MicroBiology Test 4 (copy)

Chapter 16- HOST-MICROBE INTERACTIONS

Acute Infection. An infection characterized by symptoms that develop fairly quickly and last a relatively short time

Chronic Infection. An infection that generally develops slowly and lasts for months or years

Colonization. Establishment and growth of a microorganism on a surface

Endotoxin The lipopolysaccharide (LPS) component of the outer membrane of Gram-negative bacteria; lipid A is responsible for the toxic properties of LPS

Exotoxin A toxic protein produced by a microorganism; often simply referred to as a toxin.

Immunocompromised Having a weakness or defect in the innate or adaptive defenses

Infection Colonization by a pathogen on or within the body

Infectious Disease An infection that prevents the body from functioning normally

Latent Infection Infection in which the infectious agent is present but not causing symptoms

Microbiome The total genetic information of a community of microorganisms in a given environment; also the community itself, in which case the term is often used synonymously with normal microbiota

Normal Microbiota The group of microorganisms that routinely colonize the body of a healthy individual

Opportunistic Pathogen A microbe that causes disease only when introduced into an unusual location or into an immunocompromised host

Primary Pathogen A microbe able to cause disease in an otherwise healthy individual

Virulence Factors Traits of a microbe that promote pathogenicity

MicroAssessment 16.1

The symbiotic relationship between a host and microbe can be described as mutualism, commensalism, or parasitism, depending on the relative benefit to each partner.

MicroAssessment 16.2

The microbiome protects against harmful organisms, stimulates the immune system, promotes oral tolerance, aids digestion, and produces substances that are important for human health. Increasing evidence points to the gut microbiome having some effect on brain health.

MicroAssessment 16.3

A primary pathogen can cause disease in an otherwise healthy individual; an opportunist causes disease when host immune defenses are weekend or when introduced into an unusual site. The course of infectious disease includes an incubation period, illness, and a period of convalescence. Infection can be acute, chronic, or latent; they can be localized or systemic.

MicroAssessment 16.4

Koch’s postulates can be used to establish that a given microbe causes a specific infectious disease. Molecular Koch’s postulates are used to identify the virulence factors responsible for disease.

MicroAssessment 16.5

Pathogens use adhesins, often on pili, to bind to a body surface, To colonize a surface, the pathogen must often compete with the normal microbiota, prevent binding of secretory IgA, and obtain iron. Some bacteria deliver effector proteins to epithelial cells, inducing a specific change in those cells.

MicroAssessment 16.6

Skin is the most difficult barrier for microbes to penetrate. Some pathogens cross the mucous membrane barrier by inducing mucosal epithelial cells to engulf them or by taking advantage of antigen-sampling process.

MicroAssessment 16.7

Mechanisms bacteria use to avoid destruction by phagocytes include preventing encounters with phagocytes, avoiding recognition and attachment, and surviving with phagocytes. Serum-resistant bacteria avoid the killing effects of complement system proteins. Mechanisms for avoiding antibodies include IgA protease, antigenic variation, and mimicking host molecules.

MicroAssessment 16.8

Damage can be due to exotoxins, including A-B toxins, superantigens, membrane-damaging toxins, and other toxic proteins. Endotoxin and other cell wall components in the bloodstream can trigger a widespread

Ch.12 The Eukaryotic Members of the Microbial World

Algae Eukaryotic photosynthetic organisms with relatively simple reproductive structures and no organized vascular system.

Arthropod Animal with an external skeleton and jointed appendages such as an insect or an arachnid; may act as a vector in a disease transmission

Definitive Host Organism in which a parasite undergoes sexual reproduction or matures to its adult form

Fungus Heterotrophic eukaryotic organism with a chitin-containing cell wall

Helminth A worm; parasitic helminths often have complex life cycles

Intermediate Host Organism in which a parasite undergoes asexual reproduction or is found only in its immature form

Mycosis Disease caused by fungal infection

Protists Eukaryotes that are usually single-celled and are not fungi, plants, or animals

