them into the intestinal cell
b. Exploiting antigen-sampling processes- Pathogens use M cells to cross the intestinal barrier (M cells transport material from the lumen of the intestine to the Peyer's Patches) most microbes delivered this way are destroyed by macrophages but certain pathogens have mechanisms to avoid this fate, Ex: Shigella cells survive macrophages and end up replicating, causing the phagocytes to undergo apoptosis, shigella cells then attach to the base of the epithelial cells and induce these cells to engulf them, within an epithelial cell, shigella cells cause the host actin to polymerize which then propels the bacterial cell, sometimes with enough force to push it into the next cell.
Describe mechanisms that bacteria use to avoid phagocytes, killing by complement system proteins and recognition by antibodies.
Describe the difference between exotoxins and endotoxins.
Explain how inflammation and antibodies can cause damage.
Describe how viruses bind to host cells, and how they spread to other cells.
Describe how viruses avoid immune responses and ultimately damage cells.
Describe the mechanisms of pathogenesis of dermatophytes, Candida albicans, and dimorphic fungi.
Compare and contrast the mechanisms of pathogenesis of protozoa and helminths.
the group of MO routinely found growing on the body of healthy individuals
the cultivation-independent study of microbial communities or their members by analyzing the total microbial genomes in a sample taken directly from an environment
an imbalance in the microbiome
the proposal that insufficient exposure to microbes during childhood can lead to allergies and autoimmune diseases
establishment and growth of a microbe in a particular environment
colonization by a pathogen on or within the body
symptoms do not appear or are mild enough to go unnoticed
an infection that results in disease
subjective effects of the disease experienced by the patient
objective evidence such as a rash or pus
the initial infection
an additional infection that occurs as a result of the primary infection
A microorganism or virus that causes disease in otherwise healthy individuals
causes disease only when the body's innate or adaptive defenses are compromised
degree of pathogenicity of an organism
traits of a MO that specifically allow it to cause disease
the number of microbes necessary to establish an infection
interval between initial infection and first signs and symptoms
Period of time during which symptoms and signs of disease occur
A period of early, vague symptoms that give a general feeling of illness
the stage of recuperation and recovery from the disease
Harbor an infectious agent and pass it onto others but do not have signs or symptoms
Characterized by symptoms that develop quickly but last only a short time
-ex: strep throat
develop slowly, last for months or years
never completely eliminated; microbe exists in host tissues without causing symptoms
The microbe is limited to a small area
the infectious agent is spread throughout the body
bacteria circulating in the bloodstream
life-threatening systemic inflammatory response
toxins are circulating in the bloodstream
Viral particles are circulating in the blood stream
the criteria used to determine the cause of an infectious disease by culturing the agent and reproducing the disease
Molecular koch's postulates
rely on molecular techniques to study a microbe's virulence factors
Host-parasite relationship in which the parasite persists in the host while causing minimal harm
how bacteria attach to host cells
molecule to which an adhesion attaches
Iron-binding substance produced by bacteria to scavenge iron
Enzymes that degrade IgA
Type 3 secretion System
Mechanism that allows bacteria to transfer gene products directly into host cells
characteristic mechanism of engulfment that some bacteria induce by triggering rearrangements of a cell's actin
These kill phagocytes and other cells, often by forming pores in their membranes
known for their ability to prevent phagocytosis
A protein in the cell walls of group A streptococci that is associate with virulence
proteins bind the Fc regions of antibodies
describing bacteria that have mechanisms to avoid the killing effect of complement system proteins
some antigens routinely alter the structure of their surface antigens
a toxic protein produced by a MO
An antibody preparation that protects against a given toxin
Toxin that damages the nervous system
toxin that causes diarrhea and vommiting
Toxin that damages a variety of different cell types
the A subunit is the toxic (active) portion and the B subunit binds to a specific surface molecule on cells
cytotoxins that disrupt eukaryotic cytoplasmic membranes, causing the cell to lyse
substance that lyses red blood cells
a toxin that inserts into the phospholipid bilayer of membranes, forming channels that allow fluids to enter the cell
The membrane-damaging toxin that enzymatically removes the polar head group on phospholipids
Toxins that non-specifically activate many T cells, resulting in excessive cytokine production that leads to severe reactions and sometimes fatal shock.
destroys material that binds together layers of skin
A lipopolysaccharide that makes up the outer layer of the outer membrane of the gram- negative cell wall
a range of effects that result from a systemic inflammatory response to a bloodstream infection or circulating endotoxin
Multinucleate body formed by the fusion of cells
a set of symptoms including malaise, fever, and body aches
potentially deadly overproduction of cytokines during an immune response to infection
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