Protozoa Protists that are not algae

Saprotroph Organism that takes in nutrients from dead and decaying matter

Yeasts Unicellular fungi that reproduce by budding

MicroAssessment 12.1

As saprotrophs, fungi are important recyclers of carbon and other elements. Fungi typically have chitin and glucan in their cell walls, and their membrane contains ergosterol. Most fungi grow only as molds, but some grow only as yeasts; some species are dimorphic. Fungi are classified based on characteristics of their sexual reproductive forms, but fungal identification is primarily based on the asexual reproductive forms, but fungal identification is primarily based on the asexual reproductive forms. The phyla Ascomycota, Basidomycota, and Mucromycota include some medically significant members. Many fungi are commercially important, but some cause devastating plant diseases. Some fungi form symbiotic relationships with other organisms, such as those of lichens or mycorrhizas.

MicroAssessment 12.2

Protozoa are a diverse group of single-celled organisms. They occupy a variety of habitats and are a very important part of food chains. Groups of medically important protozoa include amoebae, apicomplexa, kinetoplastids, and flagellates.

MicroAssessment 12.3

Algae are aquatic eukaryotic organisms that have chlorophyll a and carry out photosynthesis; they form the base of aquatic food chains and produce much of our atmospheric oxygen. Oomycetes are genetically related to certain types of algae but are not photosynthetic.

MicroAssessment 12.4

Helminths, including the roundworms, tapeworms, and flukes, cause serious diseases in humans. Many helminths have a complex life cycle with more than one host. They may enter a human host by ingestion with food or water, by an insect bite, or by burrowing through skin.

MicroAssessment 12.5

Arthropods such as flies, mosquitoes, fleas, lice, and ticks act as vectors for the spread of disease. Infestations of mites and lice may cause itching.

Chapter 13 - Viruses, Viroids, and Prions

Bacteriophage A virus that infects bacteria; often called a phage

Latent Infection With respect to viral infections, an infection in which the viral genome persists silently in the host cell, so new viral particles are not being produced

Lysogen A bacterium that carriers phage DNA (a prophage) integrated into its genome

Lysogenic Conversion A change in one or more of the properties of a bacterium upon acquiring a prophage

Lytic Infection A productive infection that causes the host cell to burst

Prion An infectious protein that causes a neurodegenerative disease

Productive Infection Viral infection in which more viral particles are produced

Viroid An infectious agent of plants that consists only of RNA

Virion A complete virus in its inert non-replicating form outside a host cell; also referred to as a viral particle.

MicroAssessment 13.1

Viruses consist of nucleic acid (RNA or DNA) surrounded by a protein coat and sometimes an outer lipid layer (envelope). Viruses are typically icosahedral, helical, or complex in shape. Almost all bacteriophages are non-enveloped, whereas animal viruses are either non-enveloped or enveloped. Viruses are classified based primarily on the characteristics of their genome, such as type of nucleic acid and strandedness. Viruses are often grouped by their route of transmission. They replicate only inside living cells.

MicroAssessment 13.2

Lytic phages lyse their host cells, whereas temperate phages either lyse their host or exist within the host as a prophage. Prophage genes sometimes code for product that confer new properties on the host cell. Filamentous single-stranded DNA phages are extruded from the host cell without killing the cell.

MicroAssessment 13.3

Transduction is a process by which bacterial DNA is transferred from one bacterium to another by a phage. Generalized transduction results from a DNA packaging error, whereas specialized transduction results from an error during excision of a prophage.

MicroAssessment 13.4

Animal viruses and bacteriophages share similar features in their infection cycle. Because many animal viruses are enveloped and phages are not, differences exist in the way they enter and exit a host cell. The genomes of animal viruses are diverse, influencing viral replication strategies.

MicroAssessment 13.7

Various hosts are required to cultivate different viruses; bacteriophages require bacterial host cells while animal viruses are typically cultivated in cell culture using the appropriate host cells. Plaque assays are used to quantitate bacteriophages and animal viruses that lyse their host cells. Other methods to quantitate animal viruses include direct counts, quantal assays, and hemagglutination.

MicroAssessment 13.9

Two infectious agents that are structurally simpler than viruses are viroids and prions. Viroids contain only ssRNA and non protein; prions contain protein and no nucleic acid.